A bio-based polyester memory fiber and its preparation method

Abstract

The present invention relates to the field of polyester fibers, and specifically discloses a bio-based polyester memory fiber and a preparation method thereof. By using bio-based chemical raw materials, a bio-based polyester memory fiber with a large transformation temperature range and a high shape recovery rate is obtained through a copolymerization method, effectively alleviating problems such as resource shortage and environmental pollution faced by the current economic and social development.

Description

Technical Field

[0001] The present invention belongs to the field of polyester fibers, and particularly relates to a bio-based polyester memory fiber and a preparation method thereof. Background Art

[0002] Memory fiber, also known as shape memory fiber or Shape Memory Polymer Fiber, is a kind of intelligent material with special properties. This fiber can remember the initial shape given by the outside world during the first molding, and can be deformed arbitrarily after being shaped. When specific external stimulus conditions (such as temperature, humidity, electric field, etc.) are given to the deformed fiber, it can return to the original shape. The application of shape memory fibers is very extensive, including but not limited to fields such as textiles, medical devices, sensing and actuation. For example, in textiles, shape memory fibers can be used to make products such as wedding dresses, protective clothing, and medical compression stockings. These products are convenient for folding during transportation and storage, and only need to be heated or washed with water before use to restore their original shape; in the biomedical field, shape memory polymer fibers are widely used in orthopedic implants and tissue engineering scaffolds due to their high elasticity and reversibility.

[0003] For example, Patent CN 104695041 B discloses a shape memory polyurethane prepared from a diisocyanate and a chain extender forming a hard segment, and a long-chain polyol forming a soft segment. The shape memory polyurethane is manufactured by a melt spinning method to obtain a shape memory fiber with low recovery force and significant shape fixation. Another example is Patent CN 109457306 B, which discloses a preparation method of a bidirectional shape memory fiber. The raw materials of the bidirectional shape memory fiber include benzophenone, triallyl isocyanurate, and polyethylene-vinyl acetate resin. The product obtained by melt blending and extrusion exhibits good reversible shape memory effect and shape recovery process.

[0004] At present, the global market scale of shape memory materials has reached 92 billion yuan in 2023, and the potential market is broad. However, most of the existing memory fiber raw materials come from petrochemical products. In order to alleviate the problem of resource shortage faced by the current economic and social development, the present invention provides a bio-based polyester memory fiber and a preparation method thereof. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention uses bio-based chemical raw materials to obtain a bio-based polyester memory fiber by copolymerization method, reducing the dependence on non-renewable resources such as petrochemicals.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a method for preparing a bio-based polyester memory fiber, comprising the following steps:

[0008] S1. Under nitrogen protection, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, and non-edible castor oil are used as reaction monomers. After mixing, a catalyst and acetic anhydride are added, and the mixture is stirred at 130 - 150 °C for 3 - 5 h, then heated to 200 - 220 °C and stirred for 30 - 50 min. Subsequently, the temperature is raised to 240 - 260 °C, and the mixture is stirred until the reactants become turbid and viscous, then vacuum is applied, and stirring is continued for 40 - 70 min. After washing and vacuum drying, a bio-based polyester is obtained;

[0009] S2. The bio-based polyester obtained in step S1 and the memory enhancement material are melt-spun. The specific steps are as follows: The bio-based polyester and the memory enhancement material enter a twin-screw through a hopper to form a uniformly extruded melt. Then, the melt is quantitatively transported into a spinning assembly through a metering pump, and finally extruded from a spinneret to form filaments. After cooling by side blowing and oiling on an oil roller, winding is carried out, and then drawing and orientation-induced crystallization are performed to obtain the bio-based polyester memory fiber.

[0010] Bio-based materials generally refer to materials made from raw materials such as alcohols, acids, and amines produced by biological methods sourced from natural animals and plants. Compared with petroleum products, bio-based materials are biodegradable and have low toxicity, making them an excellent choice for synthesizing polyester fibers. In the present invention, abundant and easily available non-edible castor oil is used as a reaction monomer, and a bio-based polyester is obtained by polycondensation with 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid. Then, the bio-based polyester is spun to obtain a bio-based polyester memory fiber.

