JPS6021905A - Acrylic fiber having high strength and elastic modulus and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture an acrylic fiber having high strength and elastic modulus required for an industrial or reinforcing fiber, by carrying out the dry and wet spinning of an AN polymer having high polymerization degree under a specific condition. CONSTITUTION:An AN polymer having an intrinsic viscosity of >=2.0, preferably >3.8 is dissolved in a solvent such as DMSO to obtain a spinning dope having a solution viscosity of >=2,000 poise and usually <=15,000 poise at 45 deg.C. The dope is spun by the dry and wet spinning process (the length of the path in air is set to 1-200mm. preferably 3-20mm.), drawn about 2-10 times by the primary drawing under moist heat or steam heat condition, washed with water, dried, and drawn >=1.1 times under dry heat condition to the overall draw ratio of >=10, preferably >=12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to high strength, high modulus acrylic fibers and methods of manufacturing the same.

Conventionally, acrylic fibers have been produced and sold in large quantities not only for clothing but also as architectural fiber materials such as curtains and carpets due to their excellent light resistance, dyeability, high shrinkage properties, and wool-like texture. ing. However, although this acrylic fiber has excellent color development and light resistance compared to polyester and polyamide fibers, it has low mechanical strength and is currently hardly used for industrial purposes. be.

Expanded acrylic fibers and their manufacturing methods include:
Many proposals have been made so far.

For example, JP-A-51-75119 discloses that, as a spinning stock solution, acrylonitrile (hereinafter abbreviated as AN) and its comonomer are dissolved in a concentrated aqueous solution of an inorganic salt, and polymerized by irradiation with ultraviolet rays in the presence of a catalyst. Using the obtained AN-based polymer (hereinafter referred to as AN-based polymer) solution, this polymer solution is wet-spun and stretched upon solidification. Specifically, by increasing the amount of polymer discharged per unit time (i.e., spinning draft) to the total cross-sectional area of the spinneret opening to 1:3 to 4, a directional structure is generated in the two skin parts. It is disclosed that high-strength acrylic fibers with a yield of 12 g/d or more, reaching a maximum of 16 g/d, can be obtained.

However, as described in the above-mentioned Japanese Patent Application Publication No.
However, as the average degree of polymerization of the N-based polymer increases, the strength of the resulting acrylic fiber improves.

Since increasing the degree of polymerization increases the solution viscosity of the polymer,
There is a problem in that it becomes technically difficult to handle the solution, making spinning difficult. According to the studies conducted by the present inventors, this method uses a special polymerization method called ultraviolet irradiation radical polymerization in an aqueous solution of zinc chloride and sodium chloride as a means of producing the polymer solution (spinning dope), so glass lining is not required. This method has never been used industrially because it requires a corrosion-resistant polymerization tank and requires special means and equipment to remove the heat of polymerization. Furthermore, when the spinning draft is increased as described above during wet spinning, the polymer concentration in the spinning dope can be reduced unless the solution volume is reduced.

Inability to perform stable spinning. In particular, when the degree of polymerization increases, the viscosity of the solution increases rapidly, so the polymer concentration of the spinning stock solution must be correspondingly reduced.

There is a need. Such a decrease in the polymer concentration of the spinning stock solution tends to cause the resulting fiber to devitrify or generate a large number of voids inside.

This does not necessarily lead to higher strength.

Furthermore, the acrylic fiber obtained by the method of JP-A-Sho is primarily used for producing carbon fibers, and as a matter of course, it is primarily drawn in hot water.

After drying, pass through heated rolls under no tension.

Since it requires a relaxation dry heat treatment, it has the disadvantage that no improvement in elastic modulus can be expected.

Also, JP-A-57-51810 and JP-A-57-161
117, the relative viscosity of the solution is 2.5 to 6.0 (
An acrylonitrile polymer (hereinafter referred to as AN polymer) having an intrinsic viscosity within the range of about 1.2 to 3.3) is wet-spun or dry-spun, wet-stretched, and then stretched on a heated roll under tension. Drying and then stretching (contact stretching) for at least 4 t:t, 5 times under dry heat at 140-200°C to give an effective total stretching ratio of at least 1:9, and then dry heat treatment at 170-280°C. By performing the initial module at 1300 C for 100% elongation
Acrylic fibers with a strength greater than N/tex (147,8 g/d) and a strength of 50CN/tex (5,6
5g/d), boiling crimp below 5%, max. 15%
It is disclosed that alkali-resistant acrylic fibers with tear elongation are obtained. However, as mentioned above, "an increase in the degree of polymerization of an AN-based polymer rapidly reduces the spinnability of the spinning dope made of the polymer, making stable spinning extremely difficult. When the solution concentration is reduced, there is a problem that the physical properties and performance of the obtained fibers deteriorate.

