Preparation method of copolymer polyamide material with light energy conversion function and copolymer polyamide fiber

Abstract

This invention provides a method for preparing a copolyamide material with light energy conversion function and copolyamide fibers. The preparation method includes forming a copolyamide material by reacting a C6-C12 aliphatic diamine, a C6-C12 aliphatic dicarboxylic acid, and 2-methyl terephthalic acid or dimethyl 2-methyl terephthalate through a salt polycondensation reaction or an ester exchange and amidation polycondensation reaction. The aromatic dicarboxylic acid structural units formed by the 2-methyl terephthalic acid or dimethyl 2-methyl terephthalate account for 10-30 mol% of all dicarboxylic acid structural units, and the intrinsic viscosity of the resulting copolyamide material is controlled to be not less than 0.90 dL / g. The obtained material is then melt-spun, drawn, and heat-set to form copolyamide fibers. This method is beneficial for providing a light energy conversion basis at the main chain level while taking into account melt spinning processability and fiber mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of functional polyamide materials and fiber preparation technology, specifically to a method for preparing a copolyamide material with light energy conversion function and a copolyamide fiber. Background Technology

[0002] Polyamide fibers possess good mechanical and abrasion resistance properties, as well as good processing adaptability, and are widely used in clothing fabrics and footwear uppers. They can also be used in socks, webbing, and other textiles. With the development of outdoor sports and functional textiles, polyamide fibers not only need to meet weaving and wearing requirements, but also need to have UV protection capabilities, while also ensuring durability, stability, and optical functionality.

[0003] Existing UV-protective fibers typically reduce UV transmittance by reflecting, shielding, or absorbing ultraviolet light. Common approaches involve adding inorganic fillers or external optical materials to the polymer, such as titanium dioxide and graphene, or phosphors; other approaches use rare-earth complexes or fluorescent whitening agents. While these external optical materials can improve certain optical properties, they are easily affected by dispersion state, thermal history, and interfacial compatibility during polyamide melt processing and spinning.

[0004] For functional fibers, excessively high levels of added optical components may decrease melt flow and spinning stability. Uneven distribution of added components within the fiber can also affect the uniformity of optical performance. After heat setting, washing, or prolonged light exposure, some added components may migrate or experience performance degradation.

[0005] Semi-aromatic polyamides can have their thermal and processing properties altered by introducing aromatic dicarboxylic acid structures. Routes involving methyl-substituted aromatic diacids in polyamide polymerization have also been disclosed in existing technologies. However, these technologies typically focus on the melt polymerization, heat resistance, and crystallization behavior of the resin, and sometimes also involve conventional fiber processing. They do not establish a unified structural design for maintaining the UV absorption and visible light conversion of polyamide fibers, as well as their optical properties after use.

[0006] Therefore, there is still a need for a polyamide material and fiber solution suitable for melt spinning, which can enable the fiber to absorb and convert ultraviolet light while maintaining the mechanical properties required for weaving, and maintain relatively stable optical properties after aging or washing. Summary of the Invention

[0007] The purpose of this application is to provide a method for preparing a copolyamide material with light energy conversion function, and further to provide a copolyamide fiber made from the copolyamide material, so as to improve the problems of uneven dispersion, migration attenuation and decreased melt spinning stability that easily occur when existing polyamide optical functional fibers rely too much on external light-emitting components.

[0008] In existing technologies, methyl-substituted aromatic diacids can already be used as polyamide monomers, and semi-aromatic polyamides can also be used to improve certain thermal or processing properties. Other technologies impart optical functions to polyamide fibers through rare earth complexes, phosphors, or optical brighteners. However, the former type of technology typically focuses on the melt polymerization and heat-resistant modification of the resin, without establishing a main chain structure design around the light-converting fiber. The latter type of technology mainly relies on added optical components. These added components undergo spinning, stretching, and heat setting after melt blending, making them susceptible to the effects of dispersion state and thermal history. Subsequent washing or long-term light exposure may also lead to migration or performance degradation.

[0009] The applicant discovered that for polyamide fibers, the photoconversion function and melt spinning processability are not naturally aligned, and both are constrained by usage stability. Simply increasing the proportion of aromatic structural units may enhance the polymer's UV absorption and spectral response, but the main chain rigidity and crystallization behavior will also change, potentially affecting melt flowability and stretching stability. Increasing the amount of added luminescent material can enhance light output, but dispersion uniformity, interfacial compatibility, and washability will be compromised. Pursuing only higher molecular weight to improve fiber strength may increase melt viscosity, further complicating spinning. Therefore, this application does not aim to enhance any single function, but rather achieves a relatively balanced state of photoresponse fundamentals, processability, and subsequent fiber formation capability through main chain structure design, structural unit ratio control, and limiting the polycondensation endpoint.

[0010] To achieve the above objectives, the following technical solution is adopted: In at least one embodiment, a method for preparing a copolyamide material with light energy conversion function is disclosed. The preparation method includes: forming a copolyamide material by a salt polycondensation reaction of C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid, and 2-methyl terephthalic acid; or forming a copolyamide material by a transesterification and amidation polycondensation reaction of C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid, and dimethyl 2-methyl terephthalate; wherein the aromatic dicarboxylic acid structural unit formed by the 2-methyl terephthalic acid or dimethyl 2-methyl terephthalate accounts for 10-30 mol% of all dicarboxylic acid structural units in the copolyamide material; and the intrinsic viscosity of the obtained copolyamide material is controlled to be not less than 0.90 dL / g.

[0011] In the above design, aliphatic diamines and aliphatic dicarboxylic acids together form aliphatic polyamide segments. These segments retain the chain flexibility and crystallinity required for melt processing and fiber formation. The 2-alkyl-substituted terephthalic acid monomers enter the main chain as copolymer units, ensuring that the photoresponsive structure no longer primarily depends on added particles or easily migrating additives, but rather exists stably within the polyamide molecular chain. Because the photoresponsive structure is located within the main chain, the material does not require a high concentration of added luminescent components to establish a basic light energy conversion basis during melt blending, spinning, and drawing processes. This helps reduce the impact of uneven dispersion and migration attenuation.

