WO2021148039A1 - Copolymerized polyamide 56/66 polymer, preparation method therefor, and use thereof - Google Patents

Abstract

Disclosed are a copolymerized polyamide 56/66 polymer, a preparation method therefor, and the use thereof. The method for preparing the copolymerized polyamide 56/66 polymer of the present invention comprises the following steps: (1) preparing a polyamide 56/66 salt aqueous solution according to the point 1) as below and/or 2): 1) in an inert atmosphere, mixing 1,5-pentanediamine, hexanediamine and adipic acid in water for a neutralization reaction; and 2) mixing a polyamide 56 salt crystal and a polyamide 66 salt crystal; and (2) subjecting the polyamide 56/66 salt aqueous solution to a polymerization reaction in order to obtain the polymer. The present invention further relates to spraying out a melt of the copolymerized polyamide 56/66 polymer through a spinneret plate to obtain a fine melt stream, the fine melt stream is cooled and solidified to form a strand, and a fiber post-treatment is carried out in order to obtain copolymerized polyamide 56/66 polymer fibers. The fibers prepared from the copolymerized polyamide 56/66 polymer obtained by the present invention have a higher strength, wear resistance and flame retardance, and also habe an excellent dyeability and comfort, can adapt to being used in places with a higher temperature, humidity and voltage, and is safe and environmentally friendly.

Description

Copolyamide 56/66 polymer and its preparation method and application Technical field

The invention relates to the field of fiber materials, in particular to a copolymerized polyamide 56/66 polymer, and a preparation method and application thereof.

Background technique

Polyamide has excellent comprehensive properties such as oil resistance, wear resistance, corrosion resistance, fatigue resistance, high strength, and self-lubricating. It has become the first of the five major engineering materials and has been widely used in clothing, medicine, military, industry, machinery and other industries. American scientist Dr. Carothers invented polyamide 66 by chemical synthesis in the early 1930s, commonly known as "nylon 66". DuPont built the first polyamide 66 fiber factory in 1939, with a production capacity of 4,000 tons/year, and entered the industrial production stage of polyamide. While polyamide 66 was commercialized, in 1938, French company IG Farben/Basf invented polyamide 6. At present, polyamide 66 and polyamide 6 are the largest polyamide varieties used in engineering materials and textiles.

Polyamide 56 is a new type of polyamide fiber. It is a new type of bio-based fiber made from crops, trees and other plants and their residues and inclusions through biological, chemical and physical methods. Polyamide 56 is similar to polyamide 66 in terms of oil resistance, wear resistance, corrosion resistance, fatigue resistance, high strength, and self-lubricating properties, and is superior to polyamide 6, but due to the structural difference between nylon 56 and nylon 66, nylon 56’s Dyeing performance and flame retardant performance are more excellent.

Invention Disclosure

The purpose of the present invention is to provide a copolymerized polyamide 56/66 polymer and its preparation method and application.

The present invention adopts two kinds of copolymerization modification, one is 1,5-pentanediamine, hexamethylene diamine and adipic acid are neutralized according to a certain molar ratio to obtain a polyamide 56/66 salt aqueous solution and then polymerized; the other is polyamide 56 salt crystals and polyamide 66 salt crystals are first prepared according to a certain mass percentage to obtain a polyamide 56/66 salt aqueous solution and then polymerized. Through the above two copolymerization reactions, a polyamide 56/66 copolymer can be obtained, and then melt-spinning Spinning by silk method finally obtains polyamide fiber.

The method for preparing a copolymerized polyamide 56/66 polymer provided by the present invention includes the following steps: (1) Prepare a polyamide 56/66 salt aqueous solution according to the following 1) and/or 2);

1) In an inert atmosphere, mixing 1,5-pentanediamine, hexamethylene diamine and adipic acid in water for neutralization reaction;

2) Mixing polyamide 56 salt crystals and polyamide 66 salt crystals to prepare the polyamide 56/66 salt aqueous solution;

(2) The polyamide 56/66 salt aqueous solution prepared in step (1) is polymerized to obtain a copolymerized polyamide 56/66 polymer.

