Polyamide fiber and preparation method thereof

Abstract

The present invention relates to the technical field of polymer materials, and discloses a polyamide fiber and a preparation method thereof, which comprises: (a) directly feeding a polyamide 5X melt into a spinning manifold through a melt booster pump, or heating a polyamide 5X resin to a molten state to form a polyamide 5X melt and feeding it into a spinning manifold; (b) accurately metering the polyamide 5X melt through a metering pump, and then ejecting it through a spinneret to form a melt stream, while using saturated superheated steam, slow cooling and a monomer suction device to remove oligomers, and then cooling, oiling and winding to obtain the polyamide fiber. The present invention adds a saturated superheated steam device, a slow cooling device and a monomer suction device to reduce oligomers in the spinning process, increase the component shoveling cycle, and reduce the number of broken wires. The obtained polyamide fiber has less hair, low fiber unevenness, less dyeing dark lines, good dyeing effect, and has excellent elongation at break, breaking strength, and low boiling water shrinkage.

Description

Technical Field

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

[0002] Polyamide has been widely used as clothing, industrial materials, fibers, or general engineering plastics, and in many other applications due to its excellent properties and ease of melt molding, and has therefore received widespread attention. In the process of polyamide polymerization, due to the occurrence of cyclization reaction, the polymer macromolecule chain will be broken into two segments when the intramolecular amide exchange reaction occurs, or the linear low molecular weight product directly undergoes a dehydration reaction to produce a low molecular weight polymer, referred to as oligomer. Generally speaking, an oligomer is a low molecular weight polymer ranging from a monomer to a decamer, including linear oligomers and cyclic oligomers.

[0003] Generally, oligomers cannot be processed and formed separately, and if a large amount of oligomers enter the spinning section with the slices, it will not only have serious consequences for the spinning process, but also be a huge waste of raw materials. Oligomers are mainly cyclic bodies. If the content of dimers and trimers after extraction is too high, it will affect the viscosity, number average molecular weight and molecular weight distribution of the slices, resulting in a series of negative effects such as reduced strength of the original silk and increased waste silk rate. If the content of low-molecular-weight extractables in the polymer is large, during the melt spinning process, not only will these low-molecular-weight extractables evaporate from the melt into gas, deteriorating the spinning environment, but the residual low-molecular-weight extractables will form "weak points" in the fiber. Under the action of external forces (such as stretching), these places are easy to break, causing difficulties in spinning. In addition, low-molecular-weight extractables are also easy to precipitate on the surface of the silk, resulting in an increase in hairy silk and broken single silk during stretching, and a decrease in the strength of the finished silk.

[0004] Polyamide 5X is a linear long-chain macromolecule synthesized from bio-based pentamethylenediamine and dibasic acid. The amide bond easily forms a hydrogen bond. Therefore, polyamide 5X fiber has high strength and good hygroscopicity, and the fiber regain can reach 2.0% to 5.5%. However, the volatilization of oligomers in polyamide 5X will increase the bubbles in the polyamide 5X melt and reduce the shovel plate cycle of the spinning assembly, resulting in undesirable phenomena such as floating filaments, broken single filaments and low production rate during melt drawing and spinning. Therefore, how to improve the undesirable phenomena such as floating filaments, broken single filaments and low production rate of polyamide 5X during the spinning process is a problem that needs to be solved urgently in the prior art. Summary of the invention

[0005] In order to solve the deficiencies of the existing technologies and products, that is, to solve the problems of short scraping cycle of spinning components, many floating fibers and broken filaments, and low support rate caused by the precipitation of more oligomers in the spinning process of polyamide 5X, the present invention provides a polyamide fiber and a preparation method thereof.

[0006] In order to solve the above problems, the first aspect of the present invention provides a polyamide fiber, wherein the breaking strength of the polyamide fiber is 3.5 to 9.5 cN / dtex, further 3.6 to 9.0 cN / dtex, and further 3.7 to 8.5 cN / dtex; and / or,

[0007] The elongation at break of the polyamide fiber is 15 to 90%, further 18 to 80%, further 22 to 60%; and / or,

[0008] The boiling water shrinkage of the polyamide fiber is 3-12%, further 4-11%, further 5-10%; and / or,

[0009] The polyamide fiber has a strand unevenness of ≤1.5%, further ≤1.3%, and further ≤1.1%; and / or

[0010] The polyamide fibers include undrawn yarns, pre-oriented yarns, medium-oriented yarns, highly oriented yarns, elasticized yarns, fully drawn yarns, industrial yarns, continuous bulked filaments, staple fibers, and monofilament fibers.

[0011] The second aspect of the present invention provides a method for preparing the polyamide fiber according to the first aspect of the present invention, the method comprising:

[0012] (a) directly feeding the polyamide 5X melt into the spinning manifold through a melt booster pump, or heating the polyamide 5X resin to a molten state to form a polyamide 5X melt, and then feeding it into the spinning manifold;

[0013] (b) The polyamide 5X melt is accurately metered by a metering pump and then ejected through a spinneret to form a melt stream. A saturated superheated steam device, a slow cooling device and a monomer suction device are used to remove the polyamide oligomers therein. The polyamide fiber is then obtained by cooling, oiling and winding.