[0011] In this process, the carboxyl groups of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid randomly react with the hydroxyl groups in non-edible castor oil to form a polyester mixture with similar structures but different block sequences. The castor oil-based groups in this polyester mixture can connect different block movable molecular chains through three fatty acid chains to form a microphase-separated network structure, which acts as a hard segment to maintain the permanence of the shape; while the movable molecular chains act as soft segments and can achieve the shape memory effect through their crystallization or glass transition.

[0012] In some embodiments, in step S1, the molar ratio of 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, and non-edible castor oil is (0.7 - 0.8) : (0.7 - 0.8) : 1.

[0013] In some embodiments, in step S1, the catalyst comprises magnesium acetate and potassium acetate.

[0014] In some embodiments, the mass ratio of magnesium acetate to potassium acetate is 1 : (0.9 - 1.1).

[0015] By specifically selecting a catalyst, magnesium acetate enables the obtained bio-based polyester memory fiber to have a higher nucleation and crystallization rate, and through the synergy of magnesium acetate and potassium acetate, the molecular weight distribution of the bio-based polyester is controlled to optimize the shape memory property of the polyester fiber.

[0016] In some embodiments, in step S2, the memory enhancing material is any one of a lactic acid-caprolactone copolymer, paraffin wax, or EVA.

[0017] Preferably, the memory enhancing material is a lactic acid-caprolactone copolymer.

[0018] By introducing the memory enhancing material through melting, the obtained bio-based polyester memory fiber has a wider transition temperature range and brings more glass transition temperatures and melting temperatures.

[0019] In some embodiments, in step S2, the mass ratio of the bio-based polyester to the memory enhancing material is 1:(0.1 - 0.25).

[0020] By specifically selecting the amounts of the bio-based polyester and the memory enhancing material, it is ensured that the introduction of the memory enhancing material expands the range of the shape memory transition temperature without destroying the crystallinity of the molecular chains.

[0021] In some embodiments, in step S2, the temperatures of the four zones of the twin-screw extruder are 260 - 270 °C, 270 - 290 °C, 275 - 280 °C, and 270 - 280 °C respectively; the temperature of the metering pump is 280 - 290 °C.

[0022] There are various methods for preparing polyester fibers, including wet spinning, dry spinning, and melt spinning, etc. The melt spinning method selected in the present invention has a simple production process and does not require considering the addition and recovery of solvents.

[0023] The second aspect of the present invention provides a bio-based polyester memory fiber obtained by the above preparation method, and the transition temperature range of the bio-based polyester memory fiber is 15 - 43 °C.

[0024] In some embodiments, the deformation fixation rate R of the bio-based polyester memory fiber at 35 °C f ≥73.6.

[0025] In some embodiments, the shape recovery rate R of the bio-based polyester memory fiber at 35 °C r ≥86.7%.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses rich and readily available bio-based raw materials as reaction monomers, which are polycondensed with 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid to obtain a bio-based polyester. Through melt spinning, a bio-based polyester memory fiber with a large transformation temperature range and a high shape recovery rate is obtained.

[0028] 2. The present invention controls the molecular weight distribution of the bio-based polyester by specifically selecting a catalyst to optimize the shape memory of the polyester fiber.

[0029] 3. The present invention introduces a memory enhancement material by melting, so that the obtained bio-based polyester memory fiber has a wide transformation temperature range and brings more glass transition temperatures and melting temperatures. Detailed Embodiments

[0030] The present invention will be described below in conjunction with specific implementation embodiments. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not used to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the gist or scope of the present invention.

[0031] For the convenience of those skilled in the art to implement the present invention, some raw materials and manufacturers of the examples are described as follows:

[0032] Non-edible castor oil is purchased from Inner Mongolia Weiyu Biotechnology Co., Ltd., and the model is qualified product; lactic acid-caprolactone is purchased from Jinan Daigang Biotechnology Co., Ltd.; the source of semi-refined paraffin is not limited; the source of EVA is not limited, and the vinyl acetate content is 22-26%.

