Bio-based liquid crystal copolyester, fiber and preparation method thereof

Abstract

The invention relates to a bio-based liquid crystal copolyester, a fiber and a preparation method of the bio-based liquid crystal copolyester, the structure of the liquid crystal copolyester is shown as a formula (1), wherein 30 < = x < = 60, 30 < = y < = 130, and 15 < = z < = 100. The bio-based liquid crystal copolyester disclosed by the invention is formed by polymerizing three monomers, namely 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid and vanillic acid, and the bio-based liquid crystal copolyester can be used for preparing fibers with good mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a bio-based liquid crystal copolyester, a fiber and a preparation method thereof. BACKGROUND

[0002] Liquid crystal polymer (LCP) is an intermediate state (i.e. liquid crystal state) material between isotropic liquid and completely ordered crystal, which has good fluidity of liquid and order of crystal structure. Based on this special molecular structure, liquid crystal polymer has excellent mechanical properties, thermal stability and processing properties, and is therefore applied in electronic appliances, aerospace, medical materials and information communication fields, and is known as "super engineering material in the 21st century".

[0003] Bio-based material refers to bio-based high molecular material obtained by biological conversion technology using renewable raw materials. Such materials have the characteristics of green, environmental protection, renewable raw materials and biodegradability, and can be applied to daily necessities such as packaging materials and disposable daily necessities, and biomedical fields such as drug controlled-release materials and human tissue repair materials. Therefore, it is of great significance to develop bio-based liquid crystal copolyester with the advantages of bio-based high molecular and liquid crystal polymer.

[0004] Bio-based liquid crystal copolyester not only has the biodegradability of bio-based high molecular, but also combines the excellent mechanical properties of liquid crystal polymer. It can also be prepared into bio-based liquid crystal copolyester fiber with good performance by melt spinning. The bio-based liquid crystal copolyester fiber is expected to replace petroleum-based fiber for the preparation of textiles such as car seats, sofas and interior decoration, reducing the dependence on non-renewable resources such as petrochemicals and environmental pollution.

[0005] Vanillic acid is a lignin-based aromatic monomer, and its molecular structure contains a hydroxyl group, a carboxyl group and an aromatic ring. The hydroxyl group and the carboxyl group are easily modified into esters and can be used as a potential bio-based raw material. At present, some research groups have carried out research using vanillic acid as a bio-based raw material. For example, CN113683508A discloses a vanillic acid ester environmentally friendly plasticizer and a preparation method thereof. The corresponding polyvinyl chloride (PVC) product has good mechanical properties. However, there are few studies on the preparation of bio-based liquid crystal copolyester based on vanillic acid, and the corresponding bio-based fiber product usually has poor mechanical properties. SUMMARY

[0006] The present application provides a bio-based liquid crystal copolyester, which is used for preparing fibers and can improve the mechanical properties of the fibers.

[0007] The application also provides a preparation method of the bio-based liquid crystal copolyester, which can prepare the bio-based liquid crystal copolyester with improved fiber mechanical properties.

[0008] The application also provides a bio-based liquid crystal copolyester fiber, which is prepared by drying, extruding, spinning, slow cooling, circular blowing, drawing setting, filament separation winding and heat treatment of the bio-based liquid crystal copolyester, and has good mechanical properties.

[0009] The application provides a bio-based liquid crystal copolyester in a first aspect, and the structure of the bio-based liquid crystal copolyester is shown in formula (1):

[0010]

[0011] wherein 30≤x≤60, 30≤y≤130, and 15≤z≤100.

[0012] The bio-based liquid crystal copolyester as described above is obtained by a preparation method comprising the following processes:

[0013] The acetylation product after the acetylation reaction of the raw material system comprising monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid and vanillic acid is subjected to a melt polycondensation reaction to obtain a prepolymer, and then the prepolymer after crushing and drying is subjected to a solid phase polycondensation in an inert gas atmosphere to obtain the bio-based liquid crystal copolyester;

[0014] In the raw material system, the molar percentage of 6-hydroxy-2-naphthoic acid is 20-35 mol%, the molar percentage of 4-hydroxybenzoic acid is 33-63 mol%, and the molar percentage of vanillic acid is 10-40 mol%.

[0015] The application provides a preparation method of the bio-based liquid crystal copolyester in a second aspect, comprising the following steps:

[0016] The monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid and vanillic acid are mixed with an acylating agent and a catalyst to perform an acetylation reaction to obtain an acetylation product;

[0017] The acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer;

[0018] The prepolymer is crushed and dried, and subjected to a solid phase polycondensation in an inert gas atmosphere to obtain the bio-based liquid crystal copolyester.

