A high-strength, high-modulus, fine-denier polyarylate fiber

Abstract

The invention discloses a high-strength, high-modulus, fine-denier polyarylate fiber and a preparation method thereof. The single-filament linear density of the high-strength, high-modulus, fine-denier polyarylate fiber is less than 2D, the filament breaking strength after heat treatment is greater than 27 cN / dtex, and the filament tensile modulus after heat treatment is greater than 800 cN / dtex. The preparation method comprises the following steps: (1) drying a high-molecular-weight polyarylate resin; (2) putting the high-molecular-weight polyarylate resin into a discharge barrel of a twin-screw extruder with nitrogen protection, conveying the resin into the twin screws, and simultaneously putting in four modified siloxanes; (3) extruding, drawing, and winding to obtain a fine-denier polyarylate fiber spun yarn; (4) heat-treating the fine-denier polyarylate fiber spun yarn to obtain a high-strength, high-modulus, fine-denier polyarylate fiber. The invention can realize the efficient preparation of high-strength, high-modulus, fine-denier polyarylate fiber, improve the spinning efficiency and heat treatment efficiency, save energy, improve product diversification, improve product physical properties, and greatly improve the competitiveness of the product.

Description

[0001] This application is a divisional application. Parent application number: 202011022132.6, application date: September 25, 2020, invention title: A high-strength, high-modulus, fine-denier polyarylate fiber and a preparation method thereof. Technical Field

[0002] The invention relates to the technical field of organic chemistry, and in particular to a high-strength, high-modulus, fine-denier polyarylate fiber. Background Art

[0003] Polyarylate fiber is a special fiber with excellent comprehensive properties such as high strength and modulus, high temperature resistance, low water absorption, self-flaming retardant, high wear resistance, chemical resistance, radiation resistance, and strong dimensional stability. It is widely used in bulletproof, cut-proof, puncture-proof, composite reinforcement, cable rope and other application fields. The fine denier of the fiber makes the fabric structure prepared have specific interface properties, and micro-hole structure can be formed in the fabric, which can penetrate with other materials. With high strength and high modulus performance, the comprehensive performance of the composite material can be improved. The rigid chain structure of the molecular structure of liquid crystal polyarylate fiber determines that it cannot use hot drawing to obtain a finer fiber diameter. Therefore, the diameter of the primary fiber is its final diameter. The preparation of finer liquid crystal polyarylate fibers has always been a difficult problem at home and abroad. The Vectran fiber circulating on the market has a single fiber density of 5D, which is still relatively thick compared with other special fibers. In order to obtain liquid crystal polyarylate fibers with smaller fiber size, Japan Kuraray Company adopted the "island type" spinning method, but this method is relatively complicated, costly, and not very practical. Patent CN200880006177 and Patent CN201810261002 both mention that polyarylate is fiberized by extruding from a spinneret at a temperature above the melting point, and then the physical properties of the fiber are improved by heat treatment, but neither mentions a method for preparing high-strength, high-modulus, fine-denier polyarylate fibers.

[0004] In the method of spinning "island-type" fine denier fibers, since a special spinning spinneret with a complex structure is required in the melt spinning stage, and a special process for dissolution or segmentation is required, there is a problem of extremely high cost in industrial production. It is well known that the polyarylate melt is in a liquid crystal state above the melting point and below the clearing point, and the melt has basically no extrusion swelling effect at the outlet of the spinneret hole, and it solidifies rapidly about 10 cm below the spinneret plate. When spinning fibers with high molecular weight liquid crystal polyarylate, due to the high viscosity, the shearing or stretching effect is insufficient before entering the spinneret hole, and the viscosity is very large. Only a spinneret with a larger aperture can be used to ensure high temperature and high pressure so that the high viscosity melt can be smoothly extruded, which increases the requirements for the temperature control accuracy and pressure resistance of the equipment. At the same time, this method cannot effectively achieve a high nozzle stretch ratio to make the fiber thinner. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the technical defects of the background technology and provide a high-strength, high-modulus, fine-denier polyarylate fiber and a preparation method thereof. The invention solves the technical problems of poor fluidity and harsh spinning conditions of high molecular weight polyarylate resins, and can smoothly spin high molecular weight polyarylate resins into fine deniers without requiring strict requirements on the equipment; the present invention is simple to operate and can be implemented without changing the original polyarylate melt spinning and heat treatment equipment, and has high practical application value; the present invention can realize the efficient preparation of high-strength, high-modulus, fine-denier polyarylate fibers, improve the spinning efficiency and heat treatment efficiency, save energy, increase product diversification, improve product physical properties, and greatly improve product competitiveness.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] A method for preparing high-strength, high-modulus, fine-denier polyarylate fiber comprises the following steps:

