A flame-retardant polyester fiber based on modified hydroxyapatite and its preparation method

Abstract

The present invention relates to a flame-retardant polyester fiber based on modified hydroxyapatite and a preparation method thereof, belonging to the technical field of functional fibers. The preparation method of the present invention includes the following steps: S1. Adding hydroxyapatite to a phenyl phosphate solution, performing ultrasonic treatment and heating reaction to obtain modified hydroxyapatite; S2. Granulating the modified hydroxyapatite and polyester powder to obtain a flame-retardant polyester masterbatch; S3. Spinning the flame-retardant polyester masterbatch and polyester chips to obtain a flame-retardant polyester fiber based on modified hydroxyapatite. The phosphate groups and calcium ions in the flame-retardant polyester fiber can form a protective carbon layer during the pyrolysis process to inhibit the combustion of the polyester fiber; while the aromatic groups can promote carbon formation, further enhancing the flame-retardant effect and the anti-dripping effect. The synergistic effect of the three enables the modified hydroxyapatite composite material to exhibit high efficiency and stability in flame-retardant performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional fibers, and particularly relates to a flame-retardant polyester fiber based on modified hydroxyapatite and a preparation method thereof. Background Art

[0002] Due to its excellent mechanical properties (such as high strength and high modulus), as well as excellent wrinkle resistance, easy wash and quick drying properties, and good processing properties, polyester fiber has been widely used in the textile field, and its output continues to increase. However, the limiting oxygen index of conventional polyester fiber is only 20%, which belongs to flammable fiber, and it is prone to melt dripping at high temperatures, greatly increasing the fire risk. With the increasing requirements for safety, the regulations and standards for the flame retardancy of fabrics have become more and more strict. Therefore, it is particularly urgent to develop polyester fibers with high-efficiency flame retardant properties.

[0003] Flame-retardant polyester fiber, as an important functional fiber, has been widely used in daily household textile products such as curtains, carpets, sofas, and pajamas. However, the existing flame-retardant polyester fibers still face many challenges. In particular, how to further improve their flame retardant effect on the premise of ensuring their stable performance, harmlessness to humans and the environment is one of the current research focuses. To improve the flame retardant performance of polyester fiber, researchers have tried to add different nano flame retardants by blending. Among them, hydroxyapatite, as a potential natural mineral, has attracted more and more attention. Hydroxyapatite is the main component of animal bones and teeth, with a high phosphorus content and abundant calcium ions. These characteristics play an important role in increasing the carbon layer formation rate and carbon yield, thus helping to improve the flame retardant and anti-melt dripping properties of polyester fiber.

[0004] However, although the flame retardant performance of hydroxyapatite has great potential in theory, its compatibility with the polyester matrix is poor, resulting in insufficient dispersion in the polyester matrix. This uneven dispersion makes the polyester fiber added with hydroxyapatite show poor flame retardant performance in practical applications, and has a greater negative impact on the mechanical properties (such as strength) of polyester fiber. Therefore, developing an efficient, stable and performance-balanced modification method has become the key to improving the performance of flame-retardant polyester fiber.

[0005] The invention patent CN104845025A discloses a highly modified ABS composite material using nano-hydroxyapatite loaded with a composite flame retardant and a preparation method thereof. In the preparation process of this composite material, raw materials such as nano-ATO, tricresyl phosphate, and melamine cyanurate are used as environmentally friendly composite flame retardant synergists, and they are infiltrated and loaded into nano-hydroxyapatite under high-pressure conditions, and then the flame retardant is added to the ABS material. However, there is no strong bonding between raw materials such as nano-ATO, tricresyl phosphate, and melamine cyanurate and nano-hydroxyapatite, and the compatibility of this flame retardant with polyester fibers is still poor, making it difficult to effectively improve the flame retardant performance of polyester fibers.

[0006] Wu Zhihao et al. (Preparation and properties of phosphorus-based flame retardant and α-zirconium phosphate synergistic flame retardant modified recycled polyester fibers. Proceedings of the 3rd International Symposium on Flame Retardant Materials and Technologies, 2014: 214-215.) prepared flame retardant recycled polyester (RPET) fibers by melt blending using a phosphorus-based flame retardant (FRP) and α-zirconium phosphate (α-ZrP). The limiting oxygen index of the recycled polyester fibers increased, but their mechanical properties were severely damaged because the compatibility between the nano-particle α-zirconium phosphate and polyester fibers was poor, and its dispersion performance in polyester fibers was poor, resulting in significant damage to the mechanical properties of the modified recycled polyester fibers.

