JPH0351338A - Production of high-strength and high-elastic modulus fiber - Google Patents

Abstract

PURPOSE:To obtain fiber having a structure extremely resembling completely extended crystals with a high-strength and high-elastic modulus by hot-drawing amorphous or low-crystalline thermoplastic synthetic fiber in a zone and then hot-drawing the resultant fiber in a die. CONSTITUTION:Undrawn yarn (1a) of amorphous or low-crystalline thermoplastic synthetic fiber is heated in a heating zone 6 and drawn while applying tension thereto between rollers 3 and 4, then heated with a heating die 7 and drawn while applying tension thereto between the rollers 4 and 5 to afford high-strength and high-elastic modulus fiber. Furthermore, the heating is carried out at a temperature above the glass transition point up to the melting point of the aforementioned thermoplastic synthetic fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a novel method for producing high-strength, high-modulus fibers, and more particularly relates to zone drawing/heat treatment and die drawing. This invention relates to a method for producing high-strength, high-modulus fibers having a structure extremely similar to fully stretched crystals by continuously subjecting amorphous or low-crystalline thermoplastic synthetic fibers to the following steps.

(Prior Art) As methods for producing high-strength, high-modulus fibers, there are methods that involve the development of new polymers such as aramid fibers, as well as methods that improve the higher-order structure of general-purpose polymers.

Reported methods for improving the higher-order structure of general-purpose polymers include high-pressure extrusion, high-pressure crystallization, ultra-stretching, zone stretching and heat treatment. Among these, zone stretching and heat treatment are attracting attention as effective methods. The details are described in Japanese Patent Publication No. 60-24852. In other words, zone stretching is stretching an amorphous or as low-crystalline thermoplastic synthetic fiber as possible through a short heating zone under tension while locally heating it from its surroundings at a temperature from its glass transition point to its crystallization temperature. zone heat treatment is a technology that produces highly oriented fibers with amorphous or low crystallinity.Zone heat treatment is a technique in which the fibers obtained above are subjected to short heat treatment at a temperature above the crystallization temperature while applying a high degree of tension to fully extend the molecular chains. This is a technology that locally heats the surrounding area by passing it through the tropics.

(Problem to be solved by the invention) The above method has only reached about 10% of the theoretical elastic modulus for polyethylene terephthalate, nylon, etc., and still needs to be improved in order to obtain fibers with even higher strength and higher elasticity. be.

(Means for Solving the Problems) Therefore, in the method of the present invention, an amorphous or low-crystalline thermoplastic synthetic fiber is heated in at least one short heating zone and at least one heated die. Zone stretching/heat treatment and die stretching are performed continuously by a combination of
This aims to achieve high strength and high elastic modulus. The short heating zone and die can move their position as needed.

(Function) In order to increase the strength and modulus of thermoplastic synthetic fibers, the key is how many molecular chains can be arranged in the fiber axis direction and crystallized. Zone stretching and heat treatment minimizes the softened area by heating locally,
Therefore, since stress is also concentrated, molecular chains can be oriented efficiently.

However, since the stress in this case is only tension,
- Once the non-oriented state is changed to the oriented state by zone stretching, the orientation does not improve much even if the zone stretching is repeated thereafter. On the other hand, in die stretching, since shear force acts simultaneously in addition to tension, higher orientation can be expected than in zone stretching.

However, depending on the orientation of the sample, there is a risk that the molecular chains will become stuck in the form of threads near the die, so a drawn thread that is oriented to some extent is more effective in die drawing. Therefore, by first performing zone drawing and then die drawing to compensate for these two drawbacks, it becomes possible to produce fibers with higher strength and higher elasticity.

(Example) 1 schematically shows the overall configuration of an embodiment of the present invention.

In FIG. 1, 2 is a feeding device for feeding an undrawn yarn 1a of an amorphous or as low-crystalline thermoplastic synthetic fiber that is intended to have high strength and high modulus, and 3 is a feeding device. A roller 4 securely grips the undrawn yarn 1a, a roller 4 securely grips the drawn yarn 1b and applies tension to the undrawn yarn 1a due to a peripheral speed difference with roller 3, and a roller 5 securely grips the drawn yarn IC. At the same time, a roller 4 applies tension to the drawn yarn 1b due to the peripheral speed difference between the roller 4, a short heating zone 6 for drawing under tension while locally heating the yarn, and a roller 7 drawing the yarn through a conical die while contact heating it. A heating die is used to forcibly draw the yarn 1b, and 8 is a winding device for winding up the drawn yarn 1c.

The feeding device 2 is driven in synchronization with the rollers 3, so that the undrawn yarn is fed with extremely low tension.

The heating zone 6 is designed to provide extremely localized heating. The heating temperature is set at a temperature above the glass transition point and up to the melting point, but if necessary, stretching and heat treatment under tension can be performed from the beginning at a temperature above the crystallization temperature up to the melting point to achieve highly crystalline orientation. Let it be fiber 1b. If stretching is performed at a temperature higher than the glass transition point and up to the crystallization temperature, voids will often occur, and on the contrary, there is a risk that the physical properties will deteriorate.

The heating dia is used to forcibly stretch the drawn yarn 1b, which has become highly oriented in the heating zone 6, through a conical die while contacting and heating it to further form a highly oriented and highly crystalline drawn yarn 1c. The heating temperature of the die is preferably in the same temperature range as the heating zone 6. The diameter of the die is set according to the diameter of the fiber to be drawn.

Since the rollers 3.4 and 5 accurately set the tension or stretching ratio in each section, they are a mechanism that can securely maintain gripping force and accurately control the number of rotations.

The winding device 8 is driven in synchronization with the rollers 5 so that the drawn yarn is wound with a constant tension.

Depending on the physical properties of the drawn yarn produced, the heating zone 6
A zone stretching/heat treatment section consisting of a heating diaphragm or a heating dia and a die stretching section may be sequentially added. Particularly in the case of die drawing, as mentioned above, there is a risk that the molecular chains will become stuck in the form of lint near the die. Therefore, depending on the degree of orientation of the drawn yarn 1b, the orientation of the molecular chains is gradually increased by arranging several dies and stretching rollers so that the diameter becomes smaller in sequence, rather than performing die drawing all at once.

(Effects of the Invention) According to the method of the present invention explained above, fibers with extremely high strength and high modulus of elasticity can be obtained from undrawn yarns of thermoplastic synthetic fibers that are amorphous or have as low crystallinity as possible. .

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[Brief explanation of drawings]

(abc): fiber feeding device standard roller 1st stage stretching roller Second stage stretching roller Heating section for zone stretching and heat treatment heating die for die drawing Winding device

Claims (1)

[Claims] A combination of at least one short heating zone and at least one heated die is characterized in that zone drawing/heat treatment and die drawing are continuously carried out on amorphous or low crystallinity thermoplastic synthetic fibers. A method for producing high-strength, high-modulus fiber.