US3304620A

US3304620A - Process for drying laundered garments of polyester fibers

Info

Publication number: US3304620A
Application number: US315234A
Authority: US
Inventors: Ebert Philip Edmund
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1963-10-10
Filing date: 1963-10-10
Publication date: 1967-02-21
Anticipated expiration: 1984-02-21
Also published as: GB1018259A

Description

P. E. EBERT Feb. 21, 1967 PROCESS FOR DRYING LAUNDERED GARMENTS OF' POLYESTER FIBERS 2 Sheets-Sheet l Filed Oct. 10, 1963 INVENTOR PHILIP EDMUND EBERT ATTORNEY Feb. 21, P. E. EBERT PROCESS FOR DRYING LAUNDERED GARMENTS OF POLYESTER FIBERS Filed Oct. 10, 1963 2 Sheets-Sheet 2 FlG-Z /7 TUNNEL DRYER PERFORATED V.

PLME

|5 oRYBuLB f "/ls wETBuLB STEAM SUPPLY VENT .. .v n' u 'r r w.. r .n 1

PLATE DIRECTION OF AIR FLOVI INVENTORv PHILIP EDMUND EBERT BY WZW ATTORNEY United States Patent O 3,304,620 PRUCESS FOR DRYING LAUNDERED GARMENTS GF POLYESTER FIBERS lPhilip Edmund Ehert, Wilmington, Del., assignor to E. I.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware Filed Oct. 10, 1963, Ser. No. 315,234 3 Claims. (Cl. 34-31) This invention relates to a process for drying garments and, more particularly, to a process for the drying of garments containing polyester fibers.

Commercial laundering of garments conventionally requires three major steps, 1) washing, (2) drying, .and (3) finishing. Each of these three major steps greatly increases labor costs due to the multiple handling. Finishing, in particular, requires much handling of individual garments and, is therefore the highest cost step in the process. Previous attempts to eliminate the finishing step, such as drip-dry, tumble-dry, or hot air-dry have not been entirely successful since at least some ironing or pressing usually is required to give the garment a neat appearance. This is particularly true of garments washed at about 70 to 80 C., as is the practice in commercial laundries. Even a minimum of ironing or pressing is undesirable since it is still necessary for the garment to be handled, thus maintaining a high labor cost.

It is an objective of this invention to provide an improved process for drying garments containing synthetic, linear, polyester fibers in order to obtain a dry, Wearable garment.

According to this invention there is provided a process for drying garments containing at least 65% polyethylene terephthalate fibers comprising hanging the garments, while dripping Wet, onto racks and passing them through a dryer wherein the garments are subjected to lmoist air at a temperature of l45 to 155 C. dry-bulb and 85 to 90 C. wet-bulb to produce a dry, essentially wrinklefree garment.

In the drawings, which illustrate the invention,

FIGURE l is a fio'w diagram illustrating the process of this invention.

FIGURE 2 is a schematic cross-sectional view of the drying tunnel used to dry garments in accordance with the process of this invention.

As shown in FIGURE l, garments to be dried are taken from the washer 3 and hung on racks suspended from an endless conveyor track 4. The garments are conveyed through a drip area 6 to become free of excess water, and continue on through a tunnel dryer 7 |where they are dried in drying Chamber 8. The dry garments are then removed from the conveyor at unload area 9.

Referring to FIGURE 2, moist hot air is circulated in a clockwise direction in tunnel dryer 7 by fan 10, as indicated by the arrows. Saturated steam is introduced into the circulating air at vent 11 located adjacent to -opening 12 into fan Chamber 13. The moist air is heated by steam coil 14 in the fan chamber. The dry-bulb temperature of the air is measured at dry-bulb therrnometer 15 and the wet-bulb temperature measured at wet-bulb thermometer 16. The hot, moist air from chamber 13 enters the drying Chamber 8 through a perforated bottom plate 17 and eXits through a perforated top plate 18 after passing around and through garment 20 suspended from endless conveyor track 4. The air velocity is such asto agitate the garment and to insure complete drying. When the air is maintained at the critical driy-bulb and Wet-bulb temperatures specified previously, the garment is dried in an essentially wrinkle-free condition.

In drying garments in accordance with this invention, it is essential that moist heat be used. The moisture content and the temperature |of the air are critical if the gar- 3,304,0Z0 Patented Feb. 21, 1967 ICC ment is to leave the dryer in a Wrinkle-free condition. This process, while usable in a batch operation, provides the most beneficial results when incorporated into a continuous process.

During the manufacture of polyethylene terephthalate garments the fabric is heat-set in the desired wrinkle-free configuration. This imparts an ability to resist wrinkling at normal temperatures. However, washing at elevated temperatures, such as 70 to C. for commercial laundries, sets wrinkles in the garments which are not removed during drying in conventional ways. As a result of extensive experiments, it has been found that the fabric will resume its original heat-set configuration if dried under critically controlled conditions with hot, moist air at temperatures sufficiently below that of heat setting and sufi'iciently above those at which the wrinkles became set. In evaluating such experiments a wrinkle rating is assigned to garments based on the following subjective rating scale:

(l) Extreme wrinkling;

(2) Considerabl-e Wrinkling;

(3) Moderate wrinkling;

(4) Slight Wrinkling;

(5) No wrinkling.

Garments having a wrinkle-rating greater than 4 are essentially wrinkle-free. In accordance with this invention, as illustrated in the subsequent example, drying in a current of air having a temperature of l45 to 155 C. (dry-bulb) and having a moisure content corresponding to a Wet-bulb temperature of to C. provides such garments, having the appearance of being ironed or pressed.