[0012] The 10-30 mol% range of the aforementioned aromatic dicarboxylic acid structural units is used to address the contradiction between enhanced photoresponse and weakened melt spinnability. This proportion is lower than that of highly aromatic directions, which may make the semi-aromatic polyamide too rigid, and higher than that, where only trace amounts of modification are insufficient to form an effective main-chain photoresponse. In other words, the aliphatic segments provide the spinnability base for the material, the 2-alkyl-substituted aromatic structure provides the molecular basis for UV absorption and visible light conversion, and the 10-30 mol% proportion ensures that these two effects do not overwhelm each other. Further controlling the intrinsic viscosity to no less than 0.90 dL / g allows the copolyamide to reach the lower molecular weight limit required for subsequent melt spinning, avoiding insufficient melt strength and decreased fiber mechanical properties due to excessively short molecular chains. The combination of these methods achieves a better balance between the material's photoenergy conversion basis, melt flow state, and fiber strength.

[0013] Compared to existing methyl-substituted aromatic diacid polyamides, the above preparation method does not simply select 2-methylterephthalic acid or similar monomers. Instead, it limits the 2-alkyl-substituted aromatic diacid unit to a low proportion of functional structural units, and combines this with aliphatic diamines, aliphatic dicarboxylic acids, and fiber-grade intrinsic viscosity control. Existing resin-type semi-aromatic polyamides are generally not aimed at light-converting fibers, nor do they provide a technical path that balances photoresponse and melt spinning properties through a low proportion of 2-substituted aromatic diacid units. Compared to the route of adding luminescent materials, the above preparation method places the functional basis in the main chain structure, thus reducing the necessary dependence on luminescent additives and providing a more stable structural source for maintaining performance during subsequent washing and light exposure.

[0014] In the preparation method disclosed in at least one embodiment, preferably, the C6-C12 aliphatic diamine is hexamethylenediamine, decanediamine, or a combination thereof; the C6-C12 aliphatic dicarboxylic acid is adipic acid, sebacic acid, or a combination thereof; and the molar ratio of the amino group provided by the C6-C12 aliphatic diamine to the carboxyl or ester group provided by all the dicarboxylic acid components is from 0.98:1 to 1.02:1.

[0015] In the above design, hexamethylenediamine, decanediamine, adipic acid, and sebacic acid can form relatively regular aliphatic polyamide segments. These segments provide a stable intercalation environment for the 2-alkyl-substituted aromatic dicarboxylic acid structural units, while retaining the basic suitability of aliphatic polyamides for melt processing. Controlling the molar ratio of amino to carboxyl or ester groups between 0.98:1 and 1.02:1 reduces end-group imbalance and the formation of low-molecular-weight components caused by an excess of a single functional group, making it easier for the polycondensation reaction to achieve the target intrinsic viscosity. This equivalent control, combined with the intrinsic viscosity control in claim 1, is beneficial for forming copolyamide materials with higher molecular weight and more stable main chain composition.

[0016] In the preparation method disclosed in at least one embodiment, preferably, the aromatic dicarboxylic acid structural unit accounts for 20-25 mol% of all dicarboxylic acid structural units in the copolyamide material; the intrinsic viscosity of the resulting copolyamide material is 1.00-1.10 dL / g, the content of carboxyl end groups is not higher than 40 mmol / kg, and the melting point is 245-260 degrees Celsius.

[0017] In the above design, the 20-25 mol% proportion of aromatic dicarboxylic acid structural units represents a further convergence to the 10-30 mol% range. This proportion increases the effective content of alkyl-substituted aromatic structural units at the 2-position in the main chain, while still retaining the supporting role of aliphatic segments for melt flow and stretching. An intrinsic viscosity of 1.00-1.10 dL / g provides the material with melt strength and chain entanglement more suitable for spinning; a carboxyl end-group content not exceeding 40 mmol / kg helps reduce hydrolysis and end-group side reactions during high-temperature processing and subsequent use; and a melting point of 245-260 degrees Celsius facilitates obtaining a stable melt near the conventional polyamide melt spinning temperature. These parameters are not isolated preferred conditions, but rather collectively define the polymer state suitable for the preparation of photoelectric conversion fibers.

[0018] In the preparation method disclosed in at least one embodiment, preferably, the salt polycondensation reaction comprises: preparing the C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid and 2-methylterephthalic acid into an equivalent salt or reaction mixture in a target molar ratio; performing pre-polycondensation at 220-240 degrees Celsius under an inert atmosphere; and then polycondensing for 2-4 hours at 240-265 degrees Celsius and a vacuum of 0.07-0.09 MPa.

[0019] In the above design, preparing an equivalent salt or reaction mixture beforehand improves the contact uniformity of the diamine, C6-C12 aliphatic dicarboxylic acid, and 2-methylterephthalic acid before the reaction, allowing the low proportion of aromatic structural units to enter the main chain more stably. An inert atmosphere and pre-polymerization at 220-240°C facilitate the formation of initial chain segments under milder conditions, reducing the risk of oxidation and localized side reactions in the early stages of heating. Subsequent polycondensation at 240-265°C under vacuum promotes the removal of small molecule byproducts such as moisture and drives molecular weight growth. This route is suitable for acid monomer systems and can facilitate the uniform introduction of low-proportion 2-methyl substituted aromatic units and the formation of fibrous-grade viscosity.

[0020] In the preparation method disclosed in at least one embodiment, preferably, the transesterification and amidation polycondensation reaction includes: using dimethyl 2-methyl terephthalate as the reactant monomer, carrying out a transesterification reaction at 180-220 degrees Celsius; and carrying out an amidation polycondensation reaction at 220-260 degrees Celsius and a vacuum degree of 0.07-0.09 MPa; wherein the transesterification catalyst is zinc acetate, and the amount of zinc acetate used is 0.01-0.03 wt% of the mass of the obtained copolyamide material.

[0021] In the above design, when using dimethyl ester form of 2-alkyl-substituted terephthalic acid monomers, a pre-transesterification reaction allows these monomers to enter a reaction state suitable for further amidation polycondensation under milder conditions. The amount of zinc acetate is controlled at 0.01-0.03 wt%, which promotes the transesterification process while avoiding the adverse effects of excessive catalyst on color, thermal stability, or subsequent spinning. Subsequent amidation polycondensation under vacuum conditions removes small molecule byproducts and increases the polymer molecular weight. Therefore, the dimethyl ester route provides another controllable preparation path for the introduction of 2-alkyl-substituted aromatic structural units.