[0019] In the preparation method as described above, the molar percentage of 6-hydroxy-2-naphthoic acid is 20-35 mol%, the molar percentage of 4-hydroxybenzoic acid is 33-63 mol%, and the molar percentage of vanillic acid is 10-40 mol%.

[0020] The acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer according to the preparation method described above, and the specific process is as follows:

[0021] The acetylation product is first heated to 240-270℃ at a rate of 0.5-5℃ / min, and reacted for 1-5h; then heated to 270-300℃ at a rate of 0.5-3℃ / min, and reacted for 0.5-3h; finally heated to 280-350℃ at a rate of 0.3-1.5℃ / min, and subjected to a reduced pressure polycondensation by gradually vacuumizing to obtain a prepolymer;

[0022] The vacuum degree of the reduced pressure polycondensation is 0.1kPa-40kPa, and the time is 0-2h.

[0023] The acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer according to the preparation method described above, and the specific process is as follows:

[0024] The catalyst is added in an amount of 50-1000ppm of the total weight of the monomers.

[0025] The acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer according to the preparation method described above, and the specific process is as follows:

[0026] The catalyst is one of potassium acetate, magnesium acetate, zinc acetate, sodium acetate and ammonium acetate.

[0027] The acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer according to the preparation method described above, and the specific process is as follows:

[0028] The drying temperature is 120-140℃, and the time is 12-24h.

[0029] The temperature of the solid phase polycondensation is 200-320℃, and the time is 6-24h.

[0030] The present application provides a bio-based liquid crystal copolyester fiber in a third aspect, which is obtained by drying, extruding, spinning, slow cooling, circular blowing, drawing setting, filament separation winding and heat treatment of the bio-based liquid crystal copolyester.

[0031] The temperature of the extrusion is 250-320℃.

[0032] The temperature of the slow cooling is 210-280℃.

[0033] The temperature of the circular blowing is 200-270℃.

[0034] and / or, the setting rate of the drawing is 700-1200 m / min.

[0035] and / or, the temperature of the heat treatment is 200-260℃, and the time is 12-24h.

[0036] The bio-based liquid crystal copolyester is synthesized from 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid and vanillic acid, and can be used to prepare bio-based liquid crystal copolyester fibers with good mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A synthesis route map of the bio-based liquid crystal copolyester of the present application;

[0038] Figure 2 The infrared spectra of 6-hydroxy-2-naphthoic acid (HNA), 4-hydroxybenzoic acid (HBA), vanillic acid (VA) and the bio-based liquid crystal copolyester of the present application. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described below in a clear and complete manner with reference to the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0040] The raw materials used in the following examples, unless otherwise specified, can be obtained from commercial channels; the processes used, unless otherwise specified, are conventional processes in the art.

[0041] In a first aspect, the present application provides a bio-based liquid crystal copolyester, the structure of which is shown in formula (1):

[0042]

[0043] wherein 30≤x≤60, 30≤y≤130, and 15≤z≤100.

[0044] The bio-based liquid crystal copolyester provided by the present application is synthesized from monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid and vanillic acid, and can be used to prepare fibers with good mechanical properties.

[0045] The present application does not limit the polymerization order of each monomer in the bio-based liquid crystal copolyester, and each monomer can be polymerized in any order. In a specific embodiment, the bio-based liquid crystal copolyester can be formed by polymerizing monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid in order.

[0046] In a specific embodiment, the above-mentioned bio-based liquid crystal copolyester is obtained by a preparation method comprising the following processes:

[0047] The acetylation product after the acetylation reaction of the raw material system comprising monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid is subjected to a melt polycondensation reaction to obtain a prepolymer, and then the prepolymer is crushed and dried, and then subjected to solid-phase polycondensation in an inert gas atmosphere to obtain a bio-based liquid crystal copolyester.

[0048] In the raw material system, the molar percentage of 6-hydroxy-2-naphthoic acid is 20-35 mol%, the molar percentage of 4-hydroxybenzoic acid is 33-63 mol%, and the molar percentage of vanillic acid is 10-40 mol%.

[0049] The bio-based liquid crystal copolyester obtained according to the above-mentioned preparation method can be used to prepare a bio-based liquid crystal copolyester fiber, and the prepared bio-based liquid crystal copolyester fiber has good breaking strength and elastic modulus, i.e., the bio-based liquid crystal copolyester fiber has good mechanical properties.

