JPH03161507A - Production of poly(hexamethylene)terephthalic amide fiber - Google Patents

Abstract

PURPOSE:To obtain the dense, high-strength and high-modulus title fiber having smooth surface by introducing a dope from a spinneret into a gas and then feeding the dope into a coagulating bath containing a specific liquid and further feeding a coagulated yarn into an aqueous coagulating bath and drawing the coagulated yarn by giving draft to the yarn. CONSTITUTION:A dope obtained by dissolving poly(hexamethylene)terephthalate in a sulfuric acid based solvent is introduced from a spinneret into a gas and then into a coagulating bath containing a liquid (e.g. water, aqueous solution of salt such as sodium sulfate, etc., or aqueous solution of sulfuric acid) which is precipitation agent to the polymer and simultaneously an extracting agent to the solvent. The resultant coagulated yarn is further introduced into an aqueous coagulating bath and then the coagulated yarn is drawn from the coagulating bath in rate ratio providing at least >=1.5 draft to provide the aimed fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to poly(hexamethylene) terephthalene. 3. This invention relates to a method for producing mido fibers. For more details, see high strength,
This paper relates to a method for inexpensively producing fibers with high elastic modulus and excellent heat resistance. Poly(hexamethylene) terephthalamide (hereinafter referred to as 6.
Nylon 7) is a high melting point nylon that has benzene nuclei in the polymer, and has a melting point of 370"C. This polymer has excellent heat resistance, chemical resistance, and various excellent physical properties. We can expect to obtain fiber.

[Conventional technology]

6.7 Regarding the manufacturing method of nylon fibers, many studies have been conducted for a long time on the method of manufacturing fibers by wet spinning from dope using sulfuric acid as a solvent.

For example, Japanese Patent Publication No. 38-18573 and Japanese Patent Publication No. 4
Publication No. 0-305 includes 6. A method is disclosed in which a sulfuric acid dope of T-nylon is extruded into a sulfuric acid solution having a specific concentration and temperature range to form fibers. However, the disadvantage is that vertical streaks are seen on the surface of the fibers produced by this method, and defects such as voids tend to occur inside the fibers, making it extremely difficult to produce dense and highly strong fibers. It had

[Problems to be Solved by the Invention] An object of the present invention is to provide a manufacturing method capable of stably manufacturing fibers with high strength and high elastic modulus.

[Means to solve the problem]

As a result of intensive research into a method for producing dense, high-strength fibers with no surface or internal defects from 6.7 nylon sulfuric acid dope, the inventors found that the sulfuric acid dope was directly passed through a coagulation bath of sulfuric acid aqueous solution to produce fibers. In the conventional method, in which coagulation progresses while renewing the skin layer formed on the surface, defects are very likely to occur on the fiber surface and inside.On the contrary, once a skin layer is created on the fiber surface, then the skin layer is expanded while being stretched and oriented. The inventors have discovered that a method of coagulating and desolventing the fibers through the process is effective in producing dense fibers, and has thus arrived at the present invention.

That is, the present invention provides 6.7 nylon from a dope prepared by dissolving 6.7 nylon in sulfuric acid or a solvent mainly composed of sulfuric acid. In the method for producing T nylon woven fibers, dope is introduced into the gas from a spinneret,
The polymer is then introduced into a coagulation bath containing a liquid that is a precipitant for the polymer and at the same time an extractant for the solvent, and the resulting coagulated filament is further introduced into an aqueous coagulation bath for at least 1.
6. The coagulated filament is drawn from the coagulation bath at a speed ratio that provides a draft of 5 or more. This is a method for producing T nylon fiber.

In manufacturing the fiber of the present invention, first, 6. It is necessary to prepare a dope in which T nylon polymer is dissolved in sulfuric acid or a solvent mainly composed of sulfuric acid.

The polymer concentration at this time may be appropriately selected depending on the degree of polymerization of the polymer, but it is preferably 10% by weight or more. In addition, in the fiber of the present invention, in order to ensure a desirable level of physical properties, the polymer content in the preparation is 1.5 or more, preferably 2.5 or more. Preferably, it has an intrinsic viscosity of 0 or more. This 6.7 nylon polymer is, for example,
It can be obtained by the method described in Japanese Patent No. 11634.

The solvent used to prepare the dope is sulfuric acid or a mixture based on sulfuric acid. From the viewpoint of solubility, the sulfuric acid is preferably concentrated sulfuric acid with a concentration of 96% by weight or more. It may also be so-called fuming sulfuric acid.

