JPS61160415A - Acrylic yarn having improved mechanical strength and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled yarn having improved mechanical strength, spinning and yarn-forming performances free from bonding between single yarn, by spinning an acrylonitrile polymer having high intrinsic viscosity and a narrow molecular weight distribution by a specific method under a specified condition and drawing the yarn under a specific condition. CONSTITUTION:Firstly, a solution of an acrylonitrile polymer having >=2.5 intrinsic viscosity and <=3.5Mw/Mn ratio between the number-average molecular weight and the weight-average molecular weight is extruded once from the holes of spinneret to air or an inert atmosphere, and the extruded yarn is introduced into a coagulating bath, and coagulated. Then,the prepared coagulated yarn is washed usually with hot water, etc., and drawn in such a way that total draw ratios become >=10 times, to give the aimed yarn having >=10g/d tensile strength. Preferably the raw material polymer is obtained by subjecting a monomer consisting essentially of acrylonitrile to solution polymerization in dimethyl sulfoxide while regulating the polymerization temperature and concentration of an initiator.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an acrylic fiber with excellent mechanical strength and a method for producing the same, and more specifically, it relates to an acrylic fiber with excellent mechanical strength and a method for producing the same.
Possesses the fiber characteristics of acrylic fibers such as texture,
Moreover, the present invention relates to an acrylic fiber with significantly improved mechanical strength and a method for producing the same.

[Conventional technology]

Conventionally, acrylic fibers have been produced and sold in large quantities for clothing and interior design due to their excellent dyeing properties, light resistance, and unique texture.

However, in recent years, it has become clear that asbestos, which has been used in large quantities for cement reinforcement, is carcinogenic, and legal regulations and restrictions on its use have been implemented. There is a strong demand for alternative fiber materials. Therefore, acrylic fibers, which have excellent alkali resistance and water resistance in cement slurry or during its curing, and have good miscibility, adhesion, and dispersibility in cement, are attracting attention as fibers to replace asbestos. Various acrylic fibers with improved mechanical strength, especially elastic modulus, have been proposed (for example, Japanese Patent Application Laid-Open No. 161117,
(U.S. Pat. No. 4,446,206).

In order to improve the mechanical strength of these AN-based fibers, attempts to use acrylonitrile-based polymers (hereinafter referred to as AN-based polymers) with large molecular weights have attracted attention. A method has been proposed for producing ultra-high strength AN-based fibers with a tensile strength of 20 g/d or more by using a high-molecular-weight AN-based polymer with a molecular weight of 10,000 or more, dry/wet spinning this polymer solution, and subjecting it to high-strength stretching. has been done.

The present inventors also used an AN-based polymer, which has an intrinsic viscosity of 2.5 or more, which has a considerably higher degree of polymerization than the polymers that make up ordinary acrylic fibers for clothing, and dried and dried this AN-based polymer solution. When a spinning method called wet spinning is adopted, the resulting undrawn yarn has excellent drawability, so the draw ratio can be increased, and as a result, mechanical strength and
In particular, it was discovered and proposed that acrylic fibers can be used that have extremely high tensile strength and knot strength as well as initial elastic modulus.

However, in the wet, dry, and dry/wet spinning methods that are commonly used to produce AN fibers, a method is adopted in which a polymer is dissolved in a solvent and the resulting solution is spun. , an increase in the molecular weight of the AN-based polymer rapidly increases the viscosity of this solution and deteriorates the spinnability, and in order to avoid this increase in solution viscosity, lowering the polymer concentration of the solution lowers the coagulability. Spinnability decreases. Therefore, for example, when producing fibers from a high molecular weight AN-based polymer with an intrinsic viscosity of more than 6, the spinnability of the fiber decreases significantly, making it difficult to stably spin the polymer solution on an industrial scale. Therefore, it is practically impossible, and in addition, there is a restriction that the production of such a high molecular weight A,N-based polymer itself cannot be obtained or produced on an industrial or commercial scale. In particular, when dry/wet spinning is employed, the occurrence of single filament fusion particles becomes significant, and there is a problem in that it is actually extremely difficult to obtain multifilament yarns.