In the preparation method of the above-mentioned copolymerized polyamide polymer, in step (1)-1), the mass percentage of the polyamide 56/66 salt aqueous solution may be 20% to 80%, specifically 50%, 20% ～50%, 50%～80% or 30%～70%;

The ratio of the mole of the adipic acid to the sum of the moles of the hexamethylene diamine and the 1,5-pentanediamine may be 1:1 to 1.05, and specifically may be 1:1;

Wherein, the molar content of the hexamethylene diamine in the total molar amount of the hexamethylene diamine and the 1,5-pentanediamine is 0-100%, but not 0 and 100%, and the balance is the 1 , The molar content of 5-pentanediamine;

Preferably, the molar content of hexamethylene diamine may be 35-65%, and the balance may be the molar content of the 1,5-pentanediamine; specifically, it may be 50% each.

In the preparation method of the above polyamide polymer, in step (1)-2), the mass percentage of the polyamide 56/66 salt solution can be 20% to 80%, specifically 50%, 60%, 20% to 50%, 50% to 80%, or 30% to 70%; wherein, the polyamide 56 salt crystal mass percentage content can be 0-100%, but not 0 and 100%, the balance is all The polyamide 66 salt crystal mass percentage; preferably, the polyamide 56 salt crystal mass and the polyamide 66 salt crystal mass are the percentage content can be 35-65%, and the balance is the polyamide 66 salt crystals The quality percentage.

In the method for preparing the copolymerized polyamide polymer, step (2) further includes the step of adding an auxiliary agent to carry out the polymerization reaction;

The auxiliary agent includes at least one of a molecular weight regulator, a flame retardant, an antistatic agent, an antibacterial finishing agent, and an anti-ultraviolet finishing agent;

When the polyamide 56/66 salt aqueous solution is prepared through step (1)-1) and step (2) is performed, the addition amount of the auxiliary agent is the hexamethylene diamine, the 1,5-pentanediamine and the 0.05%～0.15% of the sum of the mass of adipic acid;

When the polyamide 56/66 salt aqueous solution is prepared through steps (1)-2) and step (2) is performed, the added amount of the auxiliary agent is 0.05% to 0.15% of the weight of the polyamide 56/66 salt.

In the present invention, the additives are all commonly used reagents known in the art; wherein, the molecular weight regulator is aliphatic or aromatic monobasic acid, the dibasic acid, aliphatic or aromatic amine, hydrochloric acid, hydrogen At least one of sodium oxide and amino acid hydrochloride; the dibasic acid may specifically be adipic acid.

In the preparation method of the above-mentioned copolyamide polymer, the polymerization reaction in step (2) is carried out according to the following conditions in a)-b): a) The temperature can be 210～240℃ and the pressure can be 1.70～1.85MPa When the pressure is maintained, the pressure can be maintained for 20min～60min, specifically it can be maintained at 235℃, 1.75MPa for 2h or 240℃, 1.8MPa for 2.5h; b) Pressure is 1.75～1.85MPa After releasing to normal pressure, the temperature rises to 275～290℃, then vacuumize to -0.08MPa and stir for 10min～60min, specifically it can be stirring for 15min, 30min, 15min～30min.

In the present invention, the 1,5-pentanediamine can be 1,5-pentanediamine prepared by a biological method; the preparation method can be carried out according to the content known in the art.

The present invention also provides the copolyamide 56/66 polymer prepared by the above-mentioned preparation method.

The copolyamide 56/66 polymer prepared by the present invention has no lower physical properties compared with polyamide 66. The melting point is 247-260°C, the viscosity is 130-180ml/g, and the tensile strength is It is 60-90MPa, the bending strength is 100-130MPa, and the notched impact strength is 90-120J/m.

The present invention also provides a method for preparing polyamide fiber, which includes the following steps: the melt of the copolymer polyamide 56/66 polymer is sprayed through a spinneret to obtain a melt stream, and the melt stream is cooled After coagulation into filaments, after oiling, post-processing is performed to obtain the copolyamide 56/66 fiber.

