Polychromatic photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor as well as preparation method and application thereof

Abstract

The invention belongs to the field of textile materials, and particularly relates to a polychromatic photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor and a preparation method and application thereof. A spinning solution precursor which can be prepared by using a physical method and a simple instrument is prepared, and the spinning solution precursor can be subjected to wet spinning, so that the damage of melt spinning to photochromic microcapsules and PHA is avoided. The steps of solution preparation are simplified, required instruments are reduced, preparation of a spinning solution precursor by using a chemical method is avoided, calculation of a subsequent material preparation proportion is reduced, and industrial production can be realized. A stable PHA / PLA basic spinning solution is obtained in previous research, and in order to meet the requirement of the market for rich colors of color-changing fibers, different types of photochromic microcapsules are added according to the proportion, so that a spinning solution precursor with the required color can be obtained.

Description

Technical Field

[0001] The present invention belongs to the field of textile materials, and particularly relates to a multi-color photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of society and technology, intelligent photochromic (PC) fabrics have become high-value-added intelligent products, and have broad application prospects in the fields of textiles, military equipment, anti-counterfeiting, etc. The photochromic technology originated from the demand for camouflage materials for military concealment.

[0003] Research shows that materials can obtain photochromic properties by using special molecular configurations. Photochromism refers to the reversible color change that occurs due to the change of the molecular structure of the material under light irradiation. Organic photochromic materials show more selectivity, higher modifiability, and faster light response speed in color change. By applying photochromic compounds to various materials, functional color-changing materials with novel visual impacts and decorative effects can be obtained, which can be applied to clothing, glass, ornaments, lenses, etc.

[0004] Microcapsules are a kind of micro-container that encapsulates core materials with polymers as the wall shells. Microcapsules can play a role in encapsulating and protecting the particulate matter (drops) inside their capsules, and their particle size is generally in the range of 0.1-1000 μm. The material encapsulated inside the microcapsule body is called the core, core material, or nuclear material, while the outer capsule wall is generally called the capsule skin, shell, or wall material. Aiming at the problem that most current organic photochromic materials have low heat resistance and fatigue resistance, people often enhance their fatigue performance through microcapsule encapsulation technology. There are many materials that can be used as the microcapsule wall, such as calcium carbonate, polymethyl methacrylate (PMMA), melamine formaldehyde resin, etc. Microencapsulation can be used to add photochromic materials to the spinning solution precursor. Spiropyran, spirooxazine, and naphthopyran are selected as the core materials respectively, and then melamine formaldehyde resin is used as the wall material to prepare trichromatic color-changing microcapsules. In the preparation of the spinning precursor, melamine formaldehyde resin can prevent the internal core material from being damaged by the solvent and has a good adaptability to the solvent.

[0005] At present, the market needs fibers with diverse colors and color-changing properties to meet the requirements for adapting to the optical environment and personalized customization. Based on the existing microfluidic spinning technology, a spinning precursor can be made using trichromatic color-changing microcapsules, and finally, color-changing fibers with the three primary colors can be obtained after color change. Therefore, spinning precursors of other colors besides the three primary colors can be prepared by adding different proportions of trichromatic color-changing microcapsules, thereby obtaining fibers of the desired colors. Moreover, the prepared fibers are biodegradable and biocompatible because they use environmentally friendly polymers, polyhydroxyalkanoates (PHA) and polylactic acid (PLA), meeting the requirements of environmental protection.

[0006] Melt spinning is a process in which a spinnable polymer is extruded from the fine holes of a spinneret at a temperature above its melting point, cooled and refined into a filamentous solid, and simultaneously wound. The melting temperature of PHA is 165°C - 180°C. When the heating temperature is 10°C higher than the melting point (180°C), cracking will occur, resulting in a very narrow processing temperature range for PHA; the filaments ejected from the spinneret holes solidify slowly and are prone to adhesion, making it difficult to separate the filaments and difficult to unwind during winding. High requirements are placed on the photochromic microcapsules during the spinning process, and at the same time, it is necessary to consider whether they can be well dispersed in the spinning substrate to form a spinning solution precursor that meets the requirements. Photochromic microcapsules generally have poor heat resistance. To maximize the retention rate of photochromic microcapsules, the temperature needs to be at 150°C (Wu Shixun. Preparation and Responsiveness Study of Spiropyran Photochromic Microcapsules [D]. Donghua University, 2022. DOI: 10.27012 / d.cnki.gdhuu.2022.000857). Therefore, the spinning conditions for melt spinning are relatively harsh and difficult to achieve under general experimental conditions.