From this point of view, when considering the above-mentioned Japanese Patent Application Laid-Open No. 2003-120012, it is disclosed that the relative viscosity of the polymer used therein is 2.5 to 6.0, but the relative viscosity of the polymer actually used is at most 3.5 to 6.0. 3, suggesting the difficulty in producing acrylic fibers made of highly polymerized polymers by wet or dry spinning. In fact, the physical properties of the fiber obtained in the above-mentioned JP-A-Sho show a high modulus of elasticity, but a maximum tensile strength of 9.3 g.
/d.

The present inventors have conducted intensive research and examination on spinning and drawing methods for such highly polymerized AN-based polymers, and as a result, they have developed the novel high-strength, high-modulus acrylic fiber of the present invention and its
This led to the discovery of a manufacturing method.

That is, one object of the present invention is to create a fiber that is difficult to spin using wet or dry spinning methods, which are conventional general-purpose spinning methods, and which has good physical properties.

Another object of the present invention is to provide an acrylic fiber made of a high polymerization degree AN-based polymer, in particular a polymer with an intrinsic viscosity exceeding at least 2.0, which is difficult to form into fibers with good performance.
The present invention provides a method for producing acrylic fibers having high strength and high modulus of elasticity, which are required as industrial or reinforcing fibers, with good productivity, that is, commercially, from such high polymerization degree AN-based fibers. It is in.

These objects of the present invention can be achieved by the invention described in the claims.

Two aspects of the present invention will be described in detail below.

One of the features of the present invention is that it is an AN-based polymer.

However, such high polymerization degree polymers.

It exhibits extremely unique spinnability and cannot be spun or threaded stably and with good productivity using ordinary spinning means. For example, the solubility in the above-mentioned straight weight solvent decreases, and when dissolved in the conventional solvents such as rhodan soda, concentrated aqueous solutions of zinc chloride, nitric acid, etc., the solution tends to gel.

A uniform and stable spinning stock solution cannot be formed, resulting in extremely poor spinnability. In addition, when using a solvent with excellent solubility such as dimethyl sulfoxide (DMSO), when the concentration of the spinning dope increases, it becomes difficult to discharge it from the spinneret9, making it impossible to spin with normal spinning means. ．． On the other hand, if the polymer concentration of the spinning stock solution is lowered to obtain spinnability. Voids are formed in the coagulated yarn, and yarn breakage occurs due to stretching.

Only fiber yarns with a lot of fluff can be obtained, and the physical properties of the fibers do not necessarily exhibit high strength or high elastic modulus compared to conventional acrylic fibers.

Such spinnability. The deterioration in drawability suddenly becomes significant when the intrinsic viscosity of the AN polymer increases to about 3.5 or higher, and when the intrinsic viscosity of the AN polymer exceeds about 4.0, it becomes impossible to spin the yarn with good productivity, at least by normal wet spinning. This makes it technically extremely difficult to do so.

It is presumed that defects in spinning or spinning that accompany an increase in the degree of polymerization (intrinsic viscosity) make it difficult for the degree of polymerization of the polymer to contribute to a significant improvement in the tensile strength and elastic modulus of the fiber. However, the present invention solves the above problems by applying a specific spinning means to be described later to the spinning of this highly polymerized AN-based polymer. This made it possible to manufacture N-based fibers.

That is, the strength is 9, 5 or more and the elastic modulus is I Bog / d, especially 200 g;'
High-strength, high-modulus AN-based fibers with a strength of d or more can only be obtained industrially by dry-wet spinning the above polymer, and cannot be obtained by wet or dry spinning, which is a general-purpose industrial spinning method. It cannot be done.

Dry-wet spinning method, that is, the spinning stock solution is not directly discharged to the temperature of the coagulating liquid, but is first discharged into a microscopic space in an inert atmosphere such as air9.Then, this discharged thread is introduced into a coagulation bath to form a thread. Although the method itself is well known, it is possible to
The fact that it can only be obtained by dry-wet spinning N-based polymers is completely unknown. Hereinafter, a specific embodiment of the dry-wet spinning of the present invention will be described in detail.

