US2052974A - Manufacture of artificial thread - Google Patents

Description

Sept. l, 1936. A. GlsLoN MANUFACTURE OF ARTIFICIAL THREAD Filed Feb. 18, 1935 VENTCR ATI'ORNE Patented Sept. 1, 1936 iTED srATEs MANUFACTURE OF ARTIFICIAL THREAD Andre Gislon, Lyon, France, assgnor to Du Pont Rayon Company, New York, N. Y., a corporation of Delaware Application February 18 1933, Serial No. 657,331

In Great Britain June 22, 1932 Claims.

This invention relates to the manufacture of artificial thread formed of a cellulose derivative, such as a cellulose ester and specifically cellulose acetate. More particularly, it relates to the manufacture of artificial thread having high tenacities and also relatively high elongations.

Prior to the instant invention, when artificial thread formed of cellulose esters were stretched,

y it was noticed that as soon as the percentage i subsequent operation was stretched in a dry state or in the presence of a liquid, hereafter called the stretching medium, or when a half finished thread still containing a. portion of the solvents in the spinning solution was stretched.

Referring now to Figure 1, which is a graph of the percentage elongation as a function of the stress (in grams per denier) for a normal thread of cellulose acetate, the point A designates the elastic limit, the portion AB of the graph designates the elastic stage, and the point C designates the breaking point.

Figure 2 is a similar graph for the same thread stretched in the dry state until the elongation is Figure 3 is a similar gra-ph for the same thread which has been stretched 75% in the presence of a stretching medium consisting of 42% acetic acid.

Figure 4 is a similar graph for the same thread which has been stretched 25% in the presence of a stretching medium consisting of aqueous acetone (acetone with '75% water).

Referring to the graphs and particularly' those illustrated in Figures 2, 3 and 4, it will be noticed that none of them discloses a curve similar to that 4shown in Figure 1. 'I'he curves shown in Figures 2, 3 and 4 do not disclose any portions corresponding in shape and direction to that designated by AB in the graph shown in Figure 1.

Threads of the type illustrated in Figures 2-4 inclusive, though they are characterized by low elongation and are no longer plastic, can be used industrially when the increase of breaking strength, i. e., tenacity, is very great. However,

the brittle nature thereof constitutes a serious disadvantage, particularly in view of their holding power at knots.

I have found that by stretching a thread formed of a cellulose derivative, such as a cellulose ester and specifically cellulose acetate, in the presence of symmetrical dichlorethane, I can secure threads which are characterized by a high breaking strength (tenacity) and high breaking elongation, even when the thread is stretched beyond an elongation of 100%. In other words, I have found that by stretching threads in the presence of symmetrical dichlorethane, I can obtain threads which, when stretched even beyond an elongation of 100% of the original length, still show in their stress-strain graph a region indicating the existence of a notable plastic stage.

The nature and objects of the invention will become apparent from the following descripticn and appended claims.

In accordance with the principles of the instant invention, a thread formed of a cellulose derivative, such as a cellulose ester and speciiicalsymmetrical dichlorethane, whereby a thread having a high breaking strength (tenacity) and a high breaking elongation is produced.

The stretching operation may be effected continuously on a thread passing through a bath containing the dichlorethane by, for example, conducting the thread as it issues from the bath ly cellulose acetate, is stretffrh'ed in the presence of 4over a roller having a peripheral speed which is 2 or 3 times greater than the speed at which the thread is fed into the bath.

The stretching operation may be carried out on a finished thread in a subsequent distinct operation. Alternatively, it may be carried out in combination with the process of producing the thread, for example, as by the dry spinning process.

The principles of the instant invention are also applicable for the purpose of stretching artiiicial threads in skeins. In such a procedure the skein may be disposed on two pegs immersed in the stretching medium and the thread stretched by moving the pegs further apart from each other by some suitable mechanism. Preferably, the pegs are also rotated in order that the portions of the thread in contact therewith may be continually changed. Alternatively, an extensible Winding device or some other similar mechanism maybe used to effect the stretching operation.

The stretching limit, which is a function of the temperature of the bath, the stretching speed and also the initial properties of the thread may vary within wide limits, depending on the desired final properties. However, since a thread having a high breaking strength (tenacity) and a high elongation is desired, the thread is usually stretched at least 100% of its original length.