[0014] Compared with the prior art, the implementation of the present invention has at least the following advantages:

[0015] 1. The oligomers, viscosity, moisture content and terminal amino groups of the polyamide 5X resin synthesized by the present invention are suitable, and the polymerization deashing and extraction and removal of oligomers are not required, and the spinning can be carried out directly, thereby reducing the production cost.

[0016] 2. The polyamide 5X fiber of the present invention is prepared by adding saturated superheated steam and modifying the slow cooling and monomer suction device. In the spinning process, there are fewer oligomers, a longer component shoveling cycle, and fewer broken fibers. The obtained polyamide 5X fiber has fewer hairs, a lower fiber unevenness, fewer dyeing dark lines, and a good dyeing effect. The fiber has excellent elongation at break, breaking strength, and lower boiling water shrinkage. The spinning and dyeing finished product rate is high. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] As mentioned above, the first aspect of the present invention provides a polyamide fiber, wherein the breaking strength of the polyamide fiber is 3.5 to 9.5 cN / dtex, further 3.6 to 9.0 cN / dtex, and further 3.7 to 8.5 cN / dtex; and / or,

[0019] The elongation at break of the polyamide fiber is 15 to 90%, further 18 to 80%, further 22 to 60%; and / or,

[0020] The boiling water shrinkage of the polyamide fiber is 3-12%, further 4-11%, further 5-10%; and / or,

[0021] The polyamide fiber has a strand unevenness of ≤1.5%, further ≤1.3%, and further ≤1.1%; and / or

[0022] The fibers include the polyamide fibers including undrawn yarns, pre-oriented yarns (POY), medium-oriented yarns (MOY), highly oriented yarns (HOY), textured yarns (DTY), fully drawn yarns (FDY), industrial yarns (IDY), continuous bulked filaments (BCF), staple fibers, and monofilament fibers.

[0023] In some embodiments of the present invention, the manufacturing rate of the polyamide fiber is ≥93%, further ≥94%, and further ≥95%.

[0024] In some embodiments of the present invention, the number of broken fibers of the polyamide fiber is ≤2 (number of times / 24h), further ≤1 (number of times / 24h), and further ≤0 (number of times / 24h).

[0025] In some embodiments of the present invention, the number of the polyamide fiber filaments is ≤2 (pieces / 9 kg package), further ≤1 (pieces / 9 kg package), and further ≤0 (pieces / 9 kg package).

[0026] In some embodiments of the present invention, the dyeing M rate of the polyamide fiber is ≥93%, further ≥94%, and further ≥95%.

[0027] A second aspect of the present invention provides a method for preparing the polyamide fiber as described above, the method comprising:

[0028] (a) directly feeding the polyamide 5X melt into the spinning manifold through a melt booster pump, or heating the polyamide 5X resin to a molten state to form a polyamide 5X melt, and then feeding it into the spinning manifold;

[0029] (b) The polyamide 5X melt is accurately metered by a metering pump and then ejected through a spinneret to form a melt stream. A saturated superheated steam device, a slow cooling device and a monomer suction device are used to remove the polyamide oligomers therein. The polyamide fiber is then obtained by cooling, oiling and winding.

[0030] According to a preferred embodiment of the present invention, the method for removing polyamide oligomers therein by using a saturated superheated steam device, a slow cooling device and a monomer suction device specifically comprises: a saturated superheated steam device is provided in the spinning manifold, the saturated superheated steam entering the spinning manifold is heated again by the manifold and then sprayed from the lower side of the spinneret, the polyamide oligomers overflowing from the spinneret holes and the fiber surfaces are dissolved in the saturated superheated steam, and a slow cooling device is provided under the spinneret to increase the slow cooling temperature, inhibit the crystallization and precipitation thereof, thereby preventing the oligomers from forming on the spinneret. and the bottom thereof crystallize to form white flocculent crystals, keeping the spinneret and the bottom thereof clean, and then the polyamide oligomers dissolved in the saturated superheated steam are taken away by monomer suction, and the monomer suction hood in the monomer suction device has an automatic constant temperature heating function to ensure that the oligomers will not crystallize at the suction hood inlet, effectively reducing the contamination of the spinneret and the bottom thereof, and the monomer suction hood inlet by polyamide oligomers, extending the scraping cycle of the spinning assembly, reducing the injection head wire and single filament breakage caused by oligomers in the spinning process, and improving the spinning production stability and manufacturing rate.

[0031] In some embodiments of the present invention, the temperature of the saturated superheated steam before entering the spinning beam is 80-200°C, further 90-180°C, and further 100-160°C.

[0032] In some embodiments of the present invention, the pressure of the saturated superheated steam before entering the spinning beam is 0.8-2.2 bar, further 1.0-2.0 bar, and further 1.2-1.8 bar.

[0033] In some embodiments of the present invention, the slow cooling temperature is 180-320°C, further 220-300°C, further 240-280°C.

[0034] In some embodiments of the present invention, the slow cooling height is ≤5 cm, further ≤4 cm, and further ≤3 cm.

[0035] In some embodiments of the present invention, the pressure of the monomer extraction is ≥0.6 MPa, further ≥0.65 MPa, and further ≥0.7 MPa.

