JP2023110109A - Production method of polyamide 4 fiber - Google Patents

Abstract

To provide a production method of a polyamide-4 fiber by a wet spinning method that does not require removal of residual components, and a production method of the polyamide-4 fiber by a wet spinning method that does not require use of expensive materials.SOLUTION: A production method of polyamide-4 fiber comprises: a step of dissolving polyamide-4 in a solvent to obtain a spinning solution; a step of wet spinning using the spinning solution to obtain an undrawn fiber; and a step of drawing the undrawn fiber to obtain the polyamide-4 fiber, wherein the polyamide-4 has a weight average molecular weight (Mw) of 400,000 or more and a molecular weight distribution (Mw/Mn) of 1.0 to 4.5, the solvent is a solvent containing no methylene chloride and containing formic acid, the spinning solution has a dissolved polyamide-4 concentration of 10 wt.% or more, and a coagulation bath used for the wet spinning is an organic solvent containing an alkyl acetate solvent.SELECTED DRAWING: None

Description

There is an application for application of Article 30, Paragraph 2 of the Patent Act. (2) On November 10, 2019, presented at the poster presentation of the 2019 Fiber Society Autumn Research Presentation

The present invention relates to a method for producing polyamide 4 fibers by wet spinning.

Polyamide 4 obtained by polymerizing 2-pyrrolidone is expected as a material with excellent mechanical properties. In addition, since it exhibits biodegradability, it is attracting attention as a material that can contribute to solving the problem of microplastics. Fibers obtained by spinning polyamide 4 are considered to be applications in which the physical properties of polyamide 4 can be utilized, and have been researched and developed for a long time. However, since the melting point and the decomposition temperature of polyamide 4 are close to each other, it is considered difficult to fiberize polyamide 4 by melt spinning. Therefore, a wet spinning method has been studied as a fiberization method with less thermal abuse.

Patent Document 1 describes a technique of dissolving polyamide 4 in formic acid and methylene chloride to prepare a spinning solution and performing wet spinning. Patent Document 2 describes a technique of preparing a spinning solution by dissolving polyamide 4 in formic acid and methylene chloride and performing wet spinning using a coagulation bath composed of a lower alkyl ester. In Patent Document 3, a spinning solution is prepared by dissolving polyamide 4 in a solvent selected from formic acid and a mixture of formic acid and water, and wet spinning is performed using a coagulation bath consisting of an aqueous solution of at least one formate. technique is described. Patent Document 4 describes a technique of preparing a spinning solution by dissolving zinc chloride in an aqueous solution of zinc chloride or a mixed aqueous solution containing zinc chloride as a main component and other inorganic salts, and performing wet spinning. In Comparative Example 2 of Patent Document 5, a spinning solution containing polyamide 4 having a weight average molecular weight of 564,335 and a number average molecular weight of 270,234 and formic acid was used, and a coagulation bath containing methanol was used. It is described that undrawn fibers of polyamide 4 were obtained by a wet spinning process. However, it is stated that the undrawn fibers could not be drawn. Patent Literature 6 describes a technique of dissolving polyamide 4 in an ionic liquid to prepare a spinning solution and subjecting it to wet or dry-wet spinning or gel spinning to obtain polyamide 4 fibers.

U.S. Pat. No. 4,094,945 JP-A-53-24420 JP-A-57-25413 Japanese Patent Publication No. 36-5165 JP 2019-137934 A WO2015/186364

In the methods described in Patent Documents 1 and 2, residual methylene chloride may pose a problem, and it is necessary to remove it. Moreover, the methods described in Patent Documents 3 and 4 require the removal of salt components, which complicates the operation. The method described in Patent Document 5 does not appear to be capable of drawing undrawn fibers. Since the method described in Patent Document 6 uses an expensive ionic liquid, it has been difficult to industrialize. An object of the present invention is to provide a method for producing polyamide 4 fibers by a wet spinning method that does not require removal of residual components. Another object of the present invention is to provide a method for producing polyamide 4 fibers by a wet spinning method that does not require the use of expensive materials.

