High strength high modulus nylon fiber and method of making

Abstract

This invention relates to the field of nylon technology and discloses a high-strength, high-modulus nylon fiber and its preparation method. The invention involves melt extrusion and melt spinning of nylon resin and polyamide phosphate flame retardant in a ratio of 100g:(1-8)g, followed by winding, stretching, and heat setting to obtain high-strength, high-modulus nylon fiber. The polyamide phosphate flame retardant contains a large number of bispiral phenyl phosphate flame-retardant structures, exhibiting excellent flame-retardant properties. It eliminates the need for inorganic flame retardants such as magnesium hydroxide, aluminum hydroxide, and montmorillonite. Furthermore, the flame retardant's molecular backbone contains amide bonds, and its terminal positions also contain a large number of amide bonds, forming strong hydrogen bond interactions with nylon. Adding an appropriate amount of flame retardant has a certain reinforcing effect on the nylon fiber, significantly improving its breaking strength and initial modulus, thus expanding the practical applications of nylon fiber in fireproof clothing, refractory materials, and other fields.

Description

Technical Field

[0001] This invention relates to the field of nylon technology, specifically to a high-strength, high-modulus nylon fiber and its preparation method. Background Technology

[0002] Nylon fiber possesses advantages such as light weight, good elasticity, and high abrasion resistance, and is widely used in textiles, resin castings, medical devices, and other fields. However, ordinary nylon fiber is easily flammable and lacks flame retardancy, hindering its practical application in fire-resistant clothing and refractory materials. Therefore, flame-retardant modification of nylon fiber is of great significance. Flame retardants mainly include inorganic flame retardants such as magnesium hydroxide, hydrotalcite, and montmorillonite, as well as organic flame retardants such as phosphorus-based and bromine-based flame retardants. The addition of inorganic flame retardants is relatively large, significantly impacting the mechanical and other properties of the material.

[0003] Chemical modification methods for nylon fibers include blending, irradiation grafting, and microwave grafting. Blending is simple to operate and inexpensive; adding flame retardants to nylon resin and fibers can effectively improve the flame retardant properties of the fibers. However, the poor compatibility between the flame retardant and the nylon matrix can negatively impact the mechanical properties of both the resin matrix and the fibers. Patent CN113668081B discloses a method for preparing flame-retardant nylon composite fibers, which involves blending polyacrylamide / montmorillonite flame-retardant composite microspheres with nylon and spinning this mixture. This improves the flame retardant properties and mechanical effects of the composite fibers. However, this patent requires the addition of inorganic flame retardants such as magnesium hydroxide and montmorillonite, resulting in a relatively large amount of these additives. Summary of the Invention

[0004] This invention provides a high-strength, high-modulus nylon fiber and its preparation method, which eliminates the need for inorganic flame retardants such as magnesium hydroxide, thus solving the problem of poor flame retardancy of nylon fibers while maintaining good mechanical strength and modulus.

[0005] The technical solution of this invention: A method for preparing high-strength, high-modulus nylon fibers: (1) Triethylamine, 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene and pentaerythritol diphosphate diphosphoryl chloride were added to N,N-dimethylformamide. After the reaction, the solution was poured into ethanol, filtered, and the product was washed with ethanol and dried to obtain the flame retardant precursor.

[0006] (2) Add flame retardant precursor, chloroacetamide, and potassium carbonate to N,N-dimethylformamide. After the reaction, pour the solution into water, filter, wash the product with water and ethanol, and dry to obtain polyamide phosphate flame retardant. The preparation reaction formula is as follows: .

[0007] (3) 100g: (1-8)g of nylon resin and polyamide phosphate flame retardant were melt-extruded through a twin-screw extruder, and then the granules were melt-spun in a spinning machine. After winding, the fibers were stretched and heat-set by a hot stretching machine to obtain high-strength and high-modulus nylon fibers.

[0008] Furthermore, in (1), the ratio of triethylamine, 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene, and pentaerythritol diphosphate diphosphoryl chloride is (3-3.3) mol: 1 mol: (1.35-1.44) mol.

[0009] Furthermore, the reaction in (1) is carried out at 60-90℃ for 18-24h.

[0010] Furthermore, in (2), the ratio of flame retardant precursor, chloroacetamide, and potassium carbonate is 100g: (8-20)g: (15-40)g.

[0011] Furthermore, the reaction in (2) is carried out at 60-80℃ for 10-18h.

[0012] Furthermore, in (3), the temperature of the twin-screw extruder in zones 1-5 is 180-245℃, and the screw speed is 50-80r / min.

[0013] Furthermore, in (3), the spinning temperature of the spinning machine is 240-260℃ and the spinning speed is 700-1000m / min.

[0014] Furthermore, the stretching ratio in (3) is 3.3-4 times.

[0015] Furthermore, (3) the heat setting temperature is 90-120℃ and the time is 10-30min.

