CN110055601B - Wet spinning method of polyacrylonitrile fiber and polyacrylonitrile fiber - Google Patents

Abstract

The present invention relates to a wet spinning method of polyacrylonitrile fiber and polyacrylonitrile fiber. The main technical scheme adopted is: a method for wet spinning of polyacrylonitrile fibers, comprising the following steps: spinning: spinning liquid is extruded through spinning holes of a spinning assembly to obtain a spinning stream; coagulation and molding: The spinning thin stream enters a coagulation bath for coagulation and molding to obtain spun fibers; thermal drawing treatment: multi-stage thermal drawing treatment is performed on the spun fibers; water washing treatment: the fibers after the thermal drawing treatment are subjected to water washing treatment; Drying and heat-setting treatment: drying and heat-setting treatment are sequentially performed on the washed fibers to obtain polyacrylonitrile fibers. A polyacrylonitrile fiber is prepared by the above-mentioned wet spinning method of polyacrylonitrile fiber. The invention is mainly used for ensuring the spinnability of the spinning solution in the spinning process and improving the mechanical properties of the polyacrylonitrile fiber.

Description

A kind of wet spinning method of polyacrylonitrile fiber and polyacrylonitrile fiber

technical field

The invention relates to the technical field of polyacrylonitrile fibers, in particular to a wet spinning method of polyacrylonitrile fibers and polyacrylonitrile fibers.

Background technique

Polyacrylonitrile fiber is one of the three major synthetic fibers in the world. It has the advantages of good elasticity, soft hand feeling and good warmth retention. It is called "synthetic wool", so it is widely used in clothing, decoration, outdoor textiles and other fields. However, the limiting oxygen index (LOI) value of polyacrylonitrile fiber is only 17-18.5%, which is one of the extremely flammable synthetic fibers, which is easy to cause fire and threaten people's life and property safety during use. Therefore, flame retardant polyacrylonitrile fiber has also become a hot spot in the development and research of synthetic fiber industries in various countries.

Because the polymer chemical modification method has the advantages of less amount of flame retardant monomer, the longest flame retardant effect and lower cost, companies such as Eastman in the United States, Courtaulds in the United Kingdom, and Zhongyuan in Japan all use this method to produce flame retardants. Fire polyacrylonitrile fiber. Although my country began to study the production technology of flame retardant acrylic fiber in the 1960s, due to the slow development of production technology and equipment, the spinning technology of flame retardant acrylic fiber is almost blank, and it has not been industrialized on a large scale.

The inventors of the present invention found that the research in the prior art basically focused on the improvement of the LOI (limiting oxygen index) of polyacrylonitrile fibers, but the resulting spinning solution had poor spinnability in the spinning process, and the The decrease of mechanical properties of polyacrylonitrile fibers is less taken into account.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a wet spinning method of polyacrylonitrile fiber and polyacrylonitrile fiber, the main purpose is to ensure the spinnability of the spinning solution in the spinning process and improve the mechanical properties of the fiber.

To achieve the above object, the present invention mainly provides the following technical solutions:

On the one hand, an embodiment of the present invention provides a wet spinning method of polyacrylonitrile fiber, which comprises the following steps:

Spinning: The spinning solution is extruded through the spinneret holes of the spinneret assembly to obtain a spinning stream;

Coagulation and molding: the spinning thin stream enters the coagulation bath for coagulation and molding to obtain primary fibers;

Heat-drawing treatment: heat-drawing the spun fibers;

Washing treatment: Washing the fibers after heat drawing treatment;

Drying and heat-setting treatment: drying and heat-setting treatment are sequentially performed on the washed fibers to obtain polyacrylonitrile fibers.

The purpose of the present invention and the solution to its technical problems can be further achieved by adopting the following technical measures.

Preferably, in the step of the thermal drawing treatment, the drawing medium is glycerin; and/or the thermal drawing treatment is a multi-stage thermal drawing treatment; wherein, the temperature of the previous stage of thermal drawing is lower than that of the latter stage. The temperature of the primary thermal drawing; preferably, the temperature of the thermal drawing treatment is 100-130°C.

Preferably, in the step of thermal drawing treatment, the nascent fibers are subjected to three-stage thermal drawing treatment; wherein, the temperature of the first-stage thermal drawing is 100-105°C, and the temperature of the first-stage thermal drawing The multiple is 1.2 to 2 times; and/or the temperature of the second-stage hot drawing is 110-120°C, and the second-stage heat-drawing multiple is 2 to 3 times; and/or the temperature of the third-stage heat drawing is 125～130℃, the multiple of the third-stage thermal drawing is 1.2～2 times.

