JPS6128015A - Production of poly(p-phenylenebenzo-bis-thiazole fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fibers having a high strength and modulus and improved heat resistance without void, by dissolving a poly(p-phenylenebenzo- bis-thiazole) in methanesulfonic acid based solvent in a specific high concentration, and spinning the resultant solution by an air gap method. CONSTITUTION:Poly(p-phenylenebenzo-bis-thiazole) expressed by the formula is dissolved in a solvent consisting essentially of methanesulfonic acid in 11- 18wt% concentration. The resultant optically anisotropic solution is preferably extruded into an aqueous methanesulfonic acid based coagulation bath by an air gap method, i.e. a spinneret is separated from the coagulating bath, preferably 2-20mm. air gap to give the aimed fibers.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to polyparaphenylenebenzobisthiazole fiber (hereinafter referred to as PBT fiber), and more specifically, it has high strength, high modulus, and excellent heat resistance. P.B.
The present invention relates to a method for producing T fiber.

(Prior art and its problems) Conventionally, as a method for producing PBT fibers having excellent mechanical properties, for example, PBT having the chemical structural formula of formula (1) is mixed with about 10 M% methanesulfonic acid (hereinafter referred to as MSA). ) to prepare a solution having optical anisotropy, and then this solution is used as a spinning stock solution (dope), and water or a solution in which some MSA is dissolved is used as a coagulation bath for spinning by an air gap method. Methods of forming fibers are known.

However, a large number of voids were observed in the fibers obtained in this way, which caused the inherent high strength of PBT fibers to deteriorate.
It was found that excellent mechanical properties such as high modulus were not fully realized. In order to reduce these voids, spinning conditions such as slowing down the coagulation speed of the dope, such as increasing the dope discharge speed, increasing the draft, increasing the concentration of MSA in the coagulation solution, or lowering the temperature of the coagulation solution, are recommended. A slight improvement can be made by adjusting.

However, even with these methods, it is not possible to suppress voids to the extent that they do not adversely affect the mechanical properties of the fibers. It was found that the quality of the yarn became very poor, yarn breakage occurred frequently, and the spinning operation became extremely difficult.

(Means for Solving the Problems) An object of the present invention is to provide a PBT fiber having high strength, high modulus, and excellent heat resistance.

The present inventors have investigated various methods for forming fibers in order to stably produce fibers that are void-free and have excellent mechanical properties.

By the way, voids in fibers produced by wet spinning are
These are generated during the coagulation process, and the easiest way to suppress them is to adjust the conditions of the coagulation bath as described above. However, as the present inventors continued their research focusing on the PBT concentration of the dope, which is not directly related to the conditions of the coagulation bath, they found that the concentration of 1.
If it exceeds 0%, the viscosity of the dope increases, but surprisingly, spinning using a spinning stock solution with a concentration of 11% by weight or higher, which has a high viscosity, is very effective in achieving the purpose of the present invention. As a result of this discovery and further research, we have arrived at the present invention.

(Summary of the Invention) The present invention provides a method for converting PBT into a solvent mainly composed of MSA.
This is a method for producing PBT fibers, characterized in that spinning is carried out by an air gap method from an optically anisotropic solution obtained by dissolving i amount % or more and 18] i amount % or less.

PBT used in the present invention is, for example, Mac"r
Omolecules (1981)% Volume 14, No. 9
PBT can be obtained by the method described on pages 15 to 920, but a higher degree of polymerization is preferable in terms of providing fibers with higher strength and higher modulus. In other words, preferable PBT has an intrinsic viscosity ('7 inh) of 10.0 As mentioned above, more preferably 1nh is 15.0 or more. 1i here
nh means PBT0.1g to MSA 100cc
It is calculated based on the relative viscosity at 35°C of a solution dissolved in .

It is desirable that the PBT used in the present invention be sufficiently dried before dope preparation.