[0036] In some embodiments of the present invention, the temperature of the monomer extraction hood is 100-260°C, further 120-230°C, further 140-200°C.

[0037] In some embodiments of the present invention, the diameter of the spinneret is ≤88 mm, further ≤77 mm, and further ≤66 mm.

[0038] According to some embodiments of the present invention, in the polyamide fiber preparation process, the component scraping cycle is ≥16h, further ≥18h, and further ≥20h.

[0039] The present invention has no particular limitation on the devices and operating conditions used for cooling, oiling and winding described in step (b). Conventional operations in the art may be used, and those skilled in the art may select as needed according to actual conditions.

[0040] In some embodiments of the present invention, the polyamide 5X resin includes 1,5-pentanediamine structural units and dibasic acid structural units, and the polyamide 5X resin contains polyamide oligomers with a number average molecular weight of 2000 or less, and the content of the polyamide oligomers is 1.0 wt % or less.

[0041] According to some embodiments of the present invention, the number average molecular weight of the polyamide 5X resin is greater than 2000. The number average molecular weight is calculated using gel permeation chromatography (hereinafter referred to as GPC) from the elution curve of each sample obtained under the measurement conditions of the examples described later, based on the area of ​​the region below the molecular weight from the number average molecular weight of 2000 or more to the end of the detection of the main peak surrounded by the baseline and the elution curve, and is calculated by standard polymethyl methacrylate (standard PMMA).

[0042] The polyamide resin of the present invention contains a polyamide oligomer having a number average molecular weight of 2,000 or less as determined by GPC measurement under the same conditions as above.

[0043] According to some embodiments of the present invention, the content of the polyamide oligomer is 0.95 wt % or less, further 0.9 wt % or less.

[0044] In some preferred embodiments of the present invention, the pentamethylenediamine may be pentamethylenediamine of chemical origin or biological origin, and further may be 1,5-pentamethylenediamine of biological origin.

[0045] In some preferred embodiments of the present invention, more than 90 mol % of the dibasic acid structural units are derived from adipic acid.

[0046] According to some embodiments of the present invention, the dibasic acid structural unit of the polyamide 5X resin also includes one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid and octadecanedioic acid, terephthalic acid, isophthalic acid and phthalic acid.

[0047] According to some embodiments of the present invention, the polyamide oligomer is selected from at least one of the following structures:

[0048]

[0049] wherein n1 and n2 are selected from integers of 1 to 8; preferably, n1 and n2 are selected from integers of 1 to 6; more preferably, n1 and n2 are each independently an integer of 1 to 5; further preferably, n1 is 2, 3 or 4; n2 is 2, 3, 4 or 5;

[0050] m1 and m2 are respectively selected from integers of 2 to 18; preferably, m1 and m2 are each independently integers of 4 to 16; further preferably, m1 is 4, 8 or 10, and m2 is 4, 8 or 10.

[0051] According to some embodiments of the present invention, the polyamide 5X resin comprises a first polyamide having a structure as shown in Formula I:

[0052]

[0053] The number average molecular weight of the first polyamide is greater than 2000, and the content of the first polyamide in the polyamide 5X resin is greater than 85 wt %, further greater than 90 wt %, further greater than 95 wt %. For example, the content of the first polyamide in the polyamide 5X resin is 99-99.98 wt %.

[0054] In some embodiments of the present invention, the relative viscosity of the polyamide 5X resin is 2.3 to 3.6, preferably 2.4 to 3.5, and more preferably 2.5 to 3.4.

[0055] In some embodiments of the present invention, the water content of the polyamide 5X resin is 300 to 900 ppm, preferably 350 to 800 ppm, and more preferably 400 to 700 ppm.

[0056] In some embodiments of the present invention, the terminal amino group content of the polyamide 5X resin is 40 to 70 mol / ton, preferably 43 to 60 mol / ton, and more preferably 45 to 55 mol / ton.

[0057] According to some embodiments of the present invention, the method for preparing the polyamide 5X resin comprises:

[0058] (1) In an inert gas atmosphere, 1,5-pentanediamine, a dibasic acid, and water are uniformly mixed to prepare a polyamide salt solution;

[0059] (2) heating the salt solution of polyamide until the pressure in the reaction system rises to 0.5-2.4 MPa, exhausting and maintaining the pressure, at the end of which the temperature of the reaction system is 235-268° C., reducing the pressure to reduce the pressure in the reaction system to 0-0.2 MPa, at the end of which the temperature of the reaction system is 248-282° C., and evacuating to obtain a polyamide 5X melt;

[0060] (3) discharging the melt obtained in step (2), and cutting into strands and pellets.

[0061] In some embodiments of the present invention, in step (1), the molar ratio of 1,5-pentanediamine to the dibasic acid is (1-1.08):1.

[0062] In some embodiments of the present invention, in step (2), the vacuuming is performed to make the relative vacuum degree in the reaction system be -0.02 MPa to -0.08 MPa.

[0063] In some embodiments of the present invention, the vacuum time is maintained for 18 to 70 minutes.

[0064] In some embodiments of the present invention, the vacuum end temperature is controlled at 263-278°C.