Preferably, in the step of washing with water: the temperature of the washing with water is 50-70° C., and the time of washing with water is 1-3 min.

Preferably, the drying step in the drying and heat-setting treatment steps is: vacuum drying the fibers after the water washing treatment; preferably, the drying treatment temperature is 40-50° C., and the drying treatment time is 12-24 h ;and / or

The heat setting treatment steps in the drying and heat setting treatment steps include:

Relaxation heat setting: the dried fibers are subjected to relaxation heat setting; preferably, in the relaxation heat setting step, glycerol is selected as the medium for negative drafting; preferably, in the relaxation heat setting step, the temperature is 140～ 150℃, negative draft rate -30% to -10%;

Washing: washing the fibers after the relaxation heat setting treatment; preferably, the temperature of the washing is 60-80°C, and the washing time is 3-5 minutes;

Drying and heat-setting: drying and heat-setting the washed fibers; preferably, the drying and heat-setting temperature is 50-60° C., and the drying and heat-setting time is 12-24 h; preferably, the drying and heat-setting Under vacuum conditions.

Preferably, the diameter of the spinneret is 0.065-0.1 mm.

Preferably, in the step of solidifying and forming: the solidifying bath includes:

First-stage coagulation bath: the first-stage coagulation bath includes solvent and water; wherein, the solvent in the first-stage coagulation bath is selected from one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide; Preferably, the solvent content in the first-stage coagulation bath is 30-60%; preferably, the temperature of the first-stage coagulation bath is 30-60°C;

Secondary coagulation bath: the secondary coagulation bath includes solvent and water; wherein, the solvent in the secondary coagulation bath is selected from one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide; Preferably, the solvent content in the secondary coagulation bath is 15-25%; preferably, the temperature of the secondary coagulation bath is 60-80°C;

Wherein, the spinning thin stream first enters the primary coagulation bath for coagulation and formation to obtain coagulated filaments, and the coagulated filaments then enter the secondary coagulation bath for coagulation and formation.

Preferably, the coagulation time of the spinning fine stream in the first-stage coagulation bath is 20-100s, and the negative draft ratio is -50% to -20%; and/or

The coagulation time of the coagulated thread in the secondary coagulation bath is 30-120s, and the stretching ratio is 1.2-1.5 times.

Preferably, the spinning solution is prepared by the polymerization reaction of main monomer acrylonitrile, comonomer, solvent and initiator;

Preferably, the comonomer is selected from halogenated olefins with a halogen content greater than that in vinyl chloride; preferably, the comonomer is selected from one or both of vinylidene chloride and vinylidene bromide;

Preferably, acrylonitrile accounts for 40-60% of the mass of the total monomer, and the comonomer accounts for 40-60% of the mass of the total monomer; wherein, the mass of the total monomer is the sum of the mass of the main monomer and the comonomer;

Preferably, the solvent is one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide;

Preferably, the initiator is azobisisobutyronitrile;

Preferably, the conversion rate of the polymerization reaction is greater than 90%;

Preferably, the solid content of the spinning solution is 30-40%;

Preferably, the use temperature of the spinning solution is 30-60°C.

On the other hand, an embodiment of the present invention provides a polyacrylonitrile fiber, wherein the fineness of the polyacrylonitrile fiber is 1.7-2.2 dtex; the strength of the polyacrylonitrile fiber is 2.2-3.2 cN/dtex; The elongation of the polyacrylonitrile fiber is 26-38%; preferably, the limiting oxygen index LOI value of the polyacrylonitrile fiber is 26.5-30%; preferably, the polyacrylonitrile fiber is made of any one of the above The polyacrylonitrile fiber is prepared by the wet spinning method.

Compared with the prior art, the wet spinning method of polyacrylonitrile fiber and polyacrylonitrile fiber of the present invention have at least the following beneficial effects:

1. The wet spinning method of polyacrylonitrile fiber proposed by the present invention adopts "the step of firstly drawing with water and then washing with water" instead of "the step of firstly washing with water and then drawing" in the prior art. The inventors of the present invention found that by using the method of "washing first and then drawing" in the prior art, the draftability of the fibers during hot water drafting and high temperature drafting is very poor, that is, the spinning solution may have poor draftability using the existing spinning process. Poor spinnability. However, the inventor proposed for the first time that after coagulation and molding, first drafting and then washing with water; in this way, the solvent content in the nascent fibers from the coagulation bath is relatively high, and the solvent will play a role in plasticizing between molecular chains in the fibers, which is beneficial to The draft ratio of hot drafting is improved, thereby solving the technical problem of poor spinnability.