The present inventors have completed the present invention as a result of earnest investigations to solve the above problems.
The present invention includes the following aspects.
(1) dissolving polyamide 4 in a solvent to obtain a spinning solution;
a step of wet spinning using the spinning solution to obtain an undrawn fiber;
A step of drawing the undrawn fibers to obtain polyamide 4 fibers;
including
The polyamide 4 has a weight average molecular weight (Mw) of 400,000 or more and a molecular weight distribution (Mw/Mn) of 1.0 to 4.5,
The solvent is a solvent containing no methylene chloride and containing formic acid,
The spinning solution has a dissolved polyamide 4 concentration of 10% by weight or more,
The coagulation bath used for wet spinning is an organic solvent containing an alkyl acetate solvent,
A method for producing a polyamide 4 fiber, wherein the drawing temperature in the drawing step is 160° C. or more and 240° C. or less, and the draw ratio is 2 times or more.
(2) The production method according to (1), wherein the polyamide 4 fiber has a tensile strength of 3 cN/dtex or more.
(3) The production method according to (1) or (2), wherein the polyamide 4 fiber is a polyamide 4 multifilament.
(4) The production method according to (3), wherein the number of filaments of the polyamide 4 multifilament is 5 to 200.

According to the method for producing polyamide 4 fibers of the present invention, it is not necessary to perform complicated operations for removing impurity components after wet spinning. Moreover, according to the method for producing polyamide 4 fibers of the present invention, there is no need to use expensive materials.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram which shows one aspect|mode of the wet spinning of this invention.

The method for producing a polyamide 4 fiber of the present invention includes a step of dissolving polyamide 4 in a solvent to obtain a spinning solution (hereinafter sometimes referred to as step A), wet spinning using the spinning solution, A step of obtaining undrawn fibers (hereinafter sometimes referred to as step B), and a step of drawing the undrawn fibers to obtain polyamide 4 fibers (hereinafter sometimes referred to as step C). is not particularly limited. According to the method for producing a polyamide-4 fiber of the present invention, a polyamide-4 fiber having high tensile strength can be produced.

(Process A)
Step A of the present invention is a step of dissolving polyamide 4 in a solvent to obtain a spinning solution.

<Polyamide 4>
Polyamide 4 used in step A of the present invention is a polymer obtained by polymerizing 2-pyrrolidone. The weight average molecular weight (Mw) of polyamide 4 is not particularly limited, but the lower limit of the weight average molecular weight (Mw) of polyamide 4 can be selected from 400,000, 450,000, 500,000, and the like. If the weight average molecular weight (Mw) is less than 400,000, the resulting polyamide 4 fiber tends to have low tensile strength. Moreover, the upper limit of the weight average molecular weight (Mw) of polyamide 4 can be selected from 1,000,000, 900,000, 800,000, 700,000 and the like. When the weight-average molecular weight (Mw) is more than 1,000,000, the spinnability of polyamide 4 tends to deteriorate.

The molecular weight distribution (Mw/Mn) of polyamide 4 is not particularly limited, but ranges from 1.0 to 4.5, 1.0 to 4.0, 1.0 to 3.5, 1.0 to 3.0 etc. can be selected. Polyamide 4 fibers obtained from polyamide 4 having a small molecular weight distribution value tend to have high tensile strength. The weight-average molecular weight and number-average molecular weight are measured by gel permeation chromatography (GPC) using a solution of sodium trifluoroacetate dissolved in hexafluoroisopropanol at a concentration of 10 mM as a solvent. It can be calculated by converting with the molecular weight of methyl.

Polyamide 4 can be produced by polymerizing 2-pyrrolidone by a known polymerization method. For example, it can be manufactured with reference to the method described in JP-A-2019-137934.

2-pyrrolidone used as a raw material includes those produced from petroleum, those produced from bio-derived resources such as γ-aminobutyric acid using microorganism-derived enzymes, and the like. Commercial products produced from petroleum are readily available.

<Spinning solution>
The solvent for dissolving polyamide 4 in step A of the present invention is a solvent containing formic acid. Solvents containing formic acid include solvents consisting of formic acid only and solvents consisting of formic acid and other solvents. Examples of the other solvent include, but are not limited to, water, hexafluoroisopropanol, trifluoroacetic acid, and the like. These can be used individually by 1 type or in combination of 2 or more types. The concentration of formic acid in the solvent consisting of formic acid and other solvents is 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, etc. can be selected from The solvent for dissolving polyamide 4 in step A of the present invention is preferably a solvent that does not contain methylene chloride.

The concentration of polyamide 4 in the spinning solution is not particularly limited, but the lower limit of the concentration of polyamide 4 can be selected from 10% by weight, 12% by weight, 14% by weight, 16% by weight, 18% by weight, 20% by weight, and the like. can. The upper limit of the polyamide 4 concentration can be selected from 60% by weight, 50% by weight, 40% by weight, and the like.

