A polyamide, a high-shrinkage polyamide fiber, its preparation method and applications

Abstract

This invention discloses a polyamide, a high-shrinkage polyamide fiber, its preparation method, and its applications. The polyamide has a structural formula comprising structural units I, II, and III, wherein structural unit I has a molar fraction of 50-52 parts; structural unit II has a molar fraction of 35-48 parts; and structural unit III has a molar fraction of 1-15 parts; the total molar fraction of structural unit I, II, and III is 100 parts. The polyamide preparation method of this invention is simple, and the high-shrinkage polyamide fiber obtained from it exhibits high boiling water shrinkage, good melt compatibility, excellent fiber mechanical properties, low monofilament breakage rate, and excellent dyeing performance.

Description

Technical Field

[0001] This invention relates to the field of polyamide materials technology, specifically to a polyamide, a high-shrinkage polyamide fiber, its preparation method, and its applications. Background Technology

[0002] Polyamide fiber is one of the earliest synthetic fibers to be industrially produced and plays a pivotal role in the field of synthetic fibers. There are many types of polyamide fibers, but polyamide 6 and polyamide 66 are currently the most widely produced and used industrially. Their main applications include: socks, lace underwear, shapewear, sports underwear, wedding dresses, casual jackets, sportswear, raincoats, windbreakers, quick-drying clothing, winter clothing, outdoor tents, sleeping bags, and backpacks; while its industrial yarns are widely used in applications such as tire cords, drive belts, hoses, ropes, fishing nets, tires, and parachutes.

[0003] Currently, bio-based polyamide materials, such as polyamide 56 fiber, are receiving widespread attention due to their renewable and bio-friendly properties. Bio-based polyamide 56 fiber is produced using renewable bio-based raw materials, with monomers prepared through biotechnology and then polymerized. The raw materials for polyamide 56 fiber are produced using biological methods, making it a green material that does not rely on petroleum resources and does not cause serious environmental pollution. Furthermore, it can reduce carbon dioxide emissions and mitigate the greenhouse effect. Compared to existing petroleum-based polyamides on the market, polyamide 56 fiber, in addition to its environmentally friendly raw materials and processing, possesses superior mechanical properties, quick-drying and moisture-wicking properties (a standard moisture regain of 6%, closer to cotton, compared to 4-5% for ordinary nylon), skin-friendliness, abrasion resistance, good softness, and low-temperature dyeability. Therefore, it is widely used in the textile industry, such as in civilian filaments, staple fibers, industrial yarns, continuous bulked filaments, and monofilaments. However, the boiling water shrinkage rate of polyamide 56 fiber is generally below 15%, thus limiting its application in high-shrinkage fiber fields.

[0004] Chinese patent document CN111519276A discloses a high-shrinkage polyamide fiber, its preparation method, and its applications. The high-shrinkage polyamide fiber is a blend of polyamide 6 and polyamide 56. Specifically, the high-shrinkage polyamide fiber has a boiling water shrinkage rate of 30-60%, and contains 20-80 wt% polyamide 56 and 80-20 wt% polyamide 6. This polyamide 56 / polyamide 6 blend fiber possesses high shrinkage performance and softness, making it suitable for high-shrinkage fabrics. Its extremely high quality allows for applications in high-end clothing and other similar uses. Although the boiling water shrinkage rate of this blend fiber can reach 30%-60%, it is primarily prepared using a blending spinning method. The production process requires the addition of a blending additive device. Uneven stirring or an inappropriate addition ratio can affect its melt compatibility (e.g., high number of monofilament breakages), ultimately impacting the fiber's mechanical and dyeing properties (e.g., lower dyeing double A rate and poor dyeing uniformity).

[0005] There are currently no reports on the preparation of polyamide fibers and polyamides with high shrinkage properties using copolymerization methods. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects in the production of high-shrinkage polyamide fibers, where uneven stirring or improper addition ratios during the process lead to poor melt compatibility of the polyamide, thus affecting the mechanical properties, number of monofilament breaks, and dyeing performance of the polyamide fibers. This invention provides a polyamide, high-shrinkage polyamide fibers, their preparation method, and applications. The polyamide preparation method of this invention is simple, and the high-shrinkage polyamide fibers obtained from it exhibit high boiling water shrinkage, good melt compatibility, excellent fiber mechanical properties, low number of monofilament breaks, and excellent dyeing performance.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0008] This invention provides a polyamide whose structural formula includes the structural units represented by I, II, and III below:

[0009]

[0010]

[0011] Among them, the molar fraction of structural unit I is 50-52 parts;

[0012] The molar fraction of structural unit II is 35-48 parts;

[0013] The molar fraction of structural unit III is 1-15 parts;

[0014] The total number of molar parts of structural unit I, structural unit II and structural unit III is 100.

[0015] In this invention, the ratio of the molar number of structural unit I to the sum of the molar numbers of structural unit II and structural unit III is preferably (1-1.1):1, for example, 1:1.

[0016] In this invention, the molar fraction of the structural unit I is preferably 50-51 parts, for example 50 parts or 51 parts.