Examples of substances that can be mixed with sulfuric acid include chlorosulfuric acid, fluorosulfuric acid, dichloroacetic acid, acetic acid, and phosphorus pentoxide.

The dope used in the present invention may contain various additives, such as stabilizers such as ammonium sulfate.

The dope prepared in this way is then spun into a gas and then passed through step 6 of this procedure. The obtained coagulated filament is further aqueous in a coagulation bath (hereinafter referred to as the first bath) containing a liquid that is a precipitant for the T-nylon polymer and an extractant for sulfuric acid, which is a solvent. It is necessary to extrude into a coagulation bath (hereinafter referred to as the second bath).

It is preferred, especially for industrial production, that the dope be degassed, filtered and metered before passing through the spinneret. The shape, number of holes, size of the holes, etc. of the spinneret are not particularly limited. The hole size is usually 0.05~0.5f
Fl! A diameter of I is used. The linear speed of the dope extruded from the spinneret is also not particularly limited;
It may be determined based on productivity and the desired yarn diameter. The dope extruded from the spinneret must first pass through a gas. By providing this gas gap between the spinneret and the surface of the first bath, elongation deformation occurs only in this gap area, and the skin layer formed on the fiber surface in the first bath is not renewed. It can be introduced into two baths and can be made into yarn with a clean fiber surface. Examples of the gas used at this time include air, nitrogen, and argon, but air is most preferred from the viewpoint of economy, operability, and the like. The length of the gas gap is not particularly limited, but is usually set between 0.3 and 5 cI11. By setting this gap length large, the maximum elongation deformation rate in this portion can be increased, and the winding speed can be increased.

The first bath used in the present invention contains a liquid that is a precipitant for the 6.7 nylon polymer and at the same time an extractant for the solvent sulfuric acid, such as water or sodium sulfate. An aqueous salt solution containing a salt dissolved therein, an aqueous sulfuric acid solution, etc. are used. The bath temperature of the first bath at this time is appropriately set depending on the coagulation bath used, and is conventionally set between 0°C and 70°C.

More generally, it is preferable to set the temperature 5'C to 10"C higher than the lowest temperature at which the yarn can be pulled up from the first bath.

The yarn drawn out from the first bath is led to a second bath, where the skin layer formed in the first bath is stretched and oriented while the yarn coagulation and solvent removal are further advanced. It is necessary to solidify and desolvent to the extent that defects are not formed. The second bath is an aqueous AT garden bath, in which water or an aqueous sulfuric acid solution is used.
In this second bath,
It is necessary to apply a draft of 1.5 or more. Here, the draft is a value obtained by dividing the linear velocity of the yarn drawn out from the second bath by the linear velocity of the yarn drawn out from the first bath. If the draft is less than 1.5, defects such as voids will occur inside the yarn during the washing and drying process performed after the second bath, which is not preferable.

After leaving the second bath, the yarn is washed to completely remove residual sulfuric acid inside the yarn, and then dried. Further, by hot drawing at 250°C to 340°C, fibers with high strength and high modulus can be obtained.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples. In the Examples, the intrinsic viscosity of the polymer, the strength and elongation characteristics of the fibers, and the density of the fibers were measured by the methods shown below.

Method for measuring field viscosity〉 Intrinsic viscosity (ηinh) is determined by dissolving a polymer in 98.5% concentrated sulfuric acid at a concentration (C) of 0.4 g/100 cc at 25°C. Measured by method.

C Method for measuring the strength and elongation properties of fibers The strength, elongation and initial modulus of the fibers were measured in accordance with JIS standards using a constant speed elongation type strength and elongation tester at a gripping length of 2cm.
+s, tensile speed 50%/min, load-elongation rate Iih line was read and calculated, number of measurements was 10.
Expressed as the average value.

<Fiber Density> The density value was measured at 30°C by the density gradient tube method using carbon tetrachloride and toluene.

Example 1 A 6.7 nylon polymer having an intrinsic viscosity (ηinh) of 1.8 was dissolved in 97% by weight concentrated sulfuric acid to a concentration of 14% by weight at room temperature for 5 hours with stirring. At this time, 5% by weight of ammonium sulfate as a stabilizer was previously dissolved in concentrated sulfuric acid. Following dissolution of the polymer, it was degassed under vacuum for 3 hours before spinning. The viscosity of this dope at 25°C is 300
There was 0 voice.

This dope has a diameter of 0. It was extruded from a spun metal with one 2 mm pore, and after running through approximately 2 cm of air,
It was extruded into a first bath of water at ~10°C.