[0022] In the preparation method disclosed in at least one embodiment, preferably, a polycondensation stabilizer is added during the salt polycondensation reaction or the transesterification and amidation polycondensation reaction. The polycondensation stabilizer is a phosphite or hypophosphite, and its amount is 0.1-0.5 wt% of the mass of the obtained copolyamide material. The obtained copolyamide material is then melt-blended with an antioxidant and a light stabilizer. The antioxidant includes antioxidant 1076, and the light stabilizer is a benzotriazole compound.

[0023] In the above design, the polycondensation stabilizer acts during the polymerization stage, reducing the risks of oxidative yellowing, end-group oxidation, and localized side reactions during high-temperature polycondensation, thus enabling the more stable formation of copolyamides containing 2-alkyl-substituted aromatic structural units. Antioxidant 1076 primarily functions in melt blending and spinning thermal history, while benzotriazole light stabilizers improve weather resistance under UV irradiation. This stabilizing system is not simply the addition of conventional auxiliaries, but rather works in conjunction with the main chain's photoresponsive structure to control performance degradation during polymerization, melt spinning, and subsequent use.

[0024] In the preparation method disclosed in at least one embodiment, preferably, the light stabilizer is UV-327 or UV-328, and the amount of the light stabilizer is 0.2-0.5 wt% of the mass of the obtained copolyamide material; the preparation method further includes melt blending the obtained copolyamide material with 0.01-0.20 wt% of a luminescent aid, wherein the luminescent aid is a rhodamine B derivative, a coumarin 6 derivative, or an Eu(β-diketone)3 complex.

[0025] In the above design, UV-327 and UV-328 provide UV stabilization at low dosages, which helps reduce the impact of excessive light stabilizer on melt rheology and material color. The luminescent additive is set as an optional reinforcing component, and its dosage is controlled at 0.01-0.20 wt%. This dosage makes the luminescent additive more suitable as a spectral enhancement method, rather than replacing the copolyamide backbone as the main functional source. Therefore, this application can provide enhancement space for products requiring stronger visible light output while maintaining the backbone-type light energy conversion route.

[0026] In at least one embodiment, a copolyamide fiber with light energy conversion function is also disclosed, wherein the copolyamide fiber is obtained by melt spinning, stretching and heat setting of the copolyamide material with light energy conversion function prepared by the preparation method of the copolyamide material with light energy conversion function as described in any of the above embodiments.

[0027] In the above design, melt spinning enables the copolyamide to form continuous nascent filaments, the drawing process improves molecular chain orientation, and the heat setting process stabilizes fiber size and crystallinity. Because the 2-alkyl-substituted aromatic dicarboxylic acid structural unit is located in the polyamide backbone, this photoresponsive structure can enter the fiber bulk along with the polymer chain, rather than relying primarily on a dispersed state as with added particles. Therefore, the fiber is more conducive to maintaining light energy conversion-related properties during forming and subsequent use, and can meet the basic requirements of textile materials for continuity and mechanical properties.

[0028] In the fiber samples given in the embodiments of this application, when the average ultraviolet absorbance in the 320-400 nm wavelength band was tested using an integrating sphere UV-Vis diffuse reflectance or transmission method, the sample yielded 87%-90%. When tested using an integrating sphere-fluorescence spectrophotometer with an excitation wavelength of 365 nm and an emission integration range of 600-800 nm, the relative integrated emission intensity of the sample was 0.69-0.76; in embodiments with added luminescent additives, this relative integrated emission intensity reached 0.76; in embodiments without added luminescent additives, this relative integrated emission intensity was not less than 0.68. When comparing the transmission spectrum changes of the same sample under conditions of no direct ultraviolet radiation and direct ultraviolet radiation of 200-400 nm using the integrating sphere method, the conversion ratio in the 380-420 nm violet output band was not less than 30%, and the conversion ratios in the 420-450 nm blue output band and the 620-780 nm red output band showed positive changes. The above data are used to illustrate that, under the specific embodiment conditions, the fiber samples formed by melt spinning, stretching and heat setting can demonstrate the corresponding light energy conversion effect, but it does not mean that all samples not prepared according to the embodiment conditions will reach the same value.

[0029] In the copolyamide fiber disclosed in at least one embodiment, preferably, the C6-C12 aliphatic diamine is hexamethylenediamine, decanediamine, or a combination thereof; the C6-C12 aliphatic dicarboxylic acid is adipic acid, sebacic acid, or a combination thereof; the aromatic dicarboxylic acid structural unit accounts for 20-25 mol% of all dicarboxylic acid structural units in the copolyamide; the carboxyl end group content of the copolyamide is not higher than 40 mmol / kg, and the melting point is 245-260 degrees Celsius.

[0030] In the above design, the linear aliphatic monomer source helps maintain good chain segment regularity and melt spinning adaptability of the fiber matrix. 20-25 mol% of aromatic dicarboxylic acid structural units provides a more suitable content of photoresponsive structures for the fiber backbone. The content of carboxyl end groups and the melting point range further define the thermal stability and processing boundaries of the fiber material, enabling the copolyamide fiber to form a more stable balance between its photoelectric conversion function and fiber formation stability.

[0031] In the copolyamide fiber disclosed in at least one embodiment, preferably, the copolyamide fiber comprises a polycondensation stabilizer, an antioxidant, and a light stabilizer; the polycondensation stabilizer is a phosphite or phosphonic acid, the content of which is 0.1-0.5 wt% of the mass of the copolyamide; the antioxidant includes antioxidant 1076; the light stabilizer is UV-327 or UV-328; the monofilament linear density of the copolyamide fiber is 2-15 dtex, the equivalent monofilament diameter is 40-200 μm, and the breaking strength is not less than 3.5 cN / dtex.