[0017] In this invention, the molar fraction of the structural unit II is preferably 37-48 parts, for example 37 parts, 40 parts, 43 parts, 45 parts, 47 parts or 48 parts.

[0018] In this invention, the molar number of structural unit III is preferably 3.4-15 parts, more preferably 5-14 parts, and even more preferably 5-13 parts, for example 5 parts, 7 parts, 10 parts or 13 parts.

[0019] In this invention, those skilled in the art will understand that the polyamide may be named PA56I.

[0020] In this invention, the melting point of the polyamide can be 200-256℃, preferably 210-253℃, more preferably 220-252℃, for example 223℃, 232℃, 241℃, 246℃, 250℃ or 252℃.

[0021] In this invention, the relative viscosity of the polyamide can be 2.2-3.0, preferably 2.3-2.9, more preferably 2.4-2.8, for example 2.5, 2.6, 2.7, 2.75 or 2.8.

[0022] In this invention, the amino content of the polyamide can be 30-60 mmol / kg, preferably 35-55 mmol / kg, more preferably 40-52 mmol / kg, for example 43, 45, 46, 47, 50 or 52 mmol / kg.

[0023] In this invention, those skilled in the art will understand that the oligomers of the polyamide are generally polymers with a molecular weight of 500-2000 g / mol produced by the condensation of monomers.

[0024] In this invention, the oligomer content of the polyamide can be ≤0.9wt%, preferably ≤0.8wt%, more preferably ≤0.7wt%, for example 0.7, 0.6, 0.5, 0.4 or 0.3wt%.

[0025] In this invention, the molecular weight distribution of the polyamide can be 1.3-2.4, preferably 1.5-2.2, more preferably 1.5-2.0, for example 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0.

[0026] The present invention also provides a method for preparing the polyamide, comprising the following steps:

[0027] The polyamide is obtained by sequentially prepolymerizing and polycondensing a polyamide salt solution prepared from pentanediamine, adipic acid, and isophthalic acid; wherein the pressure of the prepolymerization is 1.2-2.4 MPa.

[0028] In this invention, as those skilled in the art will know from common sense, pentanediamine, upon participating in the reaction, forms structural unit I. Adipic acid, upon participating in the reaction, forms structural unit II. Isophthalic acid, upon participating in the reaction, forms structural unit III.

[0029] In this invention, the solvent in the polyamide salt solution can be a conventional solvent in the art capable of dissolving the pentanediamine, the adipic acid, and the isophthalic acid, such as water or ethanol.

[0030] In this invention, the preparation method of the polyamide salt solution can be conventional in the art, such as mixing the pentanediamine, adipic acid, isophthalic acid and solvent evenly.

[0031] In this invention, the concentration of the polyamide salt solution can be conventional in the art, preferably 50-70 wt.%, for example 54 wt.%, 55 wt.%, 56 wt.%, 58 wt.%, 60 wt.%, or 62 wt.%.

[0032] In this invention, the pH value of the polyamide salt solution can be conventional in the art, preferably 6.8-9.0, such as 7.3, 7.6, 7.8, 7.9, 8.0 or 8.2.

[0033] In this invention, the molar ratio of the pentanediamine to the total amount of adipic acid and isophthalic acid can be (1-1.1):1, for example, 1:1.

[0034] In this invention, the molar ratio of pentanediamine, adipic acid, and isophthalic acid can be (50-52):(35-48):(1-15), preferably (50-51):(37-48):(3.4-15), more preferably (50-51):(37-48):(5-14), for example 50:45:5, 50:43:7, 50:40:10, or 50:37:13.

[0035] In this invention, the pressure of the prepolymer can be 1.5, 1.7, 1.8, 2.0, 2.2 or 2.3 MPa, preferably 1.5-2.2 MPa.

[0036] In this invention, the prepolymerization temperature can be 205, 215, 218 or 220°C, preferably 210-240°C, and more preferably 215-235°C.

[0037] In this invention, after the prepolymerization is completed, it is preferable to further include pressure holding and flash evaporation steps.

[0038] The pressure holding and flash evaporation are conventional operations in the field.

[0039] In this invention, the pressure of the polycondensation can be -(0-0.1)MPa, preferably -(0.02-0.08)MPa, for example -0.03, -0.05, -0.06 or -0.07MPa.

[0040] In this invention, the polycondensation temperature can be 230-280℃, for example 263, 265, 268, 270, 275 or 278℃, preferably 240-275℃.

[0041] Those skilled in the art will understand that the product obtained directly after polycondensation is generally referred to as polyamide melt.

[0042] In this invention, the polycondensation process may further include a cooling step.

[0043] Those skilled in the art will understand that the solid product obtained after cooling is generally referred to as polyamide resin.

[0044] The temperature after the cooling step can be 10-50°C, preferably 20-50°C, such as 30°C, 40°C or 45°C.

[0045] The present invention also provides a polyamide prepared by the preparation method described above.

[0046] The present invention also provides a high-shrinkage polyamide fiber, the material of which is polyamide as described above.