[0008] (1) Raw material drying: drying the raw material high molecular weight polyarylate resin to remove moisture; the molecular weight of the high molecular weight polyarylate resin is greater than 30w;

[0009] (2) melt blending: the dried high molecular weight polyarylate resin is put into the feed barrel of a twin-screw extruder with nitrogen protection, and the resin is continuously fed into the twin screws at a certain melt spinning temperature; at the same time, a certain proportion of modified siloxane is accurately fed into the twin screws using a loss-in-weight scale feeding system; the modified siloxane includes polyhydroxymethylsiloxane, polyphenylmethylsiloxane, hydroxypolyphenylmethylsiloxane, and polyhydroxyphenylsiloxane; the proportion of each modified siloxane is 0.3 to 10 mol% of the amount of the high molecular weight polyarylate resin;

[0010] (3) extrusion winding: extruding the fiber, stretching it at a high nozzle draw ratio, and winding it under the above-mentioned twin-screw spinning process to obtain fine-denier polyarylate fiber spun yarn;

[0011] (4) Heat treatment: The fine-denier polyarylate fiber spun yarn is heat treated at an optimal heat treatment temperature to obtain a high-strength and high-modulus fine-denier polyarylate fiber.

[0012] Preferably, in step (1), the polyarylate resin can be prepared by melt polymerization of two or more of the following monomers, such as p-hydroxybenzoic acid, hydroquinone, terephthalic acid, isophthalic acid, 6-hydroxy-2-naphthoic acid, biphenyl dicarboxylic acid, dihydroxybiphenyl, hydroquinone, and naphthalene diol.

[0013] Preferably, in step (1), the molecular weight of the high molecular weight polyarylate resin is 30w-40w, more preferably 35w, the melt viscosity is 60pa·s, and the melting point is 310°C.

[0014] Preferably, in step (1), the high molecular weight polyarylate resin is placed in a vacuum drying oven at 150° C. to remove moisture.

[0015] Preferably, in the step (2), the melt spinning temperature is 250-350°C.

[0016] Preferably, in step (2), the molar mass ratio of the polyhydroxymethylsiloxane, polyphenylmethylsiloxane, hydroxypolyphenylmethylsiloxane and polyhydroxyphenylsiloxane is (0.3-2):(1-10):(0.3-4):(4-6).

[0017] Preferably, in step (3), the temperature during extrusion is 315-350°C; more preferably 320-340°C; further preferably 325-330°C.

[0018] Preferably, in step (3), the screw pressure during extrusion is 4 to 8 MPa; more preferably, 5 to 7 MPa; and even more preferably, 6 MPa.

[0019] Preferably, in step (3), the component temperature during extrusion is 315-350°C; more preferably 320-340°C; further preferably 325-330°C.

[0020] Preferably, in the step (3), the assembly pressure during extrusion is 3 to 7 MPa; more preferably, 3.5 to 6 MPa; and even more preferably, 4 to 5 MPa.

[0021] Preferably, in step (3), the spinneret aperture during extrusion is 0.1 to 0.5 mm; more preferably 0.15 to 0.3 mm; further preferably 0.16 mm.

[0022] Preferably, in the step (3), the number of holes in the spinneret during the extrusion is 1 to 1000f; more preferably, it is 10 to 100f; and further preferably, it is 20f.

[0023] Preferably, in the step (3), V0 during extrusion is 10 to 40 m / min; more preferably 15 to 30 m / min; further preferably 20 to 25 m / min.

[0024] Preferably, in step (3), V during extrusion fIt is 200 to 5000 m / min, more preferably 1000 to 4000 m / min, and further preferably 1800 to 3800 m / min.

[0025] Preferably, in the step (3), the nozzle stretch ratio during the stretching is 20 to 300; more preferably 50 to 200; further preferably 80 to 160.

[0026] Preferably, in step (4), the temperature of the heat treatment is 240-300°C; more preferably 250-280°C; further preferably 260°C.

[0027] Preferably, in step (4), the heat treatment time is 5 to 50 hours; more preferably 8 to 30 hours; further preferably 10 hours.