Therefore, the present inventors further investigated this acrylic fiber, which has extremely excellent mechanical strength, and found that the intrinsic viscosity of the AN-based polymer was 2.5 or more, especially 3.0. For polymers with a high degree of polymerization exceeding We have discovered that there are many important things that can be done, and have come up with the present invention.

[Problem to be solved by the invention]

An object of the present invention is to provide an industrially advantageous method for producing acrylic fibers that are multifilament yarns with excellent spinning and spinning performance, no adhesion between single yarns, and excellent mechanical strength.

[Means for Solving the Problems] The object of the present invention is to reduce the intrinsic viscosity to at least 2.
5. The acrylonitrile polymer having a ratio of M- to Mn of 3.5 or less has a tensile strength of at least Lo
The object of the present invention is to obtain an acrylic fiber having an excellent mechanical strength of at least g/d. The combined solution is used as a spinning dope, and the spinning dope is discharged through a spinneret into air or an inert atmosphere, then introduced into a coagulation bath to coagulate, and the coagulated yarn is stretched at an overall draw ratio of at least 10 times. This can be achieved by forming a drawn yarn with a tensile strength of Log/d or more.

Here, the intrinsic viscosity is a value determined by the following measurement method.

"Method for measuring intrinsic viscosity" Put 75 ml of dried polymer (sample) into a 25 ml flask, and put 0. Add dimethylformamide containing IN sodium thiocyanate and dissolve completely.

The specific viscosity of the obtained solution was measured at 20° C. using an Ostwald viscometer, and determined by the following formula.

The feature of the present invention is to use an AN-based polymer that has a significantly higher degree of polymerization than conventionally commercially available acrylic fibers as well as AN-based polymers constituting known acrylic fibers. Furthermore, Mw/Mn, which represents the molecular weight distribution of the AN-based polymer, must be at least 3.5. To obtain a multifilament that not only has a tensile strength of about 10 g/d or more but also exhibits extremely high values of other mechanical properties such as knot strength and loop strength, and has no adhesion between single filaments. I can do it.

That is, in conventional acrylic fibers, an increase in the degree of polymerization of the polymer constituting the fiber causes an increase in the viscosity of the spinning dope, making spinning difficult, so it is necessary to reduce the polymer concentration.

On the other hand, if the polymer concentration of the spinning dope is lowered, a large amount of solvent is removed after yarn formation, which makes the fiber structure more likely to become porous and devitrified, making it impossible to achieve high strength.

In addition, unlike acrylic fibers, the polymer is not melt-spun as is, but the polymer is usually dissolved in various solvents, and the solution of this polymer dissolved in the solvent is used as a spinning dope, and the spinning process is carried out using wet, dry or dry methods.・When making fibers by means such as wet spinning, it is necessary to remove the solvent.

Usually, an aqueous solution is used to remove the solvent, but voids are generated because the volume shrinkage cannot be followed by the removal of the solvent.

In order to eliminate these voids, drying and densification is performed, but the Journal of the Japanese Society of Textile Technology Vol. 1.29. As shown in Na 8 (1973), when the polymer concentration is low, a coagulated thread with many voids is obtained, so the voids are difficult to disappear even after the drying process, and the strength and elongation properties are also low. .

On the other hand, increasing the degree of polymerization increases the viscosity of the stock solution when the polymer is dissolved in a solvent, and the polymer concentration must be reduced in terms of stability and spinnability of the stock solution.

Therefore, with a polymer having a high degree of polymerization, densification is difficult due to the adverse effect of a decrease in polymer concentration, and since adhesion between single yarns is likely to occur, high-strength yarns cannot necessarily be obtained, especially in multifilaments.

The acrylic fiber according to the present invention has an intrinsic viscosity of at least 2.5, preferably 3.0, and a Mw/Mn of 3.5 or less,
Preferably 1.1-3.0, more preferably 1.2-2
．． The basic feature is that it is made of a polymer with a high degree of polymerization of 0, and thereby has a mechanical strength, such as a tensile strength of Log/d or higher, preferably 12 g/d or higher, and a loop strength of 4.5 g/d or higher, preferably exhibits excellent physical properties of 5.0 g/d or more, making it possible to obtain a multifilament with good spreadability and no adhesion between single filaments.

