US2025376A - Conditioned material and method of preparing same - Google Patents

Description

Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE CONDITIONED MATERIAL AND METHOD OF PREPARING SAIVKE No Drawing. Application April 12, 1932, Serial No. 604,860

4 Claims.

This invention relates to conditioning films and more particularly to a process for aging a Wound roll of regenerated cellulose film to produce a roll of tightly wound film which exhibits no appreciable tendency to distort, as well as the product resulting from said process.

Films or sheets of regenerated cellulose are commonly made by casting viscose or other solutions of cellulose into a coagulating and regencrating bath, passing the freshly formed film through purification baths and over numerous drier rolls and finally winding it in a tight roll. If the film is to be coated or rendered moistureproof, it is subsequently passed in a continuous manner through a coating machine and rewound onto another roll. These rolls of material are either slit and rewound into smaller rolls or are reeled and cut into sheets.

The slit rolls which go to the user are uniformly hard, evenly and quite tightly wound, and are carefully packed in metallic receptacles, such as cans, or wrapped in moisture-proof material to insure protection against handling and varying humidity. However, a good many instances have been noted where the rolls could not be used on automatic machinery because they would not unwind evenly. Such rolls showed deformities of the film particularly near the core where the circular shape of the roll was seriously impaired, due probably to a shrinkage of the film.

oftentimes these rolls were so deformed that when the film was unwound the tension on the web constantly varied and, as a consequence, sagging, wrinkling and frequent breaks were produced. Furthermore, because of the original tightness of these rolls, which increased with time due to the shrinkage or other physical changes, and especially in the case of a film coated with a lacquer or moistureproofing composition comprising, for example, nitrocellulose, a gum, a wax and a plasticizer, adjacent layers often adhered together, making it impossible to unwind with practical efficiency.

It is extremely difiicult to get uniform gauge in every mill roll for the entire width of the roll, and when this kind of film is slit, especially into ribbons less than three inches in width and wound to form the final roll, there is a tendency of the windings to telescope. This is probably due to the enormous pressure occasioned by the shrinkage on the high gauge side which causes the film to slide toward the low gauge side and produce what is commonly termed telescoping. Telescoping might take place in two days or two weeks, whether the roll is wrapped or not, de-

pending upon certain factors, such as, for example, the diameter and width of the roll.

It is my theory that the above-mentioned phenomenon is in some manner associated with the strains present in the cast film and that by relieving the strains it may be overcome. Irrespective of whether my theory is correct, I have found that, by aging the material before making the final roll thereof, the previously described defects may be substantially inhibited and a roll of material produced which exhibits substantially no tendency to distort or telescope upon storage.

It is therefore an object of this invention to provide a tightly wound roll of material, such as, for example, a film of regenerated cellulose, either plain, coated or moistureproofed, which exhibits no appreciable tendency to distort, whereby the practical efficiency of the subsequent fabricating processes in which the material is contemplated to be used is not reduced.

Another object of this invention is to provide a process for appreciably inhibiting the distortion of a film tightly wound in a roll which comprises aging a roll of wound material, for example a film of regenerated cellulose of the ordinary, coated or moistureproofed variety, prior to forming it in the final roll which is to be used in the subsequent fabrication processes.

Other objects will become apparent from the following description and appended claims.

In accordance with an illustrative embodiment of this invention, a continuous film of regenerated cellulose is made by casting viscose or other solutions of cellulose into a coagulating and regenerating bath, conducting the freshly formed film through purifying baths and over numerous drier rolls, and finally winding it into a roll commonly termed a green or mill roll. If desired, prior to the passage of the film over the drier rolls, it may be immersed or passed through a bath containing a softener, such as glycerin or some other suitable substance. In the event that the film of regenerated cellulose is to be coated or moistureproofed, the film is subsequently passed, in a continuous manner, through a coating machine and tightly rewound onto another roll, which is hereafter termed a green roll, of moistureproof or coated material.

In accordance with the principles of this invention, the green rolls of ordinary film of regenerated cellulose or green rolls of coated or moistureproofed variety of regenerated cellulose prepared as above-described are stored, such as, for example, at room temper-?ture in an atmosphere of relative humidity of 30 to 40. The green rolls,

' tain conditions.

if a complete seasoning of the film is desired,. should be stored under conditions above-mentioned for two weeks or more. It has, however, been found that by aging the rolls for a period of time up to 72 hours, preferably 40 hours, a high quality final product is secured. It is to be noted that the conditions under which the aging is secured will relieve at least a large portion of the internal strains present in the film.