[0028] A high-strength, high-modulus, fine-denier polyarylate fiber is prepared by using the above-mentioned method for preparing a high-strength, high-modulus, fine-denier polyarylate fiber.

[0029] Preferably, the single-filament linear density of the high-strength and high-modulus fine-denier polyarylate fiber is less than 2D, the bundle breaking strength after heat treatment is greater than 27 cN / dtex, and the bundle tensile modulus after heat treatment is greater than 800 cN / dtex.

[0030] The method for preparing high-strength, high-modulus, fine-denier polyarylate fibers as described above can also be used to prepare high-strength, high-modulus, special-shaped and hollow polyarylate fibers.

[0031] Basic principles of the present invention:

[0032] The present invention is found out through in-depth research on the ability to stably spin high molecular weight fine-denier polyarylate fibers using conventional equipment and processes, and to prepare high-strength and high-modulus fine-denier polyarylate fibers by heat treatment.

[0033] The present invention provides a high-strength, high-modulus, fine-denier polyarylate fiber and a preparation method thereof, which improves the fluidity of polyarylate, and is particularly aimed at improving the spinning process of liquid crystal polyarylate with a higher molecular weight, and preparing a high-strength, high-modulus, fine-denier liquid crystal polyarylate fiber. Compared with low-molecular-weight liquid crystal polyarylate, the initial fiber strength prepared by high-molecular-weight liquid crystal polyarylate is higher, and the mechanical properties of the fiber can reach a higher level after a short period of heat treatment, which can greatly improve production efficiency and increase production capacity. However, for the spinning of liquid crystal polyarylate with a high relative molecular weight, due to the high melt viscosity of the system, the temperature control accuracy and the pressure resistance of the equipment are required to be high, which increases the difficulty of spinning, and it is also impossible to use conventional processes to prepare fine-denier fibers with a high nozzle drawing ratio, and a special method is needed here to reduce its melt viscosity. The present invention adopts a twin-screw extruder spinning, and improves the spinning fluidity of liquid crystal polyarylate with a higher molecular weight by adding modified siloxane, and prepares a high-strength, high-modulus, fine-denier liquid crystal polyarylate fiber.

[0034] Specifically, the present invention adds and introduces a certain proportion of four modified siloxanes (polyhydroxymethylsiloxane, polyphenylmethylsiloxane, hydroxypolyphenylmethylsiloxane, polyhydroxyphenylsiloxane) at the feeding stage of high molecular weight polyarylate resin during twin-screw melt spinning to achieve interface lubrication and reduce the surface adhesion of the resin, thereby achieving the purpose of improving the fluidity of the high molecular weight polyarylate resin inside the screw and improving the passability of the polyarylate resin in the components and spinnerets, thereby alleviating the overly stringent requirements on the equipment during the melt spinning of high molecular weight polyarylate, preparing fine denier polyarylate fibers at a higher nozzle stretch ratio, and preparing high-strength and high-modulus fine denier polyarylate fibers through a short-time heat treatment, thereby achieving improved fiber quality, improved production efficiency, and reduced cost.

[0035] Among them, the hydroxyl group (-OH) on the hydroxyl-containing modified siloxane molecular chain undergoes a condensation reaction with the carboxyl group (-COOH) on the end of the polyarylate macromolecule during the twin-screw melt extrusion process, and the formed chemical bonds anchor the siloxane on the polyarylate macromolecule chain, making it difficult to escape; while the methyl-containing modified siloxane chain has high flexibility, which can improve the internal lubricity of the interface, reduce the adhesion of the resin surface, and improve the fluidity of the resin; the combination of hydroxyl-containing modified siloxane and methyl-containing modified siloxane can play a synergistic role and greatly improve the fluidity of the resin in the screw, components, and spinneret.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention solves the technical problems of poor fluidity and harsh spinning conditions of high molecular weight polyarylate resins, and can smoothly spin high molecular weight polyarylate resins into fine deniers without placing strict requirements on equipment;

[0038] (2) The present invention is simple to operate and can be implemented without changing the original polyarylate melt spinning and heat treatment equipment, and has high practical application value;

[0039] (3) The present invention can realize the efficient preparation of high-strength, high-modulus and fine-denier polyarylate fibers, improve the spinning efficiency and heat treatment efficiency, save energy, increase product diversification, improve product physical properties, and greatly enhance product competitiveness. DETAILED DESCRIPTION

[0040] In order to better understand the content of the present invention, further description is given below in conjunction with specific embodiments. It should be understood that these embodiments are only used to further illustrate the present invention, and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content described in the present invention, those skilled in the art make some non-essential changes or adjustments to the present invention, which still belong to the protection scope of the present invention.

