Acetate fiber. Production of acetate fiber

At all times, the textile industry was one of the most important branches of the national economy in our country, as it gave the state a huge quantity of cloth so necessary for it, which was constantly required not only for the production of clothes, but even used in the production of weapons.

That is why, almost from the first days of the existence of the USSR, chemists were given the task of obtaining artificial fabrics, as natural materials were sorely lacking. As a result, acetate fiber was created.

What it is?

In fairness, it should be noted that this is not the name of any particular type of fabric , but several types of artificial fibers. In all cases, they are made from cellulose acetate. The most common fiber is triacetyl cellulose, as well as ordinary acetate fiber, produced from secondary cellulose acetate.

Important qualities of man-made fibers

Hygroscopicity of such tissues does not exceed 3.5%. The fiber practically does not absorb moisture, does not swell and does not precipitate even after a multiple cycle of soaking / drying. In comparison with natural tissues, artificial ones are much less exposed to microorganisms, light and heat. In addition, they are completely indifferent to the mole. These fabrics are able to withstand the heating up to 100 degrees Celsius without losing their qualities.

Things made of acetate fibers are very pleasant to look at, they are perfectly erased and dry quickly. In addition, when washing them, you need to add a lot less detergent, since dirt is easily washed out of this type of fiber.

It should be noted that weak acids and alkalis do not act on acetate fiber as destructively as in the case of natural tissues, but as a result it is saponified and loses most of its useful qualities. Concentrated inorganic acids immediately destroy it.

Microscopic structure of fiber

If you look at such a fabric in a microscope, you can see hundreds of longitudinal grooves on the surface of the fiber. Because of this, the individual yarns do not adhere well to each other, and the fabric as a whole is sufficiently elastic and does not crumple badly. Their gloss is related in appearance with natural silk, and in terms of thickness, the individual fibers are quite similar to the thread that larvae of mulberry silkworms give out . If the manufacturer is faced with the task of obtaining a fabric in which the yarns are securely bonded to each other, then the H-shaped transverse notches are made on the surface of the fibers.

In addition to increased strength, such a canvas is characterized by a very beautiful sparkling luster, and therefore it is often used for decorating purposes.

Disadvantages of acetate tissues

Unfortunately, not everything is so good: these types of artificial materials are very resistant to abrasion, it is very easy to gain static electricity, poorly colored with standard paints that are commonly used in the textile industry. To iron them follows, without raising the temperature of the iron over 115 °, since otherwise thermal deformation is possible.

Other negative qualities

Given the very high ability of acetate fiber to accumulate static charge, it is difficult to produce tissue from it. If ironing at least a little with the temperature of the iron, then on the surface of the tissue there are deep defects that can not be eliminated. Acetate fiber burns bright yellow. Quite easy to stew, then glows for a long time, releasing a large amount of dense smoke with a specific smell into the surrounding air.

Production

As you could already understand, acetate fiber is obtained from cellulose. Of course, it is preferable to use cotton, but with its lack or absence it is quite possible to use high-quality wood. After production and purification it is treated with acetic anhydride. Sulfuric acid is used as the reaction catalyst, and acetic acid is added to dissolve the resulting acetyl cellulose.

In the presence of a small amount of water, the fibers begin to saponify, resulting in diacetylcellulose. To the resulting substance, a mixture of acetone and water (95: 1) is added. Everything, the spinning mixture is ready. It is filtered, clearing the excess of coarse mechanical impurities, and then sent to a spinning machine. Acetate fiber is produced in air (dry method).

This method is also good because it does not require the use of any additional chemicals. The thick and viscous spinning mass is simply pushed through the die with a lot of holes, and then enters the steam-air chamber at a temperature of about 87 degrees Celsius. Since the production of acetate fiber requires a huge amount of water and cellulose, many factories are near Lake Baikal.

Some information about the color

A high temperature is necessary for the acetone to finally evaporate from the mixture. After that, the obtained threads are cooled, their surface is covered with oil to prevent the formation of a static charge, and then they are wound on a bobbin. For a minute, up to 600 meters of yarn is formed. In the future, it requires virtually no processing, except for just twisting in the production of thicker fibers.

How is the color? In most cases, the dye is injected at the production stage, so that the thread of the desired shade is wound on the bobbin. We have already said that acetate fiber is very poorly stained by standard means, and therefore at present 90% of fabrics are made from yarns made from spinning mixtures with specified qualities.

Nowadays thousands of varieties of special disperse paints are created. They allow you to get not just a colored fabric, but real masterpieces that have an amazing iridescent color. This impression is created due to the fact that the paint does not adhere to the surface of the yarn, as in the case with the same viscose cloth, but is part of the fabric itself.

If necessary, white dyes are used, as a result of which fabrics of almost perfect snow-white color are obtained. Since acetate fiber is very resistant to UV rays and very easy to erase, the durability of such a cloth is many times greater than that for cotton or other natural tissue.

How does the molding work?

Most often in the production of spinnerets having about 200 holes are used. If the resulting yarn is to be twisted into thick fibers or ropes, the mixture is passed through spinnerets with corrugated and crimped walls. Speaking of staple acetate fibers, their production practically does not differ from the process described above.

The peculiarity is that separate threads emerging from the forming device are immediately harvested in a bundle, which is immediately cut into pieces of the required length. In addition, staple fibers can be manufactured in the form of ribbons, which are further cut into parts of the desired length.

Basic properties of fibers

What are the main properties of acetate fiber? The thickness of the yarns produced in any case is from 11.1 tex X 25, to 16.7 tex X 25 (No. 90 / 25- 60/25). If compared with viscose fibers of the same thickness, then the acetate filaments strength is somewhat lower (by about 10-12%). But! If this fabric gets wet (yes, the same hygroscopicity in 3.5%), then the strength parameters decrease immediately by 40-45!

The tensile strength (breaking elongation) is approximately 27%, but the elastic elongation is much higher than that for the viscose fabrics repeatedly mentioned above . It is because of this that "acetates" are very badly crumpled, and the things from them for a long time look perfect.

Upgraded version

All of the above can lead the attentive reader to the idea that this type of fabric has too many drawbacks. This statement is quite true for the recent past, but today, during its production, modifying additives are almost always used, which do not have any chemical effect on acetate fiber. The formula in this case is as follows: [C6H7O2 (OH) 3-x (OCOCH3) x].

In addition, today more and more often directional heat treatment of the spinning mass is used: the molecules begin to form more ordered structures. As a result, the acetate fabric becomes much stronger, and is no longer so afraid of strong heating.

To date, such qualities are characterized by the fiber "Alon", produced by the type of staple cloth. It is very durable and resilient, has a high durability and a beautiful appearance. It was found empirically that a small amount of aluminum pyrophosphate added to the spinning mass makes it possible to obtain acetate fiber, the application of which is possible in any area where there is a danger of fire (curtains for theaters, for example).