In the above-mentioned preparation method of copolyamide 56/66 fiber, the process of spraying the melt of the copolyamide 56/66 polymer through a spinneret to obtain a trickle of the melt is as follows: The temperature of the spinning box is: the temperature of the first zone of the spinning box is 260～300℃, the temperature of the second zone is 260～300℃, the temperature of the third zone is 250～295℃, the temperature of the metering pump is 250～295℃, and the temperature of the spinning assembly can be 270 ～290℃; the metering pump rotates at 12～18rpm in the spinning box. The copolyamide polymer melt is distributed through pipelines and delivered to each spinneret with equal residence time and pressure drop; the spinning speed can be 1000～4200m/min;

The melt flows through the side blowing device for cooling and forming, and the conditions are as follows: the side blowing speed is 0.30～0.80m/min; the wind temperature can be 21～26℃, the side blowing pressure can be 420～480Pa; the side blowing speed is specific It can be 0.50m/min, 0.30～0.50m/min, 0.50～0.80m/min or 0.40～0.70m/min, the wind temperature can be 25℃, 21～25℃, 23～26℃, and the side blowing pressure is specific It can be 440Pa, 440～480Pa, 420～440Pa or 430～450Pa;

The concentration of the oiling agent for oiling can be 2-15%, specifically 5%, 10%, 2% to 5%, 5-15% or 2-10%; the oiling agent for oiling can be F5103, which is commercially available In Takemoto, Japan.

The winding speed of the solidified thread may be 500-4000m/min, specifically 950m/min, 500-950m/min, 950-4000m/min, 600-1000m/min, 500-2000m/min, 500 ～3000m/min or 600～2500m/min.

In the above-mentioned preparation method of the copolyamide 56/66 fiber, the post-processing after oiling the thread includes drawing, heat setting, winding and/or crimping to obtain the copolyamide 56/66 fiber;

The drafting is one-stage drafting, two-stage drafting or multi-stage drafting, specifically two-stage drafting, but not limited to two-stage drafting, and can be increased or decreased according to product performance requirements;

The drafting conditions are as follows: the temperature of one roll can be 60～80℃; the temperature of two rolls can be 150～230℃; the temperature of three rolls can be 150～230℃; Grade 1.01～1.10 times; specifically can be: one roll temperature 70℃, 75℃, 60～75℃, 75～80℃ or 65～75℃, two roll temperature 170℃, 180℃, 170～180℃, 150～ 180℃, 170～230℃ or 160～210℃, three-roll temperature 180℃, 170～180℃, 150～180℃, 170～230℃ or 160～210℃;

The heat setting is steam heat setting, hot plate setting, hot roll setting or water bath heat setting; the heat setting is performed under the condition of 150-230°C; the specific hot plate temperature can be 190°C, 200°C, 150-190 ℃, 190～230℃, 190～200℃ or 160～200℃;

When the prepared copolyamide 56/66 fiber is a filament, the post-processing includes the drawing, shaping, bundling, winding, cooling, drying, and packaging to obtain a copolyamide 56/66 filament ; The winding rate is 500-1000m/min, specifically 1000m/min;

When the prepared copolyamide 56/66 fibers are staple fibers, the post-processing includes the drafting, shaping, bundling, crimping, cooling, drying, cutting, and packaging to obtain copolyamide 56/66 short fibers. Fiber; The crimp rate can be 300-350m/min, specifically 300m/min, and the number of crimps can be 10-30, specifically 15.

The present invention further provides the copolyamide 56/66 fiber prepared by the above preparation method.

The polyamide fibers of the present invention can be filaments or staple fibers.

The copolyamide 56/66 fiber prepared by the present invention has high strength, abrasion resistance, flame retardancy and excellent dyeability, and its limiting oxygen index is increased to 28-35%; when it is a filament, it breaks The strength is 3.4≦12.0cN/dtex; when it is short fiber, its breaking strength is 3.0≦7.5cN/dtex. The dyeing rate and half dyeing time on acid dyes and neutral dyes are significantly improved compared with polyamide 66.