[0041] In Examples 1 to 7 and Comparative Examples 1 to 6, the polymer A is a high molecular weight polyarylate resin with a molecular weight of 35w, a melt viscosity of 60pa·s and a melting point of 310°C; the polymer B is a low molecular weight polyarylate resin with a molecular weight of 25w, a melt viscosity of 40pa·s and a melting point of 280°C.

[0042] In Examples 1 to 7 and Comparative Examples 1 to 6, the number of holes in the spinneret used for spinning is 20f.

[0043] A method for preparing high-strength, high-modulus, fine-denier polyarylate fiber comprises the following steps:

[0044] (1) Raw material drying: drying the raw material high molecular weight polyarylate resin to remove moisture;

[0045] (2) melt blending: the dried high molecular weight polyarylate resin is put into the feed barrel of a twin-screw extruder with nitrogen protection, and the resin is continuously fed into the twin screws at a certain melt spinning temperature; at the same time, a certain proportion of modified siloxane is accurately fed into the twin screws using a loss-in-weight scale feeding system; the modified siloxane includes polyhydroxymethylsiloxane, polyphenylmethylsiloxane, hydroxypolyphenylmethylsiloxane, and polyhydroxyphenylsiloxane; the proportion of each modified siloxane is 0.3 to 10 mol% of the amount of the high molecular weight polyarylate resin;

[0046] (3) extrusion winding: extruding the fiber, stretching it at a high nozzle draw ratio, and winding it under the above-mentioned twin-screw spinning process to obtain fine-denier polyarylate fiber spun yarn;

[0047] (4) Heat treatment: The fine-denier polyarylate fiber spun yarn is heat treated at an optimal heat treatment temperature to obtain a high-strength and high-modulus fine-denier polyarylate fiber.

[0048] Comparative Example 1

[0049] A method for preparing polyarylate fiber comprises the following steps:

[0050] (1) drying polymer A in a vacuum drying oven at 150° C. to remove moisture;

[0051] (2) The polymer A was melt-spun using a twin-screw extruder (without adding modified siloxane), wherein the extrusion temperature was 350°C, the screw pressure was 6 MPa, the spinneret temperature was 350°C, the assembly pressure was 6 MPa, the spinneret aperture was 0.3 mm, the free drop speed V0 was 20 m / min, and the maximum spinning speed V f The speed was 600 m / min, the nozzle stretching ratio was 30, and the primary fiber was obtained. The primary fiber strength was 8.54 cN / dtex;

[0052] (3) The spun fibers were heat treated at 290°C for 15 h to obtain polyarylate fibers, wherein the single filament density was 5D, the bundle breaking strength was 24 cN / dtex, and the tensile modulus was 730 cN / dtex.

[0053] Specifically, the process parameters involved in the preparation process of polyarylate fibers in Examples 1 to 7 and Comparative Examples 1 to 6 and the mechanical properties test results of the prepared polyarylate fibers are shown in Table 1:

[0054] Table 1 Process parameters involved in the preparation of polyarylate fibers in Examples 1 to 7 and Comparative Examples 1 to 6 and test results of mechanical properties of the prepared polyarylate fibers

[0055]

[0056]

[0057] The melting point determination method of the present invention is as follows: 10 to 20 mg of sample is taken from a DSC device, sealed in an aluminum pan, nitrogen is introduced at 50 cc / min, and the temperature is measured at a heating rate of 10°C / min. The peak of the endothermic peak is Tm. Depending on the type of polymer, a clear endothermic peak may not appear in the first measurement. In this case, the sample can be heated at a heating rate of 40°C / min for about 4 minutes at a temperature 40°C higher than the temperature at which the endothermic peak does not appear, and then completely melted, and then cooled to 25°C at 50°C / min, and then Tm can be measured in the same manner at a heating rate of 10°C / min.

[0058] The method for measuring melt viscosity of the present invention is as follows: using a capillary rheometer, the temperature of the polyarylate sample is raised to Tm+20°C, and when the sample passes through a 0.5mm nozzle, a shear rate of 1000sec-1 is applied, and the viscosity at this time is measured as the melt viscosity MV.