A spinning solution can be prepared by mixing polyamide 4 and a solvent and dissolving the polyamide 4 in the solvent. The temperature at which the polyamide 4 is dissolved in the solvent is not particularly limited, but can usually be selected in the range of 0°C to 40°C and 0°C to 30°C.

(Step B)
The step B of the present invention is a step of wet spinning using the spinning solution obtained in the step A to obtain an undrawn fiber. In the present invention, wet spinning refers to a spinning method that includes a step of extruding a spinning solution through one or more holes in a coagulation bath to process it into fibers (undrawn yarns).

One embodiment of the wet spinning of the present invention will be described with reference to FIG.
The spinning solution obtained in step A is placed in a tank. A spinning solution (spinning dope in FIG. 1) is sent from a tank to a nozzle (nozzle in FIG. 1) under nitrogen pressure, and pushed out from the nozzle hole into a coagulation bath (coagulation bath in FIG. 1). The fiber produced by extrusion is taken up by a take-up roller. An undrawn fiber can be obtained by drying the wound fiber under reduced pressure.

The coagulation bath used for wet spinning in step B is preferably an organic solvent containing an alkyl acetate solvent. Examples of alkyl acetate solvents include methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate and the like. These can be used individually by 1 type or in combination of 2 or more types.

The size of the nozzle hole is not particularly limited, but can be appropriately set within a range such as an inner diameter of 0.001 mm to 10 mm, an inner diameter of 0.01 mm to 10 mm, an inner diameter of 0.01 mm to 1 mm, and an inner diameter of 0.01 mm to 0.5 mm. can.
The number of nozzle holes may be one or plural. When the number of nozzle holes is one, the obtained fiber is monofilament, and when the number of nozzle holes is plural, the obtained fiber is multifilament. The polyamide 4 fiber of the present invention is preferably multifilament. The number of filaments of the multifilament is not particularly limited, but can be selected from 5 to 200, 20 to 200, 50 to 200, 50 to 150, and the like.

(Process C)
Step C of the present invention is a step of drawing the undrawn polyamide 4 fibers obtained in step B to obtain polyamide 4 fibers. By drawing undrawn polyamide 4 fibers, polyamide 4 fibers having high tensile strength can be produced.

<Stretching>
The drawing operation is not particularly limited, and the undrawn fibers can be drawn by a conventional uniaxial drawing device.
The lower limit of the stretching temperature can be selected from 160°C, 170°C, 180°C, 190°C, and the like. When the stretching temperature is lower than 160°C, the tensile strength tends to decrease. The upper limit of the stretching temperature can be selected from 240°C, 230°C, 220°C, 210°C, and the like. When the stretching temperature is higher than 240°C, polyamide 4 tends to decompose easily.
The draw ratio is not particularly limited, but can be selected from 2.0 times or more, 2.5 times or more, and the like. A polyamide 4 fiber having a high tensile strength can be obtained by setting the draw ratio to 2.0 times or more.

(Other process D)
The method for producing a polyamide 4 fiber of the present invention may include another step D in addition to steps A, B, and C. The other process D is not particularly limited as long as it does not impair the purpose of the present invention.

(Polyamide 4 fiber)
The polyamide 4 fiber obtained by the production method of the present invention exhibits a high tensile strength of 3 cN/dtex or more. Polyamide 4 fibers obtained by the production method of the present invention are applicable to a wide range of applications such as clothing, ropes and tire cords.

EXAMPLES The present invention will be described in detail below using examples, but the present invention is not limited to the scope of the examples.

Example 1 Production of Polyamide 4 Fiber a <Preparation of Spinning Solution>
15 g of polyamide 4 having a weight average molecular weight (Mw) of 505,000 and a molecular weight distribution (Mw/Mn) of 2.37 was weighed and mixed with 60 g of formic acid (99% formic acid). The mixture was allowed to stand at room temperature until no undissolved residue was visually observed to obtain a spinning solution having a polyamide 4 concentration of 20% by weight.

<Wet spinning>
The outline of the wet spinning apparatus is as shown in FIG.
The spinning solution obtained above was transferred to a tank and allowed to stand at room temperature for 12 hours to remove air bubbles in the solution. A nitrogen pressure of 0.2 MPa was applied to the spinning solution in the tank, extruded through a platinum nozzle (inner diameter: 0.09 mm, number of holes: 100) into an ethyl acetate coagulation bath (length of the coagulation bath: 2 m), followed by a take-up roller. rolled up. The wound undrawn fiber was dried at 40° C. under reduced pressure for 2 hours.

