JPS63152421A - Production of composite yarn equipped with core composed of long fiber surrounded by outside lapping - Google Patents

Abstract

The core composed of long-fibre yarns, preferably obtained by cracking, is raised in twist during the actual spinning operation carried out continuously on a ring-spinning frame without reaching its critical twist coefficient alpha "0, the cover of the said core being made of long fibres or short fibres. The twist coefficient of the core yarn lies between 20 and 85. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining a composite yarn with a core of long fiber yarn surrounded by an outer wrapping in a ring spinning machine.

With a core of long fiber yarn surrounded by an outer wrapping, commonly referred to as "core yarn", the production of composite yarns involves three spinning steps: spinning on a long fiber ring spinning machine, short fiber ring spinning, Spinning on a spinning machine, friction spinning, is carried out.

Although the friction spinning process can use both continuous filament, multifilament or monofilament, and fiber yarns and does not impart any twist to the core yarn, the process in a ring spinning machine
Whether using long or short fibers, only continuously spun multifilaments or monofilaments can be used as the yarns constituting the core.

Moreover, these steps in the ring spinning frame, by their appropriate design, give the core yarn a twist equal to that to which the composite yarn unit is subjected.

Therefore, the use of fiber yarns as cores in core yarn manufacturing schemes in ring spinning machines has hitherto been completely excluded, as will be described below with reference to the accompanying drawings.

In the drawings, the core is designated by 2 and the cover by 3.

FIG. 1 shows an element of a composite yarn consisting of a core 2 and a cover fiber 3, none of these elements being twisted.

If the yarn unit has a twist coefficient α or T-α・,/mN
The cover and core will have the same twist T after the application of twist if (T=number of turns per meter; mN-meter count) is applied. Now, when a yarn is twisted, a shortening effect occurs that is a non-linear function of the twist.

Therefore, the initial length l. Elements 2 and 3 of β after the application of twist. has a shorter length l. Experience has shown that the width reduction has a value close to 5% for α-80. This change is naturally independent of the direction of twist.

When the core yarn 2 is a fiber yarn (long or cotton), its two-way twist coefficient α is between 60 and 90 (6
0〈α〈90).

This spacing covers the range of coefficients used in ring spinning machines whether long or short fibers are involved.

If the unit is given a twist in the same direction as that applied to the core yarn, and thus two twists of a factor α', on top, at limited intervals, the core 2 will be overtwisted relative to the cover. Therefore, the decrease in the length Δl of the core 2 is greater than the decrease Δ′l in the length of the cover 3. Therefore, the length of the cover 3 becomes excessive relative to the core 2, resulting in an "uncovered" portion.

In the condition shown in FIG. 3, the unit is given a twist in the opposite direction to that applied to the core yarn, or a triple twist, also with a coefficient of gap defined above. There, an opposite reduction is observed: the core yarn 2 is actually not twisted, and its length therefore increases. At the same time, the cover 3 reduces its length due to the effect of twisting. In this state, the length of the core 2 becomes excessive with respect to the cover 3, and as in the case described above, an uncovered portion appears.

In addition to the drawbacks of the types mentioned above, in both cases the strength of the core yarn 2 deteriorates very quickly.

In fact, in the case shown in FIG. 3, this drop is caused by passing through the "0" point of the core yarn without being twisted. It is actually mechanically bonded by bonding discontinuous fibers (long fibers and fortiori short fibers).

These bonds are actually the result of frictional forces between the filaments. Non-twisting therefore results in a displacement of the fiber threads installed as cores.

In the case shown in FIG. 2, it is observed that the strength of the yarn disappears very quickly when the twist coefficient of the core yarn exceeds the limit value α''.In fact, it can be illustrated by the curve in FIG. There are properties suitable for each type of fiber, the strength in decanewtons is plotted on the Y-axis and the twist coefficient on the X-axis.F=f (α″) of this curve has the maximum value. . The value αno corresponding to this maximum value is called a limit coefficient. α″〉α″. For any value such as , a decrease in strength is observed.

This limiting factor depends on the fiber and yarn type used;
There are therefore suitable properties for each textile product.

In view of the practical impossibility of achieving co-aspun yarns with a core of fiber yarns in ring spinning machines, the Applicant proposes that, in order to obtain the best strength, aspun yarns are used as core yarns. In order to optimize the twist coefficient of the core yarn, we first tried to determine a method for calculating the total twist coefficient of the core yarn.

Therefore, if α′ is the coefficient of the completed thread, m
N′ is the coefficient of the completed yarn, mN is the coefficient of the completed yarn, α
If is the coefficient of the core yarn, then the twist of the core yarn is: T=cxJ"""FiV lower - (1) (Koech
lin's law) The twist of the completed yarn is T'-α'JmN'... (2) The total twist of the core yarn is T''-7' + T'... (3) Furthermore, the twist of the completed yarn is T'-α'JmN'... If the percentage of cores to yarn is k/100=h, then the number of core yarns 2 is mN-mN'/h..self (5).

The twist of the core yarn as a function of mN' and h: and the total number of twists of the core yarn can be calculated as follows:

α “-T” / 11th -m　N Now, according to formula (5), mN = mN’/h It is.

If this value is substituted into equation (8), −α ten α'
Jh (9) Therefore α″ is a function of the three variables α, α′ and h and is independent of the metric count of the yarn.

The twist coefficient at which a decrease in strength is observed is α≦α′0 I know what it should be.

If it occupies a position (which can be predetermined) in the limit and with constant values of h and α', the fiber used to obtain the best strength of α', i.e. It is possible to calculate the value of the twist coefficient of the yarn. This value is given by 2〇〇).