As mentioned above, the method for manufacturing the fiber of the present invention having such excellent physical properties requires that the polymer constituting the fiber has a significantly high degree of polymerization and that the polymer is highly oriented in the fiber axis direction. Therefore, it is the most widely used method for producing acrylic fibers (manufacturing is difficult depending on the industrially adopted wet or dry spinning methods, and the dry/wet spinning method described in detail below, that is, AN-based polymers) is the most widely used method. The spinning solution obtained by dissolving in the solvent is once discharged into air or an inert gas, preferably air, through the spinneret hole, and the discharged thread is introduced into the coagulation liquid bath via the gas microspace. It is possible to obtain the ultra-high strength acrylic fiber of the present invention only by employing a coagulation method and further employing the specific manufacturing process and conditions detailed below.

Hereinafter, the method for producing the ultra-high strength acrylic fiber according to the present invention will be explained in detail.

First, the AN-based polymer used in the present invention contains at least 90 mol% of AN, preferably 95 to 100 mol%, and 5 mol% or less, preferably 0 to 5 mol% of a vinyl compound copolymerizable with the AN. If the copolymerization ratio of the vinyl compound exceeds 5 mol%, the heat resistance and denseness of the resulting fiber will decrease, and it will not be possible to achieve the objective of the present invention. Undesirable.

The above-mentioned vinyl compound may be any compound that is copolymerizable with various known ANs (although not particularly limited, preferred copolymerizable components include acrylic acid, itaconic acid, methyl acrylate, and methyl methacrylate). , vinyl acetate, sodium allylsulfonate, sodium methallylsulfonate, sodium p-styrenesulfonate, and the like.

Although the polymerization method is not particularly limited, a polymer with Mw/Mn of 3.5 or less can be obtained by controlling the polymerization temperature so that the ratio of monomer concentration to radical concentration is as constant as possible at each time during polymerization. be able to.

In addition, in order to obtain a polymer with an intrinsic viscosity of 2.5 or more,
It is necessary to adjust the initiator concentration and polymerization temperature so that the monomer concentration relative to the radical concentration can be maintained at a constantly high value.

The above, the intrinsic viscosity is at least 2.5, and Mw/Mn
As a method for producing an AN-based polymer having a polymerization ratio of 3.5 or less, any of known suspension polymerization, emulsion polymerization, solution polymerization, etc. can be used, but it is preferable to polymerize by homogeneous solution polymerization. Gayo(, especially DMS.

solution polymerization is best.

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 dimethyl sulfoxide (DMS
O), dimethylformamide (DMA), dimethylacetamide (DMAc), rhodan soda, an aqueous solution of zinc chloride, nitric acid, etc., but preferably DMSO, D
M.A.

DMF is best, especially DMSO.

If the intrinsic viscosity is less than 2.5, there is a limit to the strength and physical properties of the obtained fiber, for example, the tensile strength is 1.
This is not preferable since it becomes difficult to produce a product with a weight of 0.8 g/d or more, preferably 12 g/d or more.

Moreover, when Mw/Mn exceeds 3.5, spinnability becomes poor or adhesion between single filaments tends to occur (as a result, it becomes difficult to industrially produce a high-strength multifilament).

The polymer concentration depends on the intrinsic viscosity of the polymer and the type of solvent, but the solvent viscosity at 45°C is at least 2.
000 voids, preferably within the range of 3,000 to 10,000 voids, preferably with a polymer concentration of about 15 to 2
It is preferably within the range of 0% by weight. 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, the spinnability will decrease and the productivity will decrease, so the stock solution is heated and the viscosity before the spinneret is adjusted to 500 to 30.
It is better to set it to 00 voice.

The spinning dope having such an intrinsic viscosity, molecular weight distribution, and solution viscosity is discharged through a spinneret placed 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 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 20 mm, preferably 2 to 20 mm. 1
It is recommended to set it to 00.

In particular, in order to stably produce the high-strength fiber of the present invention, it is undesirable for the above-mentioned inert atmosphere running distance to be less than 1 fl; on the other hand, if it exceeds 20 fl, spinning stability decreases and production of a certain quality cannot be achieved. This is not desirable as it will prevent you from doing so.