<Stretching>
One end of the undrawn fiber obtained by the above wet spinning was fixed, and the other end was pulled at a speed of 10 mm/s on a hot press adjusted to 200°C. The undrawn fiber was drawn to a length of 2.5 times (drawing ratio: 2.5 times) to obtain a polyamide fiber a.

Example 2 Production of polyamide 4 fiber b Polyamide 4 having a weight average molecular weight (Mw) of 687,000 and a molecular weight distribution (Mw/Mn) of 2.98 was used, and nitrogen pressure was applied during wet spinning. Polyamide 4 fiber b was obtained in the same manner as in Example 1, except that the pressure was set to 0.5 MPa, the drawing temperature was set to 180° C., and the draw ratio was set to 4 times.

Comparative Example 1 Production of Polyamide 4 Fiber c Polyamide 4 having a weight average molecular weight (Mw) of 615,000 and a molecular weight distribution (Mw/Mn) of 5.40 was used, and nitrogen pressure was applied during wet spinning. Polyamide 4 fiber c was obtained in the same manner as in Example 1, except that the tension was set to 0.05 MPa, the drawing speed was set to 1 mm/sec, and the draw ratio was set to 3 times.

Comparative Example 2 Production of polyamide 4 fiber d Polyamide 4 having a weight average molecular weight (Mw) of 653,000 and a molecular weight distribution (Mw/Mn) of 5.03 was used, and nitrogen pressure was applied during wet spinning. Polyamide 4 fiber d was obtained in the same manner as in Example 1, except that the pressure was set to 0.15 MPa, the drawing temperature was set to 180° C., and the draw ratio was set to 3 times.

Comparative Example 3 Production of Polyamide 4 Fiber e Polyamide 4 having a weight average molecular weight (Mw) of 378,000 and a molecular weight distribution (Mw/Mn) of 2.04 was used, and nitrogen pressure was applied during wet spinning. Polyamide 4 fiber e was obtained in the same manner as in Example 1, except that the pressure was set to 0.15 MPa, the drawing temperature was set to 180° C., and the draw ratio was set to 2.5 times.

The following measurements were performed on the polyamide 4 fibers a to e obtained in Examples and Comparative Examples. Table 1 shows the results.

<Fineness>
The fineness (dtex) was calculated by measuring the weight per unit length of the sample with an electronic balance (LIBRORAEG-455M manufactured by SHIMADZU).

<Elastic modulus>
For the elastic modulus of the fiber, a tensile test was performed at room temperature using an ORIENTEC tensile tester (STA-1150) with a test piece length of 20 mm and a tensile speed of 30 mm/min to obtain a stress-strain curve. . Then, the slope of the straight line portion at the initial stage of the curve was calculated to obtain the elastic modulus (GPa).

<Tensile strength>
The tensile strength of the fiber was measured using an ORIENTEC tensile tester (STA-1150) under the conditions of a test piece length of 20 mm and a tensile speed of 30 mm/min at room temperature. cN) was obtained. The strength (unit: cN/dtex) calculated using the fineness measured above was taken as the tensile strength.

From Table 1, it can be seen that the polyamide 4 fibers a and b produced by the polyamide 4 fiber production method of the present invention exhibit higher tensile strength (3 cN/dtex or more) than the polyamide 4 fibers c to e.

Claims (4)

dissolving polyamide 4 in a solvent to obtain a spinning solution;
a step of wet spinning using the spinning solution to obtain an undrawn fiber;
A step of drawing the undrawn fibers to obtain polyamide 4 fibers;
including
The polyamide 4 has a weight average molecular weight (Mw) of 400,000 or more and a molecular weight distribution (Mw/Mn) of 1.0 to 4.5,
The solvent is a solvent containing no methylene chloride and containing formic acid,
The spinning solution has a dissolved polyamide 4 concentration of 10% by weight or more,
The coagulation bath used for wet spinning is an organic solvent containing an alkyl acetate solvent,
A method for producing a polyamide 4 fiber, wherein the drawing temperature in the drawing step is 160° C. or more and 240° C. or less, and the draw ratio is 2 times or more. 2. The production method according to claim 1, wherein the polyamide 4 fiber has a tensile strength of 3 cN/dtex or more. 3. The manufacturing method according to claim 1 or 2, wherein the polyamide 4 fiber is a polyamide 4 multifilament. The production method according to claim 3, wherein the polyamide 4 multifilament has 5 to 200 filaments.