A polyhydroxyalkanoate fiber and microfluidic preparation method thereof

Abstract

The present invention belongs to the field of fiber preparation technology, and specifically relates to a polyhydroxyalkanoate fiber and a microfluidic preparation method thereof. The microfluidic preparation method of the present invention comprises the following steps: preparing a PHA solution and a PLA solution separately; the PHA solution is obtained by adding polyhydroxyalkanoate to dichloromethane and heating; the PLA solution is obtained by adding polylactic acid to dichloromethane; the PHA solution and the PLA solution are mixed to obtain a spinning solution; the spinning solution is subjected to microfluidic spinning and dried to obtain the polyhydroxyalkanoate fiber; the coagulation bath for the microfluidic spinning is selected from ethanol. The present invention adopts a simple microfluidic spinning process, which does not require a high-voltage power supply or large equipment during the spinning process. The operation is simple and safe, and the prepared fiber strands are relatively uniform and have good mechanical properties. The spinning method adopted ensures that the fiber is not affected by temperature during the forming process, thus avoiding the problem of processing and forming difficulties caused by the temperature sensitivity of the material.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber preparation, and particularly relates to a polyhydroxyalkanoate fiber and a microfluidic preparation method thereof. Background Art

[0002] Polyhydroxyalkanoate (PHA) is a general term for a class of high-molecular polyesters synthesized by microorganisms. Its molecular structure is a linear alkanoate with hydroxyl groups. It is produced by microbial fermentation. Compared with other degradable materials, it has the environmentally friendly characteristics of being non-fossil prepared and degradable in seawater.

[0003] Since PHA materials are easily degraded by heat and their decomposition temperature is close to the processing temperature, they are difficult to process and shape, and processing into fibers is even more difficult. The research on the formation of polyhydroxyalkanoate fibers and their blended fibers is currently mainly carried out through electrospinning, dry spinning or conventional melt spinning methods, and there are few studies on the use of wet spinning methods. Secondly, since the crystallization rate of polyhydroxyalkanoates is relatively slow, it is easy to cause adhesion between rollers during the melt spinning process, and the spinnability is poor, which limits the development of polyhydroxyalkanoate fiber forming, especially the industrial preparation of polyhydroxyalkanoate fibers. Therefore, it is very necessary to provide a spinning technology for polyhydroxyalkanoate fibers.

[0004] Microfluidic spinning, a wet spinning method, can precisely control and manipulate the flow of microscale liquids within microchannels with high precision and freedom, overcoming the limitations of existing spinning methods that hinder microscopic manipulation of fibers. Compared to conventional spinning processes, microfluidic spinning can be performed at room temperature and pressure, offering advantages such as a shorter production process, lower environmental requirements, higher spinning efficiency, and lower energy consumption. It holds great promise for the development of new biomass and functional fibers. Using microfluidic spinning technology to spin PHA is simple, low-cost, and avoids the effects of temperature on fiber formation.

[0005] At present, there are three main spinning methods for PHA fibers: electrospinning, melt spinning and dry spinning.

[0006] 1. Electrospinning

[0007] At present, electrospinning is one of the main means of preparing PHA fibers. PHA can be dissolved in solvents such as chloroform and N,N-dimethylamide. The polymer solution is spray-spun in a strong electric field to produce polymer fibers. PHA nanofibers can be prepared using the electrospinning process. Nanofibers have special properties such as large specific surface area and small pore size. However, electrospinning generally produces irregularly arranged nanofiber mats, and their mechanical properties are often lower than those of conventional fibers. Patent CN 104452107A discloses a method for preparing a highly elastic polyhydroxyalkanoate porous fiber material. The main steps are to add polyhydroxyalkanoate to a mixed solvent of chloroform and acetone under stirring conditions, stirring to obtain a uniform polyhydroxyalkanoate electrospinning solution, and transferring the spinning solution to a glass syringe, fixing it on an electrospinning device for electrospinning, and collecting the obtained fiber membrane and vacuum drying it at 40-60°C for 6-12h to prepare a polyhydroxyalkanoate porous fiber membrane with high elasticity. Its breaking elongation can reach more than 500%, but the tensile strength is still insufficient. Figure 1 shown.