[0047] In this invention, the high-shrinkage polyamide fiber can be a fully drawn yarn, a pre-oriented yarn, a textured yarn, a medium-oriented yarn, a highly oriented yarn, a short fiber, a continuous bulky filament, or a monofilament, preferably a fully drawn yarn or a textured yarn, such as a fully drawn yarn.

[0048] In this invention, the boiling water shrinkage rate of the high-shrinkage polyamide fiber can be 13-45%, for example 14-40%, such as 16.8%, 22.5%, 27.6%, 32.5%, 35.8% or 39%, preferably 22.5-39%.

[0049] In this invention, the 10% elongation elastic recovery rate of the high-shrinkage polyamide fiber can be ≥95%, preferably ≥95.5%, more preferably ≥96%, and even more preferably ≥96.4%, for example 96.4%, 97.1%, 97.3%, 98%, 98.2%, or 98.7%.

[0050] In this invention, the 20% constant elongation elastic recovery rate of the high-shrinkage polyamide fiber can be ≥88%, preferably ≥88.2%, more preferably ≥88.3%, and even more preferably ≥88.5%, for example 88.5%, 88.9%, 89.6%, 90.3%, 91.2%, or 92.3%.

[0051] In this invention, the dyeing uniformity (grey card) of the high-shrinkage polyamide fiber can be ≥3.5, preferably ≥3.6, more preferably ≥3.8, and even more preferably ≥4.0, such as 4.0, 4.5 or 4.7.

[0052] In this invention, the dyeing double A rate of the high-shrinkage polyamide fiber can be ≥92%, preferably ≥92.5%, more preferably ≥93%, and even more preferably ≥93.5%, for example 93.5%, 94.2%, 95.4%, 96%, 97.8%, or 98.5%.

[0053] In this invention, the unevenness of the high-shrinkage polyamide fiber can be ≤1.0%, preferably ≤0.95%, more preferably ≤0.9%, and even more preferably ≤0.85%, for example 0.85%, 0.83%, 0.8%, 0.75%, 0.72%, or 0.62%.

[0054] In this invention, the tensile strength of the high-shrinkage polyamide fiber can be 3.0-8.0 cN / dtex, preferably 3.2-7.0 cN / dtex, more preferably 3.4-6.5 cN / dtex, and even more preferably 3.6-5.5 cN / dtex, for example 3.6, 3.8, 4.3, 4.5, 4.9 or 5 cN / dtex.

[0055] In this invention, the elongation at break of the high-shrinkage polyamide fiber can be 10%-20%, preferably 21%-30%, more preferably 31%-40%, and even more preferably 40.5%-50%, for example 48.2%, 47.4%, 46.4%, 45.5%, 44.6% or 40.5%.

[0056] In this invention, the initial modulus of the high-shrinkage polyamide fiber can be 15-45 cN / dtex, preferably 18-43 cN / dtex, more preferably 23-40 cN / dtex, and even more preferably 26-39 cN / dtex, for example 29.5, 30.3, 32.8, 34.6, 36.4 or 38.2 cN / dtex.

[0057] In this invention, the fineness of the high-shrinkage polyamide fiber can be ≤300dtex, preferably ≤250dtex, more preferably ≤200dtex, and even more preferably ≤150dtex, for example 44, 33 or 78dtex.

[0058] In this invention, those skilled in the art will understand that the component scraping cycle of the high-shrinkage polyamide fiber refers to the cleaning cycle of the oligomers under the component during the production process.

[0059] In this invention, the component scraping cycle of the high-shrinkage polyamide fiber can be ≥12h, preferably ≥14h, more preferably ≥16h, for example 16, 18, 20 or 24h.

[0060] In this invention, the number of monofilament breaks of the high-shrinkage polyamide fiber can be ≤4 per spinning position 24h, preferably ≤3 per spinning position 24h, more preferably ≤2 per spinning position 24h, for example 2, 1 or 0 per spinning position 24h.

[0061] In this invention, the yield of the high-shrinkage polyamide fiber can be ≥95%, preferably ≥95.5%, more preferably ≥96%, and even more preferably ≥96.5%, for example 96.5%, 97.2%, 97.6%, 98%, 98.5% or 98.8%.

[0062] The present invention also provides a method for preparing the high-shrinkage polyamide fiber, which includes the following steps:

[0063] The polyamide can be spun as described above.

[0064] In this invention, when the polyamide is in the form of resin, a resin melting step is generally included before spinning.

[0065] In this invention, the spinning process can be conventional in the art, and preferably includes the following steps:

[0066] (1) The polyamide melt is transported to the inlet of the spinning box through the melt pipeline and sprayed out through the spinneret of the spinning box to obtain the nascent filament;

[0067] (2) Cool, stretch and heat set the nascent filaments to obtain high shrinkage polyamide fibers.

[0068] In step (1), the temperature of the spinning box can be 240-290℃, preferably 250-288℃, more preferably 260-285℃, for example 265, 270, 275, 280, 283 or 285℃, and even more preferably 277-283℃.

[0069] In step (1), the pressure of the spinning assembly of the spinning box can be 10-25 MPa, preferably 12-23 MPa, such as 12, 13, 14 or 15 MPa, and more preferably 14-18 MPa.