[0050] In a second aspect, the present application provides a preparation method of the bio-based liquid crystal copolyester, comprising the following steps:

[0051] The monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid are mixed with an acylating agent and a catalyst, and then subjected to an acetylation reaction to obtain an acetylation product.

[0052] The acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer.

[0053] The prepolymer is crushed and dried, and then subjected to solid-phase polycondensation in an inert gas atmosphere to obtain a bio-based liquid crystal copolyester.

[0054] The object of preparation of the present application is a bio-based liquid crystal copolyester, specifically, the bio-based liquid crystal copolyester is formed by polymerizing monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid in the presence of an acylating agent and a catalyst, and the bio-based liquid crystal copolyester can be used to prepare a bio-based liquid crystal copolyester fiber with good mechanical properties.

[0055] The present application does not limit the specific type of inert gas, for example, the inert gas can be at least one of nitrogen and argon.

[0056] The present application is not limited to the specific operation of the acetylation reaction, as long as the above-mentioned 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, vanillic acid are mixed with the acylating agent and the catalyst to perform the acetylation reaction. In a specific embodiment, the above-mentioned acetylation reaction can be performed using a Hastelloy polymerization kettle.

[0057] In a specific embodiment, the molar percentage of 6-hydroxy-2-naphthoic acid is 20-35 mol%, the molar percentage of 4-hydroxybenzoic acid is 33-63 mol%, and the molar percentage of vanillic acid is 10-40 mol%.

[0058] When the parameters of the molar percentage of the above-mentioned 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, vanillic acid are adjusted within the above-mentioned range, a bio-based liquid crystal copolyester capable of improving the mechanical properties of fibers can be obtained.

[0059] Further, the acetylation product is subjected to a melt polycondensation reaction to obtain a prepolymer, and the specific process is as follows:

[0060] The acetylation product is first heated to 240-270°C at a rate of 0.5-5°C / min, and reacted for 1-5h; then heated to 270-300°C at a rate of 0.5-3°C / min, and reacted for 0.5-3h; finally heated to 280-350°C at a rate of 0.3-1.5°C / min, while gradually reducing the pressure to perform vacuum polycondensation, to obtain a prepolymer;

[0061] The vacuum degree of the vacuum polycondensation is 0.1 kPa-40 kPa, and the time is 0-2h.

[0062] The present application is not limited to the specific operation of the melt polycondensation reaction, as long as the parameters of the rate, temperature and time of the melt polycondensation reaction meet the limitations of the present application. When the parameters of the vacuum degree and time of the above-mentioned vacuum polycondensation are adjusted within the above-mentioned range, the viscosity of the final bio-based liquid crystal copolyester will be affected. The present inventors have found that a lower vacuum degree is not good for removing by-products, and a higher vacuum degree although better for removing by-products, but may cause significant climbing of the rod or even explosive polymerization, therefore when the parameters of the vacuum degree and time of the above-mentioned vacuum polycondensation are adjusted within the above-mentioned range, an appropriate viscosity can be obtained.

[0063] In a specific embodiment, the amount of acylating agent added is 1.0-2.0 times the total moles of hydroxyl groups in the hydroxyl-containing monomers; and / or, the amount of catalyst added is 50-1000 ppm of the total weight of the monomers.

[0064] Exemplarily, the addition amount of the acylating agent is in a range of 1.0 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times or any two of them of the total moles of hydroxyl groups in the hydroxyl-containing monomer.

[0065] The addition amount of the catalyst is in a range of 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm or any two of them of the total weight of the monomers.

[0066] When the addition amounts of the acylating agent and the catalyst are in the above ranges respectively, the phenolic hydroxyl groups in the monomers can be fully acetylated when the acetylation reaction is performed, and the obtained bio-based liquid crystal copolyester can be used to prepare fibers, and the prepared fibers have good mechanical properties. In addition, the present inventors have found that when the addition amount of acetic anhydride is insufficient, the viscosity of the formed bio-based liquid crystal polymer is low, and when spinning is performed, the fibers will break and even carbonize. When the addition amount is too high, excess acetic anhydride remains in the liquid crystal polymer, and gas is generated on the surface during processing, which causes the fibers to easily break during spinning.

[0067] In a specific embodiment, the acylating agent is one of acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, 2-ethylhexanoic anhydride, dichloroacetic anhydride and difluoroacetic anhydride; and / or the catalyst is one of potassium acetate, magnesium acetate, zinc acetate, sodium acetate and ammonium acetate.