[0065] In some embodiments of the present invention, in step (3), the pelletizing is carried out in water at a water temperature of 15 to 50°C.

[0066] The inert gas described in step (1) of the present invention is selected from one or more of nitrogen, argon, helium, etc., and is more preferably one or more of high-purity nitrogen, high-purity argon, and high-purity helium.

[0067] The types of dibasic acids described in the present invention are as described above and will not be described in detail here.

[0068] Unless otherwise specified, the pressures described in the present invention refer to gauge pressures.

[0069] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all the raw materials used can be obtained from commercial channels.

[0070] 1. Detection method of relative viscosity ηr

[0071] Ubbelohde viscometer concentrated sulfuric acid method: Accurately weigh 0.5±0.0002 g of the dried polyamide sample, add 50 mL of concentrated sulfuric acid (96%) to dissolve it, and measure and record the concentrated sulfuric acid flow time t0 and the polyamide solution flow time t in a 25°C constant temperature water bath.

[0072] Relative viscosity calculation formula:

[0073] Relative viscosity ηr=t / t0

[0074] Where: t: solution flow time; t0: solvent flow time.

[0075] 2. Moisture content

[0076] Take 1g of resin sample and measure it using Karl Fischer moisture meter at a detection temperature of 200°C and a detection time of 20min.

[0077] 3. Determination of terminal amino content

[0078] After dissolving the sample in trifluoroethanol, titrate it with hydrochloric acid standard solution and sodium hydroxide standard solution respectively, and calculate.

[0079] 4. Molecular weight detection method:

[0080] From the elution curve of each sample obtained using gel permeation chromatography (GPC) (vertical axis: signal intensity obtained from the detector, horizontal axis: elution time), the number average molecular weight of the main peak (polymer peak) in the elution curve was calculated by calibration with the standard sample polymethyl methacrylate (PMMA).

[0081] The measurement was performed under the following conditions.

[0082] Detector: RI detector

[0083] Column: 2 x PSS 7μPFG Linear M column 300x8.0mm Solvent: Hexafluoroisopropanol containing sodium trifluoroacetate at a concentration of 0.05 mol / L.

[0084] Temperature: 40℃

[0085] Flow rate: 1mL / min

[0086] Injection volume: 100 μL

[0087] Concentration: 3-5 g / L

[0088] Sample preparation: The polyamide resin or polyamide resin composition obtained in each embodiment is weighed in hexafluoroisopropanol containing 0.01 mol / L sodium trifluoroacetate in a manner converted to 0.5 mg / mL in terms of polyamide resin, and dissolved by stirring at room temperature for 1 hour. The resulting solution is filtered using a hydrophobic membrane filter (pore size 0.22 μm) to prepare a sample.

[0089] PMMA standard sample: A standard elution curve (calibration curve) was prepared using STANDARD 81506-1EA (number average molecular weight range: 500 to 27,000,000) manufactured by Fluka.

[0090] 5. Detection method of polyamide oligomer content:

[0091] The polyamide sample was dried at 130°C in a blast oven for 7 hours, then placed in an aluminum-plastic bag, sealed, and placed in a dryer to cool. Then, about 2g of the polyamide sample was accurately weighed. The polyamide sample was placed in a 250mL round-bottom flask, 100mL of pure water was added, and the sample was heated and refluxed with a heating jacket for 24 hours. The polyamide sample was washed three times with pure water. The polyamide sample was dried in a 130°C blast oven for 7 hours, then transferred to a pre-weighed aluminum-plastic bag, sealed, and placed in a dryer to cool. The total weight of the aluminum-plastic bag and the polyamide sample was subtracted from the weight of the aluminum-plastic bag to obtain the weight of the polyamide sample after boiling. The oligomer content was calculated by comparing the weight difference before and after boiling of the polyamide sample. Parallel samples were taken for testing of each sample. When testing the oligomer content in the melt, the melt was introduced into a closed container, and after cooling, the sample was sampled and tested according to the above method.

[0092] 6. Elongation at break

[0093] Measured according to GB / T 14344.

[0094] 7. Breaking strength

[0095] Measured according to GB / T 14344.

[0096] 8. Boiling water shrinkage

[0097] Measured in accordance with GB / T 6505-2008.

[0098] 9. Number of wire breakages

[0099] Number of broken yarns (number / 24h): Manually counted. Fewer broken yarns are considered to indicate better spinnability.

[0100] 10. Unevenness of strips

[0101] The test was carried out according to GB / T 14346-93 method.

[0102] 11. Fiber production rate

[0103] Production rate = (weight of finished fiber prepared / total weight of resin input) × 100%.

[0104] 12. M rate

[0105] The dyeing uniformity method (ASTM Z7667-1999) was used to measure the dyeing uniformity of the polyamide fiber prepared by the above preparation method, and the M rate was measured using the 5-level color judgment standard method.

[0106] M rate = (number of fibers with dyeing uniformity ≥ 4.5) / total number of all dyed fibers) × 100%.

[0107] 13. Number of hairs

[0108] The number of hair fibers is determined manually.