[0007] Therefore, it is of great significance to modify hydroxyapatite for the preparation of flame retardant polyester fibers. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a flame retardant polyester fiber based on modified hydroxyapatite and a preparation method thereof. First, hydroxyapatite is surface-modified with monophenyl phosphate to obtain modified hydroxyapatite, and then the modified hydroxyapatite is used to prepare the flame retardant polyester fiber based on modified hydroxyapatite by melt blending.

[0009] The first object of the present invention is to provide a preparation method of a flame retardant polyester fiber based on modified hydroxyapatite, including the following steps:

[0010] S1. Add hydroxyapatite to the monophenyl phosphate solution for ultrasonic treatment and heating reaction to obtain modified hydroxyapatite;

[0011] S2. Granulate the modified hydroxyapatite obtained in S1 and polyester powder to obtain a flame retardant polyester masterbatch;

[0012] S3. Spun the flame retardant polyester masterbatch obtained in S2 and polyester chips to obtain the flame retardant polyester fiber based on modified hydroxyapatite.

[0013] In one embodiment of the present invention, in S1, the phenyl phosphate solution comprises phenyl phosphate and ethanol; the mass fraction of phenyl phosphate in the phenyl phosphate solution is 10% - 20%; hydroxyapatite has good dispersibility in ethanol, which helps the modification of hydroxyapatite by phenyl phosphate.

[0014] In one embodiment of the present invention, in S1, the mass ratio of phenyl phosphate to hydroxyapatite is 1: (3 - 4). A small amount of phenyl phosphate is used to coat hydroxyapatite, making the surface of hydroxyapatite rich in aromatic benzene rings, improving its compatibility with polyester fibers and its dispersion performance in polyester fibers.

[0015] In one embodiment of the present invention, in S1, the power of the ultrasonic treatment is 200W - 500W, and the time is 30min - 50min.

[0016] In one embodiment of the present invention, in S1, the temperature of the heating reaction is 50°C - 60°C, and the time is 2h - 3h.

[0017] In one embodiment of the present invention, before S2, there is also a step of drying the modified hydroxyapatite and polyester powder. The drying temperature of the modified hydroxyapatite is 60°C - 70°C, and the drying time is 8h - 10h; the drying temperature of the polyester powder is 125°C - 135°C, and the time is 9h - 11h.

[0018] In one embodiment of the present invention, in S2, the granulation is carried out by melt blending, extrusion molding, and cooling pelletizing through a twin - screw extruder; the temperature of the granulation is 260°C - 270°C. If the processing temperature is too low, the modified hydroxyapatite and polyester powder cannot be mixed evenly, which is not conducive to granulation. If the temperature is too high, it will cause energy waste.

[0019] In one embodiment of the present invention, in S2, the mass fraction of modified hydroxyapatite in the flame - retardant polyester masterbatch is 15% - 20%.

[0020] In one embodiment of the present invention, before S3, there is also a step of drying the flame - retardant polyester masterbatch and polyester chips. The drying is to pre - crystallize at 90°C - 100°C for 3h - 4h first, and then dry at 125°C - 135°C for 10h - 14h to ensure that the final moisture content of the flame - retardant polyester masterbatch and polyester chips is lower than 100 ppm.

[0021] In one embodiment of the present invention, in S3, the spinning is carried out by a melt spinning machine, followed by oiling, pre-drawing, winding, and drawing after cooling. The process parameters of the spinning are as follows: the speed is 2600 m / min - 2800 m / min, the temperature is 270°C - 280°C, and the draw ratio is 1.5 - 2.

[0022] In one embodiment of the present invention, in S3, the mass fraction of the flame-retardant polyester masterbatch in the flame-retardant polyester fiber based on modified hydroxyapatite is 12% - 16%.

[0023] The second object of the present invention is to provide a flame-retardant polyester fiber based on modified hydroxyapatite prepared by the described preparation method.

[0024] In one embodiment of the present invention, the limiting oxygen index of the flame-retardant polyester fiber based on modified hydroxyapatite is 29.0% - 30.7%, the flame-retardant grade is V0, no melt dripping occurs, and the breaking strength is not less than 3.0 cN / dtex.

