NO143125B - PROCEDURE FOR OPERATING A TWO-RADIO SYSTEM. - Google Patents

Description

Process for the production of voluminous, stretchable yarn.

This invention relates to a method for producing voluminous, stretchable yarn. By "bulky yarn" is meant yarn that has a large volume in relation to its weight per unit of length. Wool yarn, e.g. is voluminous because the wool fibers are not very straight, but have a natural ripple or curl. The natural curl causes the woolen yarn to have less density and greater coverage than would be the case if the fibers were straight and parallel. Synthetic fibers extruded through an ordinary spinning die are usually not voluminous, but consist of essentially straight, smooth, continuous filaments without loops, rings, ripples, etc., if the filaments are not subjected to a special treatment to affect their physical structure. Non-textured, synthetic fibers essentially consist of straight, parallel fibers regardless of whether they are continuous filaments or staple fibers. It has been found to be desirable to make yarns spun from synthetic fibers voluminous.

More specifically, the invention relates to a process for the production of voluminous, stretchable yarn from synthetic, crimpable fibers containing a small amount of highly shrinkable fibers, of the kind where the crimpable fibers are crimped by shrinking the highly shrinkable fibers, after which the crimp in the crimpable fibers is fixed and the shrinkable fibers are neutralized.

By crimpable fibers is meant here synthetic fibers that can be crimped permanently. By permanent ripple is meant e.g. that a crimped yarn that is stretched will regain its original shape when the stretching force is removed. One should also take into account that the shape of each individual fiber in the yarn will be affected by the presence of the other fibers so that a fiber's return to its original shape will be affected by the other fibers in the yarn.

The crimpable filaments or fibers can e.g. consist of thermoplastic material, such as polyamides, e.g. polyepsilon-caproamide and polyhexamethylene-adip-amide; cellulose esters; polyesters, e.g. terephthalate esters of ethylene glycol and of transparahexahydroxylylene glycol; poly-alkylenes, e.g. polyethylene, and polypropylene; polyvinyls and polyacrylates, e.g. polyacrylonitrile and also copolymers of the aforementioned polymers. Commonly known is e.g. fibers of nylon polyamides, Dacron and Terylene which are polyesters and Orlon, Acrilan and Courtelle which are copolymers of polyacrylonitrile. Polyacrylonitrile fibers have proven to be particularly usable in the previously known yarn treatment processes and are also preferred in the method according to the invention. Other synthetic fiber materials can also be used.

By fibers with high shrinkability is meant not only that the fibers can shrink or contract, but also that a smaller amount of such fibers in a yarn that predominantly consists of fibers with significantly less shrinkability under conditions that will force fibers with high shrinkability to to shrink will cause the shrinkage to be so strong that the non-shrinkable or less shrinkable fibers will take on a new shape or a new course to adapt to the reduced length of the yarn. It is to be understood that the purpose of the whole thing is to achieve a differentiated shrinking effect, so that the shrinking force in the selected shrinking fibers must be large in relation to the shrinking ability of the selected crimpable fibers and in relation to the force needed to shrink yarn consisting of the selected crimpable fibers.

Production of voluminous yarn by shrinking is well known. It is also previously known to curl yarn using highly shrinkable fibres, e.g. from the U.S. Patent No. 2,810,281. The differentiated shrinkage of the two types of polyacrylonitrile fibers used in the example of U.S. Pat. patent no. 2,810,281 is in the order of 20 percent. The final yarn produced by the method according to the U.S. patent no. 2 810 281 has approx. 40 per cent non-stretchable fibers and are therefore inextensible in themselves.

As is well known, fibers with high shrinkability are not desirable in the finished product because they cannot be stretched. Therefore, such fibers must be neutralized, which can be done in different ways. It is thus previously known to produce yarn with e.g. nylon as the crimpable component and such as the highly shrinkable component, where the yarn is first crimped by shrinking the highly shrinkable fibers and where these fibers, i.e. the silk fibers, are then removed by dissolving them in a suitable solution. In this case, the finished product consists only of crimpable fibers.

According to the invention, it has been concluded that for many yarns it is possible to achieve an appropriate and advantageous neutralization of the shrunk fibers by stretching the yarn, the stretching being very precisely controlled, thereby displacing the shrunk fibers in relation to each other and the crimped fibers. The just-mentioned method according to the invention is particularly advantageous in that the shrinkable component does not disappear from the yarn, which is of particular importance when it comes to fibers of more valuable materials. Yarns produced in accordance with the invention are similar in appearance to yarns spun in the usual way, but have a high tensile strength or elongation, e.g. of an order of magnitude of 20-45 percent. The expressed stretchability is used instead of elasticity to avoid confusion with elastomeric yarn. The result of the precisely controlled stretching is not only that the shrunken fibers are displaced in relation to each other, but also that some of them may break. When the tensile stress is removed, the stretched yarn will contract as a result of the action of the crimped fibres. The yarn will therefore be stretchable, which is due to the crimped fibers, and the shrunken fibers' resistance to stretching has been permanently neutralized as a result of the stretching.