[0068] When the acylating agent and the catalyst are selected from the above agents respectively, a bio-based liquid crystal copolyester capable of improving the mechanical properties of fibers can be obtained.

[0069] In a specific embodiment, the acetylation reaction is performed under the following conditions: a reaction temperature of 100-150°C and a reaction time of 0.5-5h.

[0070] And / or, the drying temperature is 120-140°C and the time is 12-24h.

[0071] And / or, the temperature of the solid phase polycondensation is 200-320°C and the time is 6-24h.

[0072] In detail, the reaction temperature is in a range of 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or any two of them, and the reaction time is in a range of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or any two of them.

[0073] The temperature of the drying is 120℃, 130℃, 140℃, or a range defined by any two of them, and the time is 12h, 14h, 16h, 18h, 20h, 22h, 24h, or a range defined by any two of them.

[0074] When the parameters of the temperature and time of the drying are adjusted within the above ranges, the residual acetic acid or acetic anhydride can be removed, and a relatively pure bio-based liquid crystal copolyester can be obtained.

[0075] The temperature of the solid phase polycondensation is 200℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, or a range defined by any two of them, and the time is 6h, 12h, 18h, 24h, or a range defined by any two of them.

[0076] When the parameters of the temperature and time of the solid phase polycondensation are within the above ranges, a bio-based liquid crystal copolyester with improved fiber mechanical properties can be obtained. The inventors analyzed the reason and believed that it may be due to the fact that when the parameters of the temperature and time of the solid phase polycondensation are within the above ranges, the molecular chain end groups of the prepolymer can be promoted to diffuse and move in the amorphous region, and effective collision can occur to cause polycondensation reaction, thereby obtaining a bio-based liquid crystal copolyester with improved fiber mechanical properties.

[0077] The present application does not limit the specific operation of the solid phase polycondensation, as long as the parameters of the temperature and time of the solid phase polycondensation meet the limitations of the present application. In a specific embodiment, the solid phase polycondensation can be performed using a rotary kiln.

[0078] In a third aspect, the present application provides a bio-based liquid crystal copolyester fiber, which is obtained by drying, extruding, spinning, slow cooling, circular blowing, drawing setting, splitting winding, and heat treatment of a bio-based liquid crystal copolyester. The fiber has good mechanical properties.

[0079] In a specific embodiment, the temperature of the extrusion is 250-320℃; and / or, the temperature of the slow cooling is 210-280℃; and / or, the temperature of the circular blowing is 200-270℃; and / or, the rate of the drawing setting is 700-1200m / min; and / or, the temperature of the heat treatment is 200-260℃, and the time is 12-24h.

[0080] The present application does not limit the specific operation of the drying, extrusion, spinning, slow cooling, circular blowing, drawing setting, splitting winding, and heat treatment, as long as the corresponding parameters meet the limitations of the present application. When the parameters of the temperature of the extrusion, slow cooling, and circular blowing, the rate of the drawing setting, the temperature and time of the heat treatment are adjusted within the above ranges, the bio-based liquid crystal copolyester fiber prepared has good breaking strength and elastic modulus.

[0081] Exemplarily, the temperature of the extrusion is 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, or a range consisting of any two of them.

[0082] The temperature of the slow cooling is in a range of 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, or a range consisting of any two of them.

[0083] The temperature of the ring blowing is in a range of 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, or a range consisting of any two of them.

[0084] The rate of the drawing setting is in a range of 700m / min, 750m / min, 800m / min, 850m / min, 900m / min, 950m / min, 1000m / min, 1050m / min, 1100m / min, 1150m / min, 1200m / min, or a range consisting of any two of them.

[0085] The temperature of the heat treatment is in a range of 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, or a range consisting of any two of them, and the time is in a range of 6h, 12h, 18h, 24h, or a range consisting of any two of them.

[0086] The present application is described in detail by the following examples and comparative examples. The monomer components involved in the examples and comparative examples of the present application, 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, vanillic acid, are shown in Table 1:

[0087] Table 1 monomer ratio

[0088]

[0089] Example 1

[0090] This example is prepared by the following process to obtain a bio-based liquid crystal copolyester:

[0091] Step S1: According to the formula of Example 1, the monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, vanillic acid, 1.2 times the total moles of hydroxyl groups in the hydroxyl-containing monomers of acetic anhydride, 250ppm of potassium acetate based on the total weight of the monomers are added to a Hastelloy polymerization kettle to obtain a reaction mixture.