[0025] The technical solution of the present invention has the following advantages compared with the prior art:

[0026] (1) In the preparation method of the present invention, phenyl phosphate is used to modify the surface of hydroxyapatite. On the one hand, the surface of hydroxyapatite is rich in calcium ions (Ca 2+ ), and the phosphate ester group in phenyl phosphate can form a stable calcium-phosphate ester complex with the calcium ions on the surface of hydroxyapatite through coordination, so that phenyl phosphate is firmly adsorbed on the surface of hydroxyapatite. On the other hand, the benzene ring structure in the phenyl phosphate molecule can form an affinity with the aromatic groups in the polyester through π-π stacking interaction, significantly improving the compatibility between the modified hydroxyapatite and the polyester fiber. This interaction enhances the dispersion performance of the modified hydroxyapatite in the polyester fiber, thus overcoming the original compatibility problem and improving the processing performance and mechanical properties of the polyester fiber.

[0027] (2) The hydroxyapatite in the flame-retardant polyester fiber based on modified hydroxyapatite of the present invention is rich in phosphorus elements and calcium ions, and phenyl phosphate not only contains abundant phosphorus elements but also contains aromatic char-forming agents with good thermal stability. The synergistic effect among the phosphate group, calcium ions, and aromatic groups plays a key role in the flame-retardant process. The phosphate group and calcium ions can form a protective carbon layer during pyrolysis to inhibit the combustion of the polyester fiber; while the aromatic groups can promote carbonization, further enhancing the flame-retardant effect and anti-melt dripping effect. The synergistic effect of the three makes the modified hydroxyapatite composite material show high efficiency and stability in flame-retardant performance. Description of the Drawings

[0028] To make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments of the present invention in conjunction with the accompanying drawings, where:

[0029] Figure 1 It is a schematic structural diagram of the modified hydroxyapatite in Embodiment 1 of the present invention. Specific Embodiments

[0030] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the exemplified embodiments do not limit the present invention.

[0031] In the present invention, unless otherwise specified, the technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the technical field to which the present invention belongs.

[0032] In the present invention, unless otherwise specified, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0033] In the present invention, unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods without special instructions, and the materials, reagents, etc. used can be obtained from commercial channels without special instructions.

[0034] In the present invention, unless otherwise specified, the monophenyl phosphate solution used in the embodiments of the present invention is prepared by dissolving monophenyl phosphate in ethanol.

[0035] In the present invention, unless otherwise specified, the polyester powder and polyester chips used in the embodiments of the present invention are both purchased from Yizheng Chemical Fiber, with the brand number FG650.

[0036] In the present invention, unless otherwise specified, the hydroxyapatite powder used in the embodiments of the present invention is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with the brand number H684219, and the particle size is about 60nm - 80nm. Embodiment 1

[0037] The flame-retardant polyester fiber based on modified hydroxyapatite and its preparation method in this embodiment specifically include the following steps:

[0038] S1. First, slowly add hydroxyapatite powder into a 15% monophenyl phosphate solution by mass fraction, then first perform ultrasonic treatment at 350W for 40 min, then heat the solution to 55°C and stir for reaction for 2.5 h, and finally remove the excess solvent by rotary evaporation, wash with deionized water and dry to obtain modified hydroxyapatite (Figure 1 ); wherein, the mass ratio of monophenyl phosphate to hydroxyapatite is 1:3.5;

[0039] S2. The modified hydroxyapatite is vacuum-dried at 65 °C for 9 h; the polyester powder is vacuum-dried at 130 °C for 10 h, and after mixing, melt blending, extrusion molding, and cooling and pelletizing are carried out by a twin-screw extruder. The temperature of the twin-screw extruder is 265 °C to obtain a flame-retardant polyester masterbatch with a mass fraction of modified hydroxyapatite of 18%;

[0040] S3. The flame-retardant polyester masterbatch and polyester chips are pre-crystallized in a forced-air oven at 95 °C for 3.5 h, and then continuously dried at 130 °C for 12 h to make the final moisture of the flame-retardant polyester masterbatch and polyester chips lower than 100 ppm. After mixing, spinning, oiling after cooling, pre-drawing, winding, and drawing are carried out by a melt spinning machine. The speed of the melt spinning machine is 2700 m / min, the temperature is 275 °C, and the draw ratio is 1.8 to obtain a flame-retardant polyester fiber based on modified hydroxyapatite with a mass fraction of the flame-retardant polyester masterbatch of 14%. Example 2

[0041] The flame-retardant polyester fiber based on modified hydroxyapatite and its preparation method in this example specifically include the following steps:

[0042] S1. First, hydroxyapatite powder is slowly added to a 10% monophenyl phosphate solution, then ultrasonic treatment is carried out at 200 W for 50 min, then the solution is heated to 50 °C and stirred for 3 h, and finally the excess solvent is removed by rotary evaporation, washed with deionized water and dried to obtain modified hydroxyapatite; wherein, the mass ratio of monophenyl phosphate to hydroxyapatite is 1:3;

