A modified polyamide and its preparation method and fiber

Abstract

The present invention belongs to the technical field of polyamide fibers, and specifically relates to a modified polyamide and a preparation method and fiber thereof. The present invention provides a modified polyamide having a structure shown in Formula I: wherein Q is a semi-aromatic amide structural unit, R is a phosphorus-containing semi-aromatic amide structural unit, and P is a polyamide structural unit; a is 3 to 6, b is 4 to 8, and c is 120 to 250. The present invention introduces an aromatic ring structure and a phosphorus-containing group into a polyamide molecular chain through an amide exchange reaction to prepare a modified polyamide having an aromatic ring structure and a phosphorus-containing flame-retardant structure and a fiber thereof; the rigid benzene ring structure of the main chain and the phosphorus-containing aromatic ring structure of the side group are used to improve the drafting performance during spinning, and the steric hindrance of the aromatic ring structure of the side group is used to improve the flowability and spinnability. Combining the contribution of the main chain and the side group benzene ring to the spinnability and drafting performance of the modified polyamide, the purpose of improving the mechanical strength of the modified polyamide fiber is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyamide fibers, and in particular relates to a modified polyamide and a preparation method and fiber thereof. Background Art

[0002] Polyamide fiber is the earliest synthetic fiber to be industrially produced in the world. It has excellent mechanical properties, wear resistance and moisture absorption properties, and is widely used in various fields of people's lives. According to different application fields, polyamide fiber is divided into civil fiber and industrial fiber. In special application fields such as cord fabrics, parachutes, and climbing ropes, higher requirements are placed on the mechanical properties of polyamide fiber.

[0003] The existing method for preparing polyamide fibers with high mechanical properties mainly uses high-viscosity polyamide chips combined with subsequent spinning, drawing and shaping process adjustments to improve the mechanical properties of polyamide fibers. However, the mechanical strength of general high-mechanical-performance polyamide fibers is 7.0-9.0 cN / dtex, which cannot meet the requirements of special application fields for the mechanical strength of polyamide fibers, and its mechanical strength still needs to be improved. Summary of the invention

[0004] In view of this, the present invention provides a modified polyamide and a preparation method and fiber thereof; the polyamide fiber prepared from the polyamide provided by the present invention has higher breaking strength and breaking elongation, and can meet the requirements of special applications for the mechanical strength of polyamide fibers.

[0005] In order to solve the above technical problems, the present invention provides a modified polyamide having a structure shown in Formula I:

[0006]

[0007] Wherein, Q is a semi-aromatic amide structural unit, R is a phosphorus-containing semi-aromatic amide structural unit, and P is a polyamide structural unit;

[0008] a is 3 to 6, b is 4 to 8, and c is 120 to 250.

[0009] Preferably, Q has a structure shown in any one of Formulas 1 to 5:

[0010]

[0011]

[0012] Wherein, x is any integer from 4 to 14.

[0013] Preferably, R has a structure shown in any one of Formulas 6 to 8:

[0014]

[0015] Wherein, y is any integer from 4 to 14.

[0016] Preferably, the P has a structure shown in any one of Formulas 9 to 11:

[0017]

[0018] The polyamide structural unit includes a polyamide 66 structural unit, a polyamide 6 structural unit or a polyamide 56 structural unit.

[0019] The present invention also provides a method for preparing the modified polyamide described in the above technical solution, comprising the following steps:

[0020] Dissolving an aromatic dibasic acid and a first aliphatic diamine in a first solvent, and performing a first salt-forming reaction to obtain a semi-aromatic amide salt;

[0021] dissolving the phosphorus-containing aromatic dibasic acid and the second aliphatic diamine in a second solvent, and performing a second salt-forming reaction to obtain a phosphorus-containing semi-aromatic amide salt;

[0022] The semi-aromatic amide salt, the phosphorus-containing semi-aromatic amide salt, the molecular weight regulator and water are mixed to carry out a melt polycondensation reaction to obtain a functional polymer;

[0023] The functional polymer and polyamide are mixed and subjected to amide exchange reaction to obtain the modified polyamide.

[0024] Preferably, the molar ratio of the aromatic dibasic acid to the first aliphatic diamine is 1:0.98-1.05;

[0025] The molar ratio of the phosphorus-containing aromatic dibasic acid to the second aliphatic diamine is 1:0.98-1.05;

[0026] The temperatures of the first salt-forming reaction and the second salt-forming reaction are independently 60 to 90° C., and the times of the first salt-forming reaction and the second salt-forming reaction are independently 0.5 to 5 hours.