[0007] The chemical preparation of photochromic fibers has special requirements for the chemical structure of photochromic materials. Photochromic materials with active groups are required to enable them to react chemically with the active groups (such as hydroxyl groups, amino groups, etc.) that are abundantly present on various fiber substrates. Physical methods have obvious advantages, such as a simple preparation process flow, no special requirements for the chemical structure of photochromic dyes, and can quickly and simply prepare a spinning solution precursor.

[0008] As the ultraviolet light irradiation time prolongs, the absorbance of the self-adhesive polymer (PSBM-SP) latex particles of spiropyran increases, and the color gradually deepens from colorless; after 120 s of ultraviolet light irradiation, as the irradiation time prolongs, the absorbance basically remains unchanged, indicating that the color change is complete (Tang Weiran, Wang Jingyi, Lu Linxia, et al. Research on Spiropyran Photochromic Dyes and Their Applications in the Textile Field [J]. Modern Silk Science & Technology, 2024, 39(04): 27 - 31). It can be seen that the time required for color change is relatively long, and stable ultraviolet light irradiation is required, with relatively high requirements in practical applications and relatively single colors. Summary of the Invention

[0009] The melting temperature of PHA is close to the thermal degradation temperature, with only a difference of about 20 °C, and it is extremely sensitive to temperature. Therefore, the processing temperature during melt spinning is relatively narrow. Moreover, PHA has a low melting point and slow cooling rate, making it easy for filaments to merge during spinning, resulting in difficult unwinding; the temperature required for melt spinning is high, which is likely to damage the photochromic microcapsules and has high requirements for the spinning solution precursor. Therefore, the spinning conditions for melt spinning are relatively harsh and difficult to achieve under general experimental conditions.

[0010] The chemical method for preparing the spinning solution precursor requires chemical reactions, so there are special requirements for the chemical structure of the photochromic material. A photochromic material with reactive groups is needed to enable it to undergo chemical reactions with reactive groups (such as hydroxyl groups, amino groups, etc.) that are abundantly present on various fiber substrates. Many aspects need to be noted when preparing the spinning solution precursor, and the preparation process is cumbersome, with complex steps and inconvenient operation. Currently, the color-changing speed of photochromic materials is relatively slow, and the colors are relatively single. A stable ultraviolet light source is required for continuous irradiation, which has relatively high requirements in practical applications.

[0011] To solve the above-mentioned existing technical problems, the present application provides the following technical solutions:

[0012] The present invention provides a method for preparing a multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor, comprising the following steps:

[0013] S11: Heat polyhydroxyalkanoate and dissolve it in organic solvent A to obtain a PHA solution;

[0014] S12: Dissolve polylactic acid in organic solvent A to obtain a PLA solution;

[0015] S13: Mix the PHA solution and the PLA solution to obtain a spinning dope;

[0016] S14: Add one or more photochromic microcapsules prepared from different photochromic solutions to the spinning dope, and after mixing, obtain the multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor;

[0017] In the step S14, the method for preparing the photochromic microcapsules is to heat and react an aqueous solution containing a melamine formaldehyde resin prepolymer, an O / W emulsion, and a dispersant under acidic conditions; the melamine formaldehyde resin prepolymer is obtained by reacting melamine and formaldehyde under high temperature and alkaline conditions, and the O / W emulsion is obtained by reacting a photochromic solution and an aqueous solution containing sodium dodecyl sulfate (SDS);

[0018] Preparation of tricolor photochromic microcapsules. By in-situ polymerization method, using melamine formaldehyde resin as the wall material and spirooxazine, naphthopyran and spiropyran as the core materials, three photochromic microcapsules with different color-changing effects were synthesized (named PCM1, PCM2, and PCM3 respectively), all of which can change color under sunlight irradiation.

[0019] Three different photochromic materials were synthesized into photochromic microcapsules by in-situ polymerization method. The preparation process mainly consists of three steps. First is the synthesis of melamine formaldehyde resin prepolymer, second is the preparation of oil-in-water (O / W) emulsion, and finally is the encapsulation reaction.

[0020] Preferably, in the step S11, the heating temperature is 50 - 80 °C, and stirring is carried out for 4 - 8 h.

[0021] Preferably, the organic solvent A is dichloromethane.

[0022] Preferably, in the step S12, the dissolving method is stirring for 4 - 8 h.

[0023] Preferably, in the PHA solution, the concentration of PHA is 2 wt%; in the PLA solution, the concentration of PLA is 14 wt%.

[0024] Preferably, in the step S13, the mixing method is to carry out magnetic stirring at room temperature (25 ± 5 °C) for 30 - 60 min, then carry out magnetic stirring at room temperature for another 30 - 60 min, and carry out ultrasonic dispersion for 30 - 60 min.