As the coagulation bath, an aqueous solution of the same solvent as the polymer solvent is used as in the wet spinning method, and the coagulated thread is washed and desolvated in hot water and/or steam, and then
Stretched ~10 times.

After further dry densification, dry heat stretching is performed 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 160 to 270°C, preferably 200 to 250°C.

The single yarn denier of the fiber is not particularly limited, but it is usually 3d.
The following yarns can be easily obtained.

The AN-based fiber of the present invention thus obtained has extremely excellent mechanical properties such as a tensile strength of at least log/d and a knot strength of 2.5 g/d or more.

〔Effect of the invention〕

According to the present invention, AN-based fibers having high fiber properties, especially mechanical strength, can be stably obtained from AN-based polymers with a relatively high degree of polymerization, and can be used not only for clothing but also for industrial purposes. In many fields, such as industrial or industrial use, fiber reinforcement, etc.
Specifically, it can be used for canvas, asbestos substitutes, sewing thread, hoses, etc., and its usefulness is extremely large.

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

Note that the measurement of M n /M w was obtained by the following method.

The molecular weight distribution curve was determined from the GPC curve measured using the following measuring device and conditions by the GPC method, and Mn, M
− was calculated.

Equipment: Two-layer immersion chromatograph, GPC
: 244 (WATER5) column: TSK-G
EL-GMH, (2) Solvent: DMF (0,0IN
-LiC1) Flow rate: 1ml/n+in Temperature: 25°C Sample concentration: 0.1χ (wt/vol) Sample filtration: 0.5μm FHLP FILTER (MIL
LIPORE) Injection volume 4 0.5ml Detector; Differential refractive index detector R-401 (WATER5
) The molecular weight calibration curve for polyacrylonitrile was determined by the universal calibration curve method using monodisperse polystyrene as a reference.

In addition, the molecular weight conversion from polystyrene to PAN was performed using each coefficient of the following formula.

[η)-KM” 'I' ・=M, Zinbo etc. J, Chromato
gr, 55.55 ('71) * * ・-・R,L,
C1eland et al. J, Polym, Sci, 17
．． 473 ('55) <Examples 1 to 4. Comparative Examples 1 to 3> By solution polymerization in DMSO and aqueous emulsion polymerization, M
Acrylic homopolymers with different n and Mw were created. DM
In the case of solution polymerization in SO, azobisdimethylvallonitrile was used as an initiator, and in the case of aqueous emulsion polymers, ammonium persulfate was used as an initiator.

As shown in Table 1, each of the obtained polymers was dissolved in DMSO, and the polymer concentration was adjusted so that the viscosity at 45° C. was 2500 voids.

The obtained stock solutions were heated to 65° C. and subjected to dry and wet spinning using a 3000-hole spinneret.

The distance between the spinneret and the liquid level of the coagulation bath was set to 5, and a 50% DMSO aqueous solution at 15° C. was used as the coagulation bath.

Each of the obtained coagulated threads was stretched 5 times in hot water, washed with water, strain-dried at 110°C, and further subjected to dry heat secondary stretching on a hot plate. The fibers were drawn at a maximum draw ratio of 90%, and the physical properties and adhesion between the filaments are summarized in Table 1.

(Margins below this page) Table 1

Claims (1)

[Scope of Claims] 1. Intrinsic viscosity is at least 2.5, number average molecular weight (Mn
) and the weight average molecular weight (Mw) (Mw/Mn) is 3
．． 5 or less, and has excellent mechanical strength and has a tensile strength of at least 10 g/d. 2. The intrinsic viscosity is at least 2.5, the number average molecular weight (Mn
) and the weight average molecular weight (Mw) (Mw/Mn) is 3
．． 5 or less is once discharged into air or an inert atmosphere through a spinneret hole,
An acrylic fiber with excellent mechanical strength, characterized in that the discharged yarn is guided into a coagulation bath and coagulated, and the obtained coagulated yarn is drawn to obtain a drawn yarn with a total stretching ratio of at least 10 times. manufacturing method.