[0092] Step S2: The reaction mixture is purged with nitrogen for 15min, and then the reaction mixture is reacted at a temperature of 140℃ for 3h to allow it to be fully acetylated to obtain an acetylated product.

[0093] Step S3: After the acetylation product was heated to 250°C at a rate of 3°C / min, it was kept for 3h; then, it was heated to 280°C at a rate of 1.5°C / min, and kept for 1.5h; finally, it was heated to 310°C at a rate of 1°C / min, and subjected to a vacuum polycondensation reaction for 1h while gradually reducing the pressure to 5kPa to obtain a prepolymer. Nitrogen was filled into the Hastelloy polymerization kettle to 0.2MPa, and the prepolymer was discharged from the bottom outlet in a molten state. After cooling, it was crushed and dried at 140°C for 24h to obtain a prepolymer powder.

[0094] Step S4: The prepolymer powder was subjected to solid-phase polycondensation in a rotary kiln under a nitrogen atmosphere at a temperature of 240°C for 12h to obtain a bio-based liquid crystalline copolyester. The synthesis route is shown in Figure 1

[0095] Example 2

[0096] In this example, a bio-based liquid crystalline copolyester was prepared by the following process:

[0097] Step S1: According to the formula of Example 2, the monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid, acetic anhydride accounting for 1.3 times the total moles of hydroxyl groups in the hydroxyl-containing monomers, and potassium acetate accounting for 300ppm of the total weight of the monomers were added to a Hastelloy polymerization kettle to obtain a reaction mixture.

[0098] Step S2: The reaction mixture was purged with nitrogen for 15min, and then the reaction mixture was acetylated at a temperature of 140°C for 3h to obtain an acetylation product.

[0099] Step S3: After the acetylation product was heated to 250°C at a rate of 3°C / min, it was kept for 3.5h; then, it was heated to 280°C at a rate of 1.5°C / min, and kept for 1.5h; finally, it was heated to 310°C at a rate of 1°C / min, and subjected to a vacuum polycondensation reaction for 1h while gradually reducing the pressure to 5kPa to obtain a prepolymer. Nitrogen was filled into the Hastelloy polymerization kettle to 0.2MPa, and the prepolymer was discharged from the bottom outlet in a molten state. After cooling, it was crushed and dried at 140°C for 24h to obtain a prepolymer powder.

[0100] Step S4: The prepolymer powder was subjected to solid-phase polycondensation in a rotary kiln under a nitrogen atmosphere at a temperature of 240°C for 12h to obtain a bio-based liquid crystalline copolyester. The synthesis route is shown in Figure 1

[0101] Example 3

[0102] In this example, a bio-based liquid crystalline copolyester was prepared by the following process:​​

[0103] Step S1: The monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, vanillic acid, acetic anhydride accounting for 1.4 times the total moles of hydroxyl groups in the hydroxyl-containing monomers, and potassium acetate accounting for 300 ppm of the total weight of the monomers were added to a Hastelloy polymerization kettle according to the formulation of Example 3 to obtain a reaction mixture.

[0104] Step S2: The reaction mixture was purged with nitrogen for 15 min, and then the reaction mixture was reacted at a temperature of 140°C for 3 h to allow sufficient acetylation, to obtain an acetylated product.

[0105] Step S3: After the acetylated product was heated at a rate of 3°C / min to 250°C, it was kept at this temperature for 3.5 h; then, it was heated at a rate of 1.5°C / min to 280°C and kept at this temperature for 2 h; finally, it was heated at a rate of 1°C / min to 300°C, and at the same time, vacuum compression polymerization was carried out at 5 kPa for 1 h to obtain a prepolymer. The Hastelloy polymerization kettle was filled with nitrogen at 0.2 MPa, and the prepolymer was discharged from the kettle bottom outlet in a molten state, and then it was cooled and crushed, and dried at 140°C for 24 h to obtain a prepolymer powder.

[0106] Step S4: The prepolymer powder was placed in a rotary kiln under a nitrogen atmosphere for solid-phase polycondensation, and the solid-phase polycondensation was carried out at a temperature of 230°C for 18 h to obtain a bio-based liquid crystal copolyester. The synthesis route is shown in Figure 1 .

[0107] Example 4

[0108] In this example, a bio-based liquid crystal copolyester was prepared by the following process:

[0109] Step S1: The monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, vanillic acid, acetic anhydride accounting for 1.4 times the total moles of hydroxyl groups in the hydroxyl-containing monomers, and potassium acetate accounting for 400 ppm of the total weight of the monomers were added to a Hastelloy polymerization kettle according to the formulation of Example 4 to obtain a reaction mixture.