[0016] The beneficial technical effects of this invention are as follows: A hyperbranched polymerization reaction is carried out using 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene and pentaerythritol diphosphate diphosphoryl chloride to obtain a flame retardant precursor with a large number of phenolic hydroxyl groups at its terminal positions. This precursor then reacts with chloroacetamide to obtain a polyamide phosphate flame retardant with a large number of amide bonds at its terminal positions. This is then melt-spun with nylon resin to obtain high-strength, high-modulus nylon fibers. The polyamide phosphate flame retardant contains a large number of bispiral phenyl phosphate flame retardant structures. During combustion, it produces phosphoric acid, which promotes the dehydration and char formation of the benzene ring and the nylon matrix, forming a char barrier layer on the fiber surface. This layer provides heat insulation and isolates oxygen, resulting in excellent flame retardant performance without the need for inorganic flame retardants such as magnesium hydroxide, aluminum hydroxide, or montmorillonite.

[0017] The polyamide phosphate flame retardant of this invention has amide bonds in its main molecular chain, which has good compatibility with nylon polyamide matrix and will not affect the mechanical properties of the fiber. At the same time, the ends of the hyperbranched molecular chain also contain a large number of amide bonds, which form strong hydrogen bond interactions with nylon. Adding an appropriate amount of flame retardant has a certain reinforcing effect on nylon fibers, and the breaking strength and initial modulus are significantly improved, which expands the practical application of nylon fibers in fireproof clothing, fire-resistant materials and other fields. Detailed Implementation

[0018] The technical solution of this application will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the scope of this application.

[0019] 1,3,5-Tris(4-hydroxyphenylcarbamoyl)benzene was prepared according to the method described in the journal article Tetrahedron 66 (2010) 1389-1398, "Synthesis and properties of hyperbranched polyamide–esters derived from 1,3,5-tris(40-hydroxyphenylcarbamoyl)benzene". The structural formula is as follows: .

[0020] Example 1: (1) Add 300 mmol of triethylamine, 100 mmol of 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene and 144 mmol of pentaerythritol diphosphate diphosphoryl chloride to 1 L of N,N-dimethylformamide, heat to 60 °C, stir and react for 24 h, pour the solution into ethanol, filter, wash the product with ethanol, dry, and obtain the flame retardant precursor.

[0021] (2) Add 50g of flame retardant precursor, 4g of chloroacetamide and 7.5g of potassium carbonate to 800mL of N,N-dimethylformamide, heat to 80℃, stir and react for 10h, pour the solution into water, filter, wash the product with water and ethanol, dry, and obtain polyamide phosphate flame retardant.

[0022] (3) 1 kg of nylon resin (model nylon 66, the same below) and 10 g of polyamide phosphate flame retardant were melt-extruded through a twin-screw extruder. The temperatures of zones 1-5 were 180℃, 235℃, 245℃, 245℃, and 240℃, and the screw speed was 50 r / min. The granules were melt-spun in a spinning machine at a spinning temperature of 245℃ and a spinning speed of 700 m / min. After winding, the fibers were drawn through a hot drawing machine with a drawing ratio of 3.5 times. The fibers were then heat-set at 120℃ for 10 min to obtain high-strength, high-modulus nylon fibers.

[0023] Example 2: (1) Add 330 mmol of triethylamine, 100 mmol of 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene and 138 mmol of pentaerythritol diphosphate diphosphoryl chloride to 1.2 L of N,N-dimethylformamide, heat to 80 °C, stir and react for 18 h, pour the solution into ethanol, filter, wash the product with ethanol, dry, and obtain the flame retardant precursor.

[0024] (2) Add 50g of flame retardant precursor, 7g of chloroacetamide and 14g of potassium carbonate to 900mL of N,N-dimethylformamide, heat to 60℃, stir and react for 18h, pour the solution into water, filter, wash the product with water and ethanol, dry, and obtain polyamide phosphate flame retardant.

[0025] (3) 1 kg of nylon resin and 40 g of polyamide phosphate flame retardant were melt-extruded through a twin-screw extruder. The temperatures of zones 1-5 were 180℃, 235℃, 245℃, 245℃, and 240℃, and the screw speed was 80 r / min. The granules were melt-spun in a spinning machine at a spinning temperature of 240℃ and a spinning speed of 1000 m / min. After winding, the fibers were stretched through a hot stretching machine with a stretching ratio of 4 times. The fibers were then heat-set at 90℃ for 30 min to obtain high-strength, high-modulus nylon fibers.

[0026] Example 3: (1) Add 300 mmol of triethylamine, 100 mmol of 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene and 135 mmol of pentaerythritol diphosphate diphosphoryl chloride to 1 L of N,N-dimethylformamide, heat to 90 °C, stir and react for 18 h, pour the solution into ethanol, filter, wash the product with ethanol, dry, and obtain the flame retardant precursor.

