TW202200860A - Method for producing polyamide 4 fiber by using a wet spinning method without carrying out a procedure for removing residual components - Google Patents

Abstract

The invention aims to provide a method for producing a polyamide 4 fiber by means of a wet spinning method, in which there is no need to carry out a procedure for removing residual components. The invention also aims to provide a method for producing a polyamide 4 fiber by means of a wet spinning method that does not require use of expensive raw materials. The method for producing a polyamide 4 fiber is characterized by including: a step for dissolving polyamide 4 in a solvent so as to obtain a spinning solution; a step for performing wet spinning by using the spinning solution so as to obtain an undrawn fiber; and a step for drawing the undrawn fiber so as to obtain a polyamide 4 fiber. The polyamide 4 has a weight average molecular weight (Mw) of 400,000 or more and a molecular weight distribution (Mw/Mn) of 1.0-4.5. Instead of including methylene chloride, the solvent includes formic acid. The concentration of dissolved polyamide 4 in the spinning solution is 10 wt% or more. A coagulation bath used in the wet spinning is an organic solvent that includes an alkyl acetate solvent. In the drawing step, the drawing temperature is higher than 160 DEG C and lower than 240 DEG C, and the drawing ratio is 2 times or more.

Description

Manufacturing method of polyamide 4 fiber

The present invention relates to a method for producing polyamide 4 fibers by wet spinning. This case claims priority to Japanese Patent Application No. 2020-105823 filed on June 19, 2020, the content of which is incorporated herein by reference.

Polyamide 4 obtained by polymerizing 2-pyrrolidone is expected as a material excellent in 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 that can fully utilize the physical properties of polyamide 4, and research and development have been conducted in the past. However, since the melting point of polyamide 4 is close to the decomposition temperature, it is difficult to be fiberized by the melt spinning method. Therefore, as a fiberizing method with less thermal runaway, a wet spinning method has been studied.

In Patent Document 1, there is described a technique of preparing a spinning solution by dissolving polyamide 4 in formic acid and methylene chloride, and performing wet spinning. In Patent Document 2, there is described a technique of dissolving polyamide 4 in formic acid and methylene chloride to prepare a spinning solution, and performing wet spinning using a coagulation bath composed of a lower alkyl ester. In Patent Document 3, it is described that 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 a wet process is performed using a coagulation bath containing an aqueous solution of at least one formate. spinning technology. In Patent Document 4, there is described a technique of preparing a spinning solution by dissolving it 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, it is described that 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 is used, and a coagulation bath containing methanol is used to perform wet spinning. Undrawn fibers of polyamide 4 were obtained by the silk method. However, it is described that the unstretched fibers are not stretchable. Patent Document 6 describes a technique for preparing a spinning solution by dissolving polyamide 4 in an ionic liquid, and obtaining polyamide 4 fibers by wet or dry-wet spinning or gel spinning. prior art literature Patent Literature

Patent Document 1: Specification of US Patent No. 4,094,945 Patent Document 2: Japanese Patent Laid-Open No. 53-24420 Patent Document 3: Japanese Patent Laid-Open No. 57-25413 Patent Document 4: Japanese Patent Publication No. Sho 36-5165 Patent Document 5: Japanese Patent Laid-Open No. 2019-137934 Patent Document 6: International Publication No. 2015/186364

[Problems to be Solved by Invention]

In the method described in Patent Document 1 or 2, residual methylene chloride becomes a problem, and a removal operation is necessary. Moreover, in the method described in Patent Document 3 or 4, it is necessary to remove the salt component, and the operation becomes complicated. The method described in Patent Document 5 does not seem to be able to stretch unstretched fibers. Since the method described in Patent Document 6 uses an expensive ionic liquid, it is difficult to industrialize. An object of the present invention is to provide a method for producing a polyamide 4 fiber by a wet spinning method that does not require a residual component removal operation. Furthermore, the subject of the present invention is to provide a method for producing a polyamide 4 fiber by a wet spinning method that does not require the use of expensive materials. [Technical means to solve problems]