[0070] In step (2), the wind speed of the side blowing air during the cooling process can be 0.3-0.6 m / s, preferably 0.4-0.5 m / s, for example 0.4, 0.41, 0.43, 0.46 or 0.48 m / s.

[0071] In step (2), the temperature of the side-blowing air during the cooling process can be 16-22°C, preferably 18-21°C, for example 18, 19 or 20°C.

[0072] In step (2), the humidity of the side-blowing air during the cooling process can be 70-95%, preferably 75-90%, for example 80%, 85%, 87%, 89% or 90%.

[0073] In step (2), the cooling process generally includes an oiling step.

[0074] In step (2), the stretching process may use two or more pairs of stretching rollers, preferably two pairs of stretching rollers, such as G1 stretching roller and G2 stretching roller.

[0075] In step (2), the drawing process can be conventional in the art, and preferably includes the following steps: the cooled nascent yarn is first fed into the G1 drawing roller, and then drawn and heat-set between the G2 drawing roller and the G1 drawing roller.

[0076] The speed of the G1 drawing roller can be 1800-4000 m / min, preferably 2400-3900 m / min, such as 3000, 3600 or 3900 m / min, and more preferably 2800-3800 m / min.

[0077] The speed of the G2 drawing roller can be 4300-5500 m / min, preferably 4500-5300 m / min, more preferably 4500-5100 m / min, for example 4500, 4500 or 4800 m / min.

[0078] In step (2), the stretching ratio can be 1.2-3.0, for example 1.23, 1.28, 1.3, 1.5, 1.6 or 3, preferably 1.23-2.6, more preferably 1.23-2.3.

[0079] In step (2), the heat setting temperature can be 140-180℃, preferably 150-175℃, more preferably 150-170℃, for example 150, 155, 160 or 170℃.

[0080] In step (2), after the heat setting, a winding step is generally also included.

[0081] The present invention also provides an application of the polyamide or the high-shrinkage polyamide fiber as described above in the textile field.

[0082] In this invention, the textile field can be the fields of weaving, knitting, carpets, monofilaments, civilian filaments, industrial filaments, continuously expanded filaments, and staple fibers, etc.

[0083] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0084] The reagents and raw materials used in this invention are all commercially available.

[0085] The positive and progressive effects of this invention are as follows:

[0086] First, the polyamide component of this invention includes biomass-derived pentanediamine. Pentanediamine is produced by a biological method, is a green material, does not rely on petroleum resources, does not cause serious environmental pollution, and can reduce carbon dioxide emissions and mitigate the greenhouse effect.

[0087] Secondly, the oligomer content of the polyamide of the present invention is relatively low (≤0.7wt%) (the oligomer content of existing polyamides is generally 0.9-1.1wt%, while the polyamide of the present invention is about 0.2-0.4wt%) lower than that of existing polyamides). During the spinning process, the component scraper cycle is longer (≥16h), production consumption is reduced, and the fiber production yield is greatly improved.

[0088] Third, the high-shrinkage polyamide fiber obtained from the polyamide of this invention has high shrinkage, high elasticity, and excellent dyeing and mechanical properties. The boiling water shrinkage rate of the high-shrinkage polyamide fiber can be 16-45%, the elastic recovery rate at 10% constant elongation can be ≥96%, the elastic recovery rate at 20% constant elongation can be ≥88%, the dyeing uniformity (grey calender) can be ≥3.5 grade, the dyeing double A rate can be ≥92%, the breaking strength can be 3.0-8.0 cN / dtex, the breaking strength elongation can be ≤50%, and the initial modulus can be 15-45 cN / dtex.

[0089] Fourth, the high-shrinkage polyamide fiber obtained from the polyamide of this invention can be produced using conventional fiber spinning equipment without the need for modification of the spinning equipment, which can reduce production costs and bring greater benefits to spinning enterprises. The high-shrinkage polyamide fiber of this invention has stable production, fewer broken monofilaments (the number of broken monofilaments can be ≤2 / 1 spinning station 24h), and high fiber yield (the yield can be ≥97%).

[0090] Fifth, the high-shrinkage polyamide fiber obtained from the polyamide of the present invention can be applied to the fields of woven and knitted fabrics, carpets, monofilaments, and staple fibers. Detailed Implementation

[0091] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0092] The raw materials used in the following examples and comparative examples are all commercially available.

[0093] Example 1 (Specifications: 44dtex / 48f)

[0094] 1. Preparation of polyamide:

[0095] (1) A polyamide salt solution with a concentration of 56 wt% was prepared by mixing pentanediamine, adipic acid, isophthalic acid, and water evenly, and the pH of the polyamide salt solution was adjusted to 7.8. The molar ratio of pentanediamine to the total amount of adipic acid and isophthalic acid was 1:1. The molar ratio of pentanediamine, adipic acid, and isophthalic acid was 50:48:2.

[0096] (2) The polyamide salt solution was prepolymerized at 1.5 MPa pressure and 220°C, then subjected to pressure holding and flash evaporation, and then polycondensed at -0.03 MPa pressure and 278°C, and cooled at 40°C.