[0033] Example 1

[0034] A preparation method of a bio-based polyester memory fiber, comprising the following steps:

[0035] S1. Under nitrogen protection, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid and non-edible castor oil are used as reaction monomers in a molar ratio of 0.75:0.75:1. After mixing, based on the mass of the reaction monomers, 0.05 wt% of magnesium acetate, 0.05 wt% of potassium acetate and 2 wt% of acetic anhydride are added. Stir at 140 °C for 4 h, then raise the temperature to 210 °C and stir for 40 min, then raise the temperature to 250 °C. When the reactants become turbid and viscous, evacuate, continue stirring for 60 min, wash with acetone, and dry in vacuum at 80 °C to constant weight to obtain a bio-based polyester;

[0036] S2. Melt-spin the bio-based polyester and the lactic acid-caprolactone copolymer obtained in step S1 at a mass ratio of 1:0.17. The specific steps are as follows: Feed the bio-based polyester and the memory enhancing material into a twin-screw extruder through a hopper to form a uniformly extruded melt. The temperatures of the four zones of the twin-screw extruder are 265 °C, 280 °C, 277 °C, and 275 °C respectively. Then, quantitatively transport the melt to the spinning assembly through a metering pump. The temperature of the metering pump is 285 °C. Finally, extrude the melt from a spinneret to form filaments, cool the filaments through side blowing, apply oil through an oil roller, and finally wind the filaments. Then, perform drawing orientation-induced crystallization to obtain the bio-based polyester memory fiber.

[0037] Example 2

[0038] A preparation method of a bio-based polyester memory fiber includes the following steps:

[0039] S1. Under nitrogen protection, use 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid, and non-edible castor oil as reaction monomers at a molar ratio of 0.7:0.7:1. After mixing, based on the mass of the reaction monomers, add 0.05 wt% of magnesium acetate, 0.045 wt% of potassium acetate, and 2 wt% of acetic anhydride. Stir at 130 °C for 5 h, then raise the temperature to 200 °C and stir for 50 min. Then raise the temperature to 240 °C, stir until the reactants become turbid and viscous, then evacuate, continue stirring for 70 min, wash with acetone, and dry in a vacuum at 80 °C to constant weight to obtain the bio-based polyester.

[0040] S2. Melt-spin the bio-based polyester and the lactic acid-caprolactone copolymer obtained in step S1 at a mass ratio of 1:0.1. The specific steps are as follows: Feed the bio-based polyester and the memory enhancing material into a twin-screw extruder through a hopper to form a uniformly extruded melt. The temperatures of the four zones of the twin-screw extruder are 260 °C, 270 °C, 275 °C, and 270 °C respectively. Then, quantitatively transport the melt to the spinning assembly through a metering pump. The temperature of the metering pump is 280 °C. Finally, extrude the melt from a spinneret to form filaments, cool the filaments through side blowing, apply oil through an oil roller, and finally wind the filaments. Then, perform drawing orientation-induced crystallization to obtain the bio-based polyester memory fiber.

[0041] Example 3

[0042] A preparation method of a bio-based polyester memory fiber includes the following steps:

[0043] S1. Under nitrogen protection, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid and non-edible castor oil are used as reaction monomers in a molar ratio of 0.8:0.8:1. After mixing, based on the mass of the reaction monomers, 0.05 wt% of magnesium acetate, 0.055 wt% of potassium acetate and 2 wt% of acetic anhydride are added. Stir at 150 °C for 3 h, then raise the temperature to 220 °C and stir for 30 min. Then raise the temperature to 260 °C. When the reactants become turbid and viscous, evacuate to vacuum, continue stirring for 40 min, wash with acetone, and dry at 80 °C under vacuum until constant weight to obtain the bio-based polyester.