[0008] 2. Melt spinning

[0009] Melt spinning involves extruding a spinnable polymer from the spinneret holes at a temperature above its melting point, cooling it down to a filamentous solid, and then winding it. PHA's melting temperature is 165°C-180°C. When heated 10°C above its melting point (180°C), it will crack, resulting in a very narrow processing temperature range for PHA. The filaments ejected from the spinneret holes solidify slowly and tend to stick together, making them difficult to separate and unwind after winding. Therefore, melt spinning requires demanding spinning conditions and is difficult to achieve under typical experimental conditions.

[0010] 3. Dry spinning

[0011] Dry spinning is a process in which a polymer solution is squeezed from a spinneret into a forming channel, and hot air is blown into the channel to evaporate the solvent, and the resulting silk thread is curled at a certain speed. During dry forming, the evaporation of the solvent causes the polymer to undergo desolvation, and the fluidity of the stream drops sharply, causing it to turn into a solid state. The PHA fibers made by dry spinning have plastic deformation properties after forming, and can be stretched and post-treated to obtain fibers with better performance. However, the storage time of the nascent fibers must be strictly controlled, otherwise they will become brittle and will not be able to be post-stretched. Zhu Shuqi et al. used a 16% PHBV / chloroform solution to dry-spin fibers. The nascent fibers were stretched 2-5 times at 70°C and then heat-set at 120°C for a fixed elongation. After stretching and post-treatment, the breaking strength of the PHBV fibers was 0.6-1.8 cN / dtex, and the elongation at break was 40-95%. Figure 2 shown.

[0012] The current prior art has the following defects:

[0013] 1. The melting temperature of PHA is close to its thermal degradation temperature, which is only about 20°C away. It is extremely sensitive to temperature. Therefore, the processing temperature range of melt spinning is relatively narrow. However, PHA has a low melting point and slow cooling, which makes it easy to double the yarns during spinning, making unwinding difficult.

[0014] 2. PHA has high crystallinity and severe post-crystallization phenomenon, and the breaking strength of pure PHA fiber is relatively low;

[0015] 3. When using electrospinning, a high voltage power supply is used, and the mechanical properties of the spun fibers are often lower than those of conventional fibers. Summary of the Invention

[0016] To address the processing and forming difficulties caused by the temperature sensitivity of PHA, a microfluidic spinning method was used. This method avoids the influence of temperature on the spinning process and fiber formation, and does not require high-voltage power supplies or large equipment, making it easy to operate and low-cost. To improve the mechanical properties of PHA fibers, PHA was modified and physically blended with polylactic acid (PLA) for spinning. This simple process and good results were achieved.

[0017] In order to solve the above-mentioned technical problems, this application provides the following technical solutions:

[0018] The present invention provides a microfluidic preparation method for polyhydroxyalkanoate fibers, wherein the spinning process is safe and simple, and comprises the following steps:

[0019] S11: prepare PHA solution and PLA solution respectively;

[0020] The PHA solution is obtained by adding polyhydroxyalkanoate (PHA) to dichloromethane and heating at 50-80° C. for 4-8 hours; the PLA solution is obtained by adding polylactic acid (PLA) to dichloromethane;

[0021] S12: mixing the PHA solution and the PLA solution to obtain a spinning solution;

[0022] S13: performing microfluidic spinning on the spinning solution and drying to obtain the polyhydroxyalkanoate fiber; the coagulation bath of the microfluidic spinning is selected from ethanol, and the extrusion rate is 1-3 mL / h.

[0023] Preferably, the PHA is selected from P34HB (poly-3-hydroxybutyrate-4-hydroxybutyrate) or PHB (poly-3-hydroxybutyrate).

[0024] Preferably, in step S11, polyhydroxyalkanoate and polylactic acid are added to dichloromethane under stirring conditions and mixed by magnetic stirring.

[0025] Preferably, the concentration of the solute in the PHA solution is 2-8 wt %.

[0026] Preferably, the concentration of the solute in the PLA solution is 8-12 wt %.