[0097] 2. Preparation of high-shrinkage polyamide fibers:

[0098] (1) The polyamide melt obtained in step 1 is transported to the inlet of the spinning box through the melt pipeline, and is ejected through the spinneret of the spinning box to form nascent filament. The temperature of the spinning box is 285℃; the pressure of the spinning assembly of the spinning box is 15MPa.

[0099] (2) The nascent filaments are cooled, oiled, drawn, heat-set, and wound to obtain high-shrinkage polyamide fibers. The side-blowing air velocity is 0.43 m / s, the side-blowing air temperature is 19℃, and the side-blowing air humidity is 90%. Two pairs of drawing rollers are used in the drawing process. The oiled nascent filaments are first fed into the G1 drawing roller, and then drawn and heat-set between the G2 and G1 drawing rollers. The speed of the G1 drawing roller is 3000 m / min, the speed of the G2 drawing roller is 4500 m / min, the draw ratio is 1.5, and the heat-setting temperature is 170℃.

[0100] Example 2 (Specifications: 44dtex / 48f)

[0101] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:47:3.

[0102] Example 3 (Specifications: 44dtex / 48f)

[0103] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:45:5.

[0104] Example 4 (Specifications: 44dtex / 48f)

[0105] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:43:7.

[0106] Example 5 (Specifications: 44dtex / 48f)

[0107] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:40:10.

[0108] Example 6 (Specifications: 44dtex / 48f)

[0109] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:37:13.

[0110] Example 7 (Specifications: 44dtex / 48f)

[0111] The only difference from Example 1 is that in the preparation of polyamide, the prepolymerization temperature in step (2) is 205°C.

[0112] Comparative Example 1 (Specifications: 44 dtex / 48 f)

[0113] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:50:0.

[0114] Comparative Example 2 (Specifications: 44 dtex / 48 f)

[0115] The only difference from Example 1 is that in the preparation of polyamide, the molar ratio of pentanediamine, adipic acid and isophthalic acid in step (1) is 50:32:18.

[0116] Comparative Example 3 (Specifications: 44 dtex / 48 f)

[0117] The only difference from Example 1 is that in the preparation of polyamide, the prepolymerization pressure in step (2) is 0.6 MPa.

[0118] Comparative Example 4 (Specifications: 44 dtex / 48 f)

[0119] The only difference from Example 1 is that in the preparation of the high-shrinkage polyamide fiber, step (1) involves melting polyamide 6 resin to obtain polyamide 6 melt. The polyamide melt is then transported to the inlet of the spinning box through a melt pipe and ejected through the spinneret of the spinning box to form nascent filaments. The temperature of the spinning box is 285°C, and the pressure of the spinning assembly in the spinning box is 15 MPa.

[0120] Comparative Example 5 (Specifications: 44 dtex / 48 f)

[0121] The only difference from Example 1 is that in the preparation of the high-shrinkage polyamide fiber, step (1) involves melting polyamide 66 resin to obtain polyamide 66 melt. The polyamide melt is then transported through a melt pipe to the inlet of the spinning box, where it is ejected through the spinneret to form nascent filaments. The temperature of the spinning box is 285°C, and the pressure of the spinning assembly in the spinning box is 15 MPa.

[0122] Comparative Example 6 (Specifications: 44 dtex / 48 f)

[0123] The only difference from Example 1 is that in the preparation of the high-shrinkage polyamide fiber, step (1) involves mixing and melting polyamide 56 resin and polyamide 6 resin at a mass ratio of 70:30 to obtain a polyamide 56 and polyamide 6 mixed melt. The polyamide 56 and polyamide 6 mixed melt is transported to the inlet of the spinning box through a melt pipeline and ejected through the spinneret of the spinning box to form nascent filaments. The temperature of the spinning box is 285°C; the pressure of the spinning assembly in the spinning box is 15 MPa.

[0124] The structural units in the structural formulas of the polyamides prepared in Examples 1-7 and Comparative Examples 1-3 The molar fractions are shown in Table 1 below.

[0125] Table 1

[0126] Example 1 50：48：2 Example 2 50：47：3 Example 3 50：45：5 Example 4 50：43：7 Example 5 50：40：10 Example 6 50：37：13 Example 7 50：48：2 Comparative Example 1 50：50：0 Comparative Example 2 50：32：18 Comparative Example 3 50：48：2

[0127] Effect Example

[0128] The polyamide or high-shrinkage polyamide fibers obtained in Examples 1-7 and Comparative Examples 1-6 were tested according to the following methods, and the test results are shown in Tables 2 and 3:

[0129] (1) Fineness: determined according to GB / T14343.

[0130] (2) Fracture strength, cv%: determined according to GB / T 14344-2008.

[0131] (3) Elongation at break, cv%: determined according to GB / T 14344-2008.

[0132] (4) Initial modulus: determined according to GB / T 14344-2008.

[0133] (5) Boiling water shrinkage rate: determined according to GB / 6505-2008 "Test method for heat shrinkage rate of chemical fiber filament".