The copolymer polyamide material of the present invention is applied to the fields of automobile industry, electronic and electrical appliance industry, electric and steam components, mechanical equipment, clothing, and daily chemical products. Among them, the automobile industry includes engines, motors, and parts of the car body; the electronic and electrical industries include precision electronic instrument parts, electronic and electrical insulation parts, lighting appliances, electronic and electrical parts, such as rice cookers, vacuum cleaners, and high-frequency electronics. Food heaters, etc.; the electrical components include terminals, sockets, switches; the mechanical equipment industry includes insulating gaskets, baffle seats, turbines, propeller shafts, sliding bearings, train brake coupling discs, nuts, bolts, screws, Nozzles, conveyor belts, fan blades, gears, impellers; the clothing and daily necessities include men’s and women’s and children’s clothing, duvet cover fabrics, socks, raincoats, curtains, and carpets, as well as skates, snowboard parts, tennis rackets, glasses, combs, Packaging bag.

The best way to implement the invention

The experimental methods used in the following examples are conventional methods unless otherwise specified.

The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

The performance test methods in the following embodiments are as follows:

Viscosity: Ubbelohde viscometer method (concentrated sulfuric acid method);

Melting point and cold crystallization temperature: GB T 19466.1-2004, Plastic Differential Scanning Calorimetry (DSC);

Limiting oxygen index: GB T 2406-1993, Oxygen index method for plastic combustion performance test method;

Flame retardant performance: measured according to UL94 method;

Tensile strength: measured in accordance with ASTM D638;

Bending strength: measured according to ASTM D790 method;

Notched impact strength: Measured in accordance with ASTM D256 method.

Example 1. Preparation of copolymerized polyamide polymer

Prepare a polyamide 56/66 salt aqueous solution with a mass concentration of 50%. Under the protection of a nitrogen atmosphere, gradually add hexamethylene diamine to the 1,5-pentanediamine aqueous solution, and then gradually add adipic acid to control the hexamethylene diamine The molar ratio of 1,5-pentanediamine to adipic acid is 0.5:0.5:1. A polyamide salt aqueous solution with a mass concentration of 50% is injected into the reactor, and the pressure is maintained for 2.5 hours under the conditions of a temperature of 240° C. and a pressure of 1.8 MPa. Then the pressure in the reactor was released, the temperature was increased, the temperature was controlled at 283°C, and the system was evacuated to reduce the system pressure to -0.08MPa, and the system was continuously stirred for 15 minutes in a vacuum state to obtain a copolymerized polyamide 56/66 polymer.

The physical and chemical parameters of the copolyamide polymer prepared in this embodiment are as follows:

The melting point is 247°C, the cold crystallization temperature is 70°C, the viscosity is 153.4ml/g, the tensile strength is 75.3MPa, the bending strength is 118.1MPa, and the notched impact strength is 103.8J/m.

Example 2. Preparation of copolymerized polyamide polymer

A polyamide 56/66 mixed salt solution with a mass concentration of 60% was prepared, and 30 Kg of the same mass of polyamide 56 salt solution and polyamide 66 salt solution were taken. The prepared polyamide 56/66 salt solution is injected into the reactor, and the pressure is maintained for 2 hours under the conditions of controlling the temperature at 235° C. and the pressure at 1.75 MPa. Release the pressure in the reactor, wait for the temperature to rise to 270°C, evacuate the system to reduce the pressure of the system to -0.08MPa, and continuously stir for 30 minutes in a vacuum state to obtain a copolymerized polyamide polymer.

The physical and chemical parameters of the copolyamide polymer prepared in this embodiment are as follows:

The melting point is 250°C, the cold crystallization temperature is 72°C, the viscosity is 168.8ml/g, the tensile strength is 88.7MPa, the bending strength is 127.5MPa, and the notched impact strength is 116.3J/m.

Example 3 Preparation of polyamide filament

The aforementioned copolyamide polymers prepared in Examples 1 and 2 of the present invention were respectively spun under the following conditions to obtain polyamide filaments: the melt of the copolyamide polymer was sprayed through a spinneret to obtain a stream of melt. The temperature of the spinning box is: the temperature of the first zone of the spinning box is 285℃, the temperature of the second zone is 285℃, the temperature of the third zone is 285℃, the temperature of the metering pump is set to 285℃, and the temperature of the spinning assembly can be 285℃. Pump speed is 16rpm/min, spinning speed is 1000m/min, side blowing speed is 0.50m/min; wind temperature is 25℃, side blowing pressure is 450Pa, winding speed is 950m/min, oiling agent (oiling agent is F5103, (Commercially purchased in Takemoto, Japan), the concentration is 10%, the draft ratio and heating temperature are: one draft ratio 3.20; two draft ratio 1.10; the temperature of the first roller of the drafting box is 70°C; the temperature of the second roller is 180°C; the temperature of the hot plate is 200°C, three The roll temperature is 180°C, and the polyamide filament is obtained by winding at 1000 m/min.