[0109] Preparation Example 1

[0110] (1) Under nitrogen conditions, 1,5-pentanediamine, adipic acid and water are uniformly mixed, wherein the molar ratio of 1,5-pentanediamine to adipic acid is 1.05:1, to prepare a 65wt.% nylon salt solution, wherein the percentage is the mass percentage of the nylon salt solution; the pH value of the nylon salt solution when the concentration is 10wt.% is 7.83.

[0111] (2) The above solution was heated, and the pressure in the reaction system was raised to 2.2 MPa, which took 1 hour and 30 minutes, then the solution was vented and the pressure was maintained at 2.42 MPa. The temperature of the reaction system was 250°C at the end of the pressure maintenance, which took 3 hours. The pressure was then reduced to 0.002 MPa (gauge pressure), and the temperature of the reaction system was 270°C after the pressure reduction, which took 1 hour. The reaction system was evacuated to maintain a relative vacuum degree of -0.05 MPa, and the evacuation time was 28 minutes. The temperature after the evacuation was 273°C, and a polyamide melt was obtained.

[0112] (3) The melt obtained in step (2) is melted and discharged, and then cut into strands and pelletized to obtain polyamide 56 resin; the pelletizing is carried out in water, the water temperature is 19° C., the roller speed is 500 rpm, and the pelletizing time is 23 min.

[0113] Preparation Example 2

[0114] (1) Under nitrogen conditions, 1,5-pentanediamine, sebacic acid and water are uniformly mixed, wherein the molar ratio of 1,5-pentanediamine to sebacic acid is 1.07:1, to prepare a 60wt.% nylon salt solution, wherein the percentage is the mass percentage of the nylon salt solution; the pH value of the nylon salt solution when the concentration is 10wt.% is 7.8.

[0115] (2) The above solution was heated, and the pressure in the reaction system was raised to 2.2 MPa, which took 1 hour and 30 minutes, then the solution was vented and the pressure was maintained at 2.4 MPa. The temperature of the reaction system was 245°C at the end of the pressure maintenance, which took 3 hours. The pressure was then reduced to 0.002 MPa (gauge pressure), and the temperature of the reaction system was 260°C after the pressure reduction, which took 1 hour. The reaction system was evacuated to maintain a relative vacuum degree of -0.05 MPa, and the evacuation time was 25 minutes. The temperature after the evacuation was 268°C, and a polyamide melt was obtained.

[0116] (2) The melt obtained in step (2) is melted and discharged, and then cut into strands and pelletized to obtain polyamide 510 resin; the pelletizing is carried out in water, the water temperature is 18° C., the roller speed is 510 rpm, and the pelletizing time is 25 min.

[0117] Example 1

[0118] The polyamide 56 resin obtained in Preparation Example 1 was added to the spinning equipment through a feeder, and evenly distributed to the spinning assembly after single-screw heating. The spinning box temperature was 282° C. It was ejected through a spinneret to form a melt stream. The spinneret had an aperture of 0.22 mm, a length of 0.605 mm, and 48 holes. The spinning box is equipped with a saturated superheated steam device. After entering the spinning box, the saturated superheated steam is heated again by the box and then sprayed from the bottom of the spinneret. The polyamide oligomer overflowing from the spinneret hole and the fiber surface is dissolved in the saturated superheated steam. At the same time, a slow cooling device is provided under the spinneret to increase the slow cooling temperature and inhibit its crystallization. Then the polyamide oligomer dissolved in the saturated superheated steam is taken away by monomer suction, and the monomer suction hood in the monomer suction device has an automatic constant temperature heating function. The temperature of the saturated superheated steam before entering the spinning box is 120°C, the pressure of the saturated superheated steam before entering the spinning box is 1.6 bar, the slow cooling temperature is 250°C, the slow cooling height is 3 cm, the pressure of the monomer suction is 0.65 MPa, the temperature of the monomer suction hood is 150°C, and the diameter of the spinneret is 77 mm. Then it is cooled and formed by a side blowing device. The wind temperature of the side blowing device is 18°C, the wind humidity is 85%, and the wind speed is 0.42 m / s. The cooled and formed filament bundle is oiled and passed through the spinning shaft, and then pulled to the first and second guide wire discs and wound into a yarn cake on a winder. The speed of the first guide wire disc is 4490m / mi, the speed of the second guide wire disc is 4510m / mi, and the winding speed is 4500m / min to obtain polyamide 56 pre-oriented yarn (POY).

[0119] Example 2

[0120] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the temperature of the saturated superheated steam before entering the spinning manifold was adjusted to 130°C.

[0121] Example 3

[0122] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the slow cooling temperature was adjusted to 280°C.

[0123] Example 4

[0124] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the slow cooling height was adjusted to 2 cm.

[0125] Example 5

[0126] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the pressure of monomer suction was adjusted to 0.75 MPa.

[0127] Example 6

[0128] Polyamide 510 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the polyamide 510 resin prepared in Preparation Example 2 was used instead of the polyamide 56 resin.

[0129] Comparative Example 1

[0130] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that there was no saturated superheated steam device and slow cooling device.

[0131] Comparative Example 2

[0132] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that there was no saturated superheated steam device.

[0133] Comparative Example 3

[0134] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that there was no slow cooling device.