[0032] In the above design, condensation stabilizers, antioxidants, and light stabilizers work together to reduce the risk of performance degradation of the fiber under conditions of polymerization residue, melt processing, and UV exposure. The monofilament linear density and equivalent monofilament diameter are used to adapt the fiber dimensions to weaving and wear applications, while a breaking strength of not less than 3.5 cN / dtex provides mechanical protection for the fiber's practical use. Therefore, the copolyamide fiber not only possesses a main-chain light-responsive structure but also balances textile processing and durability.

[0033] In summary, this application achieves a balance between the photoresponsiveness of the main chain and melt spinning processability in the copolymer polyamide material by combining a low proportion of 2-alkyl-substituted aromatic dicarboxylic acid structural units with aliphatic polyamide segments and controlling the fiber-grade intrinsic viscosity. Furthermore, through near-equivalent feeding and control of end groups and melting points, along with a stable system and fiber forming conditions, the resulting copolymer polyamide fiber can simultaneously achieve photoelectric conversion functionality, the mechanical properties required for weaving, and stability in use. This technology differs from the resin route that simply prepares methyl-substituted aromatic dicarboxylic acid polyamides, and also from the composite route that relies on external luminescent materials to impart optical functions to polyamide fibers. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments. The described embodiments are used to explain the technical solutions of the present invention and should not be construed as limiting the scope of protection. Unless otherwise specified, the implementation methods, examples, and technical features in this specification can be combined with each other.

[0035] This invention provides a method for preparing a copolyamide material with light energy conversion function, comprising the following steps: S1, subjecting C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid, and 2-methyl terephthalic acid to a salt polycondensation reaction, or subjecting C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid, and dimethyl 2-methyl terephthalate to an ester exchange and amidation polycondensation reaction to form a copolyamide material; S2, melt-blending the obtained copolyamide material with a stabilizer system to obtain a spinning melt; S3, extruding the spinning melt through a spinneret to form nascent filaments; S4, stretching and heat-setting the nascent filaments to obtain copolyamide fibers with light energy conversion function. The aromatic dicarboxylic acid structural unit formed by 2-methyl terephthalic acid or dimethyl 2-methyl terephthalate accounts for 10-30 mol% of all dicarboxylic acid structural units in the copolyamide material, and the intrinsic viscosity of the resulting copolyamide material is not less than 0.90 dL / g.

[0036] In S1, the C6-C12 aliphatic diamine can be hexamethylenediamine, decanediamine, or a combination thereof. The C6-C12 aliphatic dicarboxylic acid can be adipic acid, sebacic acid, or a combination thereof. The 2-alkyl-substituted terephthalic acid monomer is preferably 2-methyl terephthalic acid or dimethyl 2-methyl terephthalate; in optional embodiments, 2-ethyl terephthalic acid or dimethyl 2-ethyl terephthalate may also be used as a similar monomer. The molar ratio of the amino group provided by the aliphatic diamine to the carboxyl or ester group provided by all the dicarboxylic acid forming components is preferably 0.98:1 to 1.02:1. This molar ratio is used to ensure that the diamine component and the dicarboxylic acid forming component are in a near-equivalent state, thereby reducing the risk of end-group imbalance and insufficient polycondensation.

[0037] The aliphatic diamine and C6-C12 aliphatic dicarboxylic acid together form an aliphatic polyamide segment. This segment provides the material with the chain flexibility required for melt processing and fiber formation. After the 2-alkyl-substituted terephthalic acid monomer enters the main chain as a copolymer unit, it can form a photoresponsive structure within the polyamide molecular chain. Because this photoresponsive structure is located within the main chain, the material does not need to rely on a high content of added luminescent components to establish basic light energy conversion capabilities, which helps to reduce the impact of uneven dispersion and migration attenuation of added particles.

[0038] When aromatic dicarboxylic acid structural units account for 10-30 mol% of all dicarboxylic acid structural units, a balance can be achieved between enhanced photoresponsiveness and melt spinning properties. If the proportion is too low, there will be insufficient photoresponsive structural units in the main chain, resulting in weaker contributions to UV absorption and visible light conversion. If the proportion is too high, the rigidity and crystallization behavior of the main chain will change significantly, and the melt flow state and draw stability will be easily affected. Further, the aromatic dicarboxylic acid structural units preferably account for 20-25 mol% of all dicarboxylic acid structural units. Within this preferred range, the content of photoresponsive structural units in the main chain is relatively high, while the supporting role of aliphatic polyamide segments for melt spinning can still be maintained.

[0039] The intrinsic viscosity of the resulting copolyamide material is preferably 1.00-1.10 dL / g, the carboxyl end-group content is preferably not higher than 40 mmol / kg, and the melting point is preferably 245-260 degrees Celsius. Intrinsic viscosity reflects molecular weight; controlling it within the above range is beneficial for forming melt strength suitable for melt spinning. A lower carboxyl end-group content reduces the risk of end-group side reactions during high-temperature processing and in humid environments. When the melting point is in the range of 245-260 degrees Celsius, the material can form a stable melt near the conventional polyamide melt spinning temperature, avoiding increased thermal degradation pressure due to excessively high melting points.

[0040] When using the salt polycondensation route, aliphatic diamines, C6-C12 aliphatic dicarboxylic acids, and 2-methylterephthalic acid can be formulated into a polyamide salt according to the target molar ratio, or a reaction mixture can be prepared. Pre-polymerization is then carried out at 220-240°C under an inert atmosphere. After pre-polymerization, the system is heated to 240-265°C and polycondensed under a vacuum of 0.07-0.09 MPa for 2-4 hours. This route is suitable for acid monomer systems. By first forming an equivalent salt or a homogeneous reaction mixture, the uniformity of the distribution of 2-methyl aromatic diacid in the reaction system can be improved. The combination of pre-polymerization and vacuum polycondensation can remove small molecule byproducts such as water and promote molecular weight growth to the fiber-grade range.

[0041] When using the transesterification and amidation polycondensation route, dimethyl 2-methyl terephthalate can be used as the reactant monomer. In this route, a transesterification reaction is first carried out at 180-220 degrees Celsius, with zinc acetate as the catalyst. The amount of zinc acetate used is 0.01-0.03 wt% of the mass of the resulting copolyamide material. Subsequently, an amidation polycondensation reaction is carried out at 220-260 degrees Celsius and a vacuum of 0.07-0.09 MPa to continuously remove small molecule byproducts and increase the polymer molecular weight to the target range. If the amount of zinc acetate is too low, the transesterification process may be too slow; if the amount is too high, residual metal ions may affect the color and subsequent spinning stability.