[0134] (6) Relative viscosity: The relative viscosity was determined by the concentrated sulfuric acid method using an Ubbelohde viscometer. The steps are as follows: 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 flow time t0 of the concentrated sulfuric acid and the flow time t of the polyamide slice sample solution in a constant temperature water bath at 25 °C.

[0135] The formula for calculating relative viscosity is: Relative viscosity V N =t / t0;

[0136] t — time it takes for the solution to flow through;

[0137] t0 — Solvent flow time.

[0138] (7) Moisture content: determined by Karl Fischer moisture titrator.

[0139] (8) Production rate: Production rate = (mass of finished fiber prepared / total mass of polyamide melt or resin added) × 100%.

[0140] (11) Oligomer content (molecular weight generally 500-2000 g / mol): Accurately weigh approximately 2 g of polyamide sample, record the actual mass of the polyamide sample (m1), place it in a 250 mL round-bottom flask, add 100 mL of deionized water, heat under reflux at 97℃~100℃ for 24 hours, take the water-extracted polyamide sample and wash it three times with deionized water, then dry the polyamide sample at 130℃ for 7 hours, and weigh the polyamide sample after water extraction (m2). Calculate the oligomer content by comparing the weight difference of the polyamide sample before and after water extraction. Oligomer content (%) = (m1-m2) / m1*100%.

[0141] (12) Amino: After dissolving polyamide in trifluoroethanol, titrate it with standard hydrochloric acid solution and standard sodium hydroxide solution respectively, and calculate.

[0142] (13) Number of times a single filament breaks: manually counted.

[0143] (14) Yarn unevenness: Yarn unevenness refers to the degree of variation in thickness of yarn along its own length, including uneven yarn diameter and uneven linear density. The testing equipment is the Uster yarn evenness tester.

[0144] (15) Dyeing uniformity (grey card) / grade: FZ / T50008 Test method for dyeing uniformity of nylon filament.

[0145] (16) Dyeing double A rate: Dyeing double A rate = (weight of fibers dyed with Hickory uniformity ≥ 4.5) / total weight of all dyed fibers) × 100%.

[0146] (17) Elastic recovery rate:

[0147] A YG061 yarn tensile strength tester was used, and the test parameters were set according to the test method of GB / T14344-2003. The tensile interval was 500 mm, the pre-tension was 0.1 cN / dtex, and the tensile speed was 500 mm / min. After stretching to the set elongation (E = 10% or 20%), the instrument stopped stretching and relaxed for 60 seconds, then returned to its original position. The test was repeated 10 times.

[0148] (18) Molecular weight distribution: determined according to GPC.

[0149] Table 2

[0150]

[0151] Table 3

[0152]

[0153]

[0154] As shown in Table 3, compared with the method of obtaining polyamide fibers by blending polyamide 56 fibers and polyamide 6 fibers in Comparative Example 6, the polyamide fibers obtained by polymerization reaction and then spinning in Examples 1-6 have better melt uniformity (fewer times of monofilament breakage) and better dyeing performance (higher dyeing uniformity and higher dyeing double A rate).

Claims

1. A high-shrinkage polyamide fiber, characterized in that, The structural formula of the polyamide, which is the material thereof, consists of structural units represented by the following I, II and III: ； wherein, the molar fraction of structural unit I is 50 to 52 parts; the molar fraction of structural unit II is 35 to 48 parts; the molar fraction of structural unit III is 1 to 15 parts; the sum of the molar fractions of said structural unit I, said structural unit II and said structural unit III is 100 parts; wherein, the melting point of said polyamide is 220 to 256°C, the relative viscosity of said polyamide is 2.2 to 3.0, the molecular weight distribution of said polyamide is 1.3 to 2.0, and the oligomer content of said polyamide is ≤0.9 wt%.

2. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, wherein, the ratio of the molar fraction of said structural unit I to "the sum of the molar fractions of said structural unit II and said structural unit III" is (1 to 1.1):1; or, the molar fraction of said structural unit I is 50 to 51 parts; or, the molar fraction of said structural unit II is 37 to 48 parts; or, the molar fraction of said structural unit III is 3.4 to 15 parts; or, the melting point of said polyamide is 220 to 252°C; or, the relative viscosity of said polyamide is 2.3 to 2.9; or, the amino group content of said polyamide is 30 to 60 mmol / kg; or, the molecular weight distribution of said polyamide is 1.5 to 2.

0.

3. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, the molar fraction of said structural unit III is 5 to 14 parts; and / or, the relative viscosity of said polyamide is 2.4 to 2.8; and / or, the amino group content of said polyamide is 35 to 55 mmol / kg.

4. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, the molar fraction of said structural unit III is 5 to 13 parts; and / or, the amino group content of said polyamide is 40 to 52 mmol / kg.

5. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, The preparation method of said polyamide comprises: sequentially subjecting a polyamide salt solution prepared from pentanediamine, adipic acid and isophthalic acid to prepolymerization and polycondensation to obtain said polyamide; wherein the pressure of said prepolymerization is 1.2 to 2.4 MPa.