[0135] Comparative Example 4

[0136] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the temperature of the saturated superheated steam before entering the spinning manifold was adjusted to 70°C.

[0137] Comparative Example 5

[0138] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the slow cooling temperature was adjusted to 150°C.

[0139] Comparative Example 6

[0140] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the slow cooling height was adjusted to 6 cm.

[0141] Comparative Example 7

[0142] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the pressure of monomer suction was adjusted to 0.5 MPa.

[0143] Comparative Example 8

[0144] Polyamide 56 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that the diameter of the spinneret was adjusted to 95 mm.

[0145] Comparative Example 9

[0146] Polyamide 510 pre-oriented yarn (POY) was prepared according to the same process as in Example 1, except that there was no saturated superheated steam device and slow cooling device, and the polyamide 510 resin prepared in Preparation Example 2 was used instead of the polyamide 56 resin.

[0147] Examples 7-12

[0148] The polyamide 56 pre-oriented yarn or polyamide 510 pre-oriented yarn prepared in Examples 1-6 was respectively passed through a yarn guide and a yarn cutter to the first roller, and then subjected to heat stretching in a hot box, followed by cooling and shaping using a cooling plate, and a certain twist was obtained by a false twister, and then passed through a tension online detector, the second roller, and then through a network nozzle to add a network, and then passed through a third roller, a broken wire sensor, and an oil tanker to add oil, and finally wound to obtain polyamide 56 plus stretch yarn (DTY) or polyamide 510 plus stretch yarn (DTY). The processing speed was 600 m / min, the stretch ratio was 1.28, the D / Y ratio was 1.65, and the hot box temperature was 185°C.

[0149] Comparative Examples 10-18

[0150] The polyamide 56 pre-oriented yarn or polyamide 510 pre-oriented yarn prepared in Comparative Examples 1-9 is passed through a yarn guide and a yarn cutter to the first roller, and then is heat-stretched in a hot box, and then cooled and shaped by a cooling plate, and a certain twist is obtained by a false twister, and then passed through a tension online detector, a second roller, and then a network is added through a network nozzle, and then passed through a third roller, a broken wire sensor, and an oil tanker for oiling, and finally wound to obtain polyamide 56 plus stretch yarn (DTY) or polyamide 510 plus stretch yarn (DTY). The processing speed is 600m / min, the stretch ratio is 1.28, the D / Y ratio is 1.65, and the hot box temperature is 185°C.

[0151] Example 13

[0152] The polyamide 56 resin prepared in Example 1 was added to the spinning equipment through a feeder, and evenly distributed to the spinning assembly after being heated by a single screw, and the spinning box temperature was 280° C. The resin was ejected through a spinneret to form a melt stream, and the spinneret had an aperture of 0.22 mm, a length of 0.605 mm, and 48 holes. A saturated superheated steam device is provided in the spinning manifold. The saturated superheated steam after entering the spinning manifold is heated again by the manifold and then sprayed from the bottom of the spinneret. The polyamide oligomer overflowing from the spinneret hole and the fiber surface is dissolved in the saturated superheated steam. At the same time, a slow cooling device is provided under the spinneret to increase the slow cooling temperature and inhibit its crystallization. Then the polyamide oligomer dissolved in the saturated superheated steam is taken away by monomer suction, and the monomer suction hood in the monomer suction device has an automatic constant temperature heating function. The temperature of the saturated superheated steam before entering the spinning manifold is 130°C, the pressure of the saturated superheated steam before entering the spinning manifold is 1.5 bar, the slow cooling temperature is 260°C, the slow cooling height is 3 cm, the pressure of the monomer suction is 0.6 MPa, the temperature of the monomer suction hood is 120°C, and the diameter of the spinneret is 77 mm. Then it is cooled and formed by a side blowing device. The wind temperature of the side blowing device is 20°C, the wind humidity is 90%, and the wind speed is 0.40 m / s. The cooled and formed filament bundle is oiled and passed through the spinning shaft, and then pulled to the first pair of cold rollers and the second pair of hot rollers. The speed of the first pair of cold rollers is 2840m / min, and the speed of the second pair of cold rollers is 4830m / min. The winding speed is 4800m / min, the drafting multiple is 1.7, and the setting temperature is 165°C to obtain polyamide 56 fully drawn filament (FDY).

[0153] Embodiment 14

[0154] Polyamide 510 fully drawn filament (FDY) was prepared according to the same process as in Example 13, except that the polyamide 510 resin prepared in Preparation Example 2 was used instead of the polyamide 56 resin prepared in Preparation Example 1.

[0155] Comparative Example 19

[0156] Polyamide 56 fully drawn filament (FDY) was prepared by the same process as in Example 13, except that there was no saturated superheated steam device and slow cooling device.

[0157] Comparative Example 20

[0158] Polyamide 56 fully drawn filament (FDY) was prepared according to the same process as in Example 13, except that there was no saturated superheated steam device.

[0159] Comparative Example 21

[0160] Polyamide 510 fully drawn filament (FDY) was prepared according to the same process as in Example 13, except that there was no saturated superheated steam device and the polyamide 510 resin prepared in Preparation Example 2 was used instead of the polyamide 56 resin.