[0110] Step S2: The reaction mixture was purged with nitrogen for 15 min, and then the reaction mixture was reacted at a temperature of 140°C for 3.5 h to allow sufficient acetylation, to obtain an acetylated product.

[0111] Step S3: After the acetylation product was heated to 250°C at a rate of 3°C / min, it was kept for 3.5 h; then, it was heated to 280°C at a rate of 1.5°C / min and kept for 2 h; finally, it was heated to 300°C at a rate of 1°C / min, and a vacuum was gradually applied to 5 kPa for a vacuum polycondensation reaction of 0.5 h to obtain a prepolymer. Nitrogen was filled into the Hastelloy polymerization kettle to 0.2 MPa, and the prepolymer was discharged from the bottom outlet in a molten state. After cooling, it was crushed and dried at 140°C for 24 h to obtain a prepolymer powder.

[0112] Step S4: The prepolymer powder was placed in a rotary kiln under a nitrogen atmosphere for solid-phase polycondensation at a temperature of 220°C for 24 h to obtain a bio-based liquid crystalline copolyester. The synthesis route is shown in Figure 1 .

[0113] Example 5

[0114] The bio-based liquid crystalline copolyester was prepared by the following process:

[0115] Step S1: According to the formula of Example 5, monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid, 1.5 times the total moles of hydroxyl groups in the hydroxyl-containing monomers of acetic anhydride, and 400 ppm of potassium acetate based on the total weight of the monomers were added to a Hastelloy polymerization kettle to obtain a reaction mixture.

[0116] Step S2: The reaction mixture was purged with nitrogen for 15 min, and then the reaction mixture was acetylated at a temperature of 140°C for 4 h to obtain an acetylation product.

[0117] Step S3: After the acetylation product was heated to 250°C at a rate of 3°C / min, it was kept for 3.5 h; then, it was heated to 280°C at a rate of 1.5°C / min and kept for 2.5 h; finally, it was heated to 300°C at a rate of 1°C / min, and a vacuum was gradually applied to 5 kPa for a vacuum polycondensation reaction of 0.5 h to obtain a prepolymer. Nitrogen was filled into the Hastelloy polymerization kettle to 0.2 MPa, and the prepolymer was discharged from the bottom outlet in a molten state. After cooling, it was crushed and dried at 140°C for 24 h to obtain a prepolymer powder.

[0118] Step S4: The prepolymer powder was placed in a rotary kiln under a nitrogen atmosphere for solid-phase polycondensation at a temperature of 220°C for 24 h to obtain a bio-based liquid crystalline copolyester. The synthesis route is shown in Figure 1 .

[0119] Comparative Example 1

[0120] The preparation of the bio-based liquid crystalline copolyester provided by this comparative example is consistent with that of Example 5, except that:

[0121] The monomer components are: 4-hydroxybenzoic acid 50 mol%, vanillic acid 50 mol%.

[0122] The bio-based liquid crystalline copolyester prepared in the above Examples 1-5 is used for fiber manufacturing.

[0123] Application Example 1

[0124] The bio-based liquid crystalline copolyester fiber is prepared by the following method:

[0125] After drying treatment of the bio-based liquid crystalline copolyester in Example 1, melt extrusion is carried out through an extruder with a temperature of 290°C, and fiber filaments are sprayed through a spinning assembly, slow cooling at 265°C, circular blowing at 255°C, drawing setting at 800 m / min, and separate winding, to prepare bio-based liquid crystalline copolyester primary fibers; under nitrogen protection, the bio-based liquid crystalline copolyester primary fibers are heat treated at 240°C for 12 h to obtain bio-based liquid crystalline copolyester fibers.

[0126] Application Example 2

[0127] The bio-based liquid crystalline copolyester fiber is prepared by the following method:

[0128] After drying treatment of the bio-based liquid crystalline copolyester in Example 2, melt extrusion is carried out through an extruder with a temperature of 290°C, and fiber filaments are sprayed through a spinning assembly, slow cooling at 260°C, circular blowing at 250°C, drawing setting at 800 m / min, and separate winding, to prepare bio-based liquid crystalline copolyester primary fibers; under nitrogen protection, the bio-based liquid crystalline copolyester primary fibers are heat treated at 240°C for 12 h to obtain bio-based liquid crystalline copolyester fibers.