[0027] Preferably, before the melt polycondensation reaction, the method further comprises: mixing the semi-aromatic amide salt, the phosphorus-containing semi-aromatic amide salt, the molecular weight regulator and water to perform a prepolymerization reaction;

[0028] The molar ratio of the semi-aromatic amide salt to the phosphorus-containing semi-aromatic amide salt is 3-6:4-8;

[0029] The pressure of the prepolymerization reaction is 0.5-2.5 MPa; the temperature of the prepolymerization reaction is 200-250° C.; and the time of the prepolymerization reaction is 1-3 hours.

[0030] Preferably, the vacuum degree of the melt polycondensation reaction is 10 to 200 Pa; the temperature of the melt polycondensation reaction is 220 to 280° C.; and the time of the melt polycondensation reaction is 1 to 3 hours.

[0031] Preferably, the mass ratio of the functional polymer to the polyamide is 10 to 20:100;

[0032] The temperature of the amide exchange reaction is 260-280° C.; the time of the amide exchange reaction is 0.5-3 h.

[0033] The present invention also provides a modified polyamide fiber, which is prepared from the modified polyamide described in the above technical solution or the modified polyamide prepared by the preparation method described in the above technical solution.

[0034] The present invention provides a modified polyamide having a structure shown in Formula I: Formula I; wherein, Q is a semi-aromatic amide structural unit, R is a phosphorus-containing semi-aromatic amide structural unit, and P is a polyamide structural unit; a is 3 to 6, b is 4 to 8, and c is 120 to 250. The invention introduces aromatic ring structures and phosphorus-containing aromatic ring groups into polyamide molecular chains to provide a modified polyamide having an aromatic ring structure in the main chain and a phosphorus-containing aromatic ring flame-retardant structure in the side group; the rigid benzene ring structure of the main chain and the phosphorus-containing aromatic ring structure of the side group are used to reduce the hydrogen bonding effect between the polyamide molecular chains, thereby reducing the formation of hydrogen bonds in the polyamide molecules, increasing the proportion of amorphous regions of the modified polyamide, and further improving its drafting performance during spinning; the steric hindrance of the side group aromatic ring structure is used to increase the distance between the polyamide molecular chains, thereby reducing the molecular chain entanglement of the high-viscosity polyamide, reducing its structural viscosity index, and improving its flowability and spinnability. In summary, the contribution of the main chain and side group benzene rings to the drafting performance during spinning and the side group aromatic rings to the spinnability of high-viscosity polyamide are combined to achieve the purpose of improving the mechanical strength of the modified polyamide fiber.

[0035] The present invention also provides a method for preparing the modified polyamide described in the above technical solution, comprising the following steps: dissolving an aromatic dibasic acid and a first aliphatic diamine in a first solvent, performing a first salt-forming reaction, and obtaining a semi-aromatic amide salt; dissolving a phosphorus-containing aromatic dibasic acid and a second aliphatic diamine in a second solvent, performing a second salt-forming reaction, and obtaining a phosphorus-containing semi-aromatic amide salt; mixing the semi-aromatic amide salt, the phosphorus-containing semi-aromatic amide salt, a molecular weight regulator, and water, and performing a melt polycondensation reaction to obtain a functional polymer; mixing the functional polymer and polyamide, and performing an amide exchange reaction to obtain the modified polyamide. The present invention first prepares a functional polymer by melt polycondensation reaction of an aromatic dibasic acid and a phosphorus-containing dibasic acid, and then introduces a rigid benzene ring structure and a phosphorus-containing flame retardant structure into a polyamide molecular chain by an amide exchange reaction; the rigid benzene ring structure and the phosphorus-containing flame retardant structure of the functional polymer are combined with the polyamide molecular chain by an amide exchange reaction, which will not reduce the polymerization degree and molecular weight of the polyamide molecular chain, and the addition ratio of the functional components can be flexibly designed to obtain a modified polyamide fiber with high mechanical properties. DETAILED DESCRIPTION

[0036] The present invention provides a modified polyamide having a structure shown in Formula I:

[0037]

[0038] Wherein, Q is a semi-aromatic amide structural unit. In the present invention, Q preferably has a structure shown in any one of Formulas 1 to 5:

[0039] More preferably Here, x is preferably an integer of 4-14, and more preferably an integer of 6-12.