The dope used in the present invention may also contain small amounts of other polymers (eg, polyparaphenylenehenzobisoxazole). In addition, stabilizers, matting agents, etc. may be included within a range that does not impede the effects of the present invention.

MSA used as the main solvent of the present invention may be used alone, but in an amount up to about 10% by weight, chlorosulfonic acid,
A mixture of sulfuric acid, polyphosphoric acid, etc. may be used.

The concentration of PBT in the dope used in the present invention is required to be at least 11% by weight in order to obtain void-free fibers, and in order to obtain a dope with uniform optical anisotropy,
It should not exceed 18% by weight. A particularly preferred concentration of PBT is 14-16% by weight.

The dope used in the present invention needs to be optically anisotropic in order to obtain high-strength, high-modulus fibers with uniform molecular orientation as spun.

To give optical anisotropy to the dope, 11% of PBT is added to the solvent.
It is sufficient to add up to 18% by weight to obtain a uniform solution. Whether or not it has optical anisotropy is determined by the fact that the obtained dope has a unique metallic luster, and when a part of it is taken and observed with a polarizing microscope, it does not show a dark field even when observed in a crossed nicol state.
It can be easily identified by its bright color tone.

In order to dissolve PBT into a solvent mainly composed of MSA, it is common to mix the required amount of solvent and PBT at room temperature in advance, and then stir the mixture while gradually raising the temperature. However, in order to increase the dissolution rate of PBT and obtain a dope more quickly, it is desirable to gradually add P and BT to a preheated solvent while stirring. At this time, it is also effective to reduce the pressure in the melting container at an appropriate time to make PBT and the solvent compatible with each other in order to speed up the melting rate. Also, the operation is PB
In order to prevent T from deteriorating, it is preferable to carry out the process under a nitrogen stream.

In order to suppress the decomposition of PBT, the stirring temperature during the PBT dissolution is preferably 150°C or lower, more preferably 120°C or lower, and most preferably 100°C or lower. It is desirable that the stirring be carried out for a sufficient amount of time until a uniform dope with no residue is obtained until the PBT is dissolved.

The obtained dope is preferably stirred under reduced pressure before spinning to remove air contained therein. This dope is filtered and weighed in a known manner and subjected to spinning.

The extrusion temperature of the dope during spinning is not particularly critical, but it is preferably 150°C or lower in order to suppress the decomposition of PBT, even if it is for a short time, and 30°C or lower in order to have fluidity that can be extruded. ℃ or higher is preferable. More preferably, the temperature is 70°C or higher and 100°C or lower.

The diameter of the spinneret used for producing the fiber of the present invention is not particularly limited, but is usually selected from the range of 0.01 to 0.2n.

In order to obtain fibers with a sufficient degree of orientation, the spinning must be carried out in the so-called air-gap manner, ie the spinneret must be kept separate from the coagulation bath.

In order to perform stable spinning, the air gap length should be 2n.
Above, it is preferable to lower the amount by 20 ml.

Further, although air is normally used as the atmosphere in the air gap, nitrogen, argon, or the like may be used to avoid surface oxidation of PBT.

The coagulating liquid of the coagulating bath used in the present invention is not particularly limited, and examples thereof include water, methanesulfonic acid aqueous solution, ethylene glycol,
Selected from methanol etc. A coagulation bath partially containing methanesulfonic acid is industrially advantageous because it can be used in combination with a solvent, and is also preferred from the viewpoint of moderating the coagulation rate.

The temperature of the coagulation bath varies somewhat depending on the type of coagulation liquid used, but for example, in the case of water, a temperature of 1° C. or more and 70° C. or less is desirable. If the temperature is too high, the coagulation rate may be too fast, making it technically difficult to obtain fibers with desirable mechanical strength.

In order to obtain fibers with high strength and high modulus, it is preferable that the draft and spinning speed be high, but if they are too high, excessive tension will be applied to the fibers during spinning, causing yarn breakage. Usually, sufficiently satisfactory results can be obtained at a draft and spinning speed of about 80% corresponding to the maximum allowable tension.