6. The high-shrinkage polyamide fiber as described in claim 5, characterized in that, the solvent in said polyamide salt solution is water or ethanol; and / or, the preparation method of said polyamide salt solution comprises the following steps: uniformly mixing said pentanediamine, said adipic acid, said isophthalic acid and a solvent; and / or, the concentration of said polyamide salt solution is 50 to 70 wt.%; and / or, the pH value of said polyamide salt solution is 6.8 to 9.0; and / or, the molar ratio of said pentanediamine to "the total amount of said adipic acid and said isophthalic acid" is (1 to 1.1):1; and / or, the pressure of said prepolymerization is 1.5 to 2.2 MPa; and / or, the temperature of said prepolymerization is 210 to 240°C; and / or, after completion of said prepolymerization, steps of pressure holding and flash evaporation are further comprised; and / or, the pressure of said polycondensation is -(0 to 0.1) MPa; and / or, the temperature of said polycondensation is 230 to 280°C; and / or, a cooling step is further comprised after said polycondensation; wherein, the temperature after said cooling step is 10 to 50°C.

7. The high-shrinkage polyamide fiber as described in claim 6, characterized in that, the temperature after said cooling step is 20 to 50°C.

8. The high-shrinkage polyamide fiber as described in claim 5, characterized in that, The molar ratio of pentanediamine, adipic acid, and isophthalic acid is (50–51):(37–48):(3.4–15); and / or, The prepolymerization temperature is 215–235°C; and / or, The polycondensation temperature is 240–275°C.

9. The high-shrinkage polyamide fiber as described in claim 5, characterized in that, The molar ratio of the pentanediamine, adipic acid, and isophthalic acid is (50–51):(37–48):(5–14); and / or, The pressure of the polycondensation is -(0.02~0.08)MPa.

10. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, The high-shrinkage polyamide fiber has a boiling water shrinkage rate of 13-45%; Alternatively, the high-shrinkage polyamide fiber has an elastic recovery rate of ≥95% at 10% constant elongation; Alternatively, the high-shrinkage polyamide fiber has an elastic recovery rate of ≥88% at 20% constant elongation; Alternatively, the dyeing uniformity gray scale of the high-shrinkage polyamide fiber is ≥3.5; Alternatively, the dyeing double A rate of the high-shrinkage polyamide fiber is ≥92%; Alternatively, the unevenness of the high-shrinkage polyamide fiber is ≤1.0%; Alternatively, the tensile strength of the high-shrinkage polyamide fiber is 3.0–8.0 cN / dtex; Alternatively, the high-shrinkage polyamide fiber has a breaking elongation of 10% to 20%; Alternatively, the initial modulus of the high-shrinkage polyamide fiber is 15–45 cN / dtex; Alternatively, the fineness of the high-shrinkage polyamide fiber is ≤300 dtex; Alternatively, the number of monofilament breaks of the high-shrinkage polyamide fiber is ≤4 per spinning position for 24 hours.

11. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, The high-shrinkage polyamide fiber has a boiling water shrinkage rate of 14-40%; Alternatively, the high-shrinkage polyamide fiber has an elastic recovery rate of ≥95.5% at 10% constant elongation; Alternatively, the high-shrinkage polyamide fiber has an elastic recovery rate of ≥88.2% at 20% constant elongation; Alternatively, the dyeing uniformity gray scale of the high-shrinkage polyamide fiber is ≥3.6; Alternatively, the high-shrinkage polyamide fiber has a dyeing double A rate of ≥92.5%; Alternatively, the unevenness of the high-shrinkage polyamide fiber is ≤0.95%; Alternatively, the tensile strength of the high-shrinkage polyamide fiber is 3.2–7.0 cN / dtex; Alternatively, the high-shrinkage polyamide fiber has a breaking elongation of 21% to 30%; Alternatively, the initial modulus of the high-shrinkage polyamide fiber is 18–43 cN / dtex; Alternatively, the fineness of the high-shrinkage polyamide fiber is ≤250 dtex; Alternatively, the number of monofilament breaks of the high-shrinkage polyamide fiber is ≤3 per spinning position for 24 hours.

12. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, The high-shrinkage polyamide fiber has a boiling water shrinkage rate of 22.5% to 39%. Alternatively, the high-shrinkage polyamide fiber has an elastic recovery rate of ≥96% at 10% constant elongation; Alternatively, the high-shrinkage polyamide fiber has a 20% elongation elastic recovery rate of ≥88.3%; Alternatively, the dyeing uniformity gray scale of the high-shrinkage polyamide fiber is ≥3.8; Alternatively, the dyeing double A rate of the high-shrinkage polyamide fiber is ≥93%; Alternatively, the unevenness of the high-shrinkage polyamide fiber is ≤0.9%; Alternatively, the tensile strength of the high-shrinkage polyamide fiber is 3.4–6.5 cN / dtex; Alternatively, the high-shrinkage polyamide fiber has a breaking elongation of 31% to 40%; Alternatively, the initial modulus of the high-shrinkage polyamide fiber is 23–40 cN / dtex; Alternatively, the fineness of the high-shrinkage polyamide fiber is ≤200 dtex; Alternatively, the number of monofilament breaks of the high-shrinkage polyamide fiber is ≤2 per spinning position for 24 hours.