The present inventors have completed the present invention as a result of earnest studies in order to solve the above-mentioned problems. The present invention includes the following aspects. (1) a kind of manufacture method of polyamide 4 fiber, is characterized in that comprising: The step of dissolving polyamide 4 in a solvent to obtain a spinning solution; A step of wet spinning using the above spinning solution to obtain unstretched fibers; and The step of extending the above-mentioned unextended fibers to obtain polyamide 4 fibers; The weight average molecular weight (Mw) of the above-mentioned polyamide 4 is 400,000 or more, and the molecular weight distribution (Mw/Mn) is 1.0 to 4.5, The above-mentioned solvent is a solvent that does not contain dichloromethane and contains formic acid, In the above-mentioned spinning solution, the concentration of the above-mentioned polyamide 4 dissolved is 10% by weight or more, The coagulation bath used in the above wet spinning is an organic solvent containing an alkyl acetate solvent, The stretching temperature in the stretching step is 160° C. or more and 240° C. or less, and the stretching ratio is 2 times or more. (2) The production method according to (1), wherein the tensile strength of the polyamide 4 fiber is 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. [Effect of invention]

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

The manufacturing method of the polyamide 4 fiber of the present invention is not particularly limited as long as it includes the following steps: the step of dissolving the polyamide 4 in a solvent to obtain a spinning solution (hereinafter, sometimes described as step A); using the above The step of wet spinning the spinning solution to obtain unstretched fibers (hereinafter, sometimes referred to as step B); the step of stretching the above-mentioned unstretched fibers to obtain polyamide 4 fibers (hereinafter, sometimes abbreviated as step B) step C). According to the manufacturing method of the polyamide 4 fiber of the present invention, the polyamide 4 fiber with higher tensile strength can be manufactured.

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

＜Polyamide 4＞ The polyamide 4 used in the 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, and 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 tensile strength of the obtained polyamide 4 fiber tends to decrease. In addition, 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) exceeds 1,000,000, the spinnability of polyamide 4 tends to decrease.

The molecular weight distribution (Mw/Mn) of polyamide 4 is not particularly limited, and can be selected in the range of 1.0 to 4.5, 1.0 to 4.0, 1.0 to 3.5, 1.0 to 3.0, and the like. Polyamide 4 fibers obtained from polyamide 4 having a smaller molecular weight distribution tended to have higher tensile strengths. Furthermore, the weight average molecular weight and the number average molecular weight can be measured by gel permeation chromatography (GPC) using a solution obtained by dissolving sodium trifluoroacetate in hexafluoroisopropanol at a concentration of 10 mM as a solvent. , the measured data is calculated by converting the molecular weight of standard polymethyl methacrylate.

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 Japanese Patent Laid-Open No. 2019-137934.

The 2-pyrrolidone used as a raw material is obtained from petroleum producers, and producers of biologically derived materials such as γ-aminobutyric acid using enzymes derived from microorganisms, and the like. Commercially available products from petroleum production can be readily obtained.

<Solution for spinning> The solvent for dissolving the polyamide 4 in the step A of the present invention is a solvent containing formic acid. Examples of the solvent containing formic acid include a solvent composed of formic acid alone, and a solvent containing formic acid and other solvents. It does not specifically limit as said other solvent, Water, hexafluoroisopropanol, trifluoroacetic acid, etc. are mentioned. These can be used alone or in combination of two or more. The concentration of formic acid in the solvent containing formic acid and other solvents can be selected from 40 wt% or more, 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, 95 wt% or more, etc. . In the step A of the present invention, the solvent for dissolving the polyamide 4 is preferably a solvent that does not contain dichloromethane.

The concentration of polyamide 4 in the spinning solution is not particularly limited, and 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. The upper limit of the polyamide 4 concentration can be selected from 60% by weight, 50% by weight, 40% by weight, and the like.