[0042] In salt-based polycondensation reactions or transesterification and amidation polycondensation reactions, polycondensation stabilizers can be added. The polycondensation stabilizer can be a phosphite or hypophosphite, and its dosage is 0.1-0.5 wt% of the mass of the resulting copolyamide material. The polycondensation stabilizer acts during the high-temperature polymerization stage, reducing the risk of oxidative yellowing, localized gelation, and end-group side reactions. After the copolyamide material is formed, it can be melt-blended with antioxidants and light stabilizers. The antioxidant can include antioxidant 1076, and the light stabilizer can be a benzotriazole compound. Preferably, the light stabilizer is UV-327 or UV-328, and its dosage is 0.2-0.5 wt% of the mass of the resulting copolyamide material.

[0043] When further enhancement of visible light output is required, the obtained copolyamide material can be melt-blended with 0.01-0.20 wt% of a luminescent additive. The luminescent additive can be a rhodamine B derivative, a coumarin 6 derivative, or an Eu(β-diketone)3 complex. This luminescent additive is an optional enhancing component and is not a necessary condition for the formation of light energy conversion function. At lower addition levels, it can enhance emission performance to a certain extent while reducing adverse effects on melt rheology, tensile stability, and washability.

[0044] Melt blending of S2 can be carried out in a twin-screw extruder. The copolyamide material is preferably fed after vacuum drying, with drying conditions of 90-110 degrees Celsius for 6-12 hours, resulting in a moisture content not exceeding 0.05 wt%. The melt blending temperature can be 270-290 degrees Celsius, and the screw speed can be 80-180 rpm. After melt blending, it can be directly fed into the spinning assembly, or it can be granulated and dried again before spinning.

[0045] In step S3, the spinning melt can be extruded through a spinneret at 275-290 degrees Celsius to form nascent filaments. The aspect ratio of the spinneret orifice can be 2:1 to 4:1, and the side-blowing velocity can be 0.3-0.6 m / s. In step S4, the nascent filaments can be drawn in two or three stages, with a total draw ratio of 2.8-4.0 times. After drawing, they can be heat-set at 160-185 degrees Celsius for 30-90 seconds. Drawing improves molecular chain orientation, and heat setting stabilizes fiber size and crystallinity. The resulting copolyamide fiber has a monofilament linear density of 2-15 dtex, an equivalent monofilament diameter of 40-200 μm, and a breaking strength preferably not less than 3.5 cN / dtex.

[0046] The raw materials used in the following examples and comparative examples are all commercially available products that can be publicly verified. Hexamethylenediamine and adipic acid were commercially available in analytical grade or industrial grade, with hexamethylenediamine having a purity of not less than 98% and adipic acid a purity of not less than 99%. 2-Methylterephthalic acid and 5-methylisophthalic acid were commercially available in analytical grade, with a purity of not less than 97%. Dimethyl 2-methylterephthalate was commercially available in analytical grade, and the main peak area was confirmed to be not less than 98% by 1H NMR and GC before feeding. Triphenyl phosphite and zinc acetate dihydrate were commercially available in analytical grade or industrial grade, with triphenyl phosphite a purity of not less than 97% and zinc acetate dihydrate a content of not less than 98%. Antioxidant 1076 was NURCHEM AO-1076 supplied by Nanjing Yourui Chemical Industry Co., Ltd., and UV-328 was RIASORB UV-328 supplied by Tianjin Lianlong New Materials Co., Ltd. Rhodamine B isothiocyanate, used as an optional luminescent additive, is a commercially available analytical grade product. The standard PA66 reference material is EPR27 from Pingdingshan Shenma Engineering Plastics Co., Ltd., whose publicly available information indicates this grade is PA66 and it can be used to spin palm fiber and staple fiber. The above grade, purity, and designation information are subject to the corresponding supplier's publicly available product information or purchase batch COA.

[0047] Example 1 This embodiment uses the 2-methyl terephthalate polycondensation route to prepare copolyamide materials, and further prepares copolyamide fibers. No external luminescent additives are added in this embodiment; this is to illustrate the contribution of the 2-alkyl-substituted aromatic dicarboxylic acid structural unit in the main chain itself to the light energy conversion function.

[0048] Based on a total dicarboxylic acid forming component of 100 mol, 80 mol of adipic acid and 20 mol of 2-methylterephthalic acid were added. Hexamethylenediamine was added at a molar ratio of amino to carboxyl groups of 1.00:1. Triphenyl phosphite was added at 0.30 wt% of the target copolyamide material. The above monomers and stabilizers were added to a stirred polycondensation reactor, purged with nitrogen, and heated to 230°C for pre-polymerization for 1.5 hours. Subsequently, the temperature was raised to 255°C, and polycondensation was carried out under a vacuum of 0.08 MPa for 3 hours to obtain the copolyamide material.

[0049] The resulting copolyamide material had an intrinsic viscosity of 1.05 dL / g, a carboxyl end-group content of 32 mmol / kg, and a melting point of 252°C. After vacuum drying at 100°C for 8 hours, the copolyamide material was melt-blended with 0.20 wt% antioxidant 1076 and 0.30 wt% UV-328 in a twin-screw extruder. The blending temperature was 280°C, and the screw speed was 120 rpm.

[0050] The melt-blended spinning melt was extruded through a spinneret at 282°C. The spinneret orifice aspect ratio was 3:1, and the side-blowing velocity was 0.4 m / s. The nascent filament underwent two stages of drafting, with a total draft ratio of 3.5, followed by heat setting at 175°C for 60 seconds to obtain copolyamide fibers. The resulting fibers had a monofilament linear density of 3.4 dtex, an equivalent monofilament diameter of approximately 64 μm, and a breaking strength of 5.6 cN / dtex.

[0051] Example 2 This embodiment is basically the same as Example 1, except that 0.05 wt% of Rhodamine B isothiocyanate is added as a Rhodamine B derivative during the melt blending stage. This component is an optional reinforcing component, and the amount added is based on the mass of the copolyamide material.