[0040] In the present invention, R is a phosphorus-containing semi-aromatic amide structural unit; the R preferably has a structure shown in any one of Formulas 6 to 8:

[0041] More preferably Here, y is preferably an integer of 4 to 14, and more preferably an integer of 6 to 12.

[0042] In the present invention, the R and Q structural units jointly improve the mechanical properties of the modified polyamide, while the R structural unit as a flame retardant also improves the flame retardant properties of the modified polyamide.

[0043] In the present invention, P is a polyamide structural unit, and the polyamide structural unit preferably includes a polyamide 6 structural unit, a polyamide 66 structural unit or a polyamide 56 structural unit, and more preferably a polyamide 6 structural unit or a polyamide 66 structural unit. In the present invention, the P preferably has a structure shown in any one of formulas 9 to 11:

[0044] More preferably

[0045] In the present invention, a is 3 to 6, preferably 4 to 5; b is 4 to 8, preferably 5 to 7; c is 120 to 250, and when P is a polyamide 66 structural unit, c is preferably 120 to 140, more preferably 130 to 140; when P is a polyamide 6 structural unit, c is preferably 230 to 250, more preferably 240 to 250; when P is a polyamide 56 structural unit, c is preferably 120 to 140, more preferably 130 to 140.

[0046] The present invention also provides a method for preparing the modified polyamide described in the above technical solution, comprising the following steps:

[0047] Dissolving an aromatic dibasic acid and a first aliphatic diamine in a first solvent, and performing a first salt-forming reaction to obtain a semi-aromatic amide salt;

[0048] dissolving the phosphorus-containing aromatic dibasic acid and the second aliphatic diamine in a second solvent, and performing a second salt-forming reaction to obtain a phosphorus-containing semi-aromatic amide salt;

[0049] The semi-aromatic amide salt, the phosphorus-containing semi-aromatic amide salt, the molecular weight regulator and water are mixed to carry out a melt polycondensation reaction to obtain a functional polymer;

[0050] The functional polymer and polyamide are mixed and subjected to amide exchange reaction to obtain the modified polyamide.

[0051] In the present invention, an aromatic dibasic acid and a first aliphatic diamine are dissolved in a first solvent, and a first salt-forming reaction is performed to obtain a semi-aromatic amide salt. In the present invention, the aromatic dibasic acid preferably includes More preferably In the present invention, the first aliphatic diamine preferably has a structure shown in formula a:

[0052]

[0053] Among them, m is preferably any integer from 4 to 14, and more preferably any integer from 6 to 12.

[0054] In the present invention, the first solvent preferably includes water or ethanol, more preferably ethanol.

[0055] In the present invention, the molar ratio of the aromatic dibasic acid to the first aliphatic diamine is preferably 1:0.98-1.05, more preferably 1:1. In the present invention, the mass ratio of the total mass of the aromatic dibasic acid and the first aliphatic diamine to the mass of the first solvent is preferably 1:3-6, more preferably 1:3-4.

[0056] The present invention has no special requirements for the dissolution, as long as it can be completely dissolved. In the present invention, the temperature of the first salt-forming reaction is preferably 60 to 90°C, more preferably 70 to 80°C; the time of the first salt-forming reaction is preferably 0.5 to 5h, more preferably 1 to 4h. In the present invention, the first salt-forming reaction is preferably accompanied by stirring. In the present invention, the stirring speed is preferably 20 to 100r / min, more preferably 40 to 80r / min.

[0057] In the present invention, a phosphorus-containing aromatic dibasic acid and a second aliphatic diamine are dissolved in a second solvent, and a second salt-forming reaction is performed to obtain a phosphorus-containing semi-aromatic amide salt. In the present invention, the phosphorus-containing aromatic dibasic acid preferably includes More preferably In the present invention, the second aromatic diamine is preferably the same as the first aromatic diamine, and will not be described again. In the present invention, the second solvent preferably includes water or ethanol, more preferably ethanol.

[0058] In the present invention, the molar ratio of the phosphorus-containing aromatic dibasic acid to the second aliphatic diamine is 1:0.98-1.05, more preferably 1:1. In the present invention, the mass ratio of the total mass of the phosphorus-containing aromatic dibasic acid and the second aliphatic diamine to the mass of the second solvent is preferably 1:3-6, more preferably 1:3-4.