At this time, run about 80cm in the first bath, and
It was withdrawn from the first bath at a speed of m/min. At this time, the ratio between the linear speed of dope discharge from the spinning mass and the speed of withdrawal from the first bath was 3.1.

Next, the 11 threads from the first bath were introduced into the second bath containing hot water at about 50"C. They were run about 1m in the second bath, and the 50"
It was drawn out from the second bath and wound up at a speed of m/min. The wound thread was washed under running water to completely remove residual sulfuric acid, and then dried. The spun yarn has a density of 1.21 g/cf
fl, single fiber denier 8.5, single fiber strength 2.5g
/denier, single fiber elongation was 106%, and single fiber modulus was 34.1 g/denier.

Furthermore, this thread was transparent, and when its surface was observed under an electron microscope, it was found to be very smooth.

Next, this yarn was hot-stretched at 300°C with a draw ratio of 1.6 times, and the yarn physical properties were as follows: single fiber denier was 5.5, single fiber strength was 8.3 g/denier, and single fiber elongation was 9. .0%, resulting in a single fiber modulus of 102.2 g/denier.

Example 2 Spinning was carried out in the same manner as in Example 1, except that the first bath was a 30% by weight aqueous sodium sulfate solution at a temperature of 20-25°C. The obtained fibers had a density of 1.21 g/c, a single fiber denier of 8.3, a single fiber strength of 2.8 g/denier, a single fiber elongation of 85%, and a single fiber modulus of 42.2.
g/denier. Also, as in Example 1, this yarn was also transparent, and when the surface was observed under an electron microscope, it was found to be very smooth.

Next, this yarn was hot-stretched at 300°C at a draw ratio of 1.6 times in the same manner as in Example 1, and the yarn physical properties were as follows: single fiber denier was 5.5, and single fiber strength was 8.5 g/denier. The fiber elongation was 8.7% and the single fiber modulus was 112.1 g/denier.

Comparative Example 1 A dope prepared in the same manner as in Example 1 was prepared with a diameter of 0.1 mm.
From a spinneret with one pore of
Sulfuric acid water with a C concentration of 50% by weight? It was extruded into 8 liquids. At this time, the first bath was about 60 CI! + Try to run, 12
It was withdrawn from the first bath at a rate of m/min. At this time, the ratio of the linear speed of dope discharge from the spinneret to the speed of withdrawal from the first bath was 4.0.

The coagulated threads from the first bath were then led to a second bath containing hot water at about 50°C. Run about 1m during the second bath, 24
It was withdrawn from the second bath and wound up at a speed of m/min.

The wound thread was washed under running water to completely remove residual sulfuric acid, and then dried. Compared to Example 1.2, the spinning stability was poor and yarn breakage occurred frequently inside and outside the bath.

The spun yarn has a density of 1.18 g/ci, a single fiber denier of 3.0, a single fiber strength of 2.1 g/denier, a single fiber elongation of 35.5%, and a single fiber modulus of 38.3 g/denier.
It was denier.

In addition, this thread lacks transparency compared to the threads of Examples 1 and 2,
When the surface was observed using an electron microscope, many vertical streaks were observed on the thread surface.

Next, this yarn was hot-stretched at 300°C with a drawing ratio of 1.6 times, and the yarn physical properties were as follows: single fiber denier was 2.0, single fiber strength was 6.3 g/denier, and single fiber elongation was 6.3 g/denier. 7.0%
, the single fiber modulus was 102.2 g/denier.

〔Effect of the invention〕

Due to the spinning method of the present invention, the surface morphology of the yarn is smooth and dense, and the fiber properties of higher strength and high modulus are obtained6.
．． It became possible to produce T-nylon fibers. Furthermore, spinning stability was significantly improved compared to conventional methods.

The fibers obtained by the present invention can be used for tire cords, ropes, etc. by utilizing their heat resistance, high strength, and high modulus properties.
It is useful as a rubber reinforcing material for various belts, etc.

Claims (1)

[Claims] 1. In a method for producing poly(hexamethylene) terephthalamide fiber from a dope in which poly(hexamethylene) terephthalamide is dissolved in sulfuric acid or a solvent mainly composed of sulfuric acid, the dope is poured into a gas from a spinneret, and then this heavy The coagulated filament is introduced into a coagulation bath containing a liquid that is a precipitant for the coalescence and an extractant for the solvent, and the resulting coagulated filament is further introduced into an aqueous coagulation bath to provide a draft of at least 1.5. 1. A method for producing poly(hexamethylene) terephthalamide fiber, comprising drawing a coagulated filament from the coagulation bath at a speed ratio of: