DE2639409A1 - PROCESS FOR MANUFACTURING A STAPLE FIBER FROM OXIDIZED POLYACRYLNITRILE FIBERS - Google Patents

Description

Pipl.-lrig. Hsinz

PosbKcbrMWSnMM 2i, PcsScch 4 Amcr: .en, CiGn * 1 «Sep. 1976

No sign; ? 2590

HORGANITE-: MODMOR LIMITLD,
52 Battsrsea Church Road
London, SV / 11 3LZ, i-ngland

BRITISH SIL ?; COHBSRS LIMITE!), Thornhill Briggs Mills
Brighouse, Yorkshire, England

AB SPINNING CO. LIMITJiD,
Annitage Bridge Mills,
rluddersfield, yorkshire, england

Process for the production of a staple fiber from oxidized polyacrylonitrile fibers

The invention relates to the production of so-called high-strength carbon fiber material with high modulus values, which consists of synthetic fibers made of polyacrylonitrile (PAN), many things are oxidized under tension before carbonization and if necessary a graphitization take place »

The invention is based on the object of an improved staple fiber, an improved upper yarn, an improved Roving yarn or an improved web made of oxidized

ORIGINAL INSPECTED

To create polyacrylonitrile (PAN) for the production of a carbon fiber, in particular, but not exclusively, in the form of woven textile material.

The above-mentioned object is achieved by the original invention specified in claim 1 _{or the like}

line main application of such a carbon fiber material is in the storage or in the ^, including such Materials as reinforcement in a matrix, such as in a plastic matrix, a metal or carbon matrix to create a composite material that has high strength uno. Stability possesses o _ine produced according to the invention Staple fiber or a top yarn, roving yarn or spun from a carbon fiber produced according to the invention is also possible Applicable in cases where it is not a question of reinforcement, but where the carbon in fiber form is required will.

In general synthetic fiber technology it is recognized that the properties of a staple fiber yarn can be selected, controlled and achieved with consistency far more satisfactorily than a continuous one Filamentary Yarn »Made for most purposes where woven textiles and synthetic fibers are included although these textiles and fibers are made from continuous threads are disintegrated into the staple fiber and then spun and woven using Techniques such as those created for natural fibers are.

The production of high-strength and high modulus carbon fibers from PAN fibers, however, precludes the oxidation of the

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IrAM-FaGem a. Read is done by the fact that the relevant Fibers heated under tension in the presence of oxygen from the air or from another oxygen carrier or an oxygen generating agent is available. A difficulty is expected in terms of achieving such oxidation to the extent required. If a pile thread is used, which can hold up to one Strength has been twisted that is high enough to withstand the tension resulting from the shrinkage the treatment results, the oxygen concentration may be inadequate be. If a weaker twisted staple yarn is used, so this yarn will not withstand the shrinkage tension c

The problem outlined above is now overcome by the present invention. Through the present invention as a preparatory step, an oxidation of the continuous PAM fadan rope under the influence of heat and under tension made, which has almost no twist. Under a continuous thread rope there is a single one Geil or understood a Kehrfachseil, which consists of largely interrupted threads, with a large number of Threads, preferably 1000 to 160,000 threads per rope or rope may be provided. Under the phrase "largely none Twist "is understood to mean that at least in one rope length during the oxidation the threads do not surround each other in such a way that that there is a mutual covering of the threads concerned with regard to the access of oxygen.

The invention also creates a method by which the oxidized continuous thread rope can be divided into staple fibers, which as roving or as Upper thread or as roving thread or as a staple thread

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spun web processed and possibly into one Tissues are woven before carbonization and possibly graphitization take place.

It would be reasonable to expect that the known methods which have been used in the textile industry for dividing continuous threads into a staple length, ura to spin these threads alone or together with other fibers, are used for the division and spinning of oxidized PAH threads v / _o Attempts to use traditional methods have failed, however, for reasons that could not be fully clarified. A clean break for the required staple lengths is difficult to achieve if the filaments are spread or cut to short lengths, such as about 38 mm (1 1/2 inches), to continue on cotton machines designed for such lengths to be processed, the fiber losses are commercially unacceptable «,

In connection with difficult fibers, it is in the textile industry known to use surface treatment materials to modify the fibers _o Lndanwendung of carbon fiber textiles, especially for composite materials, but excludes the use of additives from the front which make many impurities or the finished products could adversely affect.

An extensive investigation has according to the present. invention led to the combination of steps, through ede an oxidized continuous PAN thread rope into a staple fiber, a top thread, a roving thread, a web or a woven fabric can be implemented which is suitable for conversion into carbon fibers «,

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The fundamentally decisive combination of steps for the production of a staple thread from polyeryl nitrile fibers According to the invention, there is a ripple through The effect of steam takes place and that an elongation fracture then occurs in at least one rope of the continuous threads made of polyacrylonitrile is made which has been oxidized as a rope under tension in a state almost without twist by a heating in the presence of oxygen takes place during such a limited period of time that the relevant Threads remain elastic enough to pass the steam crinkle step without resisting a break.

Under the used herein, the term "oxidation" is meant that the PAN B'äden are exposed to oxygen under tension, under conditions or in accordance with the heating in air at a temperature of 200 ⁰ C and zwisehen 30U zv C for a period / isehen 0.5 and 5 hours «,

The term "polyacrylonitrile" (PAN) polymeric materials are understood, including homopolymers, copolymers or terpolymers of acrylonitrile with other monomers, such as _o, methyl methacrylate or vinyl acetate, either alone or together with compatibly polymers, v / ie Z ₀ B. phenolic resins of Friedel-Crafts condensates _o

The PAN threads are available in a wide denier range (weight in grams of 9000 meters of a single thread). The conventional textile PAN threads generally have three denier or higher, while PAN threads that have been specially made for conversion into carbon fibers are generally about 1.5 denier. The procedure according to the present invention is particularly suitable for threads of about 1.5 denier, which are finer than those threads, those by conventional textile processes and textile machinery

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usually processed.

The degree of oxidation given to the PAN sutures in the preparatory stage depends on two conditions. The first condition yields from the physical nature, namely in values of the stiffness and tear strength of any carbon fibers » The second condition arises from the ability of the oxidized filaments to withstand conversion into staple fibers. the The first condition is important, but not critical, since there is an area of oxidation within which any Carbon fiber has useful properties.

The technology and conditions of the oxidation of PAN threads in order to achieve the required properties of high strength carbon fibers with high modulus four th form part of the present field now existing knowledge <>

The second condition is critical in view of the fact that the manufacture of the staple fibers depends on the particular item depends.

In the course of fulfilling the first condition, the PAN threads are to be treated for a sufficiently long period of time under selected temperature and oxygen concentration conditions in order to produce a carbon fiber with satisfactory strength by carbonization at a temperature of at least 100 ° C. If the extent of the oxygen treatment is too low, the resulting carbon fibers have a low strength, which can be determined by a fiber tear test; the tensile strength involved should be at least 5 x 10 6 pounds per square inch or "50" 10 pounds per square inch (34.5 GNm " ² or 0.345 GNm" ² ).

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2639408

In order to satisfy the critical second condition, 3 the oxidation of the PAN sutures is limited because the elasticity decreases as the treatment progresses, which means that the percentage elongation decreases in the event of a strain break. if If the elasticity decreases too much, the continuous ones begin Threads of the rope to burst into short lengths during the crimping step «This can now easily be established become, - and by seeking and observing Samples, the extent of oxidation can be limited so that a break on the crinkle is almost avoided, without a loss of any high strength and the high module properties of the carbon fiber occurs.

-ö ^v

During the execution of the textile treatment steps according to The invention is preferably worked with top thread, which initially has a relatively high number of consecutive threads PAN threads, which number is on the order of Ao 000 or more. These threads then become common processed. Therefore, if the preliminary oxidation step is carried out on a yarn which is a relatively small one Number of threads, the number of which is of the order of 10,000, then steam crimping is preferred executed with a multiple rope, as with six ropes, which makes a total of 60,000 threads, by the multiple rope through is routed through a single steam crumble hopper. The further one then progresses from this container Textile processing carried out on the crimped multiple rope.