[0043] S2. The modified hydroxyapatite is vacuum-dried at 60 °C for 10 h; the polyester powder is vacuum-dried at 125 °C for 11 h, and after mixing, melt blending, extrusion molding, and cooling and pelletizing are carried out by a twin-screw extruder. The temperature of the twin-screw extruder is 260 °C to obtain a flame-retardant polyester masterbatch with a mass fraction of modified hydroxyapatite of 15%;

[0044] S3. The flame-retardant polyester masterbatch and polyester chips are pre-crystallized in a forced-air oven at 90 °C for 4 h, and then continuously dried at 125 °C for 14 h to make the final moisture of the flame-retardant polyester masterbatch and polyester chips lower than 100 ppm. After mixing, spinning, oiling after cooling, pre-drawing, winding, and drawing are carried out by a melt spinning machine. The speed of the melt spinning machine is 2600 m / min, the temperature is 270 °C, and the draw ratio is 1.5 to obtain a flame-retardant polyester fiber based on modified hydroxyapatite with a mass fraction of the flame-retardant polyester masterbatch of 12%. Example 3

[0045] The flame-retardant polyester fiber based on modified hydroxyapatite and its preparation method in this embodiment specifically include the following steps:

[0046] S1. First, slowly add hydroxyapatite powder to a 20% by mass monobenzyl phosphate solution, then ultrasonically treat it at 500 W for 30 min, then heat the solution to 60 °C and stir for 2 h, and finally remove the excess solvent by rotary evaporation, wash it with deionized water and dry it to obtain modified hydroxyapatite; wherein, the mass ratio of monobenzyl phosphate to hydroxyapatite is 1:4;

[0047] S2. Vacuum-dry the modified hydroxyapatite at 70 °C for 8 h; vacuum-dry the polyester powder at 135 °C for 9 h, mix them and then carry out melt blending, extrusion molding and cooling pelletizing through a twin-screw extruder. The temperature of the twin-screw extruder is 270 °C to obtain a flame-retardant polyester masterbatch with a mass fraction of modified hydroxyapatite of 20%;

[0048] S3. Pre-crystallize the flame-retardant polyester masterbatch and polyester chips in a blast drying oven at 100 °C for 3 h, and then continue to dry at 135 °C for 10 h to make the final moisture content of the flame-retardant polyester masterbatch and polyester chips lower than 100 ppm. After mixing, carry out spinning, oiling after cooling, pre-drawing, winding and drawing through a melt spinning machine. The speed of the melt spinning machine is 2800 m / min, the temperature is 280 °C, and the draw ratio is 2 to obtain a flame-retardant polyester fiber based on modified hydroxyapatite with a mass fraction of the flame-retardant polyester masterbatch of 16%. Comparative Example 1

[0049] It is basically the same as Example 1, except that monobenzyl phosphate is replaced with phosphoric acid. Comparative Example 2

[0050] It is basically the same as Example 1, except that monobenzyl phosphate is replaced with phenol. Comparative Example 3

[0051] It is basically the same as Example 1, except that modification with monobenzyl phosphate is not carried out. Comparative Example 4

[0052] It is basically the same as Example 1, except that hydroxyapatite is replaced with calcium carbonate. Comparative Example 5

[0053] It is basically the same as Example 1, except that hydroxyapatite is replaced with calcium hydroxide. Comparative Example 6

[0054] It is basically the same as Example 1, except that modification with modified hydroxyapatite is not carried out.

[0055] Test Example

[0056] The physical properties, etc. of the flame-retardant polyester fibers (modified polyester fibers) based on modified hydroxyapatite and unmodified polyester fibers prepared in Examples 1-3 and Comparative Examples 1-6 were tested:

[0057] Limiting oxygen index: The limiting oxygen indices of the modified polyester fibers and unmodified polyester fibers were tested with reference to FZ / T 50017-2011 "Test Method for Flame Retardant Properties of Polyester Fibers - Oxygen Index Method";

[0058] Combustion test: The generation of melt drops and the flame retardant grade of the modified polyester fibers and unmodified polyester fibers were tested with reference to the standard of UL94 vertical combustion;

[0059] Breaking strength: The breaking strengths of the modified polyester fibers and unmodified polyester fibers were tested with reference to the standard of GB / T 14344-2022 "Test Method for Tensile Properties of Chemical Fibers - Filament Yarns";

[0060] Table 1 shows the relevant properties of the finally measured unmodified polyester fibers and modified polyester fibers:

[0061] Table 1

[0062]

[0063] It can be seen from Table 1 that the modified polyester fibers have a relatively high limiting oxygen index, no melt drops are generated, the flame retardant grade is V0, the flame retardant performance is good, and the breaking strength is relatively high, indicating that there is good compatibility between the modified hydroxyapatite and the polyester fibers.