2. The wet spinning method of polyacrylonitrile fiber proposed by the present invention combines "hot water drawing" and "steam drawing" in the prior art process into one (ie, hot drawing treatment). Compared with the prior art, the molecular chain relaxation time in the long process is reduced, the orientation degree is improved, and the fiber performance is improved. Further, different from the "steam drafting" in the prior art, the present application adopts three-stage thermal drafting and uses glycerol as the drafting medium to draw the fibers at high temperature. Steam drafting equipment has low requirements and strong operability.

3. The drying treatment step in the wet spinning method of polyacrylonitrile fiber proposed by the present invention adopts vacuum drying, and drying in vacuum environment is conducive to the closure of micropores in the fiber, reducing fiber defects and further improving fiber performance, and drying under vacuum conditions The temperature is lowered to prevent premature oxidation of the fibers.

4. The wet spinning method of polyacrylonitrile fiber proposed by the present invention selects suitable conditions such as the use temperature of the spinning solution, the temperature of the coagulation bath, and the concentration, which greatly improves the spinnability of the flame-retardant polyacrylonitrile spinning solution. In the hot drawing process, glycerol medium is used for multi-stage high-stretching, which improves the mechanical properties of the fiber.

The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, and to implement according to the content of the description, the preferred embodiments of the present invention are described in detail below.

Detailed ways

In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific embodiments, structures, features and effects of the application according to the present invention are described in detail below in conjunction with the preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

The wet spinning process of the polyacrylonitrile fiber in the prior art is as follows: 1. spinning, 2. coagulation, 3. washing with water, 4. hot water drawing, 5. drying, 6. steam drawing, 7. relaxation heat setting.

The inventors of the present invention have found that while the flame retardancy of polyacrylonitrile fibers is improved by the polymer modification method, if the spinning solution is spun according to the above-mentioned existing spinning process, there will be poor spinning performance and polyacrylonitrile obtained. Technical problems with poor mechanical properties of fibers.

In order to solve the above-mentioned technical problems, the present invention proposes a method for wet spinning of polyacrylonitrile fibers, which sequentially comprises the following steps:

Spinning: Wet spinning is adopted, and the diameter of the spinneret hole is 0.065-0.1 mm.

Coagulation and molding: the spinning thin stream formed after leaving the spinneret hole enters into coagulation baths with different concentrations in turn. The first-stage coagulation bath includes solvent and water; wherein, the solvent in the first-stage coagulation bath is selected from one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide. The secondary coagulation bath includes solvent and water; wherein, the solvent in the secondary coagulation bath is selected from one or more of dimethyl sulfoxide, dimethyl formamide and dimethyl acetamide.

Wherein, the content of the solvent in a coagulation bath is 30-60%, the temperature is 30-60 DEG C, the negative draft is -50% to -20%, and the coagulation time is 20-100s. The content of the solvent in the secondary coagulation bath is 15-25%, the temperature is 60-80 DEG C, the stretching is 1.2-1.5 times, and the coagulation time is 30-120s to obtain the primary fibers.

Heat-drawing treatment: The primary fibers undergo three-stage heat-drawing, the temperature is from low to high, the drawing medium is glycerin, the temperature of the first stage is 100~105℃, and the drawing is 1.2~2 times; ～120℃, the drafting is 2～3 times; the temperature of the third stage is 125～130℃, and the drafting is 1.2～2 times.

Washing treatment: Wash the fibers after the thermal drawing treatment, the washing temperature is 50-70 °C, and the washing time is 1-3 min.

Drying and heat-setting treatment: including drying and heat-setting treatment steps; wherein, drying: vacuum-drying the fibers after water washing treatment at a temperature of 40-50° C. for 12-24 hours.

The heat setting treatment steps include: relaxation heat setting, water washing, drying heat setting. Specifically, the dried fibers are subjected to relaxation heat setting, the medium is glycerin, the temperature is 140-150° C., and the negative draft is -30% to -10%. After that, the fibers after relaxation and heat setting are washed with water at a temperature of 60-80 °C and a washing time of 3-5 minutes; finally, the fibers after washing are subjected to drying and heat-setting at a temperature of 50-60 °C for 12-24 hours to obtain Polyacrylonitrile fibers; preferably, drying and heat-setting is carried out under vacuum conditions; vacuum conditions are conducive to the escape of water molecules in the fibers, the porosity is further reduced, and polyacrylonitrile fibers with better density can be prepared.