First, as a method for producing an AN polymer having an intrinsic viscosity of at least 2.0, any of known suspension polymerization, emulsion polymerization, solution polymerization, etc. can be used, but solution polymerization is preferably used. good.

Here, since the AN-based polymer has a high degree of polymerization,
The selection of the solvent is important because the solubility may decrease and a spinning dope with good spinning stability may not be obtained. Examples of this solvent include DMSo, DMA, DMF,
There are Rodan soda, zinc chloride aqueous solution, nitric acid, etc.
Preferably DMSo, DMA, DMF, especially DMS
O is the best.

In addition, the polymer concentration depends on the intrinsic viscosity of the polymer and the type of solvent, but the solvent viscosity at 45°C is low (both 2
000 poise, preferably 5000 to 10000
High concentration within the void range, preferably polymer concentration of about 5 to
15% is better. If the viscosity is less than 2000 voids, the polymer concentration will be too low, resulting in poor strength and elongation properties, and will also be disadvantageous in terms of manufacturing cost.

In addition, if the viscosity is too high, spinnability and productivity will be reduced, so it is generally preferable to keep the viscosity at 15,000 voids or less.

In the present invention, the intrinsic viscosity is the following measured value.

Approximately 75 mg of dry polymer (sample) was placed in a 25 ml flask and 0. Add dimethylformamide containing IN sodium thiocyanate and dissolve completely. The specific viscosity of the obtained solution was measured at 20° C. using an Ostold viscosity needle, and the intrinsic viscosity was calculated according to the following formula.

0.198 The spinning dope having such an intrinsic viscosity and solution viscosity is discharged through a spinneret installed on the surface of the coagulation bath, and the discharged yarn is run in a certain inert atmosphere, for example, in air. , led into a coagulation bath. Here, the distance that the discharged yarn travels in the inert atmosphere (distance 1ilII from the spinneret surface to the coagulation bath surface) varies depending on the solvent and viscosity of the spinning stock solution, but is usually 1 to 200 mm, preferably 3 ~20
It is better to set it to ++un.

In particular, in order to stably produce the high-strength, high-modulus fiber of the present invention, it is undesirable for the above-mentioned inert atmosphere running distance to be less than 1 mm, and on the other hand, if it exceeds 2,001 mm, the spinning stability decreases and a certain quality cannot be achieved. This is not preferable because fibers cannot be obtained.

As with the wet spinning method, the coagulation bath uses an aqueous solution of the same solvent as the polymer solvent, and the threads coagulated here are washed in hot water and/or steam.

The film is stretched 2 to 10 times while being desolvated.

After further dry densification, dry heat stretching is carried out by at least 1.1 times, preferably 1.5 times, to bring the total stretching ratio to 10.
It is preferably 12 times or more. The dry heat stretching temperature is preferably 150 to 270°C, preferably 200 to 250°C.

The AN-based fiber of the present invention thus obtained has extremely high mechanical properties that are incomparable to conventional AN-based fibers, such as a tensile strength of at least 9.5 g/d and an elastic modulus of 180 g/d or more.

Although the reason why the AN-based fiber of the present invention exhibits such high strength and high elasticity is not fully clear, it is because the highly polymerized AN-based polymer constituting the fiber is highly oriented in the fiber axis direction. This is thought to be based on the fact that the AN-based fiber of the present invention exhibits a degree of X-ray crystal orientation of about 93% or more.゛Even in conventional general-purpose AN-based fibers for clothing, when highly stretched, they can show a degree of X-ray orientation exceeding 90%, but as the degree of bipolymerization increases, the It becomes extremely difficult to improve the degree of orientation1
It is surprising that the AN-based fibers of the present invention exhibit a degree of X-ray crystal orientation of greater than about 93%, despite being composed of a polymer having an intrinsic viscosity of at least greater than 2.0.

In addition to the color fastness, light fastness, and weather resistance that are the characteristics of acrylic fibers, the AN-based fibers of the present invention have remarkable tensile strength and elastic modulus, making it impossible to use conventional AN-based fibers. This greatly expands the applications of AN-based fibers, not only for their industrial material applications, but also for various composite materials that use fibers as reinforcing materials or as precursors for carbon fiber production. Gender is extremely large.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example I Aqueous emulsion polymerization was carried out using a charging composition of 97% AN and 3% methyl acrylate to produce AN polymers with different intrinsic viscosity. The intrinsic viscosities of the obtained polymers are 1.2.1, respectively.
．． 8.2.2.3.1.5.3.10.2. Each of these polymers was dissolved in DMSO to prepare a spinning stock solution.