The copolymer polyamide 56/66 polymer was prepared in Examples 1 and 2 of the present invention, and the prepared filaments were marked as Sample 1 and Sample 2 respectively.

Filament performance testing data is shown in Table 1.

Table 1 Filament performance test data of copolymerized polyamide 56/66

The above-mentioned filament dyeing rate experiment. Prepare 1g/L acid blue NHFS dye standard dye liquor, prepare 10 groups of 2mL standard dye liquor dye baths, fiber 0.2g, bath ratio: 1:500, adjust the pH value of the dye liquor to 4.5, and put in the dyeing temperature setting at the same time In the dyeing machine set at 90℃, take out the samples after dyeing for 5min, 10min, 15min, 20min, 30min, 45min, 60min, 75min, 90min, 120min, rinse with water at room temperature, and peel off after drying to test the dye uptake rate. The dyeing results are shown in Table 2.

Table 2 Filament dyeing performance data of copolyamide 56/66

sample Dyeing rate/% Rate constant/min ^-1 Half dyeing time/min Sample 1 95.6 0.2471 5.95

Sample 2 92.8 0.2279 6.27

Example 4 Preparation of Copolyamide 56/66 Staple Fiber

The aforementioned copolyamide polymer prepared in Examples 1 and 2 of the present invention was prepared to obtain staple fibers under the following conditions:

The temperature of the spinning box is: the temperature of the first zone of the spinning box is 281°C, the temperature of the second zone is 282°C, the temperature of the third zone is 282°C, the temperature setting of the metering pump is 282°C, the temperature of the spinning assembly can be 285°C, and the speed of the metering pump is 13rpm/ min, spinning speed 1000m/min, side blowing speed is 0.50m/min; wind temperature is 25℃, side blowing pressure is 440Pa, winding speed is 1000m/min, oiling agent concentration is 5%, drawing ratio and heating temperature It is: one-drawing ratio 2.78; two-drawing ratio 1.05; drawing box one-roll temperature 75°C; two-roll temperature 170°C; hot plate temperature 180°C, three-roll temperature 180°C, crimping rate 300m/min, crimp number 15, The polyamide staple fiber is obtained by cutting, and the performance test data of the staple fiber is shown in Table 3.

The co-polyamide polymer was prepared in Examples 1 and 2 of the present invention, and the prepared staple fibers were marked as Sample 3 and Sample 4, respectively.

Table 3 Staple fiber performance test data

Comparative example,

The preparation method is the same as that in Example 1 of the present invention, except that no 1,5-pentanediamine is added to the raw materials to obtain polyamide 66.

Prepare a polyamide 66 salt aqueous solution with a mass concentration of 50%. Under the protection of a nitrogen atmosphere, adipic acid is gradually added to the hexamethylene diamine aqueous solution, and the molar ratio of hexamethylene diamine and adipic acid is controlled to 1:1, and the mass concentration A 50% aqueous solution of polyamide salt is injected into the reactor, and the pressure is maintained for 2.5 hours under the conditions of a temperature of 240° C. and a pressure of 1.8 MPa. Then release the pressure in the reactor, wait for the temperature to rise to 283° C., evacuate the system to reduce the pressure of the system to -0.08 MPa, and continuously stir for 15 minutes under vacuum to obtain a polyamide 66 polymer. The mechanical properties of the filaments are shown in Table 4.

The physical and chemical parameters for the preparation of polyamide 66 polymer in the comparative example are as follows:

The melting point is 253.3°C, the cold crystallization temperature is 77°C, the viscosity is 125.2ml/g, the tensile strength is 63.1MPa, the bending strength is 104.4MPa, and the notched impact strength is 91.6J/m.