[0025] Preferably, the photochromic solution is selected from the tetrachloroethylene solution of spirooxazine, the dichloromethane solution of naphthopyran or spiropyran dissolved in n-octane.

[0026] Preferably, the dispersant is selected from polyvinyl alcohol (PVA).

[0027] Preferably, the heating reaction temperature is 65 - 75 °C, and the time is 2 - 4 h.

[0028] Preferably, the high-temperature reaction temperature is 65 - 75 °C, and the time is 0.5 - 1.5 h.

[0029] Preferably, the reaction temperature of the photochromic solution and the aqueous solution containing sodium dodecyl sulfate (SDS) is 55 - 65 °C, and the time is 30 - 50 min.

[0030] Preferably, in the steps S13 and S14, the mass ratio of the PHA solution, the PLA solution and the photochromic microcapsules is 33:66:1.

[0031] Preferably, in the step S14, the mixing method is stirring at room temperature (25±5°C) for 3-6 hours.

[0032] Preferably, in the step S14, after mixing, it is left standing at room temperature for 30-60 minutes.

[0033] Specifically, the preparation method of the multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor includes the following steps:

[0034] Add the polymer polyhydroxyalkanoate (PHA) to the solvent dichloromethane under stirring conditions, and obtain a mixed solution by magnetic stirring. Then, in a round-bottom flask equipped with a condensing reflux device, heat it to 50-80°C under stirring conditions and stir well for 4-8 hours to obtain a uniformly dissolved PHA, and the solution is abbreviated as PHA; add polylactic acid (PLA) to the solvent dichloromethane under stirring conditions and stir magnetically for 4-8 hours to obtain a uniformly dissolved PLA solution; finally, blend PHA and PLA, stir magnetically at room temperature for 30-60 minutes to obtain a mixed solution, then stir magnetically at room temperature for 30-60 minutes and perform ultrasonic dispersion for 30-60 minutes to obtain a spinning dope. Add trichromatic photochromic microcapsules to the spinning dope, stir magnetically at room temperature for 3-6 hours to fully disperse the photochromic microcapsules, and obtain a spinning solution precursor with uniformly mixed photochromic microcapsules. Then stand at room temperature for 30-60 minutes to obtain a spinning solution precursor that can be used to spin photochromic fibers.

[0035] The present invention also provides a multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor prepared by the above preparation method.

[0036] The present invention also provides a PHA fiber containing photochromic microcapsules, which is obtained by microfluidic spinning of the above multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor and then drying at room temperature; the coagulation bath for the microfluidic spinning is selected from ethanol.

[0037] Specifically, the preparation method of the PHA fiber containing photochromic microcapsules is as follows: Use the microfluidic spinning process to spin the obtained spinning solution precursor. The process conditions for microfluidic spinning require anhydrous ethanol as the coagulation bath, and then dry the spun fiber at room temperature. Finally, a PHA fiber containing photochromic microcapsules can be obtained, which can change color rapidly under specific light and restore the original color within a certain time after the light source disappears.

[0038] The present invention prepares a spinning solution precursor that can be prepared by physical methods and simple instruments, and this spinning solution precursor can be wet-spun, avoiding the damage to photochromic microcapsules and PHA caused by melt spinning. The steps of solution preparation are simplified, the required instruments are reduced, the use of chemical methods to prepare the spinning solution precursor is avoided, and the calculation of the subsequent material configuration ratio is reduced, enabling industrial production. In previous research, a stable PHA / PLA base spinning solution was obtained. To meet the market's demand for colorful fibers, different types of photochromic microcapsules can be added in proportion to obtain the desired color spinning solution precursor.

[0039] The technical solution of the present invention has the following advantages compared with the prior art:

[0040] The present invention uses physical methods to prepare the photochromic microcapsule spinning solution precursor, which simplifies the solution preparation and production process. The instruments used are common and the operation is convenient. The present invention can use wet spinning and microfluidic spinning, and there are no other impacts and problems to be noted in the spinning process due to the addition of photochromic microcapsules. The spinning solution precursor of the desired color can be prepared by using different proportions and types of trichromatic microcapsules. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a picture before illumination of the spinning solution precursor containing red photochromic microcapsules in Example 1.

[0042] Figure 2 It is a picture after illumination of the spinning solution precursor containing red photochromic microcapsules in Example 1.

[0043] Figure 3 It is a picture before illumination of the spinning solution precursor containing yellow photochromic microcapsules in Example 2.