[0052] In this embodiment, the intrinsic viscosity of the copolyamide material was 1.04 dL / g, the carboxyl end group content was 34 mmol / kg, and the melting point was 251 degrees Celsius. The spinning temperature, draw ratio, and heat setting conditions were the same as in Example 1. The resulting fiber had a monofilament linear density of 3.5 dtex, an equivalent monofilament diameter of approximately 65 μm, and a breaking strength of 5.5 cN / dtex.

[0053] Example 3 In this embodiment, a copolyamide material was prepared by transesterification and amidation polycondensation of dimethyl terephthalate, and then copolyamide fibers were further prepared.

[0054] Based on a total dicarboxylic acid forming component of 100 mol, 75 mol of adipic acid and 25 mol of dimethyl terephthalate were added. Hexamethylenediamine was added at a molar ratio of amino to carboxyl or ester groups of 1.00:1. Zinc acetate dihydrate was added at 0.02 wt% of the target copolyamide material. The reaction was first carried out at 200°C for 2 hours to allow the dimethyl ester monomer to participate in transesterification and early amidation reactions. Subsequently, the temperature was raised to 250°C, and polycondensation was carried out under a vacuum of 0.08 MPa for 3 hours to obtain the copolyamide material.

[0055] The resulting copolyamide material had an intrinsic viscosity of 1.02 dL / g, a carboxyl end-group content of 35 mmol / kg, and a melting point of 256°C. This material was melt-blended with 0.20 wt% antioxidant 1076 and 0.40 wt% UV-328. The blending temperature was 282°C, and the screw speed was 110 rpm. Subsequently, melt spinning, drawing, and heat setting were performed as in Example 1, but the total draw ratio was adjusted to 3.2 times, the heat setting temperature was 170°C, and the heat setting time was 75 seconds. The resulting fiber had a monofilament linear density of 3.6 dtex, an equivalent monofilament diameter of approximately 66 μm, and a breaking strength of 5.3 cN / dtex.

[0056] Comparative Example 1 This comparative example uses ordinary PA66 without introducing 2-alkyl-substituted terephthalic acid monomers. The ordinary PA66 used is EPR27 from Pingdingshan Shenma Engineering Plastics Co., Ltd., with the same amounts of antioxidant 1076 and UV-328 as in Example 1. Melt blending, spinning, drawing, and heat setting conditions are the same as in Example 1. The resulting fibers have a breaking strength of 5.7 cN / dtex.

[0057] Comparative Example 2 In this comparative example, 5-methylisophthalic acid was used instead of 2-methylterephthalic acid in Example 1. Based on a total dicarboxylic acid forming component of 100 mol, adipic acid comprised 80 mol and 5-methylisophthalic acid comprised 20 mol. The amount of hexamethylenediamine was the same as in Example 1. The amounts of triphenyl phosphite, antioxidant 1076, and UV-328 were also the same. The polymerization, blending, and spinning conditions were the same or substantially the same as in Example 1. The resulting fiber had a breaking strength of 5.2 cN / dtex.

[0058] Comparative Example 3 This comparative example uses 2-methylterephthalic acid as the aromatic diacid monomer, but increases the proportion of aromatic dicarboxylic acid structural units formed by it to 40 mol%. Based on a total dicarboxylic acid forming component of 100 mol, adipic acid accounts for 60 mol, and 2-methylterephthalic acid accounts for 40 mol. The remaining monomers, stabilizer system, and polymerization conditions are the same as or substantially the same as in Example 1.

[0059] The resulting copolyamide material has an intrinsic viscosity of 0.96 dL / g and a melting point of 268°C. When spinning this material at 282°C, the melt pressure fluctuates significantly, leading to an increase in the number of nascent filament breaks. Increasing the spinning temperature to 292°C yields continuous nascent filaments, but the draw stability is poor. The resulting fiber has a breaking strength of 3.1 cN / dtex.

[0060] Comparative Example 4 This comparative example is essentially the same as Example 1, except that the polycondensation time is shortened to 1.5 hours, resulting in an intrinsic viscosity of 0.82 dL / g for the obtained copolyamide material. This intrinsic viscosity is lower than the range of not less than 0.90 dL / g specified in this invention.

[0061] The resulting material can be extruded through a spinneret to form nascent filaments, but these nascent filaments are more prone to breakage during the drafting process. Reducing the total draft ratio to 2.5 times yields fiber samples, but the resulting fibers have a breaking strength of only 2.9 cN / dtex, lower than the basic strength required for use as textile materials.

[0062] Test methods The intrinsic viscosity was determined using 96% sulfuric acid as solvent at 25°C. The content of carboxyl end groups was determined by end-group titration. The melting point was determined by DSC at a heating rate of 10°C / min, and the melting peak temperature from the second heating curve was used.

[0063] Ultraviolet absorbance was measured using an integrating sphere UV-Vis diffuse reflectance or transmission method, and the average ultraviolet absorbance in the 320-400 nm wavelength range was taken. Relative integrated emission intensity was measured using an integrating sphere-fluorescence spectrophotometer with an excitation wavelength of 365 nm and an integration range of 600-800 nm. The relative integrated emission intensity was normalized to the integrated intensity of the same batch of standard samples.

[0064] The light conversion ratio was determined using an integrating sphere spectral testing system. Transmission spectra of the same sample were measured under both conditions with and without direct UV radiation. The integrated value of the transmission spectrum in band B under conditions without direct UV radiation was denoted as T0(B), and the integrated value of the transmission spectrum in band B under conditions with direct UV radiation was denoted as Tuv(B). The light conversion ratio was calculated using the following formula: Light conversion ratio (B) = [Tuv(B) - T0(B)] / T0(B) × 100%.

[0065] The UV input wavelength is 200-400 nm. The violet output wavelength is 380-420 nm, the blue output wavelength is 420-450 nm, and the red output wavelength is 620-780 nm. Tensile strength was tested according to ISO 2062. Light aging resistance was tested according to ASTM G154 using a UVA-340 lamp with an irradiance of 0.89 W / m², for 8 hours of light exposure and 4 hours of condensation cycles, for a total of 168 hours. Household washing was performed according to ISO 6330, and optical performance retention was tested after 10 washes.