[0059] The present invention has no special requirements for the dissolution, as long as it can be completely dissolved. In the present invention, the temperature of the second salt-forming reaction is preferably 60 to 90°C, more preferably 70 to 80°C; the time of the second salt-forming reaction is preferably 0.5 to 5h, more preferably 1 to 4h. In the present invention, the second salt-forming reaction is preferably accompanied by stirring. In the present invention, the stirring speed is preferably 20 to 100r / min, more preferably 40 to 80r / min.

[0060] After obtaining the semi-aromatic amide salt and the phosphorus-containing semi-aromatic amide salt, the present invention mixes the semi-aromatic amide salt, the phosphorus-containing semi-aromatic amide salt, the molecular weight regulator and water to carry out a melt polycondensation reaction to obtain a functional polymer. In the present invention, before the melt polycondensation reaction, it is preferred that the semi-aromatic amide salt, the phosphorus-containing semi-aromatic amide salt, the molecular weight regulator and water are mixed to carry out a prepolymerization reaction.

[0061] In the present invention, the molecular weight regulator preferably includes one or more of terephthalic acid, adipic acid and acetic acid, more preferably adipic acid. In the present invention, the water is preferably deionized water.

[0062] In the present invention, the molar ratio of the semi-aromatic amide salt to the phosphorus-containing semi-aromatic amide salt is preferably 3-6:4-8, more preferably 3-5:4-6, and most preferably 3:4. In the present invention, the mass ratio of the total mass of the semi-aromatic amide salt and the phosphorus-containing semi-aromatic amide salt to the molecular weight regulator is preferably 100:0.05-0.2, more preferably 100:0.1-0.15. In the present invention, the mass ratio of the total mass of the semi-aromatic amide salt and the phosphorus-containing semi-aromatic amide salt to water is preferably 100:80-120, more preferably 100:90-110.

[0063] In the present invention, the pressure of the prepolymerization reaction is preferably 0.5-2.5 MPa, more preferably 1-2 MPa; the temperature of the prepolymerization reaction is preferably 200-250°C, more preferably 220-250°C; the time of the prepolymerization reaction is preferably 1-3 h, more preferably 1-2 h.

[0064] In the present invention, the prepolymerization reaction is preferably carried out in a protective atmosphere, and the protective atmosphere preferably includes nitrogen or argon, more preferably nitrogen. In the present invention, the prepolymerization reaction is preferably carried out in a polymerization kettle.

[0065] The present invention can avoid the decomposition reaction of the amide salt or the degradation side reaction of the polyamide when the aromatic amide salt and the phosphorus-containing semi-aromatic amide salt are directly polymerized at a high temperature through the prepolymerization reaction, and the present invention is conducive to the preparation of high molecular weight functional polymers through prepolymerization. In the present invention, the product of the prepolymerization reaction is a primary functional polymer with a certain degree of polymerization and a relatively small molecular weight.

[0066] In the present invention, the vacuum degree of the melt polycondensation reaction is preferably 10-200 Pa, more preferably 10-100 Pa; the temperature of the melt polycondensation reaction is preferably 220-280°C, more preferably 240-260°C; the time of the melt polycondensation reaction is preferably 1-3h, more preferably 2-3h. In the present invention, the melt polycondensation reaction is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably consistent with the protective atmosphere of the prepolymerization. The present invention preferably reduces the pressure to normal pressure under the pressure conditions of the prepolymerization reaction, and then evacuates to the vacuum degree required for the melt polycondensation reaction. The present invention has no special requirements for the method of reducing the pressure, and the conventional method in the art can be used. In the present invention, the time for reducing the pressure from the prepolymerization reaction to normal pressure is preferably 30min-120min, more preferably 60-90min.

[0067] In the present invention, the melt polycondensation reaction is preferably accompanied by stirring, and the stirring speed is preferably 20 to 100 r / min, more preferably 40 to 80 r / min.

[0068] In the present invention, the functional polymer preferably has a structure shown in formula b:

[0069]

[0070] Among them, j is preferably 30-60, more preferably 40-50; k is preferably 40-80, more preferably 50-70.

[0071] After obtaining the functional polymer, the present invention mixes the functional polymer with polyamide and performs an amide exchange reaction to obtain the modified polyamide. In the present invention, the polyamide preferably includes polyamide 6, polyamide 66 or polyamide 56, more preferably polyamide 6 or polyamide 66. In the present invention, the mass ratio of the functional polymer to the polyamide is preferably 10 to 20:100, more preferably 10 to 15:100.