[0129] Application Example 3

[0130] The bio-based liquid crystalline copolyester fiber is prepared by the following method:

[0131] After drying treatment of the bio-based liquid crystalline copolyester in Example 3, melt extrusion is carried out through an extruder with a temperature of 285°C, and fiber filaments are sprayed through a spinning assembly, slow cooling at 250°C, circular blowing at 240°C, drawing setting at 800 m / min, and separate winding, to prepare bio-based liquid crystalline copolyester primary fibers; under nitrogen protection, the bio-based liquid crystalline copolyester primary fibers are heat treated at 230°C for 24 h to obtain bio-based liquid crystalline copolyester fibers.

[0132] Application Example 4

[0133] The bio-based liquid crystalline copolyester fiber is prepared by the following method:

[0134] The bio-based liquid crystalline copolyester in Example 4 was dried and then melt-extruded through an extruder at a temperature of 280℃, and fiber filaments were sprayed through a spinning assembly, slow-cooled at 245℃, circularly blown at 235℃, drawn and set at 800m / min, and rewound after being separated into filaments, to prepare bio-based liquid crystalline copolyester as-spun fibers; the bio-based liquid crystalline copolyester as-spun fibers were heat-treated at 220℃ for 24h under nitrogen protection, to obtain bio-based liquid crystalline copolyester fibers.

[0135] Application Example 5

[0136] The bio-based liquid crystalline copolyester fibers in this application example were prepared by the following method:

[0137] The bio-based liquid crystalline copolyester in Example 5 was dried and then melt-extruded through an extruder at a temperature of 280℃, and fiber filaments were sprayed through a spinning assembly, slow-cooled at 235℃, circularly blown at 225℃, drawn and set at 800m / min, and rewound after being separated into filaments, to prepare bio-based liquid crystalline copolyester as-spun fibers; the bio-based liquid crystalline copolyester as-spun fibers were heat-treated at 210℃ for 24h under nitrogen protection, to obtain bio-based liquid crystalline copolyester fibers.

[0138] Comparative Application Example 1

[0139] The bio-based liquid crystalline copolyester in Comparative Example 1 was prepared into bio-based liquid crystalline copolyester fibers according to the method of Application Example 5.

[0140] Comparative Application Example 2

[0141] A conventional polylactic acid (PLA) fiber.

[0142] Comparative Application Example 3

[0143] A conventional polyamide (PA) fiber.

[0144] Comparative Application Example 4

[0145] A conventional polybutylene terephthalate (PBT) fiber.

[0146] Results and explanations

[0147] 1. Infrared spectrum:

[0148] Figure 2 The infrared spectrum of the liquid crystalline copolyester prepared in Example 1 of the present application.

[0149] As shown in the infrared spectrum of the liquid crystalline copolyester prepared in Example 1 of the present application. Figure 2 The phenolic hydroxyl groups in 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA), and vanillic acid (VA) are located at 3386cm -1 , 3374cm -1 , and 3484cm-1 After being prepared into the bio-based liquid crystal copolyester, the peak of phenolic hydroxyl group disappears. In addition, new absorption peaks appear at 1730 cm -1 and 1267 cm -1 The new absorption peaks are respectively attributed to the stretching vibration peaks of ester carbonyl (-C=O) and C—O—C. These evidences show that the desired bio-based liquid crystal copolyester has been successfully prepared.

[0150] 2. Performance test:

[0151] The fibers in application examples 1-5 and comparative application example 1-4 were tested for mechanical properties (including spinnability, breaking strength and elastic modulus) according to the following test methods, and the test results are shown in Table 2.

[0152] (1) Mechanical properties: the test method refers to GB / 19975-2005.

[0153] Table 2 Test results

[0154]

[0155] As can be seen from the test results in Table 2, compared with conventional bio-based fibers (polylactic acid fiber, polyamide fiber and polybutylene terephthalate fiber), the breaking strength and elastic modulus of the bio-based liquid crystal copolyester fiber prepared by using the bio-based liquid crystal copolyester of the present application are improved, which shows that the bio-based liquid crystal copolyester fiber prepared by the bio-based liquid crystal copolyester provided by the present application has good mechanical properties. In addition, the results in Table 2 show that the liquid crystal copolyester fiber prepared by using 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid and vanillic acid as structural units has good mechanical properties, and with the addition of vanillic acid, the breaking strength and elastic modulus of the bio-based liquid crystal copolyester fiber decrease, but are still much higher than those of conventional bio-based fibers (higher than those of conventional polylactic acid fiber, polyamide fiber and polybutylene terephthalate fiber). As can be seen from comparative application example 1, the 6-hydroxy-2-naphthoic acid structural unit makes outstanding contribution to the spinnability of the polymer, and when the bio-based liquid crystal copolyester does not contain 6-hydroxy-2-naphthoic acid, the bio-based liquid crystal copolyester does not have spinnability.