The stretched thread should not remain impregnated or in contact with the dichlorethane for a long period, because the swelling action of the dichlorethane continuing to function in the absence of any tension would tend to cause a convention contemplates the removal of the dichlorethane as quickly as possible after the stretching operation. This may be accomplished in various manners, for example, by evaporation or by washing. When the latter prbcedu're is employed, the washing liquor may be of any convenient liquid which is miscible with the dichlorethane and which does not form with it a solvent of the cellulose acetate. Ethers, ligroins, etc. are mentioned as illustrative of washing liquors.

En order to more fully explain the nature of the instant invention, the following specic illustrative procedures are set forth:

Example I-A 100 denier, 18 filament cellulose acetate thread, having a tenacity of 1.3 grams per denier with a breaking elongation of 29%, is

passed into a bath of symmetrical dichlorethane maintained at a temperature of 20 C. and stretched into athread of 40 deniers. The thread resulting from this operation has a tenacity of 1.65 grams per denier and 'an elongation of 29%. The duration of the stretching operation is about l minute, after which dichlorethane is quickly removed from the thread.

Example lI-A thread having the same characteristlcs as the one treated in Example I is stretched under identical conditions except that the duration of stretching is 21/2 minutes. This procedure results in a thread of 32 deniers having a tenacity of 2.2 grams per denier and a breaking elongation of l'1%-l9%.

The following table, in addition to the foregoing examples illustrates `the properties of cellulose acetate threads which have been stretched approximately twice, six and nine times the origmal length:

Original thread Final thread Tenacity I :ilonga- Tenacity longamamut in grams non per- Denier in grams tion perper denier cent per denier cent lill-18 l. 2l m. 5 47. 9 l. 8 19. 5 100-I8 l. Zi 2). 5 15. 6 l 0 17. 0 75- 13 l. 19 2l 8. 0 2. 6 1li-l1 Curves illustrating the properties of the rst and second threads as listed in the above table are shown in Figures and 6 respectively.

A thread stretched in accordance with the instant invention has abreamng elongation at knots which is remarkably high. The following table, given as an example, illustrates this by vcomparative sures:

The thread stretched in a mixture of acetone and water had received an elongation of 25%. while the thread stretched in dichlorethane had received an elongation of 300%. Y

symmetrical dichlorethane, also known ethylene chloride, the substance' contemplated as the stretching medium by the instant invention, is cheap, non-inflammable and has a boiling point of 83.7 C. It is also remarkably difierentiated not only from the stretching mediums previously mentioned but also from the compounds which approach it chemically. Non-symmetrical dichlorethane (ethylidene dichloride) cannot be used as a stretching medium as hereinbefore described. The same may be said of dichlorethylene often mentioned as a swelling agent for cellulose acetate and of trichlorethylene. Tetrachlorethane and methylene chloride used under analogous conditions would dissolve the cellulose acetate ber. Therefore, no one was able to foresee and predict the exceptional properties that it possesses as a stretching medium and which have been hereinbefore set forth.

Another important advantage resulting from the use of symmetrical dichlorethane is that the stretching medium consists of one substance instead of a mixture of substances. As a consequence, the elimination is more regular and the recovery is simpler and easier. -r

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

I claim:

1. A method of producing artificial thread having a high tenacity and high elongation which comprises treating cellulose acetate thread with a liquid composition consisting of symmetrical dichlorethane to swell the thread and stretching the thread until it is at least twice its original length 2. Amethod of producing artificial thread havg ing a high tenacity and high elongation which comprises treating cellulose acetate thread with a liquid compositionconsisting of symmetrical dichlorethane to swell the thread and stretching f the thread until it is at least twice its original length and quickly removing the dichlorethane.

3. A cellulose acetate thread which has been stretched at least 100% of its original length in the presence of symmetrical dichlorethane and having a tenacity of from 1.5 to 2.5 grams per denier, a dry elongation of 30% to 15% and a plastic stage as shown by the stress-strain graph.

4. A cellulose acetate thread which has been stretched at least. 100% of its original length in the presence of symmetrical dichlorethane and having a tenacity of 1.65 grams per denier, a dry elongation of 29% and a plastic stage as shown by the stress-strain graph.

5. A cellulose acetate thread Ywhich has -been stretched at'least 100% of its original length in the presence f symmetrical dichlorethane and having a tenacity of 2.2 grams per denierfa dry elongation of,17% to 19% and a plastic stage as shown by the stress-strain graph.

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