By comparing the technology of the present application and the prior art, it can be found that the spinning process of the present application and the prior art has the following points of difference:

(1) The present invention adopts "the step of drawing with water first and then washing with water" instead of the conventional "step of drawing with water first and then with water". The inventors of the present invention found that by using the conventional method of "washing and then drafting", the draftability of the fibers during hot water drafting and high temperature drafting is very poor, that is, the spinning solution using the conventional spinning process will have poor spinnability. . The inventors of the present invention proposed for the first time that after coagulation and molding, firstly drawing and then washing with water; in this way, the solvent content in the as-grown fibers from the coagulation bath is relatively high, and the solvent will play a plasticizing effect between molecular chains in the fibers. It is beneficial to increase the draft ratio of hot drafting, thereby solving the technical problem of poor spinnability.

(2) The present invention combines "hot water drafting" and "steam drafting" in the prior art process into one (ie, hot drafting treatment). Compared with the prior art, the molecular chain relaxation time in the long process is reduced, the orientation degree is improved, and the fiber performance is improved.

(3) Different from the "steam drafting" of the prior art, the present application adopts three-stage thermal drafting and uses glycerol as the drafting medium to draw the fibers at high temperature. Steam drafting equipment has low requirements and strong operability.

(4) Compared with the normal pressure drying in the prior art, the drying treatment step of the present invention adopts vacuum drying, and vacuum drying is beneficial to the closure of micropores in the fiber, reducing fiber defects and further improving performance, and the drying temperature under vacuum conditions can be reduced. Prevents premature oxidation of fibers.

(5) In the prior art, the fiber has been collected after the "relaxation heat setting" step. Because the purpose of performing water washing and drying heat setting after the "relaxation heat setting" step of the present invention is to clean the glycerin on the fibers after relaxation heat setting, and at the same time, in order to reduce the water content, a final step of drying heat setting is required.

Preferably, in the wet spinning method of polyacrylonitrile fiber proposed by the present invention, the spinning solution used is composed of main monomer polyacrylonitrile, comonomer (vinylidene chloride or vinylidene bromide or other halogen content) The halogenated olefin with a chlorine content greater than that in vinyl chloride; that is, as long as the halogenated olefin with a halogen content higher than the chlorine content in vinyl chloride can be used as the comonomer of the present application), an initiator and a solvent are prepared by copolymerization.

Preferably, acrylonitrile is 40-60% of the total monomer weight, and the comonomer is 40-60% of the total monomer weight; more preferably, the comonomer is 50-60% of the total monomer weight. %. Here, in the embodiment of the present invention, vinylidene chloride and/or vinylidene bromide are used as comonomers for copolymerization with acrylonitrile. Compared with the vinyl chloride used in the traditional process, vinylidene chloride and vinylidene bromide are not only reaction conditions It is mild, the process is simple and safe, and the halogen content in its own monomer is twice that of vinyl chloride, which can achieve high flame retardant performance at a lower monomer dosage.

Preferably, the initiator in the embodiment of the present invention is azobisisobutyronitrile; preferably, the initiator is 0.8-1% of the mass of the total monomer; more preferably, the initiator is the total monomer 0.91 to 1% of the mass. Here, the initiator AIBN used in the embodiment of the present invention is an azo initiator, the decomposition temperature of the initiator is above 35°C, and the initiation efficiency is high, and the conversion rate of 93.15% can be achieved within 13 hours of the reaction, which is suitable for high efficiency and low efficiency. cost industrial production.

Preferably, the solvent is a mixed solvent of one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide. Preferably, in the reaction mixture, the mass percentage concentration of the copolymerization component is 30-40%; preferably, it is 33-40%.

Preferably, in the spinning step, the solid content of the spinning solution is 30-40%.

Preferably, the use temperature of the spinning solution is 30-60°C.