Wet and dry-wet spinning were performed using these spinning solutions, and the strength and Young's modulus of the resulting large fibers were measured. The results are shown in Table 1.

The coagulation bath was a 55% DMSO aqueous solution at 20°C.
The take-up speed for one bath was 2 m/min. Also.

The length of the space in the case of dry-wet spinning was 10 mm.

The obtained undrawn yarn was stretched 6 times in hot water, washed with water and dried at 110° C. in Table 1, and then stretched in a dry heat tube at the highest stretching rate and evaluated.

It can be seen that dry-wet spun products with an intrinsic viscosity of 2 or more, particularly over 3.8, have excellent strength and elastic modulus.

Example-2 Melt in DMSO with a composition ratio of 99% AN system and 1% 2-acrylamidodimethylpropanesulfonic acid.

Liquid polymerization was performed to obtain a polymer with an intrinsic viscosity of 5.5.The polymer concentration was changed to 6% and 8% by concentration.

Stock solutions of 10% and 12% were prepared. The viscosity at 45°C is 1.300.2.100.5.200.9.800, respectively.
It was Poise.

The stock solution was heated to 80° C., the length of the space was set to 10 mm, and the solution was discharged into a 50% DMSO aqueous solution at 10° C. to obtain a coagulated thread. The coagulated thread was stretched 7 times in hot water, strain-dried at 100°C, and then further dried using a dry heat tube.

Stretching was performed by 1.8 times at 220°C. The physical properties of the obtained fibers were evaluated and summarized in Table 2.

Table 2 The higher the polymer concentration, the higher the strength and Young's modulus.
Viscosity at 5°C is 2,000 voids or more, preferably 5.00
It is desirable to increase the polymer concentration so that the void is 0 or more.

Example 3 100% AN was homogeneously solution polymerized in a DMSO solvent to obtain a polymer having an intrinsic viscosity of 6.0.

When a stock solution with a polymer concentration of 10% was prepared, the viscosity at 45° C. was 6.100 voids.

The stock solution was heated to 90°C and discharged into a 30% DMSO aqueous solution at 15°C with a space length of 15 mm.

It was pulled at a speed of 10 m/min. Stretched 6 times in hot water while washing with water, dried at 100°C, and stretched 23 times using a hot plate.
Stretching was performed by 2.0 times at 0°C.

The physical properties of the obtained fibers are as follows: denier ld, strength 12.8
g/d, elongation of 8%, and Young's modulus of 220 g/d.

Patent applicant: Toshi Co., Ltd.

Claims (1)

[Scope of Claims] (1) A tensile strength of 9.5'g/d or more and an elastic modulus of 180g obtained by dry/wet spinning an acrylonitrile polymer having an intrinsic viscosity of at least about 2.0 or more. /
High strength, high elastic modulus acrylic fiber that is d or higher. (2. In claim 1, the high strength, high modulus acrylic fiber is an acrylonitrile polymer whose intrinsic viscosity exceeds at least 3.8, and whose tensile strength is 10 g/d or more. (3) In claim 1, the acrylonitrile polymer is composed of at least 90% by weight of acrylonitrile and a black vinyl compound having a copolymerizability of 10% by weight or less, and has at least 4.0% by weight of a black vinyl compound. High-strength, high-modulus acrylic fiber composed of an acrylonitrile polymer having an intrinsic viscosity exceeding (5) A high strength, high modulus acrylic fiber having an elastic modulus of at least about 2008/d. (5) An acrylonitrile polymer having an intrinsic viscosity of at least 2.0 is dissolved in a solvent for the acrylonitrile polymer. and the solution viscosity at 45°C is at least 2000
A spinning dope of poise is prepared, and after this spinning dope is subjected to dry/wet spinning, it is first stretched by about 2 to 10 times under wet heat or steam heat. High strength and high elasticity characterized by subjecting the yarn to dry heat stretching after passing through the steps of water washing and drying, and then making the effective total stretching ratio at least 10 times that of the undrawn yarn from dry and wet spinning. Production method of acrylic fiber. (6) In claim 5, the solvent for the acrylonitrile polymer is at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide, or Production method of high strength, high modulus acrylic fiber using mixed solvent