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

(step B) Step B of the present invention is a step of wet spinning using the spinning solution obtained in Step A to obtain unstretched fibers. In the present invention, wet spinning refers to a spinning method including a step of extruding a spinning solution from one or a plurality of holes in a coagulation bath and processing it into a fibrous form (undrawn yarn).

One form of the wet spinning of the present invention is shown and described in FIG. 1 . The spinning solution obtained in Step A was put into a tank. The solution for spinning (the solution for spinning in FIG. 1 ) was supplied with nitrogen pressure to the nozzle (the nozzle in FIG. 1 ), and it was extruded from the nozzle hole into the coagulation bath (the coagulation bath in FIG. 1 ). The extruded fibers are taken up by a take-up roll. The wound fibers were dried under reduced pressure to obtain unextended fibers.

The coagulation bath used in the wet spinning of step B is preferably an organic solvent containing an alkyl acetate solvent. As an alkyl acetate solvent, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, etc. are mentioned. 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, and can be appropriately set within the range of inner diameter 0.001 mm to 10 mm, inner diameter 0.01 mm to 10 mm, inner diameter 0.01 mm to 1 mm, and inner diameter of 0.01 mm to 0.5 mm. The number of nozzle holes may be one or plural. When the number of nozzle holes is one, the obtained fibers are monofilaments, and when the number of nozzle holes is plural, the obtained fibers are multifilaments. As the polyamide 4 fiber of the present invention, a multifilament is preferable. The number of multifilament yarns is not particularly limited, and can be selected from 5 to 200, 20 to 200, 50 to 200, 50 to 150, and the like.

(step C) Step C of the present invention is a step of extending the unstretched polyamide 4 fibers obtained in step B to obtain polyamide 4 fibers. By extending the unstretched polyamide 4 fiber, a polyamide 4 fiber having higher tensile strength can be obtained.

＜Extended＞ The stretching operation is not particularly limited, and the unstretched fibers can be stretched by a previously used uniaxial stretching device. The lower limit of the extension 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 extension temperature can be selected from 240°C, 230°C, 220°C, and 210°C. When the stretching temperature is higher than 240°C, the polyamide 4 tends to be easily decomposed. The stretching ratio is not particularly limited, and can be selected from 2.0 times or more, 2.5 times or more, and the like. By setting the draw ratio to 2.0 times or more, a polyamide 4 fiber with high tensile strength can be obtained.

(Other step D) In addition to Step A, Step B, and Step C, the manufacturing method of the polyamide 4 fiber of the present invention may include other Step D. The other step D is not particularly limited as long as the object of the present invention is not impaired, and examples thereof include a degassing step of the spinning solution, a drying step of unstretched fibers, and the like.

(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. The polyamide 4 fibers obtained by the production method of the present invention can be applied to a wide range of applications such as clothing, ropes, and tire cords. Example

Hereinafter, the present invention will be described in detail 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 were weighed and mixed with 60 g of formic acid (99% formic acid). The solution was left to stand at room temperature until no dissolving residue was observed visually, and a spinning solution having a polyamide 4 concentration of 20% by weight was obtained.

＜Wet spinning＞ The outline of the wet spinning apparatus is shown in FIG. 1 above. The spinning solution obtained in the above was transferred to a tank and left to stand at room temperature for 12 hours, thereby removing air bubbles in the solution. A nitrogen pressure of 0.2 MPa was applied to the spinning solution in the tank, and it was extruded from a platinum nozzle (inner diameter 0.09 mm, 100 holes) into an ethyl acetate coagulation bath (coagulation bath length: 2 m), and coiled roll for coiling. The coiled undrawn fibers were dried under reduced pressure at 40°C for 2 hours.

＜Extended＞ One end of the above-mentioned undrawn fiber obtained by wet spinning was fixed, and the other end was drawn at a speed of 10 mm/s on a heat press adjusted to 200°C. The unstretched fiber was stretched to a length of 2.5 times (stretching 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, the nitrogen pressure was set to 0.5 MPa during wet spinning, and the stretching temperature was set to 180°C during stretching , except that the draw ratio was 4 times, it carried out similarly to Example 1, and obtained the polyamide 4 fiber b.