The coagulation bath is not particularly limited, and a moving bath or a stationary bath in which a coagulation liquid flows continuously may be used. For example, the moving bath may be devised so that the coagulating liquid is constantly supplied from the outside and the coagulating liquid is dropped along with the threads that are being coagulated.

The cut fibers are washed with water, but the method is not particularly limited. For example, the fibers may be washed directly in a running water bath to remove the dope solvent contained in the fibers. The fibers from which the solvent has been removed are then dried, but the method is not particularly limited.
For example, methods such as leaving it as it is at room temperature to dry it or heating it in an oven to dry it may be used.

(Effects of the present invention) By preparing a PBT dope with a high concentration of 11% to 18% by weight using the method of the present invention and performing spinning using an air gap method, very stable spinning with less yarn breakage can be achieved. Moreover, it is possible to obtain fibers having higher strength and higher modulus without voids than conventionally known PBT fibers.

Fibers with such excellent mechanical properties are useful, for example, as plastic reinforcements in composite material formation.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples in comparison with the prior art.

Example 1 Volume 27! MSAI in a cylindrical separable flask.

440 g of PBT ('i'1nh=15.
0) was added in 10 g portions. Immediately after the addition, stirring was carried out under reduced pressure for 5 to 15 minutes until the added polymer was familiar with MSA, and stirring was continued for 20 to 40 minutes. After obtaining a homogeneous solution with no residue, the next PBT was added. . When the amount of PBTO added exceeded 9% by weight, the solution began to exhibit optical anisotropy. After adding the entire amount of PBT (254 g, polymer concentration 15%) and obtaining a uniform optically anisotropic dope with no residual PBT melt, the pressure inside the container was reduced and the mixture was heated for 3
Stirring was continued for hours to remove air contained in the dope. At this time, the flow viscosity of the dope was measured using a B-type viscometer and was found to be approximately 32,000 poise.

The dope obtained as described above was spun using an air gap method using a spinning machine equipped with a gear pump. The doping temperature was 80° C. and the air gap length was 5 fl.

A 5°C water bath was used as the coagulation bath. The spinnability was stable, and the yarn could be wound from the Nelson roll onto the wine goo bobbin without any breakage. The obtained yarn was washed in a water bath overnight and then heated in an oven at 110°C for 5
Dry for an hour. When this fiber was observed with an optical microscope at a magnification of 400 times, no voids were observed. As a result of a mechanical test of the fiber, the strength was 13.2 g/d1 and the initial modulus was 1,350 g/d.

Example 2 Spinning was carried out in the same manner as in Example 1, except that the 7tnh of PBT and the polymer concentration of the dope were changed to the following conditions i) and ii).

Condition i) 7 inh = 13.2, concentration = 16% Condition ii) 1 inh = 16.5, concentration -13% No voids were observed in the fibers obtained under any of the conditions under an optical microscope.

Comparative Example An experiment was conducted in accordance with the method of Example 1, except that 151 g of PBT (linh=15.0) was used.

The spinning from the dope with a polymer concentration of 9.5% by weight obtained in this experiment had poor spinning stability, yarn breakage occurred, and in the end, the fibers could not be wound onto the wine goo bobbin.

When the fibers obtained in pieces were cut into a length of 2 cIn and observed under an optical microscope (400x magnification), voids were observed in about 70% of the samples.

As a result of the mechanical test of the obtained fiber, the strength was 4.2 g/d1
The initial modulus was 480 g/d.

Claims (1)

[Claims] (1) 11% by weight or more of polyparaphenylenebenzobisthiazole in a solvent mainly composed of methanesulfonic acid,
1. A method for producing polyparaphenylenebenzobisthiazole fiber, which comprises spinning an optically anisotropic solution obtained by dissolving less than % by weight using an air gap method.