[0044] Figure 4 It is a picture after illumination of the spinning solution precursor containing yellow photochromic microcapsules in Example 2.

[0045] Figure 5 It is a picture before illumination of the spinning solution precursor containing blue photochromic microcapsules in Example 3.

[0046] Figure 6 It is a picture after illumination of the spinning solution precursor containing blue photochromic microcapsules in Example 3.

[0047] Figure 7 It is the photochromic effect diagram of the spinning solution precursor of the photochromic fiber. DETAILED DESCRIPTION OF THE INVENTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited do not limit the present invention.

[0049] The preparation methods of the three primary color photochromic microcapsules adopted in each embodiment are as follows:

[0050] (1) Synthesis of melamine formaldehyde resin prepolymer

[0051] Add 7 g of melamine powder, 12 mL of 37 wt% formaldehyde solution and 24 mL of deionized water into a three-necked flask equipped with a condensation reflux device, and mix and stir. Adjust the pH value of the reaction system to 8 - 9 (using 2 wt% NaOH solution), and at the same time heat it in an oil bath to raise the temperature to 70 °C, and react for 1 h (500 rpm). After the melamine is completely dissolved, a clear and transparent melamine formaldehyde resin prepolymer solution can be obtained.

[0052] (2) Preparation of O / W emulsion

[0053] Measure 10 mL of a 0.75 wt% photochromic solution as the oil phase (spirooxazine dissolved in tetrachloroethylene / naphthopyran dissolved in dichloromethane / spiropyran dissolved in n-octane), and slowly pour it into a round-bottom flask containing a certain volume (15 mL) and concentration of sodium dodecyl sulfate (SDS) solution, and stir with a mechanical stirrer for a certain time (1000 rpm, 40 min, 60 °C) to obtain a stable O / W emulsion.

[0054] Spirooxazine dissolved in tetrachloroethylene / naphthopyran dissolved in dichloromethane / spiropyran dissolved in n-octane are three core materials, corresponding to PCM1 (blue), PCM2 (yellow), and PCM3 (red) respectively.

[0055] (3) Encapsulation reaction

[0056] Drop the melamine formaldehyde resin prepolymer solution prepared in the first step into the O / W emulsion prepared in the second step. And add 6.5 mL of a dispersant polyvinyl alcohol (PVA) solution. Adjust the pH value of the reaction system to about 6.0, and stir at a certain speed at room temperature for 30 min. Then, adjust the pH value of the reaction system to about 5.0, and at the same time heat it in an oil bath to raise the temperature to 70 °C, and react for 3 h. After the reaction is completed, ultrasonically disperse the sample in absolute ethanol, centrifuge with a high-speed centrifuge, wash 3 times, and heat and dry (60 °C, 6 h) to obtain photochromic microcapsules.

[0057] Example 1

[0058] Weigh 3.3 g of a 2 wt% PHA dichloromethane solution in a fume hood and place it in a clean glass bottle. Weigh 6.6 g of a 14 wt% PLA dichloromethane solution and add it to the weighed PHA dichloromethane solution. Then weigh 0.1 g of red photochromic microcapsules (PCM3) and pour them into the PHA / PLA solution. Place a rotor of appropriate size and label the sample name on the bottle body and the bottle cap. Place it on a magnetic stirrer, adjust the rotation speed to 400 rpm, stir for 4 h, then remove it from the magnetic stirrer and let it stand at room temperature for 30 min to obtain a spinning solution precursor that can spin red color-changing fibers. Pictures of the spinning solution precursor containing red photochromic microcapsules before and after illumination are shown in Figure 1 and Figure 2 as shown

[0059] Example 2

[0060] Weigh 3.3 g of a 2 wt% PHA dichloromethane solution in a fume hood and place it in a clean glass bottle. Weigh 6.6 g of a 14 wt% PLA dichloromethane solution and add it to the weighed PHA dichloromethane solution. Then weigh 0.1 g of yellow photochromic microcapsules (PCM2) and pour them into the PHA / PLA solution. Place a rotor of appropriate size and label the sample name on the bottle body and the bottle cap. Place it on a magnetic stirrer, adjust the rotation speed to 400 rpm, stir for 4 h, then remove it from the magnetic stirrer and let it stand at room temperature for 30 min to obtain a spinning solution precursor that can spin yellow color-changing fibers. Pictures of the spinning solution precursor containing yellow photochromic microcapsules before and after illumination are shown in Figure 3 and Figure 4 as shown

[0061] Example 3

[0062] Weigh 3.3 g of a 2 wt% PHA dichloromethane solution in a fume hood and place it in a clean glass bottle. Weigh 6.6 g of a 14 wt% PLA dichloromethane solution and add it to the weighed PHA dichloromethane solution. Then weigh 0.1 g of blue photochromic microcapsules (PCM1) and pour them into the PHA / PLA solution. Place a rotor of appropriate size and label the sample name on the bottle body and the bottle cap. Place it on a magnetic stirrer, adjust the rotation speed to 400 rpm, stir for 4 h, then remove it from the magnetic stirrer and let it stand at room temperature for 30 min to obtain a spinning solution precursor that can spin blue color-changing fibers.