It can be known from the comparison of the above physical and chemical parameters, combined with the comparison of the data in Table 1 and Table 4, that the copolyamide polymer prepared by the method of the present invention has more advantages than the polyamide 66 polymer of the comparative example. With good physical properties, the limiting oxygen index of the fiber is significantly improved, indicating that the flame retardant properties of the copolymer polyamide fiber of the present invention are significantly improved.

Table 4 Mechanical property data of polyamide 66 filament

The above-mentioned comparative example polyamide 66 filament dye uptake experiment. The experimental process is the same as in Example 3, and the experimental results are shown in Table 5.

The dye uptake rate of polyamide 66 with acid blue NHFS dye (90℃) is 60.8%, the dyeing rate constant is 0.0653, and the half dyeing time is 10.61min. According to the data in Table 2 and Table 5, the dye uptake rate of Example 1-2 of the present invention is 95.6% and 92.8%, respectively, compared with 60.8% in the comparative example, the dye uptake rate has been greatly improved; and the dyeing time is shortened This shows that the dyeing ability of the present invention has been greatly improved.

Table 5 Dyeing performance data of polyamide 66 filament

sample Dyeing rate/% Rate constant/min ^-1 Half dyeing time/min Comparison 60.8 0.0653 10.61

The filaments obtained in the above examples and comparative examples were dyed with acid blue NHFS dye, the dye amount was 2% (o.w.f.), the dyeing temperature was 100° C., and the dyeing time was 20 min. The dye fastness results are shown in Table 6.

Table 6 Color fastness test data

It can be seen from the data in Table 6 that the copolyamide material prepared by the copolyamide polymer prepared by the present invention has good color fastness, and its color fastness is better than that of ordinary polyamide 66.

In summary, it shows that the copolymer polyamide material prepared by the present invention has (1) good mechanical properties, improved tensile strength, flexural strength, and notched impact strength compared with nylon 66; (2) improved dyeing performance, and the copolymer polyamide fiber not only improves The dyeing rate has been greatly improved, and the dyeing time has been shortened. At the same time, its color fastness is not reduced, which is basically the same as or better than ordinary polyamide 66. (3) The flame retardant performance is improved, which is comparable to ordinary nylon 66. The limiting oxygen index of the fiber is significantly improved compared to that, which indicates that the flame retardant performance of the copolymer polyamide fiber of the present invention is significantly improved.

Industrial application

Compared with ordinary polyamide 66, polyamide 56 and other products, the present invention (1) has higher strength, abrasion resistance, flame retardancy and excellent dyeability and comfort; (2) can adapt to higher temperatures It is safe and environmentally friendly to use in places with, humidity and voltage; (3) Because the physical properties of polyamide 66 are not reduced compared with ordinary polyamide 66, it is convenient for subsequent further modification and processing and manufacturing; (4) Copolyamide polymer of the present invention is made by spinning The dyeing ability of polyamide filaments and staple fibers is also further improved than that of ordinary polyamide fibers.

Claims (14)