[0059] Through the experimental data of Examples 1 to 7 and Comparative Examples 1 to 6, the present invention found that:

[0060] (1) The addition of modified siloxane can improve the fluidity and reduce the melt viscosity of both low molecular weight and high molecular weight polyarylate resins;

[0061] (2) The effect of adding only hydroxyl-modified or non-hydroxyl-modified siloxane on the fluidity of polyarylate resin is worse than the effect of adding both types of siloxanes together, and the strength modulus of the prepared fiber is also relatively lower than the latter.

[0062] (3) After adding four modified siloxanes, high molecular weight polyarylate resin can achieve a melt viscosity close to that of low molecular weight polyarylate resin (about 40 Pa·s), can reach a higher maximum spinning speed, and obtain higher strength primary fiber, but it can use a shorter heat treatment time to prepare fibers with a larger relative strength modulus;

[0063] (4) When the content of modified siloxane is added too much, the fluidity of the polyarylate resin can still be improved, but the mechanical properties of the fiber will decrease instead of increase.

[0064] The addition of the four modified siloxanes of the present invention realizes high-speed fine-denier spinning of high-molecular-weight polyarylate with high nozzle stretch ratio, improves spinning efficiency and heat treatment efficiency, saves energy, and increases product diversification. The mechanical properties of the prepared heat-treated fibers are also improved, greatly enhancing the competitiveness of the products.

[0065] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by a person skilled in the art within the spirit and scope of the present invention shall also fall within the protection scope of the present invention.

Claims

1. A high-strength, high-modulus, fine-denier polyarylate fiber, characterized in that: The single-filament linear density of the high-strength and high-modulus fine-denier polyarylate fiber is less than 2D, the bundle breaking strength after heat treatment is greater than 27 cN / dtex, and the bundle tensile modulus after heat treatment is greater than 800 cN / dtex; The method for preparing the high-strength, high-modulus, fine-denier polyarylate fiber comprises the following steps: (1) Raw material drying: drying the raw material high molecular weight polyarylate resin to remove moisture; the molecular weight of the high molecular weight polyarylate resin is 30w-40w; (2) melt blending: the dried high molecular weight polyarylate resin is put into the feed barrel of a twin-screw extruder with nitrogen protection, and the resin is continuously fed into the twin screws at a certain melt spinning temperature; at the same time, a certain proportion of modified siloxane is accurately fed into the twin screws using a loss-in-weight scale feeding system; the modified siloxane includes polyhydroxymethylsiloxane, polyphenylmethylsiloxane, hydroxypolyphenylmethylsiloxane, and polyhydroxyphenylsiloxane; the proportion of each modified siloxane is 0.3 to 10 mol% of the amount of the high molecular weight polyarylate resin; (3) extrusion winding: extruding the fiber, stretching it at a high nozzle draw ratio, and winding it under the above-mentioned twin-screw spinning process to obtain fine-denier polyarylate fiber spun yarn; (4) heat treatment: heat treating the fine-denier polyarylate fiber spun yarn at an optimal heat treatment temperature to obtain high-strength and high-modulus fine-denier polyarylate fiber; In the step (2), the melt spinning temperature is 250 to 350°C; In the step (2), the molar mass ratio of the polyhydroxymethylsiloxane, polyphenylmethylsiloxane, hydroxypolyphenylmethylsiloxane, and polyhydroxyphenylsiloxane is (0.3-2): (1-10): (0.3-4): (4-6); In the step (3), the temperature during extrusion is 315-350°C; the screw pressure during extrusion is 4-8Mpa; the component temperature during extrusion is 315-350°C; the component pressure during extrusion is 3-7Mpa; the spinneret aperture during extrusion is 0.1-0.5mm; the number of spinneret holes during extrusion is 1-1000f; the V0 during extrusion is 10-40m / min; the V f The speed is 200 to 5000 m / min; the nozzle stretching ratio during the stretching is 20 to 300; In the step (4), the temperature of the heat treatment is 240 to 300° C. and the time of the heat treatment is 5 to 50 hours.

2. The high-strength, high-modulus, fine-denier polyarylate fiber according to claim 1, characterized in that: In the step (1), the molecular weight of the high molecular weight polyarylate resin is 35w, the melt viscosity is 60pa·s, and the melting point is 310°C.

3. The high-strength, high-modulus, fine-denier polyarylate fiber according to claim 1, characterized in that: In the step (1), the high molecular weight polyarylate resin is placed in a vacuum drying oven at 150° C. to remove moisture.

Images