[0064] Comparing Example 1 and Comparative Example 1, it can be seen that when replacing monophenyl phosphate with phosphoric acid, the flame retardant performance of the modified polyester fibers decreases, no melt drops are generated, but the breaking strength decreases significantly. This is because the phosphoric acid coated on the surface of hydroxyapatite has poor compatibility with the polyester fibers, making it difficult for the modified hydroxyapatite to be evenly dispersed in the polyester fibers.

[0065] Comparing Example 1 and Comparative Example 2, it can be seen that when replacing monophenyl phosphate with phenol, the flame retardant performance of the modified polyester fibers decreases, melt drops are generated, and the breaking strength decreases. This is because the phosphate group in monophenyl phosphate plays a synergistic flame retardant effect, and the chelating ability of the phosphate group with calcium ions is strong, making the binding force between monophenyl phosphate and hydroxyapatite relatively strong.

[0066] Comparing Example 1 and Comparative Example 3, it can be seen that when not using monophenyl phosphate for modification, the unmodified hydroxyapatite is difficult to be evenly dispersed in the polyester fibers, resulting in great damage to the mechanical properties of the polyester fibers and a decrease in the flame retardant performance.

[0067] Comparing Example 1 and Comparative Example 4, it can be seen that when hydroxyapatite is replaced with calcium carbonate, the flame retardancy of the modified polyester fiber decreases, there are molten droplets generated, and the breaking strength decreases. This is because the flame retardancy efficiency of calcium carbonate is much lower than that of hydroxyapatite.

[0068] Comparing Example 1 and Comparative Example 5, it can be seen that when hydroxyapatite is replaced with calcium hydroxide, the flame retardancy of the modified polyester fiber decreases, there are molten droplets generated, and the breaking strength decreases. This is because the flame retardancy efficiency of calcium hydroxide is much lower than that of hydroxyapatite.

[0069] Comparing Example 1 and Comparative Example 6, it can be seen that the limiting oxygen index of the polyester fiber without flame retardant modification is 20.1%, there are molten droplets generated in the UL-94 vertical burning test, the flame retardant grade is NR grade, the molten droplets are serious, and the flame retardancy is poor.

[0070] Obviously, the above examples are only for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing flame-retardant polyester fiber based on modified hydroxyapatite, characterized in that: The following steps are involved: S1, adding hydroxyapatite to a monophenyl phosphate solution for ultrasonic treatment and heating reaction to obtain modified hydroxyapatite; the mass ratio of the monophenyl phosphate to the hydroxyapatite is 1:(3-4); S2, granulating the modified hydroxyapatite and polyester powder described in S1 to obtain a flame retardant polyester masterbatch; S3, spinning the flame-retardant polyester masterbatch and polyester chips described in S2 to obtain the flame-retardant polyester fiber based on modified hydroxyapatite.

2. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S1, the monophenyl phosphate solution includes monophenyl phosphate and ethanol; the mass fraction of monophenyl phosphate in the monophenyl phosphate solution is 10%-20%.

3. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S1, the power of the ultrasonic treatment is 200W-500W, and the time is 30min-50min.

4. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S1, the heating reaction temperature is 50°C-60°C, and the time is 2h-3h.

5. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S2, the granulation is performed by melt blending, extrusion molding, cooling and pelletizing through a twin-screw extruder; the granulation temperature is 260°C-270°C.

6. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S2, the mass fraction of modified hydroxyapatite in the flame retardant polyester masterbatch is 15%-20%.

7. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S3, the spinning is carried out by a melt spinning machine, followed by oiling after cooling, pre-stretching, winding, and stretching; the spinning process parameters are: speed of 2600m / min-2800m / min, temperature of 270℃-280℃, and traction ratio of 1.5-2.

8. The method for preparing flame-retardant polyester fiber based on modified hydroxyapatite according to claim 1, characterized in that: In S3, the mass fraction of the flame retardant polyester masterbatch in the flame retardant polyester fiber based on modified hydroxyapatite is 12%-16%.

9. Flame-retardant polyester fiber based on modified hydroxyapatite prepared by the preparation method according to any one of claims 1 to 8.

Images