[0066] Test Results Sources of aromatic dicarboxylic acid structural units: Example 1 was 2-methyl terephthalic acid; Example 2 was 2-methyl terephthalic acid; Example 3 was dimethyl 2-methyl terephthalate; Comparative Example 1 was none; Comparative Example 2 was 5-methyl isophthalic acid; Comparative Example 3 was 2-methyl terephthalic acid; Comparative Example 4 was 2-methyl terephthalic acid.

[0067] The proportions of aromatic dicarboxylic acid structural units were as follows: Example 1: 20 mol%; Example 2: 20 mol%; Example 3: 25 mol%; Comparative Example 1: 0%; Comparative Example 2: 20 mol%; Comparative Example 3: 40 mol%; Comparative Example 4: 20 mol%.

[0068] Intrinsic viscosity: 1.05 dL / g for Example 1; 1.04 dL / g for Example 2; 1.02 dL / g for Example 3; approximately 1.00 dL / g for Comparative Example 1; 1.01 dL / g for Comparative Example 2; 0.96 dL / g for Comparative Example 3; and 0.82 dL / g for Comparative Example 4.

[0069] Melting point: Example 1: 252 degrees Celsius; Example 2: 251 degrees Celsius; Example 3: 256 degrees Celsius; Comparative Example 1: 260 degrees Celsius; Comparative Example 2: 246 degrees Celsius; Comparative Example 3: 268 degrees Celsius; Comparative Example 4: 249 degrees Celsius.

[0070] Average UV absorbance in the 320-400 nm range: 87% for Example 1; 88% for Example 2; 90% for Example 3; 62% for Comparative Example 1; 75% for Comparative Example 2; 93% for Comparative Example 3; and 86% for Comparative Example 4.

[0071] Relative integrated emission intensity at 600-800 nm under 365 nm excitation: 0.69 for Example 1; 0.76 for Example 2; 0.72 for Example 3; 0.31 for Comparative Example 1; 0.49 for Comparative Example 2; 0.73 for Comparative Example 3; and 0.66 for Comparative Example 4.

[0072] 380-420 nm violet light conversion ratio: Example 1: 32%; Example 2: 35%; Example 3: 34%; Comparative Example 1: 4%; Comparative Example 2: 13%; Comparative Example 3: 36%; Comparative Example 4: 28%.

[0073] Blue light conversion ratio at 420-450 nm: 5% for Example 1; 8% for Example 2; 6% for Example 3; 0% for Comparative Example 1; 2% for Comparative Example 2; 6% for Comparative Example 3; and 4% for Comparative Example 4.

[0074] Red light conversion ratio in the 620-780 nm range: 4% in Example 1; 9% in Example 2; 5% in Example 3; 0% in Comparative Example 1; 1% in Comparative Example 2; 5% in Comparative Example 3; and 3% in Comparative Example 4.

[0075] Fracture strength: 5.6 cN / dtex for Example 1; 5.5 cN / dtex for Example 2; 5.3 cN / dtex for Example 3; 5.7 cN / dtex for Comparative Example 1; 5.2 cN / dtex for Comparative Example 2; 3.1 cN / dtex for Comparative Example 3; and 2.9 cN / dtex for Comparative Example 4.

[0076] Emission intensity retention rate after aging: 84% for Example 1; 82% for Example 2; 83% for Example 3; 68% for Comparative Example 1; 72% for Comparative Example 2; 70% for Comparative Example 3; and 76% for Comparative Example 4.

[0077] Optical performance retention rate after 10 home washes: Example 1: 83%; Example 2: 81%; Example 3: 80%; Comparative Example 1: 70%; Comparative Example 2: 73%; Comparative Example 3: 68%; Comparative Example 4: 75%.

[0078] As can be seen from Example 1 and Comparative Example 1, without the addition of external luminescent aids, Example 1, through the main chain structure formed by 2-methylterephthalic acid, achieved higher ultraviolet absorptivity and relative integrated emission intensity. Although Comparative Example 1 exhibited higher fracture strength, it lacked a 2-alkyl-substituted aromatic dicarboxylic acid structural unit, resulting in significantly lower ultraviolet and red light conversion ratios. This indicates that the ordinary PA66 main chain cannot provide the same light energy conversion basis as the present invention.

[0079] As can be seen from Examples 1 and 2, when the aromatic unit ratio is 20 mol%, replacing 2-methylterephthalic acid with 5-methylisophthalic acid results in a decrease in relative integrated emission intensity, violet light conversion ratio, and red light conversion ratio. This result indicates that not all methyl-substituted aromatic diacids achieve the same effect. The 2-alkyl-substituted terephthalic acid structural unit plays a crucial role in the formation of the main-chain photoresponsive structure.

[0080] As can be seen from Example 1 and Comparative Example 3, increasing the proportion of aromatic dicarboxylic acid structural units formed from 2-methylterephthalic acid to 40 mol% still resulted in high UV absorbance and relative integrated emission intensity, but the melting point increased, and significant pressure fluctuations and fiber breakage occurred during spinning. The resulting fiber's breaking strength was below 3.5 cN / dtex. This result indicates that a higher proportion of aromatic structures is not necessarily better. Limiting the proportion to 10-30 mol%, especially 20-25 mol%, is beneficial for simultaneously achieving good optical response and melt spinning processability.

[0081] As can be seen from Example 1 and Comparative Example 4, under the same main chain composition, if insufficient polycondensation results in an intrinsic viscosity below 0.90 dL / g, the material can still exhibit a certain optical response, but the tensile stability and fiber breaking strength are significantly reduced. This result indicates that an intrinsic viscosity of not less than 0.90 dL / g is not an isolated molecular weight indicator, but rather an important processing boundary that enables the copolyamide material of this invention to be converted into usable fibers.

[0082] Compared to Example 1, Example 2 showed improved relative integrated emission intensity and red light conversion ratio after adding a low content of Rhodamine B derivative. This result indicates that luminescent aids can be used as an enhancement method. However, Example 1 already achieved significantly higher light energy conversion performance than Comparative Examples 1 and 2 without the addition of external luminescent aids. Therefore, the fundamental technical contribution of this invention still comes from the copolymer backbone formed by the 2-alkyl-substituted aromatic dicarboxylic acid structural unit and the aliphatic polyamide segment.