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, the nitrogen pressure was set to 0.05 MPa during wet spinning, and the stretching speed was set to 1 mm during stretching A polyamide 4 fiber c was obtained in the same manner as in Example 1, except that the draw ratio was 3 times per second.

Comparative Example 2 Production of Polyamide 4 Fiber d Polyamide 4 with a weight average molecular weight (Mw) of 653,000 and a molecular weight distribution (Mw/Mn) of 5.03 was used, and the nitrogen pressure was set to 0.15 MPa during wet spinning, and the stretching temperature was set to 180°C during stretching , except that the draw ratio was 3 times, it carried out similarly to Example 1, and obtained the polyamide 4 fiber d.

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, the nitrogen pressure was set to 0.15 MPa during wet spinning, and the stretching temperature was set to 180°C during stretching, A polyamide 4 fiber e was obtained in the same manner as in Example 1, except that the draw ratio was 2.5 times.

The following measurements were performed on the polyamide 4 fibers a to e obtained in the examples and comparative examples. The results are shown in Table 1.

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

<Modulus of elasticity> The modulus of elasticity of the fiber was measured using a tensile tester (STA-1150) manufactured by ORIENTEC Corporation. Under the conditions of a test piece length of 20 mm and a tensile speed of 30 mm/min, a tensile test was carried out at room temperature to obtain the stress. - Strain curve. Then, the slope of the straight line portion at the initial stage of the curve is calculated, and the modulus of elasticity (GPa) is obtained.

<tensile strength> The tensile strength of the fiber was obtained by using a tensile tester (STA-1150) manufactured by ORIENTEC, under the conditions of a test piece length of 20 mm and a tensile speed of 30 mm/min at room temperature. Breaking strength (cN) in tensile test. In addition, the strength (unit: cN/dtex) calculated using the fineness measured in the above is referred to as the tensile strength.

[Table 1] Polyamide 4 fiber fiber a fiber b fiber c fiber d fiber e Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Fineness [dtex] 13.5 5.9 15.0 36.4 11.4 Elastic modulus [GPa] 4.68 3.08 2.79 1.59 3.74 Tensile strength [cN/dtex] 3.03 3.14 2.66 2.56 2.21

According to Table 1, the polyamide 4 fibers a and b produced by the method for producing polyamide 4 fibers of the present invention show higher tensile strength (3 cN /dtex or more).

Fig. 1 is a conceptual diagram showing an aspect of the wet spinning of the present invention.

Claims (4)

A kind of manufacture method of polyamide 4 fiber, it is characterized in that comprising: The step of dissolving polyamide 4 in a solvent to obtain a spinning solution; A step of wet spinning using the above spinning solution to obtain unstretched fibers; and The step of extending the above-mentioned unextended fibers to obtain polyamide 4 fibers; The weight average molecular weight (Mw) of the above-mentioned polyamide 4 is 400,000 or more, and the molecular weight distribution (Mw/Mn) is 1.0 to 4.5, The above-mentioned solvent is a solvent that does not contain dichloromethane and contains formic acid, In the above-mentioned spinning solution, the concentration of the above-mentioned polyamide 4 dissolved is 10% by weight or more, The coagulation bath used in the above wet spinning is an organic solvent containing an alkyl acetate solvent, The stretching temperature in the above-mentioned stretching step is 160° C. or more and 240° C. or less, and the stretching ratio is 2 times or more. The manufacturing method of claim 1, wherein the tensile strength of the polyamide 4 fiber is 3 cN/dtex or more. The production method of claim 1 or 2, wherein the polyamide 4 fiber is a polyamide 4 multifilament. The production method of claim 3, wherein the number of polyamide 4 multifilaments is 5 to 200.

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