The following is further described in detail by specific experimental examples:

Example 1

Preparation of spinning solution: using initiator azobisisobutyronitrile, the main monomer acrylonitrile and comonomer vinylidene chloride are polymerized in solvent dimethyl sulfoxide (among them, acrylonitrile accounts for 3% of the total monomer mass. 60%, vinylidene chloride accounts for 40% of the total monomer mass, the initiator dosage is 0.8% of the total monomer mass, the solvent dosage accounts for 70% of the polymerization system mass (that is, the total mass of the reactants), and the polymerization temperature is 70 ℃ , the reaction time is 20h) to obtain a polymer solution; after the polymer solution is treated by de-monolysis and defoaming, a spinning solution is obtained. Among them, the polymerization conversion rate was 96.2%, the solid content of the spinning solution was 30%, and the use temperature of the spinning solution was 60°C, and the spinning solution was spun.

Spinning: Wet spinning is adopted, and the diameter of the spinneret hole is 0.065mm.

Coagulation and molding: after the spinning thin stream leaves the spinneret, it enters the first-stage coagulation bath (the content of dimethyl sulfoxide is 30%, the temperature is 60 ° C) and the second-stage coagulation bath (the content of dimethyl sulfoxide is 15%, at a temperature of 60° C.), coagulation and molding to obtain primary fibers. Among them, the coagulation time of the spinning thin stream in the first-stage coagulation bath is 20s, the negative draft rate is -50%, and the coagulated yarn is obtained; the coagulation time of the coagulated yarn in the second-stage coagulation bath is 30s, and the stretching ratio is 1.5 times.

Hot drawing: The primary fiber strips undergo three-stage hot drawing, the temperature is from low to high, the drawing medium is glycerin, the temperature of the first stage is 100 ℃, and the drawing is 1.2 times; the temperature of the second stage is 110 ℃, and the drawing is 1.2 times. 3 times; the third stage temperature is 125 ℃, and the draft is 1.8 times.

One-time washing: Wash the hot-drawn fibers with water at a temperature of 50°C and a wash time of 1 min.

Primary drying: vacuum drying the fibers after primary water washing at 40°C for 24 hours.

Relaxation heat setting: The thread after drying is subjected to relaxation heat setting, the medium is glycerin, the temperature is 150°C, and the negative draft rate is -30%.

Secondary washing: the fibers after relaxation and heat setting are washed twice, the washing temperature is 60°C, and the washing time is 5 minutes.

Drying and heat-setting: drying and heat-setting the fibers after the secondary water washing, drying at 50° C. for 24 hours, to obtain flame-retardant polyacrylonitrile fibers.

Example 2

Preparation of spinning solution: using initiator azobisisobutyronitrile, the main monomer acrylonitrile and comonomer dibromide are polymerized in the solvent dimethyl sulfoxide (among them, acrylonitrile accounts for 3% of the total monomer mass. 55%, vinylidene bromide accounts for 45% of the total monomer mass, the initiator dosage is 0.8% of the total monomer mass, the solvent dosage accounts for 65% of the polymerization system mass, the polymerization reaction temperature is 65°C, and the reaction time is 16h) to obtain the polymerization The spinning solution is obtained after the polymerization solution is treated by de-monolysis and defoaming. Among them, the polymerization conversion rate was 93.5%, the solid content of the spinning solution was 35%, and the use temperature of the spinning solution was 50°C, and the spinning solution was spun.

Spinning: Wet spinning is adopted, and the diameter of the spinneret hole is 0.075mm.

Coagulation molding: after the spinning thin stream leaves the spinneret, it enters the first-stage coagulation bath (the content of dimethyl sulfoxide is 60%, the temperature is 55 ° C) and the second-stage coagulation bath (the content of dimethyl sulfoxide is 25%, and the temperature is 60° C.) to solidify and form to obtain primary fibers. Among them, the coagulation time of the spinning thin stream in the first-stage coagulation bath is 60s, the negative draft rate is -35%, and the coagulated yarn is obtained; the coagulation time of the coagulated yarn in the second-stage coagulation bath is 120s, and the stretching ratio is 1.2 times.

Hot drawing: The primary fiber strips undergo three-stage hot drawing, the temperature is from low to high, and the drawing medium is glycerol. The temperature of the first stage is 102°C, and the drawing is 1.5 times; 2.5 times; the temperature of the third stage is 128℃, and the draft is 2 times.

One-time washing: Wash the hot-drawn fibers with a washing temperature of 70°C and a washing time of 2 minutes.

Primary drying: vacuum drying the fibers after primary water washing at 50°C for 12 hours.

Relaxation heat setting: The thread after drying is subjected to relaxation heat setting, the medium is glycerin, the temperature is 145°C, and the negative draft rate is -20%.

Secondary washing: the fibers after relaxation and heat setting are washed twice, the washing temperature is 80 °C, and the washing time is 3 minutes.