It is to be understood that the invention is not restricted to the precise atmospheric conditions previously set forth. While it has been found unnecessary to carefuly control these conditions, it can be readily appreciated that these factors should be carefuly regulated under cer- F'or example, unusually thick or thin films of materials other than regenerated cellulose may require more careful and exact control. The aging process, especially in connection with plain sheets or films of regenerated cellulose, may be accelerated, for example, by using a higher temperature and/or higher relative humidities than those aforementioned.

The green rolls are stored consecutively on any suitable means in the aging chamber in such a manner that they will be used in approximately the same order in which they were made, and also so that the surrounding atmosphere may freely contact therewith. As a specific illustrative embodiment of this phase of the invention, the rolls are supported on racks by means of a rod extending through the annular core, though, of course, it is obvious that other modes of supporting the rolls in storage may be used without in any Way departing from the nature or spirit of the invention. After the green rolls have been aged, they are slit and then rewound into final rolls.

The aging of rolls of regenerated cellulose as herein described does not in any way affect the slitting operation. There is no appreciable difference in the slit roll if the roll is aged or green at the time it is slit. There is, however, a decided difference after a lapse of time in the appearance of the roll.

In the case of fiat stock, it is also advantageous to permit the green rolls to season prior to reeling and cutting in order to avoid shrinkage or other physical changes in the cut sheets, which is of special importance if exact sized sheets are required. In addition, the aging appears to improve the flatness of the cut sheets, an important essential for good sheet stock.

The process previously set forth was partly described in connection with aging coated or moistureproof films of regenerated cellulose. Though this procedure is preferable with respect to this species nevertheless the invention also contemplates aging the base prior to coating or moistureproofing.

The invention also contemplates wrapping the green rolls in any suitable wrapper to form, for example, moistureproof packages, and aging or seasoning these packages in appropriate atmos pheres.

By virtue of the aging period, the moisture contained throughout the massbecomes more uniform. In addition, the physical properties of the film become more uniform in all parts of the roll and the film acquires its permanent set under the most favorable conditions. All of these features contribute to a more uniform product with subsequent better handling in the trade and fabricating processes.

In a comparative test, it was found that 13 out of 17 unseasoned rolls telescoped upon standing after they were slit, while out of 14 seasoned rolls not one developed any defects which made it unsuitable for use on automatic converting machines during the same length of time.

It should be noted that lacquered or moistureproofed regenerated cellulose film, by virtue of its slippery coating, is more susceptible to the distortion and telescoping previously described. However, by the instant invention, this undesirable feature is substantially inhibited without in any way impairing the slippery surface of the 15 material.

In the foregoing, the invention is described in connection with regenerated cellulose film of the ordinary, coated or moistureproof type, but it is to be understood that the invention is equally applicable to any sheet or film material in which internal strains are present. For example, cellulose derivative film, gelatin film, specially treated paper, such as glassine paper, etc., all possess certain strains acquired and built up during the course of their manufacture, and, when treated in accordance withthe principles of this invention, said strains will be partially or completely removed, resulting in an improved product.

Since it is obvious that various modifications may be made in the above description without departing from the nature or spirit thereof, this invention is not restricted thereto except as defined in the appended claims.

I claim:

l. A process for appreciably inhibiting distortion of a film of regenerated cellulose tightly wound in a roll which comprises aging a roll of said film in an atmosphere having a relative humidity of 30 to for a period of time sufficient d to relieve at least a large portion of the internal strains present in said film.

2. A process for appreciably inhibiting distortion of a film tightly wound in a roll which oomprises aging a roll of a film selected from the 5 class which consists of regenerated cellulose film, cellulose derivative film, gelatin film and glassine atmosphere having a relative humidity of 30 to 40, whereby at least a large portion of the internal strains present in the film will be relieved.

3. A process for appreciably inhibiting distortion of a film tightly wound in a roll which comprises aging a roll of a film selected from the class which consists of regenerated cellulose film, cellulose derivative film, gelatin film and glasslne paper for a predetermined period of time in an atmosphere having a relative humidity of 30 to 40, whereby at least a large portion of the internal strains present in the film will be relieved, and thereafter rewinding the film to form the final roll.

4. A process for appreciably inhibiting distortion of a film of regenerated cellulose tightly wound in a roll which comprises aging a roll of said film in an atmosphere having a relative humidity of 30 to 40 for a period of time sufficient to relieve at least a large portion of the internal strains present in said film, and thereafter winding to form the final roll.

CLARENCE E. COLEMAN.