The elongation break of the crimped continuous thread rope can be effected in a commercially available machine, which is used as a top-part towing machine or as an elongation-fracture converter is known without using breaker bars. It has been shown that it is useful to have two

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-S-

to use relatively gently sloping passes through such a machine in order to achieve the desired stack length for the worst possible processing, the stack length mostly being in the range between 51 mm and 150 mm (corresponding to 2 to 6 inches). Preferably, the second pass is done in a slightly modified machine known as the "multiple break machine" ₀ Las absence of break bars and the use of weak compressive forces avoids the formation of hair that might otherwise occur with break bars.

The crimped .itapelfaser obtained after performing the elongation fracture can in turn be converted into a carbon fiber, which is used, for example, as a reinforcing material in a composite. i ^£: s is ε-ber also possible that the staple fiber in question can be further treated to face yarn and Rovinggarn to manufacture, which is suitable for a spinning _o The face yarn, Rovinggarn, a product manufactured therefrom web or a product manufactured from a web of tissue can be a Experienced conversion to a carbon fiber for various uses.

With regard to the manufacture of a roving, it has been found that two steps must be followed in order to achieve the best results. These steps consist of combing the fibers in a straight line to form a top yarn and then lamellating them gently. Through the cannula: u. vx.r-dcn fluff-forming staples! Fibers of short length removed, and the weak laraing of the upper yarn results in c-in flucen-free, even, non-twisted roving for spinning.

For the purpose of interweaving, the garage spinet can be replaced by a

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Compilation winding, can be produced by twisting and by οine conical winding.

The invention is exemplified below with reference to drawings explained in more detail.

Fig. 1 shows the execution of a preparatory oxidation of a PAN rope.

Fig. 2 shows the execution of a steam crinkle and Elongation fracture step.

Fig. 3 shows the execution of a combing and lamination step for the production of a wound roving.

As shown in Fig. 1, there is a continuous suture PAN rope 1 from one or more untwisted ropes; this PAW rope 1 comes from his ball or his other pack 2 through a heated chamber 3, in which the bot-hitting rope is kept under tension, which is through two pulling rollers 4 are indicated, which pull the yarn against the inhibition which is exerted by two inhibiting rollers or rollers 5. To the chamber 3 in question is air or a other Sauer material me medium discharged through a Sinlaß 6. from the oxidized rope 10 is delivered to the chamber in a bale or other package 7 to be sent to a weaving mill to be transported, which can be provided in the same plant or at a different location.

Apart from the minimum temperature of 200 ^° C., the time and temperature conditions for the necessary oxidation for the purpose of the eventual production of a carbon thread can vary widely, depending largely on the exact property of the particular PAN material from which the threads are made are made. However, the temperature should not be a \ .- ert 300 ⁰ C over-

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step, and the treatment time should be between 0.5 and five hours.

For the purpose of producing staple fiber yarn according to Invention is given by the limitation of the treatment the loss of elasticity to the point where the rope threads burst on the crimp. This can only can be determined by a sample check of precisely determined rope masses.

In Fig. 2 it is shown how the oxidized rope 10 is released from its package 7 by means of two rollers 8, which the Lead the rope to a steam chamber (not shown) in which the rope is gripped by the cutting edge of the pinch rollers 9, which push the rope in question together in such a way that: 3 it is tightly compressed in a stuffing container 11 by the outlet 12 of which the rope emerges as a crimped and prepared, but nevertheless as a continuous thread rope 13.

The steam emitted in the ripple stage should be more atmospheric Be steam that has been dried by passing it through a water pocket.

At this stage it is common that the crimped rope 13, as indicated by the deflection indicated in the form of a dashed line in FIG. 2, in a bale or another pack 14 for drying and storage purposes, namely for further processing or for transport to another plant.