Drying and heat-setting: drying and heat-setting the fibers after secondary water washing, drying at 60° C. for 12 hours, to obtain flame-retardant polyacrylonitrile fibers.

Example 3

Preparation of spinning solution: using initiator azobisisobutyronitrile, the main monomer acrylonitrile and comonomer vinylidene chloride are polymerized in the solvent dimethylacetamide (wherein, acrylonitrile accounts for 3% of the total monomer mass. 60%, vinylidene chloride accounts for 40% of the total monomer mass, the initiator dosage is 0.8% of the total monomer mass, the solvent dosage accounts for 60% of the polymerization system mass, the polymerization reaction temperature is 65°C, and the reaction time is 20h) to obtain the polymerization The spinning solution is obtained after the polymerization solution is treated by de-monolysis and defoaming. Among them, the polymerization conversion rate was 91.8%, the solid content of the spinning solution was 40%, and the use temperature of the spinning solution was 30°C, and the spinning solution was spun.

Spinning: Wet spinning is adopted, and the diameter of the spinneret hole is 0.1 mm.

Coagulation molding: after the spinning thin stream leaves the spinneret, it enters the first-stage coagulation bath (the content of dimethylacetamide is 56%, and the temperature is 30 ° C) and the second-stage coagulation bath (the content of dimethylacetamide is 56%). 20% at a temperature of 80° C.) to form primary fibers. Among them, the coagulation time of the spinning thin stream in the first-stage coagulation bath is 100s, and the negative draft rate is -20%, so as to obtain coagulated filaments; 1.4 times.

Hot-drawing: The primary fiber strips undergo three-stage hot-drawing, the temperature is from low to high, the drawing medium is glycerin, the temperature of the first stage is 105℃, and the drawing is twice; 2 times; the temperature of the third stage is 130 ℃, and the draft is 1.2 times.

One-time washing: Wash the hot-drawn fibers with a washing temperature of 60°C and a washing time of 3 minutes.

Primary drying: vacuum-drying the fibers after primary water washing at 45°C for 18 hours.

Relaxation heat setting: The thread after drying is subjected to relaxation heat setting, the medium is glycerin, the temperature is 150°C, and the negative draft rate is -10%.

Secondary washing: the fibers after relaxation and heat setting are washed twice, the washing temperature is 70 °C, and the washing time is 4 minutes.

Drying and heat-setting: drying and heat-setting the fibers after the secondary water washing, at a temperature of 55° C., and drying for 18 hours to obtain flame-retardant polyacrylonitrile fibers.

Example 4

Preparation of spinning solution: using initiator azobisisobutyronitrile, the main monomer acrylonitrile and comonomer vinylidene chloride are polymerized in the solvent dimethylformamide (wherein, acrylonitrile accounts for 3% of the total monomer mass. 50%, vinylidene chloride accounts for 50% of the total monomer mass, the initiator dosage is 0.9% of the total monomer mass, the solvent dosage accounts for 65% of the mass of the polymerization system, the polymerization temperature is 68 ° C, and the reaction time is 22h) to obtain the polymerization The spinning solution is obtained after the polymerization solution is treated by de-monolysis and defoaming. Among them, the polymerization conversion rate was 92.4%, the solid content of the spinning solution was 35%, and the use temperature of the spinning solution was 40°C, and the spinning solution was spun.

Spinning: Wet spinning is adopted, and the diameter of the spinneret hole is 0.1 mm.

Coagulation molding: After the spinning thin stream leaves the spinneret, it enters the first-stage coagulation bath (the content of dimethylformamide is 40%, the temperature is 50 ° C) and the second-stage coagulation bath (the content of dimethylformamide is 40%). 15%, and the temperature is 70° C.) to solidify and form to obtain primary fibers. Among them, the coagulation time of the spinning thin stream in the first-stage coagulation bath is 80s, the negative draft rate is -25%, and the coagulated yarn is obtained; the coagulation time of the coagulated yarn in the second-stage coagulation bath is 80s, and the stretching ratio is 1.3 times.

Hot drawing: The primary fiber strips undergo three-stage hot drawing, the temperature is from low to high, and the drawing medium is glycerol. The temperature of the first stage is 103°C, and the drawing is 1.8 times; 2.6 times; the third stage temperature is 122°C, and the draft is 1.5 times.

One time washing: Wash the hot-drawn fibers with water at a temperature of 65°C and a wash time of 3 minutes.