[0161] Table 1 Polyamide 5X resin performance test results

[0162]

[0163] Table 2 Polyamide 5X POY fiber performance test results

[0164]

[0165]

[0166] Table 3 Polyamide 5X DTY fiber test results

[0167]

[0168] Table 4 Polyamide 5X FDY fiber test results

[0169]

[0170] Tables 1 to 4 show that: the present invention effectively reduces the contamination of the spinneret and the bottom of the spinneret and the inlet of the monomer suction hood by polyamide 5X oligomers during the spinning process by adding saturated superheated steam, slow cooling and monomer suction devices, prolongs the shoveling cycle of the spinning assembly, reduces the phenomenon of injection head wire and broken single wire caused by oligomers during the spinning process, and improves the stability and production rate of spinning production, so that the obtained polyamide 5X fiber has less hair, low fiber unevenness, less dyeing dark lines, good dyeing effect, and excellent elongation at break, breaking strength, lower boiling water shrinkage, and higher spinning and dyeing yield. The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical scheme of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A polyamide fiber, characterized in that: The breaking strength of the polyamide fiber is 3.5 to 9.5 cN / dtex; the breaking elongation of the polyamide fiber is 15 to 90%; the boiling water shrinkage of the polyamide fiber is 3 to 12%; the strand unevenness of the polyamide fiber is ≤1.5%; The polyamide fibers include undrawn yarns, pre-oriented yarns, medium-oriented yarns, highly oriented yarns, textured yarns, fully drawn yarns, industrial yarns, continuous bulked filaments, staple fibers, and monofilament fibers; The preparation method of the polyamide fiber comprises the following steps: (a) directly feeding the polyamide 5X melt into the spinning manifold through a melt booster pump, or heating the polyamide 5X resin to a molten state to form a polyamide 5X melt, and then feeding it into the spinning manifold; (b) The polyamide 5X melt is accurately metered by a metering pump and then ejected through a spinneret to form a melt stream. A saturated superheated steam device, a slow cooling device and a monomer suction device are used to remove the polyamide oligomers therein. The polyamide fiber is then obtained by cooling, oiling and winding. The slow cooling height is ≤5 cm; the slow cooling temperature is 180-320° C.; and the diameter of the spinneret is ≤88 mm.

2. The polyamide fiber according to claim 1, characterized in that The breaking strength of the polyamide fiber is 3.6 to 9.0 cN / dtex; And / or, the elongation at break of the polyamide fiber is 18 to 80%; And / or, the boiling water shrinkage of the polyamide fiber is 4 to 11%; And / or, the polyamide fiber has a strand unevenness rate of ≤1.3%.

3. The polyamide fiber according to claim 1, characterized in that The breaking strength of the polyamide fiber is 3.7 to 8.5 cN / dtex; And / or, the elongation at break of the polyamide fiber is 22-60%; And / or, the boiling water shrinkage of the polyamide fiber is 5 to 10%; And / or, the polyamide fiber has a strand unevenness rate of ≤1.1%.

4. A method for preparing the polyamide fiber according to any one of claims 1 to 3, characterized in that: The method includes: (a) directly feeding the polyamide 5X melt into the spinning manifold through a melt booster pump, or heating the polyamide 5X resin to a molten state to form a polyamide 5X melt, and then feeding it into the spinning manifold; (b) The polyamide 5X melt is accurately metered by a metering pump and then ejected through a spinneret to form a melt stream, and a saturated superheated steam device, a slow cooling device and a monomer suction device are used to remove the polyamide oligomers therein, and then the polyamide fiber is obtained by cooling, oiling and winding; the slow cooling height is ≤5cm; the slow cooling temperature is 180-320°C; and the diameter of the spinneret is ≤88mm.

5. The method according to claim 4, characterized in that The method for removing polyamide oligomers using a saturated superheated steam device, a slow cooling device and a monomer suction device specifically includes: a saturated superheated steam device is installed in the spinning box, the saturated superheated steam entering the spinning box is heated again by the box and then sprayed in from all sides below the spinneret, the polyamide oligomers overflowing from the spinneret holes and the fiber surfaces are dissolved in the saturated superheated steam, and a slow cooling device is installed below the spinneret to increase the slow cooling temperature and inhibit its crystallization and precipitation, and then the polyamide oligomers dissolved in the saturated superheated steam are taken away by monomer suction, and the monomer suction hood in the monomer suction device has an automatic constant temperature heating function.

6. The method according to claim 5, characterized in that The temperature of the saturated superheated steam before entering the spinning manifold is 80-200°C; and / or, The pressure of the saturated superheated steam before entering the spinning manifold is 0.8-2.2 bar; and / or, The monomer suction pressure is ≥ 0.6 MPa; and / or, The temperature of the monomer suction hood is 100-260° C.; and / or, The component scraping cycle in the polyamide fiber preparation process is ≥16h.