Garments having a wrinkle rating of 3 to 4 are Wearable because the wrinkles are inconspicuous 'under normal wearing conditions. Wearable garments are provided, after washing at about 77 C., by drying in air at a drybulb temperature of at least C. and a Wet-bulb temperature of at least 77 C. Garments dried at lower dry-bulb or wet-bulb temperatures would not be regarded as Wearable without ironing or pressing. Air temperatures higher than about C. (dry-bulb) are not practically attainable in commercial operation and .may approach too closely to the original heat-setting temperature. Drying may be undesirably slow at wet-'bulb temperatures above 90 C.

Garments made from fabrics containing a high percentage of synthetic fibers, e.g., 50% or more of nylon or polyester fibers, can be used in practicing this invention. Preferably, the garment Will be made from a fabric consisting of polyethylene terephthalate fibers or a blend of polyethylene terephthalate fibers with other natural or synthetic fibers in which at least 65% of the fibers are polyethylene terephthalate fibers. Polyethylene terephthalate fibers are preferred because they adsorb relatively small amounts'of Water, and because of their easeof-care properties.

In addition to the critical conditions of the drying medium, wrinkle removal is favored by heavier fabrics, looser construction, and high polyester content. Further, directing the air flow upward assists in the drying process. Upward air flow tends to eliminate moisture concentration along the bottom edge of vthe garment, allows the air to flow through garments such as dresses and coats, and also agitates the garment.

The over-all appearance of the garment is further improved if the seams are pressed prior to the first laundering, since this tends to minimize seam pucker which detracts from the over-all appearance of the garment even though it be wrinkle-free.

In addition to garments, flat goods such as sheets and pillow cases can also be dried substantially wrinkle-free in accordance With this invention.

3 Example l Shirts made from an oxford fabric containing 65% polyethylene terephthalate and 35% cotton fibers are washed at 77 C. The highly wrinkled garments are placed, dripping wet, on hangers and hung four inches apart on a moving, endless conveyor track leading to a tunnel-type dryer. On the way to the dryer, the garments are allowed to drip for approximately minutes to remove excess water. The shirts then pass into a drying tunnel. Runs A through I are made with the conditions for each run shown iu Table I. In each of the runs the air is directed upward at 'approximately 175 feet per minute to agitate the shirts. The shirts have a residience time in the dryer of minutes and exit from 'the drying tunnel, completely dry, at the rate of about 300 per hour. The dry garments are removed from the conveying track and their wrinkle-rating determined by visual inspection. The average wrinkle-rating of the skirts of each run is recorded in Table I. Moisture is introduced into the drying tunnel by opening a valve located in a two-inch line carrying saturated steam at a pressure of 120 p.s.i.g. For a given dry-bulb temperature, the wet-bulb temperature is controlled by the amount of steam introduced to the drying tunnel, the wet-bulb readings increasing with increasing moisture content. In runs D and J, no moisture was added to the air.

From Table I it can be seen that a high wrinkle rating is obtained at only the highest dry-bulb temperature and highest moisture content, i.e., as shown -by run A. Good,

though less desirable, results are obtained at either the same high temperature and a lower moisture content (run B), or at a lower dry-bulb temperature and the high moisture content (run E). Run J is representative of maximum conventional drying conditions, and these conditions result in highly wrinkled shirts exiting from the drying tunnel. Increasing the dry-bulb temperature without increasing the wet-bulb temperature, as in run D, somewhat improves the appearance of the shirts but they still contain excessive wrinkles.

Since many different embodiments of the invention may be made Without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. In the process of drying laundered garments in a tunnel-type dryer, the improvement for producing dry, essentially wrinkle-free garments from dripping wet garments contaning at least polyethylene terephthalate fibers, which comprises hanging said wet garments on racks, continuously conveying the garments through the dryer, blowing moist air at a dry-bulb temperature of 145 to 155 C. and and a web-bulb temperature of to C. through the garments within the dryer until said wet garments dry in an essentially wrinkle-free condition, and then removing the dry garments from the conveyor.

2. A process as defined in claim 1 wherein said moist air is blown upward through the garments at sufficient Velocity to agitate the garments.

3. A process as defined in claim 2 wherein said moist air has a dry-bulb temperature of 149 C. and a wet-bulb temperature of 88 C.

References Cited by the Examiner UNITED STATES PATENTS 2,654,162 10/1953 Long et al. 34-46 X 2,698,488 1/1955 Cannon et al. 34-46 X 3,102,796 9/1963 Erickson 34-216 X FREDERICK L. MATTESON, JR., Primary Examner. D. A. TAMBURR-O, Assistant Examiner.

Claims

1. IN THE PROCESS OF DRYING LAUNDERED GARMENTS IN A TUNNEL-TYPE DRYER, THE IMPROVEMENT FOR PRODUCING DRY, ESSENTIALLY WRINKLE-FREE GARMENTS FROM DRIPPING WET GARMENTS CONTAINING AT LEAST 65% POLYETHYLENE TEREPHTHALATE FIBERS, WHICH COMPRISES HANGING SAID WET GARMENTS ON RACKS, CONTINUOUSLY CONVEYING THE GARMENTS THROUGH THE DRYER, BLOWING MOIST AIR AT A DRY-BULB TEMPERATURE OF 145* TO 155*C. AND AND A WEB-BULB TEMPERATURE OF 85* TO 90*C. THROUGH THE GARMENTS WITHIN THE DRYER UNTIL SAID WET GARMENTS DRY IN AN ESSENTIALLY WRINKLE-FREE CONDITION, AND THEN REMOVING THE DRY GARMENTS FROM THE CONVEYOR.