It will be understood that yarn produced in accordance with the invention can, if desired, contain further fibers of a different kind than the crimpable fibers and fibers with high shrinkability. Depending on the properties of these additional fibres, the properties of the finished yarn product can be modified. Two or more types of fibers with high shrinkability can be used. By carefully selecting the right fibers for the purpose in question and by carefully controlling the process conditions, it will be possible to produce yarns with predetermined properties with regard to bulkiness and stretchability.

The crimping can be done in any way. However, it is important that the yarn should be as relaxed as possible, so that fibers with a high shrinking capacity have the opportunity to shrink evenly. A suitable method of shrinking is steaming in an autoclave, where spools of yarn are placed on trays or shelves, so that the yarn is in a tension-free state.

A suitable apparatus for stretching yarn will be described below with reference to the drawing, which shows a schematic side view of the apparatus.

A hook with yarn A is placed after shrinking in the autoclave on a hook holder B which is mounted on a spindle on the machine's frame. The yarn A is passed over a device D which prevents overfeeding, around a roll Ri. The latter can be made of any suitable material and is covered by a sleeve or a layer of rubber or synthetic material with a sufficiently large coefficient of friction to prevent the yarn from slipping on the surface. The roller Ri is arranged on a spindle on the frame of the machine and can rotate freely, but this freedom can be controlled by means of a braking device which, via a spring-loaded screw D2, can exert pressure on the roller Ri.

The device D is arranged so that it leads the yarn to a position which is chosen so that the yarn can be guided over one to one and a half windings around the roll Ri.

The yarn from the roll Ri is fed between two rolls R2 and R3, each of which is provided or coated with rubber or similar yielding material. The roller R2 is attached concentrically to a shaft S which is placed in bearings on the machine's frame. One end of the shaft .S is extended and provided with a drive pulley P. The shaft S is driven over a drive belt or chain which connects the pulley P with an electric motor M. The roller R3 is a simple pressure roller which rotates freely on its spindle S2. The latter is arranged in a swing arm and the entire device with the roller and the swing arm is placed on the machine frame so that the roller R3 can be brought into contact with the roller R2, where the axes of the rollers are mutually parallel. The swing arm is spring-loaded when the rollers R2, R3 are in contact with each other, so that a pressure point is formed between the rollers.

The distance between the center of the roll R' and the location between the rolls R2 and R3 is somewhat greater than the longest staple fibers found in the yarn being stretched.

When the roller R2 is driven from the motor M, the contact point between the rollers R2 and R3 will pull the yarn forward against the braking effect of the roller Ri, which is set by means of the screw D2.

The yarn from rolls R2 and R3 is fed to a container where it is collected in a tension-free state.

In practice, the degree of friction applied to the roll Ri can be controlled between a state without friction and an upper limit which will cause the yarn fed through the machine to break. Thereby, the stroke can be controlled and set very precisely, so that the desired neutralization is achieved.

An alternative way of braking is to use two further rollers which are in contact rried with each other and which work at a speed which is lower than the rollers R2 and R3.

Although the apparatus is described in connection with the treatment of a single yarn in a discontinuous manner, it can easily be adapted for the treatment of several lengths of yarn and a continuous process, using a technique where pairs of rollers are preferred to the braking device shown in the drawing .

The invention shall be further explained with the help of some examples, where quantity, proportions and percentages refer to the weight of the material unless otherwise stated:

Example 1.

A fiber blend was made from 10% "Fibravyl" and 90% acrylic fibers ("Courtelle", 6 denier).

The fibers were carefully mixed

it, then stretched and spun under loose drawing by means of a spinning wheel with a ring runner, such as is used when spinning worsted yarn. However, the staple yarn can also be spun in any other way. The yarns produced had yarn numbers 1/5 and 2/16 (worsted count). The individual yarns were spun with a right twist and twisted with a left twist. These conditions were also followed and maintained in the subsequent examples.

The spun yarns in hoops, both single and combined, were then subjected to steaming in a tension-free state, where the steaming took place in an autoclave at approx. 105°C within five minutes.

The yarn had shrunk to about half its original length, ie a contraction of 50 percent of the spin length.

Then the yarn or yarns were temporarily stretched approximately to their original spinning length by means of the one in fig. 1 shown apparatus. The finished yarns had pile lengths of approximately 70 per cent of the original spinning lengths and could be stretched 40-50 per cent without the extension becoming permanent.

Example 2.