13. The high-shrinkage polyamide fiber as described in claim 1, characterized in that, The high-shrinkage polyamide fiber has an elastic recovery rate of ≥96.4% at 10% constant elongation. Alternatively, the high-shrinkage polyamide fiber has an elastic recovery rate of ≥88.5% at 20% constant elongation; Alternatively, the dyeing uniformity of the high-shrinkage polyamide fiber is ≥4.0 grade (gray card). Alternatively, the high-shrinkage polyamide fiber has a dyeing double A rate of ≥93.5%; Alternatively, the unevenness of the high-shrinkage polyamide fiber is ≤0.85%; Alternatively, the tensile strength of the high-shrinkage polyamide fiber is 3.6–5.5 cN / dtex; Alternatively, the high-shrinkage polyamide fiber has a breaking elongation of 40.5% to 50%; Alternatively, the initial modulus of the high-shrinkage polyamide fiber is 26–39 cN / dtex; Alternatively, the fineness of the high-shrinkage polyamide fiber is ≤150 dtex; Alternatively, the number of monofilament breaks in the high-shrinkage polyamide fiber is 0 per 1 spinning position for 24 hours.

14. A method for preparing high-shrinkage polyamide fiber as described in any one of claims 1 to 13, characterized in that, It includes the following steps: spinning the polyamide.

15. The method for preparing high-shrinkage polyamide fibers as described in claim 14, characterized in that, The spinning process includes the following steps: (1) The polyamide melt is transported to the inlet of the spinning box through the melt pipeline and sprayed out through the spinneret of the spinning box to obtain nascent yarn; (2) Cool, stretch and heat set the nascent filament to obtain high shrinkage polyamide fiber.

16. The method for preparing high-shrinkage polyamide fibers as described in claim 15, characterized in that, In step (1), the temperature of the spinning box is 240–290°C; And / or, in step (1), the pressure of the spinning assembly of the spinning box is 10-25 MPa; And / or, in step (2), the wind speed of the side-blowing air during the cooling process is 0.3 to 0.6 m / s; And / or, in step (2), the temperature of the side-blowing air during the cooling process is 16-22°C; And / or, in step (2), the humidity of the side-blowing air during the cooling process is 70-95%; And / or, in step (2), the stretching process uses two or more pairs of stretching rollers; And / or, in step (2), the stretching ratio is 1.2 to 3.0; And / or, in step (2), the heat setting temperature is 140 to 180°C.

17. The method for preparing high-shrinkage polyamide fibers as described in claim 16, characterized in that, The temperature of the spinning box is 250–288°C; And / or, in step (1), the pressure of the spinning assembly of the spinning box is 12-23 MPa; And / or, in step (2), the temperature of the side-blowing air during the cooling process is 18-21°C; And / or, in step (2), the stretching process uses two pairs of stretching rollers, G1 stretching roller and G2 stretching roller; And / or, in step (2), the heat setting temperature is 150 to 175°C.

18. The method for preparing high-shrinkage polyamide fibers as described in claim 16, characterized in that, The temperature of the spinning box is 260–285°C; And / or, in step (1), the pressure of the spinning assembly of the spinning box is 14-18 MPa; And / or, in step (2), the humidity of the side-blowing air during the cooling process is 75-90%; And / or, in step (2), the stretching ratio is 1.23 to 2.6; And / or, in step (2), the heat setting temperature is 150 to 170°C.

19. The method for preparing high-shrinkage polyamide fibers as described in claim 16, characterized in that, The temperature of the spinning box is 277–283°C; And / or, in step (2), the wind speed of the side-blowing air during the cooling process is 0.4 to 0.5 m / s; And / or, in step (2), the drawing process includes the following steps: the cooled nascent yarn is first fed into the G1 drawing roller, and then drawn and heat-set between the G2 drawing roller and the G1 drawing roller. And / or, in step (2), the stretching ratio is 1.23 to 2.

3.

20. The method for preparing high-shrinkage polyamide fibers as described in claim 19, characterized in that, The speed of the G1 drawing roller is 1800–4000 m / min; And / or, the speed of the G2 drawing roller is 4300-5500 m / min.

21. The method for preparing high-shrinkage polyamide fibers as described in claim 19, characterized in that, The speed of the G1 drawing roller is 2400–3900 m / min; And / or, the speed of the G2 drawing roller is 4500-5300 m / min.

22. The method for preparing high-shrinkage polyamide fibers as described in claim 19, characterized in that, The speed of the G1 drawing roller is 2800-3800 m / min; And / or, the speed of the G2 drawing roller is 4500-5100 m / min.

23. An application of a high-shrinkage polyamide fiber as described in any one of claims 1 to 13 in the textile field.

24. The application as described in claim 23, characterized in that, The textile field refers to the fields of woven fabrics, knitted fabrics, carpets, monofilaments, civilian filaments, industrial filaments, continuously expanded filaments, or staple fibers.

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