1. A method for preparing semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties, characterized in that the method comprises the steps of:

1) pretreatment: soaking the semi-aromatic polyamide and the copolymer thereof in deionized water at 70-100 ℃ for 12-72 h, and then drying;

2) physical blending: physically blending the pretreated semi-aromatic polyamide and the copolymer thereof, the flame retardant and the plasticizer at high temperature and high speed to obtain a blend; wherein the blending temperature is 80-150 ℃, the blending speed is 1000-2000 r/min, and the blending time is 10-50 min;

3) melt spinning: the blend is subjected to melt spinning to prepare the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property.

2. The method for preparing semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to claim 1, wherein the structural formula of the semi-aromatic polyamide and the copolymer thereof is as follows:

wherein n is 10-500, x + y is more than 0 and less than or equal to 1, and x is not equal to 0

At least one of;

R₁＝-(CH₂)₂-、-(CH₂)₄-、-(CH₂)₆-、-(CH₂)₉-and- (CH)₂)₁₀-at least one of;

R₂＝-(CH₂)₄-and/or- (CH)₂)₈-；

R₃＝-(CH₂)₅-、-(CH₂)₆-、-(CH₂)₇-、-(CH₂)₈-、-(CH₂)₉-、-(CH₂)₁₀-and- (CH)₂)₁₁-at least one of.

3. The method for preparing semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to claim 1 or 2, wherein the step 1) of soaking the semi-aromatic polyamide and the copolymer thereof in deionized water at 70 to 100 ℃ for 12 to 72 hours is repeated for 2 to 5 times.

4. The method for preparing a semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to any one of claims 1 to 3, wherein the drying treatment in step 1) is: and (3) drying the soaked semi-aromatic polyamide and the copolymer thereof in a vacuum drying oven at the temperature of 95-115 ℃ for 24-72 h.

5. The method for preparing semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to any one of claims 1 to 4, wherein in step 2), the flame retardant is selected from: aluminum diethylphosphinate, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and derivatives thereof, inorganic salts zinc stannate, organic montmorillonite, nano silicon dioxide, mineral hybrid or phenylphosphite hybrid boehmite.

6. The method for preparing semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to claim 5, wherein the particle size of the flame retardant is 10 to 200 μm.

7. The method for preparing a semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to any one of claims 1 to 6, wherein in the step 2), the plasticizer is a carboxylic acid amide-containing compound; ethylene bis-12-hydroxystearamide, N-ethylene bis-stearamide or oleamide is preferred.

8. The method for preparing a semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to any one of claims 1 to 7, wherein the melt spinning process in step 3) is: the blend is processed by a melt spinning machine through a feeding step → screw extrusion step → spinning box step → primary yarn preparation step of spinneret spinning, and finally, the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property is prepared through strand cooling step → winding step → stretching step → shaping step;

further, in the step 3), the melt spinning process parameters are as follows: the spinning temperature is 260-335 ℃, the winding speed is 400-3000 m/min, and the drafting speed is 3-6;

further, in the step 3), spinneret holes on a spinneret plate used for melt spinning are circular, polygonal or hollow spinneret holes, and the number of the spinneret holes is 32-256.

9. A semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties, characterized in that the semi-aromatic polyamide fiber is produced by the method of any one of claims 1 to 8.

10. The semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties according to claim 9, wherein the fineness of the flame retardant semi-aromatic polyamide fiber is 0.9 to 10 dtex;

further, the flame-retardant semi-aromatic polyamide fiber has a mechanical strength of 2.3 to 14.8 cN/dtex;

further, the limit oxygen index of the flame-retardant semi-aromatic polyamide fiber is not less than 30%.

Background

Conventionally, nylon 6, nylon 66, and the like are known as polyamide fibers, and they are used for various industrial material applications because they have high strength, high toughness, and excellent durability. The limit oxygen index of the polyamide fiber is only 21-24%, and the fire spread caused by ignition or combustion supporting of the fiber product seriously harms the life and property safety of people. Therefore, these conventional polyamide fibers still have problems of insufficient heat resistance and chemical resistance and poor flame retardancy. Therefore, it is imperative to develop polyamide fibers having excellent flame retardancy, high heat resistance and chemical resistance.