A method for preparing a copolymerized polyamide 56/66 polymer, including the following steps: (1) Prepare a polyamide 56/66 salt aqueous solution according to the following 1) and/or 2); 1) In an inert atmosphere, mixing 1,5-pentanediamine, hexamethylene diamine and adipic acid in water for neutralization reaction; 2) Mixing polyamide 56 salt crystals and polyamide 66 salt crystals to prepare the polyamide 56/66 salt aqueous solution; (2) The polyamide 56/66 salt aqueous solution prepared in step (1) is polymerized to obtain a copolymerized polyamide 56/66 polymer. The preparation method according to claim 1, characterized in that: in step (1)-1), the mass percentage of the polyamide 56/66 salt solution is 20% to 80%; The ratio of the moles of the adipic acid to the sum of the moles of the hexamethylene diamine and the 1,5-pentanediamine is 1:1 to 1.05; In step (1)-2), the mass percentage of the polyamide 56/66 saline solution is 20% to 80%. The preparation method according to claim 1 or 2, characterized in that: in step (2), an auxiliary agent is also added to carry out the step of the polymerization reaction. The preparation method according to claim 3, wherein the auxiliary agent includes at least one of a molecular weight regulator, a flame retardant, an antistatic agent, an antibacterial finishing agent, and an anti-ultraviolet finishing agent. The preparation method according to claim 3, characterized in that: when the polyamide 56/66 salt solution is prepared through step (1)-1) and step (2) is performed, the addition amount of the auxiliary agent is the same as the hexamethylene used. 0.05% to 0.15% of the sum of the mass of the diamine, the 1,5-pentanediamine and the adipic acid. The preparation method according to claim 3, characterized in that: when the polyamide 56/66 salt solution is prepared through step (1)-2) and step (2) is performed, the added amount of the auxiliary agent is the polyamide 56/66 0.05% to 0.15% of the mass of the salt. The preparation method according to claim 1, characterized in that: the polymerization reaction in step (2) is carried out according to the following conditions in a)-b): a) at a temperature of 210 to 240°C and a pressure of 1.70 to 1.85 When the pressure is MPa, the pressure holding time is 1 to 3 hours; b) After releasing the pressure from 1.75 to 1.85 MPa to normal pressure, the temperature is increased to 275 to 290°C, and then evacuated to -0.08 MPa and stirred for 20 minutes to 60 minutes. The copolyamide 56/66 polymer prepared by the preparation method of any one of claims 1-4. The copolyamide 56/66 polymer according to claim 8, characterized in that: the performance parameters of the copolyamide 56/66 polymer are as follows: the melting point is 247-260°C, and the viscosity is 130-180ml/g , The tensile strength is 60-90MPa, the bending strength is 100-130MPa, and the notched impact strength is 90-120J/m. A method for preparing copolyamide 56/66 fiber, comprising the following steps: the melt of the copolyamide 56/66 polymer of claim 8 or 9 is sprayed through a spinneret to obtain a trickle of the melt, said The fine flow of the melt is cooled and solidified into filaments, and after oiling, post-processing is performed to obtain the copolyamide 56/66 fiber. The preparation method according to claim 10, characterized in that: the process of spraying the melt of the copolyamide polymer through a spinneret to obtain a trickle of the melt is as follows: in a spinning box, the spinning The temperature of the spinning box is: the temperature of the first zone of the spinning box is 260～300℃, the temperature of the second zone is 260～300℃, the temperature of the third zone is 250～295℃, the temperature of the metering pump is 250～295℃, and the temperature of the spinning assembly is 270～290℃. The metering pump rotates at 12-18rpm in the spinning box, and the copolyamide polymer melt is distributed through pipelines and delivered to each spinneret with equal residence time and pressure drop; spinning speed is 1000-4200m /min; The thin melt flow is cooled and formed by the side blowing device, and the conditions are as follows: the side blowing speed is 0.30～0.80m/min; the wind temperature is 21～26°C, and the side blowing pressure is 420～480Pa; The concentration of the oiling agent for oiling is 2-15%. The preparation method according to claim 10 or 11, characterized in that: the post-processing after oiling the thread includes drawing, heat setting, winding and/or crimping to obtain the copolyamide fiber; The drafting is one-stage drafting, two-stage drafting or multi-stage drafting; The drafting conditions are as follows: the temperature of the first roll is 60～80℃; the temperature of the second roll is 150～230℃; the temperature of the three rolls is 150～230℃; the drafting ratio is 2.50～3.50 times for the first level, and 1.01～2 for the second level. 1.10 times; The heat setting is steam heat setting, hot plate setting, hot roll setting or water bath heat setting; the heat setting is carried out under the condition of 150-230°C; When the copolyamide 56/66 fibers are filaments, the post-processing includes drawing, shaping, bundling, winding, cooling, drying, and packaging to obtain polyamide filaments; The winding speed is 500～1000m/min; When the copolyamide 56/66 fibers are staple fibers, the post-processing includes drawing, shaping, bundling, crimping, cooling, drying, cutting, and packaging to obtain polyamide staple fibers; The crimp rate is 300-350 m/min, and the number of crimps is 10-30. The copolyamide 56/66 fiber prepared by the preparation method of any one of claims 10-12. The copolyamide 56/66 fiber according to claim 13, characterized in that: the performance parameters of the copolyamide 56/66 fiber are as follows: the limiting oxygen index is 28 to 35%; when it is a filament, it breaks The strength is 3.4≦12.0cN/dtex; when it is a short fiber, its breaking strength is 3.0≦7.5cN/dtex.