[0027] Preferably, in step S11, condensation reflux is used during heating, and stirring is performed.

[0028] Preferably, in step S11, the PLA solution is obtained by adding dichloromethane to polylactic acid (PLA) and stirring at room temperature (25±5° C.) for 4-8 hours.

[0029] Preferably, in the spinning solution, the volume ratio of polyhydroxyalkanoate to polylactic acid is 1-2:1-2.

[0030] Furthermore, in the spinning solution, the volume ratio of polyhydroxyalkanoate to polylactic acid is 1:1, 1:2 or 2:1.

[0031] Preferably, in step S12, the mixing method is stirring for 30-60 minutes, ultrasonically dispersing for 30-60 minutes, and magnetically stirring at room temperature for 30-60 minutes.

[0032] Preferably, in step S13, the microfluidic spinning is followed by drying at room temperature.

[0033] The present invention also provides a polyhydroxyalkanoate fiber prepared by the above preparation method, which has high breaking strength and breaking elongation.

[0034] The technical solution of the present invention has the following advantages over the prior art:

[0035] 1. The present invention adopts a simple microfluidic spinning process, which does not require a high-voltage power supply or large equipment during the spinning process. The operation is simple and safe, and the prepared fiber strands are relatively uniform and have good mechanical properties.

[0036] 2. The spinning method used makes the fiber unaffected by temperature during the forming process, thus avoiding the problem of processing difficulties caused by the temperature sensitivity of the material;

[0037] 3. Dichloromethane is used as the solvent, which is much less toxic than the commonly used chloroform and is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The tensile curves of the fiber membranes electrospun at different mass ratios of acetone and chloroform.

[0039] Figure 2 The stress-strain curves of dry-spun PHBV nascent fibers and fibers stretched at different ratios after heat treatment.

[0040] Figure 3 This is the tensile curve of P34HB / PLA fiber at different spinning speeds.

[0041] Figure 4 Optical microscope image (a) and scanning electron microscope image (b) of PHB / PLA fiber with a volume ratio of 1:2. DETAILED DESCRIPTION

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0043] Example 1

[0044] Weigh 1g of P34HB powder, slowly add the weighed P34HB to 49g of dichloromethane solvent, transfer the mixed solution to a round-bottom flask with a condenser reflux device and stir, heat to 60°C during stirring, and stir for about 6 hours to obtain a P34HB solution. Weigh 6g of PLA particles, slowly add the weighed PLA to 44g of dichloromethane solvent, and magnetically stir at room temperature for about 6 hours to obtain a PLA solution. Measure 4mL of P34HB solution and 8mL of PLA solution, blend them, magnetically stir for 30min at room temperature, ultrasonically disperse for 40min, and then magnetically stir for 30min to obtain a spinning solution. The spinning solution is transferred to a plastic syringe, and microfluidic spinning is performed with anhydrous ethanol as the coagulation bath at an extrusion speed of 1.5mL / h. The obtained fiber is dried at room temperature. The average diameter of the fiber obtained under this condition is 49.13μm, and the elongation at break is as high as close to 400% ( Figure 3 ).

[0045] Example 2

[0046] Weigh 1g of P34HB powder, slowly add the weighed P34HB to 49g of dichloromethane solvent, transfer the mixed solution to a round-bottom flask with a condenser reflux device and stir, heat to 60°C during stirring, and stir for about 6 hours to obtain a P34HB solution. Weigh 6g of PLA particles, slowly add the weighed PLA to 44g of dichloromethane solvent, and magnetically stir at room temperature for about 6 hours to obtain a PLA solution. Measure 4mL of P34HB solution and 8mL of PLA solution, blend them, magnetically stir for 30min at room temperature, ultrasonically disperse for 40min, and then magnetically stir for 30min to obtain a spinning solution. The spinning solution is transferred to a plastic syringe, and microfluidic spinning is performed with anhydrous ethanol as the coagulation bath at an extrusion speed of 2mL / h. The obtained fiber is dried at room temperature. The average diameter of the fiber obtained under this condition is slightly increased to 51.69μm, the strip uniformity is good, and the breaking strength is high ( Figure 3 ).