Primary drying: vacuum-drying the fibers after primary water washing at 48°C for 20 hours.

Relaxation heat setting: The thread after drying is subjected to relaxation heat setting, the medium is glycerin, the temperature is 140°C, and the negative draft rate is -15%.

Secondary washing: the fibers after relaxation and heat setting are washed twice, the washing temperature is 65 ℃, and the washing time is 5 minutes.

Drying and heat-setting: drying and heat-setting the fibers after the secondary water washing, drying at 58° C. for 20 hours, to obtain flame-retardant polyacrylonitrile fibers.

The fineness, strength, elongation, limiting oxygen index LOI value of the polyacrylonitrile fibers prepared in Examples 1-4 were tested, and the test results are shown in Table 1.

Table 1 is the performance data of the polyacrylonitrile fibers prepared in Examples 1-4 and the acrylic fibers of the prior art Veliklon FR grades

Fineness strength Elongation LOI value Example 1 1.7dtex 2.2cN/dtex 38% 30% Example 2 2.0dtex 2.8cN/dtex 30% 29.5% Example 3 2.2dtex 3.2cN/dtex 26% 26.5% Example 4 2.1dtex 3.0cN/dtex 35% 28% FR grade acrylic vinyl 2.2-22dtex 2.5-2.6cN/dtex 30-35% 26-30%

At present, Fushun Acrylic Polyethylene Chemical Plant, the largest acrylic polyvinyl fiber manufacturer in China, produces Veliklon FR acrylic fibers with a strength of 2.5-2.6cN/dtex and an elongation of 30-35%.

It can be seen from Table 1 that the strength of the fibers prepared in this application is 2.2-3.2 cN/dtex, and the elongation is 26-38%. Length increased by 8%. It can be seen that the performance of the polyacrylonitrile fiber prepared by the polyacrylonitrile fiber spinning method provided by the embodiment of the present invention is better, and the flame retardant performance of the polyacrylonitrile fiber prepared by the embodiment of the present invention is also the same as that of the FR grade of Veliklon The flame retardant properties of the fibers are comparable. Therefore, the polypropylene fibers prepared in the embodiments of the present invention not only have better flame retardant properties, but also ensure the mechanical properties of the polyacrylonitrile fibers.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the present invention. within the scope of the technical solution of the invention.

Claims (20)

1. A wet spinning method of polyacrylonitrile fibers is characterized by comprising the following steps:

spinning: extruding the spinning solution through a spinneret orifice of a spinneret assembly to obtain spinning trickle;

solidification and forming: the spinning trickle enters a coagulating bath for coagulation and forming to obtain nascent fiber;

hot drawing treatment: carrying out hot drawing treatment on the nascent fiber;

and (3) water washing treatment: washing the fiber subjected to the hot drawing treatment with water;

drying and heat setting treatment: drying and heat setting the washed fiber in sequence to obtain polyacrylonitrile fiber; wherein the drying treatment comprises the following steps: carrying out vacuum drying treatment on the washed fiber; the heat setting treatment step comprises:

and (3) relaxation heat setting: performing relaxation heat setting on the dried fiber;

washing with water: washing the fiber subjected to the relaxation heat setting treatment with water;

drying and heat setting: and drying and heat setting the washed fiber.

2. The wet spinning method of polyacrylonitrile fiber according to claim 1, characterized in that, in the step of the hot drawing process,

the drawing medium is glycerol; and/or

The hot drawing treatment is multi-stage hot drawing treatment; wherein the temperature of the previous stage of hot drawing is lower than that of the next stage of hot drawing.

3. The wet spinning method of polyacrylonitrile fiber according to claim 2, characterized in that the temperature of the hot drawing treatment is 100 to 130 ℃.

4. The wet spinning method of polyacrylonitrile fiber according to any one of claims 1 to 3, characterized in that, in the step of the hot drawing treatment, the nascent fiber is subjected to a three-stage hot drawing treatment; wherein,

the temperature of the first-stage hot drawing is 100-105 ℃, and the multiple of the first-stage hot drawing is 1.2-2 times; and/or

The temperature of the second-stage hot drawing is 110-120 ℃, and the multiple of the second-stage hot drawing is 2-3 times; and/or

The temperature of the third-stage hot drawing is 125-130 ℃, and the multiple of the third-stage hot drawing is 1.2-2 times.

5. A method for wet spinning polyacrylonitrile fibers according to any one of claims 1 to 3, characterized in that in the step of water washing treatment: the temperature of the water washing treatment is 50-70 ℃, and the time of the water washing treatment is 1-3 min.