The next process step - after the crimped rope is dry - consists in an elongation break, which is called

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the following step is illustrated in the lower part of FIG is. The crimped rope 13 is of two folds 15 to one first interruption arrangement 16 delivered, in which the yarn is drawn off by two draw rollers 17 and by two pinch rollers as long as it is held until the between these rolls stretched Tear threads in an average length, which depends on the distance between the rollers 17 and the rollers 18. A suitable one The interruption arrangement is known as a cable shell or strain break transducer, and a suitable adjustment distance A for the first interruption arrangement 16 is 23 cm (corresponding to 8.5 inches).

It should be noted that not all threads between the 7 / alzen and 18 will tear the same length, or in the same place, or at the same time. The breaking of the individual threads depends on their own thickness as well as on the change in thickness and on the tension distribution between the threads in the respective ski section. Accordingly, the torn ones ground each other The threads overlap and run in front of each other, uir> 'λIs staple fibers bzxf, staple thread 18 to maintain cohesion.

Drjr thread 19, which consists of relatively long staple fibers, then arrives at a second interruption or. leash arrangement 20, which is preferably a down tear arrangement is and the two pull rollers 21 and two pinch rollers 22 ε-uf- ' has, which are arranged closer together, namely in a distance from B equal to 16 cm (6 inches). In this Wej.se a staple thread 23 with a shorter pile length achieved, which averages 5.4 to 16 cm (equivalent to 2 to 6 inches) long.

The thread 23 can then, as indicated schematically, put together v / ground, such as by winding on a spool or

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Drum 24 to be used for transport or storage to be available for further processing. The thread in question can, however, also be used for the next treatment step be passed on in combing and lamination consists.

In Fig. 3 it is shown how the staple thread 23 from the bobbin 24 through the cylinder 25 of a rectilinear combing arrangement is included, which is indicated generally at 26 and which represents a known textile machine which is used for removal of short fibers and hair.

From the chimney arrangement 26, the combed thread 27 is guided through the take-off rollers 28 and the counter rollers 29 of a lamination machine in which the so-called winders 30 hold the fibers ³¹ successively in such a way that they are drawn off in alignment as a uniform upper yarn.

The lamination process is usually repeated several times in order to obtain a spinnable roving of staple filaments which are sufficiently cohesive to enable the processing required to produce a uniformly aligned and aligned arrangement of filaments or fibers. As shown, the roving 31 can be wound onto a spool 32.

Rovings made in the manner described above, are suitable for depositing in an arrangement, for spinning into yarn sliver using fixed processes and, if necessary, for weaving. The carbonization can be effected at any of the roving, spun yarn, or fabric stages.

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Claims (4)

_13_ 2639A09 claims 1. A method for producing a staple thread from oxidized polyacrylonitrile fibers for the final production of high-strength carbon thread with high modulus values, characterized in that at least one rope (10), which consists of continuous threads of the oxidized polyacrylonitrile, is formed into a staple thread (23) is converted so that the rope (10) in question is subjected to steam crimping (10) and then an elongation break (16, 20), and that the continuous threads as rope (1 to 10) under tension (5, 6) in a largely torsion-free manner State are oxidized by being heated in the presence of oxygen (3, 6) for a period of time which is limited so that the threads concerned remain elastic enough to withstand the steam crimping step (9, 11) without breaking. 2. The method according to claim 1, characterized in that multiple ropes (10) together a steam crimping thereby are subjected to that they are passed through a single filling container (11). 3. The method according to claim 1, characterized in that the elongation break in two successive elongation break stages (16-A, 20-A) without the use of interruption brackets. 4. The method according to claim 1, characterized in that threads are used in a thread denier of about 1.5 and that with a staple length of fibers after elongation rupture of mainly in the range between 5.4 and 16 cm is worked. 709810/1065 Method for producing a roving from a staple thread produced by the method according to claim 1, characterized in that the "relevant staple thread (23) is converted into a roving (31) in that a rectilinear combing (2β) is carried out, in which fluff-forming fibers of shorter length are removed, whereupon a lamination (28-30) is carried out in such a way that a lint-free, tough, untwisted roving (31) is obtained which has an evenly aligned and aligned arrangement of fibers » 709810/1065 Blank page