[0156] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A bio-based liquid crystal copolyester, characterized in that, The structure of the bio-based liquid crystal copolyester is shown in formula (1): Wherein, 30≤x≤60, 30≤y≤130, 15≤z≤100.

2. The bio-based liquid crystal copolyester according to claim 1, characterized in that, It is obtained through a preparation method including the following process: The acetylation product of a raw material system including monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid and vanillic acid is subjected to melt polycondensation to obtain a prepolymer. The prepolymer is then pulverized, dried and subjected to solid-phase polycondensation in an inert gas atmosphere to obtain the bio-based liquid crystal copolyester. In the raw material system, the molar percentage of 6-hydroxy-2-naphthoic acid is 20-35 mol%, the molar percentage of 4-hydroxybenzoic acid is 33-63 mol%, and the molar percentage of vanillic acid is 10-40 mol%.

3. A method for preparing the bio-based liquid crystal copolyester according to any one of claims 1-2, characterized in that, Includes the following steps: The monomers 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and vanillic acid were mixed with an acylation reagent and a catalyst and then subjected to an acetylation reaction to obtain the acetylated product. The acetylated product was subjected to melt polycondensation to obtain a prepolymer; The prepolymer was pulverized, dried, and then subjected to solid-phase polycondensation in an inert gas atmosphere to obtain the bio-based liquid crystal copolyester.

4. The method for preparing the bio-based liquid crystal copolyester according to claim 3, characterized in that, The molar percentage of 6-hydroxy-2-naphthoic acid is 20-35 mol, the molar percentage of 4-hydroxybenzoic acid is 33-63 mol, and the molar percentage of vanillic acid is 10-40 mol.

5. The method for preparing the bio-based liquid crystal copolyester according to claim 3, characterized in that, The specific process of subjecting the acetylated product to melt polycondensation to obtain the prepolymer is as follows: The acetylated product was first heated to 240-270°C at a rate of 0.5-5°C / min and reacted for 1-5 h; then, the temperature was increased to 270-300°C at a rate of 0.5-3°C / min and reacted for 0.5-3 h; finally, the temperature was increased to 280-350°C at a rate of 0.3-1.5°C / min while gradually decompression polymerization was carried out under vacuum to obtain the prepolymer. The vacuum degree of the compression polymerization is 0.1 kPa-40 kPa, and the time is 0-2 h.

6. The method for preparing the bio-based liquid crystal copolyester according to claim 3, characterized in that, The amount of the acylation reagent added is 1.0-2.0 times the total molar number of hydroxyl groups in the hydroxyl-containing monomer; And / or, the amount of catalyst added is 50-1000 ppm of the total weight of the monomers.

7. The method for preparing the bio-based liquid crystal copolyester according to claim 3 or 6, characterized in that, The acylation reagent is one of acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, 2-ethylhexanoic anhydride, dichloroacetic anhydride, and difluoroacetic anhydride; And / or, the catalyst is one of potassium acetate, magnesium acetate, zinc acetate, sodium acetate, and ammonium acetate.

8. The method for preparing the bio-based liquid crystal copolyester according to claim 3, characterized in that, The conditions for the acetylation reaction are: reaction temperature 100-150℃, reaction time 0.5-5h; And / or, the drying temperature is 120-140°C and the time is 12-24 hours; And / or, the solid-phase polycondensation is carried out at a temperature of 200-320°C for a time of 6-24 hours.

9. A bio-based liquid crystal copolyester fiber, characterized in that, The bio-based liquid crystal copolyester described in any one of claims 1-2 is obtained by drying, extrusion, spinning, slow cooling, ring blowing, stretching and setting, splitting and winding, and heat treatment.

10. The bio-based liquid crystal copolyester fiber according to claim 9, characterized in that, The extrusion temperature is 250-320℃; And / or, the slow cooling temperature is 210-280°C; And / or, the temperature of the annular blowing is 200-270°C; And / or, the stretching and shaping rate is 700-1200 m / min; And / or, the heat treatment is performed at a temperature of 200-260°C for a time of 12-24 hours.

Images