[0063] Example 4

[0064] Weigh 3.3 g of a 2 wt% PHA dichloromethane solution in a fume hood and place it in a clean glass bottle. Weigh 6.6 g of a 14 wt% PLA dichloromethane solution and add it to the weighed PHA dichloromethane solution. Then weigh 0.05 g of blue photochromic microcapsules (PCM1) and 0.05 g of yellow photochromic microcapsules (PCM2) and pour them into the PHA / PLA solution. Place a rotor of appropriate size and label the sample name on the bottle body and the bottle cap. Place it on a magnetic stirrer, adjust the rotation speed to 400 rpm, stir for 4 h, then remove it from the magnetic stirrer and let it stand at room temperature for 30 min to obtain a spinning solution precursor capable of spinning green color-changing fibers.

[0065] Application Example 1

[0066] Use the microfluidic spinning process to spin the obtained spinning solution precursor. The process conditions for microfluidic spinning require absolute ethanol as the coagulation bath, and then dry the spun fibers at room temperature to obtain PHA fibers containing photochromic microcapsules. The specific steps are as follows:

[0067] Draw the spinning solution into a syringe, and adjust the propulsion speed by an injection pump. The spinning speed is 2 - 5 mL / min; the spinning solution enters the absolute ethanol coagulation bath, and the fibers are fixed and formed. Then they are collected and wound by a drum-type collecting device and air-dried to obtain photochromic PHA / PLA fibers. These fibers change color rapidly under specific light and restore their original color within a certain time after the light source disappears.

[0068] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation methods. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. And the obvious changes or variations derived therefrom are still within the protection scope of this invention.

Claims

1. A preparation method of a multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor, characterized in that, It includes the following steps: S11: Heat polyhydroxyalkanoate and dissolve it in organic solvent A to obtain a PHA solution; S12: Dissolve polylactic acid in organic solvent A to obtain a PLA solution; S13: Mix the PHA solution and the PLA solution to obtain a spinning dope; S14: Add one or more photochromic microcapsules prepared from different photochromic solutions to the spinning dope, and after mixing, obtain the multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor; In step S14, the preparation method of the photochromic microcapsules is obtained by heating and reacting an aqueous solution containing a melamine formaldehyde resin prepolymer, an O / W emulsion, and a dispersant under acidic conditions; the melamine formaldehyde resin prepolymer is obtained by reacting melamine and formaldehyde under high temperature conditions in an alkaline medium, and the O / W emulsion is obtained by reacting a photochromic solution and an aqueous solution containing sodium dodecyl sulfate.

2. The preparation method according to claim 1, characterized in that, In step S11, the heating temperature is 50 - 80 °C, and stir for 4 - 8 h.

3. The preparation method according to claim 1, characterized in that, The organic solvent A is dichloromethane.

4. The preparation method according to claim 1, wherein, In step S13, the mixing method is to carry out magnetic stirring at room temperature for 30 - 60 min, then carry out magnetic stirring at room temperature for another 30 - 60 min, and carry out ultrasonic dispersion for 30 - 60 min.

5. The preparation method according to claim 1, characterized in that, The photochromic solution is selected from a perchloroethylene solution of spirooxazine, a dichloromethane solution of naphthopyran, or a n-octane solution of spiropyran.

6. The preparation method according to claim 1, characterized in that, In steps S13 and S14, the mass ratio of the PHA solution, the PLA solution, and the photochromic microcapsules is 33:66:

1.

7. The preparation method according to claim 1, characterized in that, In step S14, the mixing method is to stir at room temperature for 3 - 6 h.

8. The preparation method according to claim 1, characterized in that, In step S14, after mixing, let it stand at room temperature for 30 - 60 min.

9. A multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor prepared by the preparation method according to any one of claims 1 - 8.

10. A PHA fiber containing photochromic microcapsules, characterized in that, It is obtained by microfluidic spinning of the multicolor photochromic polyhydroxyalkanoate / polylactic acid fiber spinning precursor according to claim 9 and then drying at room temperature; the coagulation bath for the microfluidic spinning is selected from ethanol.

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