[0027] (2) Add 50g flame retardant precursor, 10g chloroacetamide and 20g potassium carbonate to 900mL N,N-dimethylformamide, heat to 65℃, stir and react for 18h, pour the solution into water, filter and wash the product with water and ethanol, dry and obtain polyamide phosphate flame retardant.

[0028] (3) 1 kg of nylon resin and 80 g of polyamide phosphate flame retardant were melt-extruded through a twin-screw extruder. The temperatures of zones 1-5 were 180℃, 235℃, 245℃, 245℃, and 240℃, and the screw speed was 80 r / min. The granules were melt-spun in a spinning machine at a spinning temperature of 260℃ and a spinning speed of 800 m / min. After winding, the fibers were drawn through a hot drawing machine with a drawing ratio of 3.3 times. The fibers were then heat-set at 120℃ for 10 min to obtain high-strength, high-modulus nylon fibers.

[0029] The difference between Comparative Example 1 and Example 1 is that no polyamide phosphate flame retardant is added.

[0030] (1) 1 kg of nylon resin was melt-spun in a spinning machine at a spinning temperature of 245°C and a spinning speed of 700 m / min. After winding, the fiber was stretched by a hot stretching machine with a stretching ratio of 3.5 times. The fiber was then heat-set at 120°C for 10 min to obtain nylon fiber.

[0031] The difference between Comparative Example 2 and Example 1 is the addition of a flame retardant precursor.

[0032] (1) 1 kg of nylon resin and 10 g of flame retardant precursor were melt-extruded through a twin-screw extruder. The temperatures of zones 1-5 were 180℃, 235℃, 245℃, 245℃, and 240℃, and the screw speed was 50 r / min. The granules were melt-spun in a spinning machine at a spinning temperature of 245℃ and a spinning speed of 700 m / min. The wound fibers were then stretched in a hot stretching machine with a stretching ratio of 3.5 times. The fibers were then heat-set at 120℃ for 10 min to obtain nylon fibers.

[0033] The main difference between Comparative Example 3 and Example 1 is the addition of 4,4'-biphenyl.

[0034] (1) Add 200 mmol of triethylamine, 150 mmol of 4,4'-biphenyl and 144 mmol of pentaerythritol diphosphate diphosphoryl chloride to 1 L of N,N-dimethylformamide, heat to 60 °C, stir and react for 24 h, pour the solution into ethanol, filter, wash the product with ethanol, dry and obtain flame retardant precursor.

[0035] (2) Add 50g of flame retardant precursor, 4g of chloroacetamide and 7.5g of potassium carbonate to 800mL of N,N-dimethylformamide, heat to 80℃, stir and react for 10h, pour the solution into water, filter, wash the product with water and ethanol, dry, and obtain phosphate flame retardant.

[0036] (3) 1 kg of nylon resin and 10 g of phosphate flame retardant were melt-extruded through a twin-screw extruder. The temperatures of zones 1-5 were 180℃, 235℃, 245℃, 245℃, and 240℃, and the screw speed was 50 r / min. The granules were melt-spun in a spinning machine at a spinning temperature of 245℃ and a spinning speed of 700 m / min. The wound fibers were then stretched in a hot stretching machine with a stretching ratio of 3.5 times. The fibers were then heat-set at 120℃ for 10 min to obtain nylon fibers.

[0037] The difference between Comparative Example 4 and Example 1 is the addition of 1,3,5-tris(4-hydroxyphenyl)benzene.

[0038] (1) Add 300 mmol of triethylamine, 100 mmol of 1,3,5-tris(4-hydroxyphenyl)benzene and 144 mmol of pentaerythritol diphosphate diphosphoryl chloride to 1 L of N,N-dimethylformamide, heat to 60 °C, stir and react for 24 h, pour the solution into ethanol, filter, wash the product with ethanol, dry, and obtain the flame retardant precursor.

[0039] (2) Add 50g of flame retardant precursor, 4g of chloroacetamide and 7.5g of potassium carbonate to 800mL of N,N-dimethylformamide, heat to 80℃, stir and react for 10h, pour the solution into water, filter, wash the product with water and ethanol, dry, and obtain phosphate flame retardant.

[0040] (3) 1 kg of nylon resin and 10 g of phosphate flame retardant were melt-extruded through a twin-screw extruder. The temperatures of zones 1-5 were 180℃, 235℃, 245℃, 245℃, and 240℃, and the screw speed was 50 r / min. The granules were melt-spun in a spinning machine at a spinning temperature of 245℃ and a spinning speed of 700 m / min. The wound fibers were then stretched in a hot stretching machine with a stretching ratio of 3.5 times. The fibers were then heat-set at 120℃ for 10 min to obtain nylon fibers.