[0044] S2. The bio-based polyester obtained in step S1 and the lactic acid-caprolactone copolymer are melt-spun at a mass ratio of 1:0.25. The specific steps are as follows: The bio-based polyester and the memory enhancement material enter the twin-screw through the hopper to form a uniform melt extrusion. The temperatures of the four zones of the twin-screw are 270 °C, 290 °C, 280 °C, and 280 °C respectively; then the melt is quantitatively transported to the spinning assembly through a metering pump, and the temperature of the metering pump is 290 °C; finally, it is extruded from the spinneret to form filaments, cooled by side blowing air, oiled on the oil roller, and finally wound, and then drawn and orientation-induced crystallization is carried out to obtain the bio-based polyester memory fiber.

[0045] Example 4

[0046] This example provides a preparation method of a bio-based polyester memory fiber. The specific implementation method is the same as that of Example 1, except that in step S2, the lactic acid-caprolactone copolymer is replaced by the same amount of semi-refined paraffin.

[0047] Example 5

[0048] This example provides a preparation method of a bio-based polyester memory fiber. The specific implementation method is the same as that of Example 1, except that in step S2, the lactic acid-caprolactone copolymer is replaced by the same amount of EVA.

[0049] Example 6

[0050] This example provides a preparation method of a bio-based polyester memory fiber. The specific implementation method is the same as that of Example 1, except that in step S1, the amounts of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid remain unchanged, and their molar ratio to non-edible castor oil is 0.75:0.75:1.1.

[0051] Example 7

[0052] This example provides a preparation method of a bio-based polyester memory fiber. The specific implementation method is the same as that of Example 1, except that in step S1, the amounts of 6-hydroxy-2-naphthoic acid and p-hydroxybenzoic acid remain unchanged, and their molar ratio to non-edible castor oil is 0.75:0.75:0.9.

[0053] Example 8

[0054] This example provides a method for preparing bio-based polyester memory fibers. The specific implementation is the same as that of Example 1, except that in step S1, magnesium acetate is replaced by an equal amount of potassium acetate.

[0055] Example 9

[0056] This example provides a method for preparing bio-based polyester memory fibers. The specific implementation is the same as that of Example 1, except that in step S1, potassium acetate is replaced by an equal amount of magnesium acetate.

[0057] Comparative Example 1

[0058] This comparative example provides a method for preparing bio-based polyester memory fibers. The specific implementation is the same as that of Example 1, except that:

[0059] S2. The bio-based polyester obtained in step S1 is melt-spun. The specific steps are as follows: The bio-based polyester enters a twin-screw through a hopper to be uniformly extruded as a melt, and then the melt is quantitatively transported to a spinning assembly through a metering pump. Finally, it is extruded from a spinneret to form a filament, cooled by side air blowing, oiled on an oil roller, and finally wound, and then drawn for orientation-induced crystallization to obtain bio-based polyester memory fibers.

[0060] Performance test:

[0061] Shape memory performance test

[0062] The shape memory performance of the fibers is tested by the thermal cycle stretching method on an Instron 5566 universal material testing machine. After the fibers are subjected to a certain tensile load at a certain temperature, the length changes. After the load is released, the deformation fixation rate R f and the shape recovery rate R r are calculated according to the magnitude of the deformation. Among them, the deformation fixation rate R f is used to describe the ability of the fiber to fix the instantaneous deformation; the shape recovery rate R r is used to describe the ability of the fiber to recover its original shape after deformation. The specific steps are as follows:

[0063] The bio-based polyester memory fibers provided in each example are heated to 35 °C and stretched by 15% (record the total deformation D t ), and this elongation is maintained. Then it is cooled to 21 °C and the load is released. The fiber will undergo partial retraction, and the part of the deformation that fails to retract is the fixed deformation D f ; Next, the fiber is reheated to 35 °C, and the fiber will gradually return to its original shape. However, usually, the deformation of the fiber is difficult to fully recover, and the instrument will automatically record the recovered deformation D rRepeat the above test cycle three times, and calculate the deformation fixation rate R and the shape recovery rate R respectively according to the following formula 1 and formula 2: f and the shape recovery rate R r :

[0064] Formula 1: R f =(D f / D t )×100%;

[0065] Formula 2: R r =(D r / D t )×100%.