[0083] Example 3 demonstrates that a copolyamide material with suitable intrinsic viscosity, carboxyl end-group content, and melting point can also be obtained using dimethyl 2-methyl terephthalate via transesterification and amidation polycondensation. The resulting fibers exhibit a breaking strength of not less than 3.5 cN / dtex and demonstrate high UV absorptivity, relative integrated emission intensity, and forward conversion ratio. This indicates that, in addition to the salt polycondensation route, the dimethyl ester monomer route can also be used to achieve the preparation method of this invention.

[0084] The above examples and comparative examples illustrate that this invention does not simply select a single aromatic diacid monomer, nor does it rely on external luminescent additives to impart optical functions to polyamide fibers. This invention uses 2-alkyl-substituted terephthalic acid monomers as monomer boundaries, while controlling the proportion of aromatic dicarboxylic acid structural units to 10-30 mol%, and limiting the intrinsic viscosity to not less than 0.90 dL / g. This combined boundary is then combined with a stable system and transformed into fibers through melt spinning, drawing, and heat setting steps, enabling the copolyamide material to balance the main chain's light energy conversion foundation, fiber processing stability, and retention of optical properties after use.

Claims

1. A method for producing a copolyamide material having a function of converting light energy, characterized by, include: A copolyamide material is formed by polycondensation of C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid, and 2-methyl terephthalic acid via a salt-based polycondensation reaction, or by polycondensation of C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid, and dimethyl 2-methyl terephthalate via transesterification and amidation reactions; wherein the aromatic dicarboxylic acid structural units formed by the 2-methyl terephthalic acid or dimethyl 2-methyl terephthalate account for 10-30 mol% of all dicarboxylic acid structural units in the copolyamide material; and the intrinsic viscosity of the resulting copolyamide material is controlled to be not less than 0.90 dL / g.

2. The method for preparing the copolyamide material with light energy conversion function according to claim 1, characterized in that, The C6-C12 aliphatic diamine is hexamethylenediamine, decanediamine, or a combination thereof; the C6-C12 aliphatic dicarboxylic acid is adipic acid, sebacic acid, or a combination thereof; the molar ratio of the amino group provided by the C6-C12 aliphatic diamine to the carboxyl or ester group provided by all the dicarboxylic acid components is from 0.98:1 to 1.02:

1.

3. The method for preparing a copolyamide material with light energy conversion function according to claim 1 or 2, characterized in that, The aromatic dicarboxylic acid structural unit accounts for 20-25 mol% of all dicarboxylic acid structural units in the copolyamide material; the intrinsic viscosity of the resulting copolyamide material is 1.00-1.10 dL / g, the content of carboxyl end groups is not higher than 40 mmol / kg, and the melting point is 245-260 degrees Celsius.

4. The method for preparing a copolyamide material with light energy conversion function according to claim 1, characterized in that, The salt polycondensation reaction comprises: preparing an equivalent salt or reaction mixture of the C6-C12 aliphatic diamine, C6-C12 aliphatic dicarboxylic acid and 2-methylterephthalic acid in a target molar ratio; performing pre-polycondensation at 220-240 degrees Celsius under an inert atmosphere; and then polycondensing for 2-4 hours at 240-265 degrees Celsius and a vacuum of 0.07-0.09 MPa.

5. The method for preparing a copolyamide material with light energy conversion function according to claim 1, characterized in that, The transesterification and amidation polycondensation reaction includes: using dimethyl 2-methyl terephthalate as the reactant monomer, carrying out a transesterification reaction at 180-220 degrees Celsius; and carrying out an amidation polycondensation reaction at 220-260 degrees Celsius and a vacuum of 0.07-0.09 MPa; wherein the transesterification catalyst is zinc acetate, and the amount of zinc acetate used is 0.01-0.03 wt% of the mass of the obtained copolyamide material.

6. The method for preparing a copolyamide material with light energy conversion function according to claim 1, characterized in that, A polycondensation stabilizer is added to the salt polycondensation reaction or the transesterification and amidation polycondensation reaction. The polycondensation stabilizer is a phosphite or hypophosphite, and its amount is 0.1-0.5 wt% of the mass of the obtained copolyamide material. The obtained copolyamide material is then melt-blended with an antioxidant and a light stabilizer. The antioxidant includes antioxidant 1076, and the light stabilizer is a benzotriazole compound.

7. The method for preparing a copolyamide material with light energy conversion function according to claim 6, characterized in that, The light stabilizer is UV-327 or UV-328, and the amount of the light stabilizer is 0.2-0.5 wt% of the mass of the obtained copolyamide material; the preparation method further includes melt blending the obtained copolyamide material with 0.01-0.20 wt% of a luminescent aid, wherein the luminescent aid is a rhodamine B derivative, a coumarin 6 derivative, or an Eu(β-diketone)3 complex.

8. A copolyamide fiber with light energy conversion function, characterized in that, The copolyamide fiber is obtained by melt spinning, stretching and heat setting of the copolyamide material with light energy conversion function prepared by the preparation method of the copolyamide material with light energy conversion function as described in any one of claims 1-7.

9. The copolyamide fiber according to claim 8, characterized in that, The C6-C12 aliphatic diamine is hexamethylenediamine, decanediamine, or a combination thereof; the C6-C12 aliphatic dicarboxylic acid is adipic acid, sebacic acid, or a combination thereof; the aromatic dicarboxylic acid structural unit accounts for 20-25 mol% of all dicarboxylic acid structural units in the copolyamide; the carboxyl end group content of the copolyamide is not higher than 40 mmol / kg, and the melting point is 245-260 degrees Celsius.

10. The copolyamide fiber according to claim 8 or 9, characterized in that, The copolyamide fiber comprises a polycondensation stabilizer, an antioxidant, and a light stabilizer; the polycondensation stabilizer is phosphite or hypophosphite, and its content is 0.1-0.5 wt% of the copolyamide; the antioxidant includes antioxidant 1076; the light stabilizer is UV-327 or UV-328; the monofilament linear density of the copolyamide fiber is 2-15 dtex, the equivalent monofilament diameter is 40-200 μm, and the breaking strength is not less than 3.5 cN / dtex.