[0072] In the present invention, the temperature of the amide exchange reaction is preferably 260-280° C., more preferably 265-275° C.; the time of the amide exchange reaction is preferably 0.5-3 h, more preferably 0.5-1.5 h.

[0073] In the present invention, the functional polymer and the polyamide undergo an amide exchange reaction in a molten state.

[0074] In the present invention, the functional polymer prepared is preferably in a molten state. In the present invention, when the polyamide is a molten polyamide, the device for the transamide reaction preferably includes a polymerization kettle and a polymerization pipeline, more preferably a polymerization kettle. When the polyamide is a polyamide slice, the functional polymer and the polyamide slice are preferably melt-blended in a twin-screw extruder to perform the transamide reaction.

[0075] The invention can introduce more R structural units through amide exchange reaction, thereby improving the flame retardancy of the modified polyamide.

[0076] The present invention synthesizes an aromatic ring structure and a flame retardant structure into a functional polymer through a melt polycondensation reaction, and the functional polymer improves the flame retardancy of the modified polyamide while improving the mechanical properties of the modified polyamide. In the process of preparing the functional polymer, only small molecular water is removed, and no harmful chemical substances are discharged, which has the characteristics of being green and environmentally friendly.

[0077] The functional polymer prepared by the present invention is combined with the polyamide molecular chain through an amide exchange reaction, and a high-performance polyamide fiber with high mechanical properties and flame retardant properties is obtained through melt spinning. The proportion and addition path of the functional polymer can be flexibly adjusted according to demand. The preparation method of the high-performance polyamide fiber has the characteristics of small addition amount, flexible and efficient, and long-lasting performance.

[0078] The present invention also provides a modified polyamide fiber, which is prepared from the modified polyamide described in the above technical solution or the modified polyamide prepared by the preparation method described in the above technical solution. In the present invention, the method for preparing the polyamide fiber is preferably to use the modified polyamide for melt spinning. In the present invention, the temperature of the melt spinning is preferably 270 to 310°C, more preferably 280 to 300°C; the winding speed in the melt spinning is preferably 2500 to 4000 m / min, more preferably 3000 to 4000 m / min; the draft ratio in the melt spinning is preferably 5 to 6, more preferably 5.0 to 5.5.

[0079] In the present invention, the breaking strength of the modified polyamide fiber is preferably 9.8 to 11.7 cN / dtex, the breaking elongation is preferably 8 to 15%, and the limiting oxygen index is preferably 30 to 36%.

[0080] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0081] Preparation of modified polyamide

[0082] Example 1

[0083] 5 mol (830.65 g) of terephthalic acid and 5 mol (581 g) of hexamethylenediamine were dissolved in 4235 g of ethanol, and a first salt-forming reaction was carried out at 70° C. (accompanied by stirring at a speed of 50 r / min) for 1 h to obtain hexamethylenediamine terephthalate;

[0084] 5 mol (1731 g) of 9,10-dihydro-9-oxa-10-phosphorylphenanthrene-succinic acid (DDP) and 5 mol (581 g) of hexamethylenediamine were dissolved in 6936 g of ethanol, and a second salt-forming reaction was carried out at 60° C. (accompanied by stirring at a speed of 50 r / min) for 1 h to obtain hexamethylenediamine DDP salt;

[0085] 3 mol (847 g) of hexamethylenediamine terephthalate, 4 mol (1850 g) of hexamethylenediamine DDP salt, 2697 g of deionized water and 2.7 g of adipic acid were added to a polymerization kettle, nitrogen was introduced to replace the air in the polymerization kettle to maintain a pressure of 2.0 MPa, and a prepolymerization reaction was carried out at 250° C. for 2 h, and then the pressure was released to normal pressure in 30 min, and then evacuated to a vacuum degree of 200 Pa, and melt polycondensation reaction was carried out at 260° C. (accompanied by stirring at a speed of 50 r / min) for 2 h to obtain a functional polymer in a molten state;

[0086] The functional polymer in a molten state is mixed with the polyamide 6 in a molten state at a mass ratio of 10:100, and an amide exchange reaction is carried out at 270° C. for 1 hour to obtain a modified polyamide 6; the structural formula of the modified polyamide 6 is:

[0087]

[0088] Example 2

[0089] 5 mol (830.65 g) of isophthalic acid and 5 mol (861.55 g) of decanediamine were dissolved in 5077 g of ethanol, and a first salt-forming reaction was carried out at 80° C. (accompanied by stirring at a speed of 50 r / min) for 1 h to obtain decanediamine isophthalate;

[0090] Dissolve 5 mol (1781.55 g) of 2,3-dicarboxypropyl diphenylphosphine oxide (DPOIA) and 5 mol (861.55 g) of decanediamine in 7930 g of ethanol, and perform a second salt-forming reaction at 80° C. (accompanied by stirring at a speed of 50 r / min) for 1 h to obtain decanediamine DPOIA salt;

[0091] 3 mol (1015.32 g) of decanediamine isophthalate, 4 mol (2114.48 g) of decanediamine DPOIA salt, 3130 g of deionized water and 3.5 g of terephthalic acid were added to a polymerization kettle, nitrogen was introduced to replace the air in the polymerization kettle to maintain a pressure of 1.8 MPa, and after a prepolymerization reaction at 260° C. for 1 hour, the pressure was released to normal pressure in 60 minutes, and then evacuated to a vacuum degree of 100 Pa, and melt polycondensation reaction was carried out at 250° C. (accompanied by stirring at a speed of 50 r / min) for 2 hours to obtain a functional polymer in a molten state;

[0092] The functional polymer in a molten state is mixed with the polyamide 66 in a molten state at a mass ratio of 15:100, and an amide exchange reaction is carried out at 275° C. for 1 hour to obtain a modified polyamide 66; the structural formula of the modified polyamide 66 is:

[0093]

[0094] Example 3

[0095] 5 mol (1080.95 g) of 1,4-naphthalenedicarboxylic acid and 5 mol (581 g) of hexamethylenediamine were dissolved in 6648 g of ethanol, and a first salt-forming reaction was carried out at 80° C. (accompanied by stirring at a speed of 50 r / min) for 1 h to obtain hexamethylenediamine naphthalenedicarboxylate;

[0096] 5 mol (1070.75 g) of 2-carboxyethylphenylphosphinic acid (CEPPA) and 5 mol (861.55 g) of decanediamine were dissolved in 7730 g of ethanol, and a second salt-forming reaction was carried out at 80° C. (accompanied by stirring at a speed of 50 r / min) for 1 h to obtain decanediamine CEPPA salt;

[0097] 3 mol (997.17 g) of hexamethylenediamine naphthalate, 4 mol (1545.84 g) of decanediamine CEPPA salt, 2561 g of deionized water and 3.5 g of adipic acid were added to a polymerization kettle, nitrogen was introduced to replace the air in the polymerization kettle to maintain a pressure of 2.0 MPa, and after a prepolymerization reaction at 260° C. for 1 hour, the pressure was released to normal pressure in 60 minutes, and then evacuated to a vacuum degree of 100 Pa, and melt polycondensation reaction was carried out at 250° C. (accompanied by stirring at a speed of 50 r / min) for 2 hours to obtain a functional polymer in a molten state;

[0098] The functional polymer in a molten state is mixed with the polyamide 56 in a molten state at a mass ratio of 15:100, and an amide exchange reaction is carried out at 275° C. for 1 hour to obtain a modified polyamide 56; the structural formula of the modified polyamide 56 is:

[0099]

[0100] Preparation of modified polyamide fibers

[0101] Example 4

[0102] The modified polyamide 6 prepared in Example 1 is melt-spinned to obtain modified polyamide 6 fibers;

[0103] The melt spinning temperature was 280°C, the take-up speed was 3000 m / min, and the draft ratio was 5.5.

[0104] Example 5

[0105] The modified polyamide 66 prepared in Example 2 is melt-spinned to obtain modified polyamide 66 fibers;

[0106] The melt spinning temperature was 280°C, the take-up speed was 3500 m / min, and the draft ratio was 5.2.

[0107] Example 6

[0108] The modified polyamide 56 prepared in Example 3 is melt-spun to obtain modified polyamide 56 fibers;

[0109] The melt spinning temperature was 280°C, the take-up speed was 4000 m / min, and the draft ratio was 5.0.