α〈α″−α′F1−...α0) Furthermore, 1. From experience, in order to cover all the cores, h≦0
．． 3.

8 α□7−α″11111−α′1I3Xr 7α″□
7 = 75, αmsx = too, h = 0.3 or 30%, αlI, 1l = 75-10040.3 = 20.2.

Direct total of α α1IaX = α″mix −α’m1n7α”−10
0, α'1Iin =so, h□, =0.1 or -10%, α□, t=100-5i0. It becomes D-84,2. Therefore, 20.2≦α≦84.2.

For example, if 90 is chosen as the value of α' (which includes the current value in spinning to obtain yarns with a closed structure), then α-80-90,/l Co = 30.7.

In standard staple fiber spinning, such yarns are not viable because the strength of the very slightly bonded fibers is too small and cannot withstand further processing.

On the other hand, in cut filament technology such yarns are perfectly acceptable and can be used as core yarns in core-spun composite yarns.

The invention therefore relates to a method for obtaining a composite yarn with a core surrounded by an outer wrapping, which method comprises spinning carried out in a ring spinning machine without the core made from long-staple yarn reaching its critical twist factor. It is characterized by untwisting during operation, and the cover of the core is made of long fibers or short fibers.

According to an embodiment of the invention, the twist coefficient of the core yarn is 20 and 8.
It is between 5 and 5.

With the core-spun yarns obtained, the above-mentioned drawbacks, i.e. the excessive length of the core relative to the cover, or the excessive length of the cover relative to the core, are eliminated, for example, by fibers with a twist factor close to 30 and therefore very slightly inclined relative to the core yarn. The possibility of occurrence disappears.

The invention will become clearer from the examples below which explain the invention without restricting it in any way.

The material adapted to constitute the core consists of long fibers of high modulus aramid mN90.

The critical twist factor for this material is α″.−80. The value of h is 0.3 and =30%.

The metric count (mN') of the cover, consisting of a mixture of short cotton fibers and flamed viscose representing 70% of the core yarn units, is mN'-27.

The twist coefficient α' determined in the complete yarn required for spinning staple fibers is 90.

Calculation of the coefficient α of the core yarn is (Equation 10) % Formula % Therefore, the core yarn in the direction Z with respect to the twist is T = cxF17N, T = 30.7J 0 = 291
t/m. The finished yarn has a twist of T'-α'F'N;T' = 90r/t/
m is in the Z direction.

The total twist of the core yarn is: T"-T+T'i T"-291+467=758t
/m After the twist of the core yarn is untwisted, the coefficient becomes α″−T″/π, α″=758/J] ding=79.9, and the limiting factor α″G=80 determined above. .

Moreover, the core spun yarn obtained can have quite remarkable strength.

The strength of the short fibers covering the composite yarn is a function only of the strength of the core yarn.

If, respectively, Km,' is the strength per kilometer of the finished yarn in KIl, KmS is the strength per kilometer of the core yarn, F' is the cutting strength of the finished yarn, and F is the strength of the core yarn. When F ′−KmS ′/
mN'...QllF-KmS'/mN...
(b) Here, if F=F', then K m S'/m N'= K m S/m
N...a3 Therefore, N is KmS-120 of the core yarn after untwisting, so KmS' = 120 x 27/90 = 36 km.

70% of this strength comes from the short fibers that cover the cellulose fibers.
It's quite striking compared to the threads that occupy this area.

Yarn made from such 100% short fibers is 18 kn.
It has a KmS of about +.

Covering with long fibers provides a slight doping of the overall strength of the yarn.

The greatest advantage of the method of the present invention is that in a standard ring spinning machine, the core of the composite yarn can be made from long fiber yarn of synthetic resin of possible origin and the cover can be made from any known synthetic, artificial or natural fiber. It will be appreciated that it is possible to obtain core-spun composite yarns that can also be made of short or long fibers. The parts that are not covered cannot be seen.

Moreover, the yarns thus obtained, which can be obtained in a count range between 1 and 100, are of quite remarkable strength, as mentioned above.

Since the foregoing description of specific embodiments fully illustrates the general nature of the invention, it is easy to depart from the general concept by making variations and/or variations by applying current knowledge. It will be understood that the specific embodiments may be applied without modification, and such adaptations and variations are therefore within the meaning and scope of equivalency of the disclosed embodiments. It is to be understood that the language and terminology used herein are for purposes of description and not for limitation.

[Brief explanation of the drawing]

FIG. 1 is a highly diagrammatic representation of the composite yarn before twist is applied to either the core or the cover. Figures 2 and 3 also highly diagrammatically illustrate several types of twists that can be applied to a composite yarn whose core has undergone an a-z twist. FIG. 4 is a curve showing the strength of the composite yarn as a function of the twist coefficient of the core yarn. 2- Core yarn, 3- Cover FIG-2FIG-3 also FIG-4

Claims (1)

[Claims] 1. A method for producing a composite yarn having a core made of long fibers surrounded by an outer wrapping, wherein the method reaches a critical twist value of the core. A method for producing the composite yarn, comprising spinning the core on a ring spinning machine without spinning, untwisting the core during the spinning process, and allowing the core to be covered with fibers of any length. 2. The method according to claim 1, wherein the core is made from long fibers obtained by cutting. 3. The method according to claim 1, wherein the core yarn has a twist coefficient of 20 to 85. 4. The method according to claim 2, wherein the core yarn has a twist coefficient of 20 to 85.