[0041] The tensile properties of nylon fibers were tested according to GB / T 14337-2022.

[0042] Nylon fibers are combed, twisted, and wound into yarn, which is then knitted into fabric. The oxygen index is tested according to GB / T 5454-1997.

[0043] Table 1 Fiber Properties

[0044] The nylon fibers in Comparative Example 1 had a low limiting oxygen index and poor flame retardant properties. The polyamide phosphate flame retardant added in Example 1 contained a large amount of bispirocyclic phenyl phosphate flame retardant structures (…). When burned, it produces phosphoric acid, which promotes the dehydration of benzene rings and the nylon matrix into char, forming a char barrier layer on the fiber surface. This layer provides insulation and isolates oxygen, resulting in excellent flame retardant properties. Furthermore, the main molecular chain of the flame retardant contains amide bonds. It has good compatibility with the nylon polyamide matrix and will not affect the mechanical properties of the fiber. At the same time, the ends of the hyperbranched molecular chains also contain a large number of amide bonds. The flame retardant forms strong hydrogen bonds with nylon, and the addition of an appropriate amount of flame retardant has a certain reinforcing effect on nylon fibers, significantly improving their tensile strength and initial modulus. In Examples 2 and 3, different amounts of flame retardant were added, and the nylon fibers also exhibited good flame retardant properties and mechanical strength.

[0045] The flame retardant precursor of Comparative Example 2 does not contain amide bonds at its terminal positions, resulting in lower compatibility and interaction with the nylon matrix compared to Example 1. Consequently, the breaking strength and initial modulus of the nylon fibers are lower than those of Example 1.

[0046] The flame retardant precursor obtained by polymerizing 4,4'-biphenyl and pentaerythritol diphosphate diphosphoryl chloride in Comparative Example 3 is a linear molecular chain containing phenolic hydroxyl groups only at both ends. After reacting with chloroacetamide, it contains amide bonds only at both ends. The amide bond content is very low, resulting in low compatibility with the nylon matrix and low hydrogen bonding forces. Consequently, the nylon fiber has low breaking strength and initial modulus.

[0047] Comparative Example 4 uses 1,3,5-tris(4-hydroxyphenyl)benzene as raw material to prepare flame retardant precursors and phosphate flame retardants that contain amide bonds only at the end positions. The amide bond content is lower than that of the polyamide phosphate flame retardant in Example 1. The compatibility with the nylon matrix and the hydrogen bonding force are lower than those in Example 1, resulting in lower breaking strength and initial modulus of nylon fibers.

[0048] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A process for the production of high-strength high-modulus nylon fiber, characterized by, The preparation method includes: melting and extruding nylon resin and polyamide phosphate flame retardant in a ratio of 100g:(1-8)g through a twin-screw extruder, then melting and spinning the granules in a spinning machine, and then stretching and heat-setting the wound fibers through a hot stretching machine to obtain high-strength and high-modulus nylon fibers. The preparation method of the polyamide phosphate flame retardant includes: (1) Add triethylamine, 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene and pentaerythritol diphosphate diphosphoryl chloride to N,N-dimethylformamide, heat to 60-90℃, stir and react for 18-24h, pour the solution into ethanol, filter and wash the product, dry and obtain flame retardant precursor. (2) Add flame retardant precursor, chloroacetamide and potassium carbonate to N,N-dimethylformamide, heat to 60-80℃, stir and react for 10-18h, pour the solution into water, filter and wash the product, dry and obtain polyamide phosphate flame retardant.

2. The method for preparing high-strength, high-modulus nylon fibers according to claim 1, characterized in that, The temperature of the twin-screw extruder in zones 1-5 is 180-245℃, and the screw speed is 50-80 r / min.

3. The method for preparing high-strength, high-modulus nylon fibers according to claim 1, characterized in that, The spinning temperature of the spinning machine is 240-260℃, and the spinning speed is 700-1000m / min.

4. The method for preparing high-strength, high-modulus nylon fibers according to claim 1, characterized in that, The stretching ratio is 3.3-4 times.

5. The method for preparing high-strength, high-modulus nylon fibers according to claim 1, characterized in that, The heat setting temperature is 90-120℃, and the time is 10-30 minutes.

6. The method for preparing high-strength, high-modulus nylon fibers according to claim 1, characterized in that, The ratio of triethylamine, 1,3,5-tris(4-hydroxyphenylcarbamoyl)benzene, and pentaerythritol diphosphate diphosphoryl chloride in (1) is (3-3.3) mol: 1 mol: (1.35-1.44) mol.

7. The method for preparing high-strength, high-modulus nylon fibers according to claim 1, characterized in that, The ratio of flame retardant precursor, chloroacetamide and potassium carbonate in (1) is 100g: (8-20)g: (15-40)g.

8. A high-strength, high-modulus nylon fiber obtained by the preparation method according to any one of claims 1-7.

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