7. The method according to claim 5, characterized in that The temperature of saturated superheated steam before entering the spinning box is 90-180℃; and / or, the pressure of the saturated superheated steam before entering the spinning manifold is 1.0-2.0 bar; And / or, the slow cooling temperature is 220-300°C; And / or, the slow cooling height is ≤4 cm; and / or, the pressure of the monomer suction is ≥0.65MPa; and / or, the temperature of the monomer suction hood is 120-230° C.; And / or, the diameter of the spinneret is ≤77 mm; And / or, the component scraping cycle in the polyamide fiber preparation process is ≥18h.

8. The method according to claim 5, characterized in that The temperature of saturated superheated steam before entering the spinning box is 100-160℃; and / or, the pressure of the saturated superheated steam before entering the spinning manifold is 1.2-1.8 bar; And / or, the slow cooling temperature is 240-280°C; And / or, the slow cooling height is ≤3 cm; and / or, the pressure of the monomer suction is ≥0.7 MPa; and / or, the temperature of the monomer suction hood is 140-200° C.; And / or, the diameter of the spinneret is ≤66 mm; And / or, the component scraping cycle in the polyamide fiber preparation process is ≥20h.

9. The method according to any one of claims 4 to 8, characterized in that: The polyamide 5X resin includes a 1,5-pentanediamine structural unit and a dibasic acid structural unit. The polyamide 5X resin contains a polyamide oligomer with a number average molecular weight of 2000 or less, and the content of the polyamide oligomer is 1.0 wt % or less.

10. The method according to claim 9, characterized in that The number average molecular weight of the polyamide 5X resin is greater than 2000; and / or, The content of the polyamide oligomer is less than 0.95 wt %; and / or, The 1,5-pentanediamine is of chemical or biological origin; and / or, More than 90 mol% of the dibasic acid structural units are derived from adipic acid; and / or, The dibasic acid structural units of the polyamide 5X resin also include one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid and octadecanedioic acid, terephthalic acid, isophthalic acid and phthalic acid.

11. The method according to claim 9, characterized in that The content of the polyamide oligomer is less than 0.9wt%; And / or, the 1,5-pentanediamine is 1,5-pentanediamine derived from biomass.

12. The method according to claim 9, characterized in that The polyamide oligomer is selected from at least one of the following structures: Wherein, n1 and n2 are respectively selected from integers of 1 to 8; m1 and m2 are selected from integers of 2 to 18, respectively.

13. The method according to claim 12, characterized in that n1 and n2 are each selected from integers of 1 to 6; And / or, m1 and m2 are each independently an integer of 4 to 16.

14. The method according to claim 12, characterized in that n1 and n2 are each independently an integer of 1-5; And / or, m1 is 4, 8 or 10, and m2 is 4, 8 or 10.

15. The method according to claim 12, characterized in that n1 is 2, 3 or 4; n2 is 2, 3, 4 or 5.

16. The method according to claim 9, characterized in that The polyamide 5X resin contains a first polyamide having a structure as shown in Formula I: The number average molecular weight of the first polyamide is greater than 2000, and the content of the first polyamide in the polyamide 5X resin is greater than 85 wt %.

17. The method according to claim 16, characterized in that The content of the first polyamide in the polyamide 5X resin is greater than 90 wt %.

18. The method according to claim 16, characterized in that The content of the first polyamide in the polyamide 5X resin is greater than 95 wt %.

19. The method according to claim 9, characterized in that The relative viscosity of the polyamide 5X resin is 2.3 to 3.6; and / or, The water content of the polyamide 5X resin is 300 to 900 ppm; and / or, The terminal amino group content of the polyamide 5X resin is 40 to 70 mol / ton.

20. The method according to claim 9, characterized in that The relative viscosity of the polyamide 5X resin is 2.4 to 3.5; and / or, the water content of the polyamide 5X resin is 350 to 800 ppm; And / or, the terminal amino group content of the polyamide 5X resin is 43 to 60 mol / ton.

21. The method according to claim 9, characterized in that The relative viscosity of the polyamide 5X resin is 2.5 to 3.4; And / or, the water content of the polyamide 5X resin is 400 to 700 ppm; And / or, the terminal amino group content of the polyamide 5X resin is 45 to 55 mol / ton.

22. The method according to claim 9, characterized in that The preparation method of the polyamide 5X resin comprises: (1) In an inert gas atmosphere, 1,5-pentanediamine, a dibasic acid, and water are uniformly mixed to prepare a polyamide salt solution; (2) heating the salt solution of polyamide until the pressure in the reaction system rises to 0.5-2.4 MPa, exhausting and maintaining the pressure, at the end of which the temperature of the reaction system is 235-268° C., reducing the pressure in the reaction system to 0-0.2 MPa, at the end of which the temperature of the reaction system is 248-282° C., and evacuating to obtain a polyamide 5X melt; (3) discharging the melt obtained in step (2), and cutting into strands and pellets.

23. The method according to claim 22, characterized in that In step (1), the molar ratio of 1,5-pentanediamine to the dibasic acid is (1 to 1.08):1; and / or, In step (2), the vacuuming is performed to make the relative vacuum degree in the reaction system be -0.02 MPa to -0.08 MPa; and / or, In step (2), the vacuum time is maintained for 18 to 70 minutes; and / or, In step (2), the vacuum end temperature is controlled at 263-278°C; and / or, In step (3), the pelletizing is carried out in water at a water temperature of 15 to 50°C.

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