The semi-aromatic polyamide has the advantages that the heat resistance, the corrosion resistance and the mechanical property of the semi-aromatic polyamide are improved due to the introduction of the aromatic ring in the structure of the aliphatic chain polyamide molecular chain. According to the previous research experience of flame-retardant aliphatic polyamide fibers, the flame-retardant modification technology of the aliphatic polyamide fibers comprises a post-finishing method, a blending method, a composite spinning method, a polymerization method and the like, wherein the blending method directly adds a flame retardant to obtain an ideal flame-retardant effect and is the most common method for preparing the flame-retardant fibers in industrial production. However, in the case of the semi-aromatic polyamide, the melting point temperature of the resin is as high as 290 ℃ or higher, and when the resin is melt-spun into a semi-aromatic polyamide fiber, the spinning temperature is close to the decomposition temperature of the polyamide main chain, which affects the spinning stability; on the other hand, the addition of flame retardants and their poor dispersibility also affect the stability of the entire melt and thus the spinning stability. In addition, the flame retardant performance can reach the standard by adding a higher content of flame retardant, but the mechanical strength of the fiber can be reduced, and the core flame retardant performance of the product can not reach the standard by adding a smaller amount of flame retardant.

Therefore, it is a technical problem to be solved at present that a semi-aromatic polyamide fiber with good spinnability, good flame retardant property, excellent mechanical property and high temperature resistance is developed.

Disclosure of Invention

In view of the above-mentioned drawbacks, the present invention provides a method for preparing a semi-aromatic polyamide fiber, which has excellent flame retardancy, high temperature resistance, corrosion resistance, and excellent mechanical properties, and can be used for applications such as automobile parts and electric/electronic parts.

The technical scheme of the invention is as follows:

a first technical problem to be solved by the present invention is to provide a method for preparing a semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties, the method comprising the steps of:

1) pretreatment: soaking the semi-aromatic polyamide and the copolymer thereof in deionized water at 70-100 ℃ for 12-72 h, and then drying;

2) physical blending: physically blending the pretreated semi-aromatic polyamide and the copolymer thereof, the flame retardant and the plasticizer at a high temperature and a high speed to obtain a blend, wherein the blending temperature is 80-150 ℃, the rotation speed is 1000-2000 r/min, and the blending time is 10-50 min;

3) melt spinning: the blend is subjected to melt spinning to prepare the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property.

Further, the structural formula of the semi-aromatic polyamide copolymer is as follows:

wherein n is 10-500, x + y is more than 0 and less than or equal to 1, and x is not equal to 0

At least one of;

R₁＝-(CH₂)₂-、-(CH₂)₄-、-(CH₂)₆-、-(CH₂)₈-and- (CH)₂)₁₀-at least one of;

R₂＝-(CH₂)₄-and/or- (CH)₂)₈-；

R₃＝-(CH₂)₃-、-(CH₂)₆-、-(CH₂)₇-、-(CH₂)₈-、-(CH₂)₉-、-(CH₂)₁₀-and- (CH)₂)₁₁-at least one of.

Further, in the step 1), the process of soaking the semi-aromatic polyamide and the semi-aromatic polyamide copolymer in deionized water at the temperature of 70-100 ℃ for 12-72 hours is repeated for 2-5 times.

Further, in step 1), the drying treatment refers to: and (3) drying the soaked semi-aromatic polyamide and the copolymer thereof in a vacuum drying oven at the temperature of 95-115 ℃ for 24-72 h.

Further, in step 2), the flame retardant is selected from: diethyl aluminium phosphinate, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and derivatives thereof, inorganic salt zinc stannate, organic montmorillonite, nano-silica, mineral hybrid or phenyl phosphorous acid hybrid boehmite and the like.

Further, in the step 2), the particle size of the flame retardant is 10-200 μm.

Further, in the step 2), the plasticizer is a carboxylic acid amide-containing compound; ethylene bis-12-hydroxystearamide, N-ethylene bis-stearamide, oleamide, or the like is preferable.

Further, in step 3), the melt spinning process comprises: and (3) the blend is subjected to a primary yarn preparation link of melt spinning machine through feeding → screw extrusion → spinning manifold → spinneret spinning, and finally, the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property is prepared through strand cooling → winding → stretching → shaping.

Further, in the step 3), the melt spinning process parameters are as follows: the spinning temperature is 260-335 ℃, the winding speed is 400-3000 m/min, and the drafting speed is 3-6.

Further, in the step 3), spinneret holes on a spinneret plate used for melt spinning are circular, polygonal or hollow spinneret holes, and the number of the spinneret holes is 32-256.

A second technical problem to be solved by the present invention is to provide a semi-aromatic polyamide fiber having excellent flame retardancy and mechanical properties, which is prepared by the above method.

Further, the fineness of the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property is 0.9-10 dtex.

Further, the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property has the mechanical strength of 2.3-14.8 cN/dtex.