[0110] The mechanical properties of the modified polyamide fibers prepared in Examples 4 to 6 were tested according to GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments", wherein the clamping distance was 250 mm and the tensile speed was 500 mm / min; the flame retardant properties of the fabrics woven from the modified polyamide fibers in Examples 4 to 6 were tested according to GB / T 5454-1997 "Textile Combustion Performance Test Oxygen Index Method", and the results are shown in Table 1. The present invention has no special requirements for the method of weaving fabrics using modified polyamide fibers, and the conventional method in the art can be used.

[0111] Table 1 Mechanical properties and flame retardant properties of modified polyamide fibers prepared in Examples 4 to 6

[0112] Example Breaking strength (cN / dtex) Elongation at break (%) Limiting oxygen index (%) Example 4 9.8 12.1 30.1 Example 5 10.6 14.5 33.6 Example 6 11.7 13.3 36.0

[0113] It can be seen from Table 1 that the modified polyamide fiber prepared using the modified polyamide provided by the present invention as a raw material has high mechanical strength and flame retardant properties, and can be applied to special application fields such as cord fabrics, parachutes, and climbing ropes.

[0114] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A modified polyamide having any one of the following structures:

2. The method for preparing the modified polyamide according to claim 1, The preparation method of the modified polyamide 66 comprises the following steps: Dissolve 5 mol of isophthalic acid and 5 mol of decanediamine in 5077 g of ethanol, and perform a first salt-forming reaction at 80° C. for 1 hour. During the first salt-forming reaction, stir at a speed of 50 r / min to obtain decanediamine isophthalate; Dissolve 5 mol of 2,3-dicarboxypropyl diphenylphosphine oxide and 5 mol of decanediamine in 7930 g of ethanol, and perform a second salt-forming reaction at 80° C. for 1 hour. During the second salt-forming reaction, stir at a speed of 50 r / min to obtain decanediamine DPOIA salt; 3 mol of decanediamine isophthalate, 4 mol of decanediamine DPOIA salt, 3130 g of deionized water and 3.5 g of terephthalic acid were added to a polymerization kettle, nitrogen was introduced to replace the air in the polymerization kettle to maintain a pressure of 1.8 MPa, and a prepolymerization reaction was carried out at 260° C. for 1 hour, and then the pressure was released to normal pressure in 60 minutes, and then evacuated to a vacuum degree of 100 Pa, and melt polycondensation was carried out at 250° C. for 2 hours. During the melt polycondensation reaction, stirring was carried out at a speed of 50 r / min to obtain a functional polymer in a molten state; The functional polymer in a molten state is mixed with polyamide 66 in a molten state at a mass ratio of 15:100, and an amide exchange reaction is carried out at 275° C. for 1 hour to obtain modified polyamide 66; The preparation method of the modified polyamide 56 comprises the following steps: Dissolve 5 mol of 1,4-naphthalenedicarboxylic acid and 5 mol of hexamethylenediamine in 6648 g of ethanol, and perform a first salt-forming reaction at 80° C. for 1 hour, wherein the first salt-forming reaction is accompanied by stirring at a speed of 50 r / min, to obtain hexamethylenediamine naphthalenedicarboxylate; Dissolve 5 mol of 2-carboxyethylphenylphosphinic acid and 5 mol of decanediamine in 7730 g of ethanol, and perform a second salt-forming reaction at 80° C. for 1 hour. During the second salt-forming reaction, stir at a speed of 50 r / min to obtain decanediamine CEPPA salt; 3 mol of hexamethylenediamine naphthalate, 4 mol of decanediamine CEPPA salt, 2561 g of deionized water and 3.5 g of adipic acid were added to a polymerization kettle, nitrogen was introduced to replace the air in the polymerization kettle to maintain a pressure of 2.0 MPa, and a prepolymerization reaction was carried out at 260° C. for 1 hour, and then the pressure was released to normal pressure in 60 minutes, and then evacuated to a vacuum degree of 100 Pa, and melt polycondensation was carried out at 250° C. for 2 hours. During the melt polycondensation reaction, stirring was carried out at a speed of 50 r / min to obtain a functional polymer in a molten state; The functional polymer in a molten state was mixed with the polyamide 56 in a molten state at a mass ratio of 15:100, and an amide exchange reaction was carried out at 275° C. for 1 hour to obtain modified polyamide 56.

3. A modified polyamide fiber, prepared from the modified polyamide according to claim 1 or the modified polyamide prepared by the preparation method according to claim 2.

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