6. The wet spinning method of polyacrylonitrile fiber according to any one of claims 1 to 3, characterized in that the temperature of drying treatment is 40 to 50 ℃, and the time of drying treatment is 12 to 24 hours.

7. The wet spinning method of polyacrylonitrile fibers according to any one of claims 1 to 3,

in the step of relaxation heat setting, glycerol is selected as a medium for negative drafting.

8. The wet spinning method of polyacrylonitrile fibers according to any one of claims 1 to 3,

in the step of relaxation heat setting, the temperature is 140-150 ℃, and the negative draft rate is-30% to-10%.

9. A wet spinning method of polyacrylonitrile fibers according to any one of claims 1 to 3, characterized in that, in the heat-setting treatment step:

the washing temperature is 60-80 ℃, and the washing time is 3-5 min.

10. The wet spinning method of polyacrylonitrile fibers according to any one of claims 1 to 3,

the temperature of the drying and heat setting is 50-60 ℃, and the time of the drying and heat setting is 12-24 hours; and/or

The drying heat setting is carried out under vacuum condition.

11. The wet spinning method of polyacrylonitrile fibers according to any one of claims 1 to 3, characterized in that the diameter of the spinneret hole is 0.065-0.1 mm.

12. A wet spinning method of polyacrylonitrile fibers according to any one of claims 1 to 3, characterized in that, in the step of solidification molding: the coagulation bath includes:

primary coagulation bath: the primary coagulation bath comprises a solvent and water; wherein, the solvent in the primary coagulating bath is one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide;

secondary coagulation bath: the secondary coagulation bath comprises a solvent and water; wherein, the solvent in the secondary coagulating bath is one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide;

and the spinning trickle firstly enters a first-stage coagulation bath for coagulation forming to obtain coagulated filaments, and the coagulated filaments then enter a second-stage coagulation bath for coagulation forming.

13. The wet spinning method of polyacrylonitrile fibers according to claim 12, characterized in that the solvent content in the primary coagulation bath is 30-60%; and/or the solvent content in the secondary coagulation bath is 15-25%.

14. The wet spinning method of polyacrylonitrile fibers according to claim 12, wherein the temperature of the primary coagulation bath is 30-60 ℃; and/or the temperature of the secondary coagulating bath is 60-80 ℃.

15. The wet spinning method of polyacrylonitrile fibers according to claim 12, characterized in that the coagulation time of the spinning stream in the primary coagulation bath is 20-100 s, and the negative draft ratio is-50% to-20%; and/or

The coagulation time of the coagulated filament in the secondary coagulation bath is 30-120 s, and the stretching multiple is 1.2-1.5 times.

16. The wet spinning method of polyacrylonitrile fiber according to any one of claims 1-3, 13-15, characterized in that, the spinning solution is prepared by polymerization reaction of main monomer acrylonitrile, comonomer, solvent and initiator;

wherein the comonomer is halogenated olefin with the halogen element content larger than the chlorine element content in the chloroethylene.

17. The wet spinning method of polyacrylonitrile fiber according to claim 16,

the comonomer is one or two of vinylidene chloride and ethylene dibromide; and/or

The main monomer acrylonitrile accounts for 40-60% of the total monomer mass, and the comonomer accounts for 40-60% of the total monomer mass; wherein the total monomer mass is the sum of the mass of the main monomer and the mass of the comonomer; and/or

The solvent is one or more of dimethyl sulfoxide, dimethylformamide and dimethylacetamide; and/or

The initiator is azobisisobutyronitrile.

18. The wet spinning method of polyacrylonitrile fiber according to claim 16, characterized in that,

the conversion of the polymerization reaction is greater than 90%; and/or

The solid content of the spinning solution is 30-40%; and/or

The service temperature of the spinning solution is 30-60 ℃.

19. The polyacrylonitrile fiber is characterized in that the fineness of the polyacrylonitrile fiber is 1.7-2.2 dtex; the strength of the polyacrylonitrile fiber is 2.2-3.2 cN/dtex; the elongation of the polyacrylonitrile fiber is 26-38%;

wherein the polyacrylonitrile fiber is prepared by a wet spinning method of the polyacrylonitrile fiber according to any one of claims 1 to 18.

20. The polyacrylonitrile fiber according to claim 19, wherein the limit oxygen index LOI value of the polyacrylonitrile fiber is 26.5-30%.