A fiber blend was prepared from 8% "Fibravyl" and 92% unstretched acrylic fibers ("Courtelle", 6 denier).

Yarn produced from the fiber mixture was then steamed in an autoclave, as per Example 1, where the shrinkage was about 53 percent of the original spun length, after which the yarn, after stretching, contracted to about 75 percent of the original length, so that the yarn could be stretched elastically by approximately 30 percent.

Example 3.

A fiber blend was prepared from 4% "Retractyl 30" and 96% undrawn acrylic fibers ("Orlon 42", 6 denier).

Yarn produced from the fiber mixture was exposed to steam in an autoclave where, according to Example 1, it has shrunk to about 62 percent of its original spun length, after which the yarn, after stretching, contracted to about 80 percent of its original length, so that mjan got yarn that could be stretched elastically by about 25 percent.

Example 4.

A fiber blend was prepared from 2% "Retractyl 30" and 98% undrawn acrylic fibers ("Orlon 42", 6 denier).

Yarn made from this fiber mixture was subjected to steam in an autoclave which, according to Example 1, had shrunk to about 67 percent of its original length, whereupon the yarn, after stretching, contracted to about 80 percent of its original length, so that the yarn had an elastic extensibility of approximately 25 percent.

Example 5.

A fiber blend was prepared from 8 percent "Fibravyl" and 92 percent nylon (B.N.S. nylon 66, 3 denier).

The fibers were thoroughly mixed and spun as according to example 1 and the spun yarn was subjected in spool form and in a tension-free state to steaming in an autoclave at 146°C for ten minutes. The yarn had shrunk to 50% of its original spun length and then, after stretching, had contracted to about 70% of its original length, so that the yarn had an elastic extensibility of about 40%.

Example 6.

A fiber blend was made from 8% Retractyl 30 and 92% Terylene, 4 denier.

Yarn made from this fiber mixture was subjected to steam in an autoclave which, according to Example 5, had shrunk to about 65 percent of its original length and then, after stretching, contracted to about 75 percent of its original length, so that finished yarns had an elastic extensibility of approximately 30 per cent.

In all examples, hoops with yarn were placed on shelves, so that the tension-free condition was ensured. The hemps on each shelf had the opportunity to shrink in length when in the autoclave.

Example 7.

A fiber mixture was produced from 5% acrylic fibers (3 denier, approx. 11 cm staple length) with 35-40% latent shrinkage, and 95% acrylic fibers of another type (3 denier/filament produced on a Turbostapler) with only 2 percent latent shrinkage.

The yarn was spun on a worsted machine into a yarn with yarn number 4/16. The spun yarn was steamed in the form of hespers with an autoclave at approx. 116°C at

0.7 kg per cm2 of pressure within five minutes.

The yarn was temporarily stretched to approximately twice its length in the unstretched state to spread the heat-shrunk fibers and then relaxed to its staple length in the unstretched state.

This experiment was repeated using 10% acrylic fibers with 35-40% latent shrinkage and 90% acrylic fibers with 2% latent shrinkage. The table below shows the average length in centimeters of three one-metre-long spinning samples of the above-mentioned yarn at each of the three process stages.

The individual fibers were strongly crimped and the final yarns were very voluminous while being largely stretchable.

Although the invention is described in connection with staple fiber yarn, there is nothing in the invention that requires that only staple fiber yarn be used. Continuous filament yarn can therefore be used as well as or instead of staple fiber yarn. A smaller amount of continuous filament yarn can e.g. fed into the mixture of staple fibers to achieve any desired effect, either with regard to the ornamentation or textile properties. It is more appropriate to use fibers with high shrinkability in the form of continuous filaments than in the form of staple fibers. Under such conditions, it may not prove to be appropriate to neutralize the resistance of the shrunken continuous filaments to stretching only by a stretching operation, and other methods can be used, e.g. softening or even wrinkling of the continuous filaments by passing the yarn intermittently between two rolls, at least one of which is provided with riffles, before the stretching operation is carried out. A suitable apparatus for processing single yarns or yarns consisting of several lengths is manufactured in the U.S. patent no. 2 419 320, which device is often called Turbostacker.

When staple fibers are used as crimpable fibers and/or fibers with high shrinkability, the length of the fibers is of no critical importance. The fibers can be of the same or

different lengths.

Claims (1)

Method of manufacture of voluminous, stretchable yarn of synthetic, crimpable fibers containing a small amount of highly shrinkable fibers, where the crimpable fibers are crimped by shrinking the highly shrinkable fibers, after which the crimp in the crimpable fibers is fixed and the shrunken fibers are neutralized, characterized in that the shrunken fibers are neutralized by precisely controlled stretching of the yarn to displace the shrunken fibers relative to each other and to the crimped fibers.