[0066] The test results are shown in Table 1.

[0067] Table 1 Performance test results

[0068]

[0069]

[0070] It can be seen from the data in Table 1 that the bio-based polyester memory fibers of Examples 1-3 have the best shape memory effect and a high shape recovery rate; from Examples 1 and 4-5 and Comparative Example 1, it can be seen that the memory enhancement material can, to a certain extent, enhance the deformation fixation rate and shape recovery rate of the memory fiber. In addition, if the lactic acid-caprolactone copolymer is replaced by paraffin or EVA, it will cause a decrease in the deformation fixation rate and shape recovery rate of the memory fiber.

[0071] Compared with Example 1, the non-edible castor oil used in Examples 6-7 occupies an improper proportion in the reaction monomers, resulting in a change in the molecular structure of the polyester, affecting the microphase separation and the formation of movable soft segments, and causing a decrease in the deformation fixation rate and shape recovery rate of the memory fiber. From Examples 1 and 8-9, it can be seen that the memory fiber formed by using the catalyst magnesium acetate and potassium acetate in combination has a more excellent shape memory effect than the memory fiber formed by using a single catalyst.

[0072] The above-described examples and comparative examples do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a bio-based polyester memory fiber, characterized in that, It includes the following steps: S1. Under nitrogen protection, 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid and non-edible castor oil are used as reaction monomers. After mixing, a catalyst and acetic anhydride are added, and the mixture is stirred at 130-150 °C for 3-5 h, then heated to 200-220 °C and stirred for 30-50 min, then heated to 240-260 °C. When the reactants become turbid and viscous, vacuum is pumped, and stirring continues for 40-70 min. After washing and vacuum drying, a bio-based polyester is obtained; S2. The bio-based polyester obtained in step S1 and the memory enhancing material are melt-spun. The specific steps are as follows: The bio-based polyester and the memory enhancing material enter the twin-screw through a hopper to form a uniform melt extrusion. Then, the melt is quantitatively transported to the spinning assembly through a metering pump. Finally, it is extruded from the spinneret to form filaments, cooled by side blowing, oiled on an oil roller, and finally wound. Then, drawing and orientation-induced crystallization are carried out to obtain the bio-based polyester memory fiber; In step S1, the molar ratio of 6-hydroxy-2-naphthoic acid, p-hydroxybenzoic acid and non-edible castor oil is (0.7-0.8):(0.7-0.8):1; In step S2, the memory enhancing material is any one of lactic acid-caprolactone copolymer, paraffin or EVA; In step S2, the mass ratio of the bio-based polyester and the memory enhancing material is 1:(0.1-0.25).

2. The preparation method of the bio-based polyester memory fiber according to claim 1, characterized in that, In step S1, the catalyst includes magnesium acetate and potassium acetate.

3. The preparation method of the bio-based polyester memory fiber according to claim 2, wherein, The mass ratio of magnesium acetate and potassium acetate is 1:(0.9-1.1).

4. The preparation method of the bio-based polyester memory fiber according to claim 1, characterized in that, In step S2, the temperatures of the four zones of the twin-screw are 260-270 °C, 270-290 °C, 275-280 °C, 270-280 °C respectively; the temperature of the metering pump is 280-290 °C.

5. The bio-based polyester memory fiber obtained by the preparation method according to any one of claims 1-4, characterized in that, The transition temperature range of the bio-based polyester memory fiber is 15-43 °C.

6. The bio-based polyester memory fiber according to claim 5, wherein The deformation fixation rate R of the bio-based polyester memory fiber at 35°C f ≥73.6 7. The bio-based polyester memory fiber according to claim 5, characterized in that, The shape recovery rate R of the bio-based polyester memory fiber at 35°C r ≥86.7%.

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