[0047] Example 3

[0048] Weigh 1g of P34HB powder and slowly add the weighed P34HB to 49g of dichloromethane solvent. Transfer the mixture to a round-bottom flask with a condenser reflux device and stir. During the stirring process, heat it to 60°C and stir for about 6 hours to obtain a P34HB solution. Weigh 6g of PLA particles and slowly add the weighed PLA to 44g of dichloromethane solvent. Stir magnetically at room temperature for about 6 hours to obtain a PLA solution. Measure 4mL of P34HB solution and 8mL of PLA solution, blend them, stir magnetically at room temperature for 30min, disperse them ultrasonically for 40min, and then stir magnetically for 30min to obtain a spinning solution. Transfer the spinning solution to a plastic syringe, use anhydrous ethanol as a coagulation bath, and perform microfluidic spinning at an extrusion rate of 2.5mL / h. The obtained fibers are dried at room temperature. Under these conditions, the average diameter of the fibers obtained continues to increase to 67.34μm, while the breaking strength decreases ( Figure 3 ).

[0049] Example 4

[0050] Weigh 1g of PHB powder, slowly add the weighed PHB to 49g of dichloromethane solvent, transfer the mixed solution to a round-bottom flask with a condenser reflux device and stir, heat to 60°C during stirring, stir for about 6 hours to obtain a PHB solution. Weigh 6g of PLA particles, slowly add the weighed PLA to 44g of dichloromethane solvent, and magnetically stir at room temperature for about 6 hours to obtain a PLA solution. Measure 4mL of PHB solution and 8mL of PLA solution, blend them, magnetically stir at room temperature for 30min, ultrasonically disperse for 40min, and then magnetically stir for 30min to obtain a spinning solution. Transfer the spinning solution to a plastic syringe, use anhydrous ethanol as a coagulation bath, and perform microfluidic spinning at an extrusion speed of 2mL / h. The obtained fiber is dried at room temperature. The fiber obtained under this condition has good uniformity ( Figure 4 ).

[0051] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A microfluidic preparation method for polyhydroxyalkanoate fibers, characterized in that: The steps include: S11: prepare PHA solution and PLA solution respectively; The PHA solution is prepared by adding polyhydroxyalkanoate to dichloromethane and heating at 50-80° C. for 4-8 hours; The PLA solution is obtained by adding dichloromethane to polylactic acid; S12: mixing the PHA solution and the PLA solution to obtain a spinning solution; S13: performing microfluidic spinning on the spinning solution and drying to obtain the polyhydroxyalkanoate fiber; the coagulation bath of the microfluidic spinning is selected from ethanol, and the extrusion rate is 1-3 mL / h.

2. The preparation method according to claim 1, wherein In the step S11, polyhydroxyalkanoate and polylactic acid are added to dichloromethane under stirring conditions and mixed by magnetic stirring.

3. The preparation method according to claim 1, wherein In the PHA solution, the polyhydroxyalkanoate is selected from poly-3-hydroxybutyrate-4-hydroxybutyrate or poly-3-hydroxybutyrate, and the concentration of the solute is 2-8 wt %.

4. The preparation method according to claim 1, wherein In the PLA solution, the concentration of the solute is 8-12 wt %.

5. The preparation method according to claim 1, wherein In the step S11, condensation reflux is used during heating, and stirring is performed.

6. The preparation method according to claim 1, wherein In step S11, the PLA solution is prepared by adding dichloromethane to polylactic acid and stirring at room temperature for 4-8 hours.

7. The preparation method according to claim 1, wherein In the spinning solution, the volume ratio of polyhydroxyalkanoate to polylactic acid is 1-2:1-2.

8. The preparation method according to claim 1, wherein In the step S12, the mixing method is to stir for 30-60 minutes, then ultrasonically disperse for 30-60 minutes, and then magnetically stir at room temperature for 30-60 minutes.

9. The preparation method according to claim 1, wherein In the step S13, the microfluidic spinning is followed by drying at room temperature.

10. A polyhydroxyalkanoate fiber prepared by the preparation method according to any one of claims 1 to 9.

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