Further, the semi-aromatic polyamide fiber with excellent flame retardancy and mechanical properties has a limiting oxygen index of not less than 30%.

The invention has the beneficial effects that:

the semi-aromatic polyamide fiber with excellent flame retardance and mechanical property is prepared by soaking, pretreating, physically blending and melt spinning the semi-aromatic polyimide copolymer; the fineness of the obtained fiber is 0.9-10 dtex, and the elongation at break is 10-140%; the mechanical strength is 2.3-14.8 cN/dtex, the heat resistance is 170-240 ℃ of the service temperature, and the limiting oxygen index is more than or equal to 30%; and the obtained fiber has chemical resistance to other organic solvents except concentrated sulfuric acid and trifluoroacetic acid.

Description of the drawings:

FIG. 1 is an SEM photograph of a copolymerized semi-aromatic polyamide fiber obtained in example 1.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.

Example 1

Soaking the copolymerized semi-aromatic polyamide resin PA6T-1 (the glass transition temperature of the copolymerized semi-aromatic polyamide resin is 85 ℃, the melting temperature of the copolymerized semi-aromatic polyamide resin is 295 ℃) in water at the temperature of 90 ℃ for 24 hours, and repeating the soaking for 3 times; then, drying the resin at 110 ℃ for 36 h; then 100 parts of PA6T-1, 10 parts of aluminum diethylphosphinate, 2 parts of ethylene bisstearamide were physically blended in a high speed blender: the blending temperature is 100 ℃, the rotation rate is 1500r/min, and the blending time is 30min, so as to obtain a blend; passing the blended mixture 1cm³The metering pump of the/r is sent into a single screw extruder for melting, and the technological parameters of the melt spinning are as follows: the spinning temperature is 290 ℃, the oil amount is 5mL/min, the winding speed is 800m/min, the drafting multiple speed is 3.8, the aperture of a spinneret plate is 0.04mm, the spinneret plate with 96 holes and round holes is used for melt spinning, and stretching and solidification are carried out, wherein the drafting ratio multiple is 3 times.

The performance indexes of the obtained copolymerized semi-aromatic polyamide fiber are as follows: fineness 6.3dtex (fineness in the inventive example tested according to GBT 1797-2008), breaking strength 2.9 cN/dtex; elongation at break of 80%; the service temperature was 210 ℃ and the limiting oxygen index was 32.

Wherein the molecular structural formula of the copolymerized semi-aromatic polyamide resin PA6T-1 is as follows:

example 2

Soaking the copolymerized semi-aromatic polyamide resin PA6T-2 (the glass transition temperature of the copolymerized semi-aromatic polyamide resin is 90 ℃ and the melting temperature of the copolymerized semi-aromatic polyamide resin is 289 ℃) in water at the temperature of 80 ℃ for 10 hours, and repeating for 2 times; then the resin is dried and treated,the drying temperature is 110 ℃, and the drying time is 36 h; then physically blending 100 parts of PA6T-2, 8 parts of phenyl phosphorous acid hybrid boehmite and 2 parts of ethylene bis stearamide at the blending temperature of 120 ℃, the rotation rate of 1000r/min and the blending time of 40min to obtain a blend; the blended mixture was passed through 2cm³The metering pump of the/r is sent into a single screw extruder, and the technological parameters of melt spinning are as follows: the spinning temperature is 295 ℃, the oil amount is 6.3mL/min, the winding speed is 600m/min, the drafting multiple speed is 2.5, the aperture of a spinneret plate is 0.025mm, the spinneret plate with 64 holes and circular holes is used for melt spinning, and the spinning is carried out for stretching and solidification, the drafting ratio multiple is 3 times, and the winding speed is 600 m/min.

The performance indexes of the obtained copolymerized semi-aromatic polyamide fiber are as follows: fineness of 10.3dtex, breaking strength of 3.2 cN/dtex; elongation at break 92%; the service temperature was 220 ℃ and the limiting oxygen index was 34.

Wherein the molecular structural formula of the copolymerized semi-aromatic polyamide resin PA6T-2 is as follows: .

Comparative example 1

The preparation process is the same as example 1, except that: without the pretreatment process of soaking in water at 90 ℃ for 24h, the performance indexes of the obtained fiber are as follows: fineness number: 21dtex, breaking strength 1.1 cN/dtex; elongation at break 181%; the use temperature was 231 ℃.

Comparative example 2

The procedure is as in example 1, except that "100 parts of PA6T-1, 10 parts of aluminum diethylphosphinate, 2 parts of ethylene bisstearamide were melt-extruded at 280"; as a result, uniform continuous fibers cannot be obtained at all.