CN113956501B - Modified lignin and preparation method thereof, modified lignin-reinforced polyvinyl alcohol fiber and preparation method and application thereof - Google Patents
Modified lignin and preparation method thereof, modified lignin-reinforced polyvinyl alcohol fiber and preparation method and application thereof Download PDFInfo
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- CN113956501B CN113956501B CN202111355929.2A CN202111355929A CN113956501B CN 113956501 B CN113956501 B CN 113956501B CN 202111355929 A CN202111355929 A CN 202111355929A CN 113956501 B CN113956501 B CN 113956501B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
- C08H6/00—Macromolecular compounds derived from lignin, e.g. tannins, humic acids
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D10/00—Physical treatment of artificial filaments or the like during manufacture, i.e. during a continuous production process before the filaments have been collected
- D01D10/02—Heat treatment
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/06—Wet spinning methods
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/12—Stretch-spinning methods
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/12—Stretch-spinning methods
- D01D5/14—Stretch-spinning methods with flowing liquid or gaseous stretching media, e.g. solution-blowing
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/10—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one other macromolecular compound obtained by reactions only involving carbon-to-carbon unsaturated bonds as constituent
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/18—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from other substances
Abstract
The invention provides modified lignin and a preparation method thereof, modified lignin-reinforced polyvinyl alcohol fiber and a preparation method and application thereof, and relates to the technical field of composite materials. The preparation method of the modified lignin provided by the invention comprises the following steps: mixing lignin and a gluconic acid solution, and carrying out esterification reaction to obtain the modified lignin. According to the invention, the gluconic acid solution is adopted to modify lignin, the raw materials are green, environment-friendly and renewable, the modification process is simple and controllable, and the obtained modified lignin can enhance the mechanical property and the processability of the polyvinyl alcohol fiber.
Description
Technical Field
The invention relates to the technical field of composite materials, and particularly relates to modified lignin and a preparation method thereof, a modified lignin-reinforced polyvinyl alcohol fiber and a preparation method and application thereof.
Background
Lignin, the natural polymer with the highest aromatic ring content in nature, is the second largest renewable resource next to cellulose, and mainly originates from papermaking black liquor and by-products of biorefinery. Due to the low utilization of lignin, most of the lignin is consumed only as fuel. The method for preparing the biomass chemicals by using the lignin as the raw material has important significance for reducing the dependence of the industrial boundary on non-renewable resources.
The lignin as additive is used in polyvinyl alcohol and other polymer to raise the mechanical performance and degradability of the product. However, poor aggregation of lignin in polymers such as polyvinyl alcohol can cause deterioration of the mechanical properties of the polymer. In order to further improve the mechanical property and the processability of the lignin-polyvinyl alcohol fiber, an additional polar small molecule reinforcement such as graphene oxide, cellulose nanocrystals and the like is often required to be added, which, however, will greatly increase the cost of the raw material and is not beneficial to the practical application in industry.
Disclosure of Invention
The invention aims to provide modified lignin and a preparation method thereof, and modified lignin-reinforced polyvinyl alcohol fiber and a preparation method and application thereof. The modified lignin reinforced polyvinyl alcohol fiber prepared by using the modified lignin as the additive has higher mechanical property and processability.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of modified lignin, which comprises the following steps:
and mixing the lignin and the gluconic acid solution, and carrying out esterification reaction to obtain the modified lignin.
Preferably, the concentration of the gluconic acid solution is 30-60 wt%; the dosage ratio of the lignin to the gluconic acid solution is 1 g: 15-25 mL.
Preferably, the temperature of the esterification reaction is 120-160 ℃; the esterification reaction time is 12-48 h.
The invention provides the modified lignin prepared by the preparation method in the technical scheme.
The invention also provides a preparation method of the modified lignin reinforced polyvinyl alcohol fiber, which comprises the following steps:
mixing the modified lignin, the polyvinyl alcohol and the solvent in the technical scheme to obtain spinning solution;
extruding the spinning dope into a coagulation bath to form gel fibers;
and sequentially carrying out air drafting and hot drafting on the gel fiber to obtain the modified lignin reinforced polyvinyl alcohol fiber.
Preferably, the mass ratio of the modified lignin to the polyvinyl alcohol is 0.5-5: 10; the mass fraction of polyvinyl alcohol in the spinning solution is 7-50%; the molecular weight of the polyvinyl alcohol is 5000-186000 g/mol.
Preferably, the coagulating bath is one or more of acetone, methanol, ethanol and butanol.
Preferably, the temperature of the hot drawing is 80-240 ℃.
The invention provides the modified lignin reinforced polyvinyl alcohol fiber prepared by the preparation method in the technical scheme.
The invention also provides application of the modified lignin reinforced polyvinyl alcohol fiber in the technical scheme in the textile field or the building field.
The invention provides a preparation method of modified lignin, which comprises the following steps: mixing lignin and a gluconic acid solution, and carrying out esterification reaction to obtain the modified lignin. According to the invention, the gluconic acid solution is adopted to modify lignin, the raw materials are green, environment-friendly and renewable, the price is low, the modification process is simple and controllable, and the obtained modified lignin can enhance the mechanical property and the processability of the polyvinyl alcohol fiber.
The invention also provides a preparation method of the modified lignin reinforced polyvinyl alcohol fiber, which comprises the following steps: mixing the modified lignin, the polyvinyl alcohol and the solvent in the technical scheme to obtain spinning solution; extruding the spinning dope into a coagulation bath to form gel fibers; and sequentially carrying out air drafting and hot drafting on the gel fiber to obtain the modified lignin reinforced polyvinyl alcohol fiber. The modified lignin prepared by the method has an anti-plasticizing effect, and can promote the formation of polyvinyl alcohol gel fiber crystals and improve the mechanical strength of fibers; the polar part of the modified lignin and the polyvinyl alcohol form hydrogen bonds and are uniformly dispersed in a polyvinyl alcohol matrix, the entanglement of polyvinyl alcohol molecular chains is reduced, the mobility of chain segments of the polyvinyl alcohol molecules above the glass transition temperature is increased, the maximum drafting rate of the fiber is obviously enhanced, the orientation of amorphous chain segments of the fiber is improved under the action of air drafting and heat drafting, the free volume is reduced, the structural defects of the fiber are healed, and the fiber is beneficial to absorbing, transferring and transferring loads, so that higher mechanical performance and processability are realized.
The invention also provides the application of the modified lignin reinforced polyvinyl alcohol fiber in the textile field or the building field, and the modified lignin reinforced polyvinyl alcohol fiber prepared by the invention can be applied to fiber reinforced composite materials, precursor fibers of carbon fibers and industrial textiles such as conveyor belts, cords, fishing nets and canvasses.
Drawings
FIG. 1 is a SEM image of the tensile fracture cross section of modified lignin-reinforced polyvinyl alcohol fibers prepared in comparative example 1 and examples 1 to 3;
FIG. 2 is an infrared spectrum of unmodified lignin and modified lignin 3;
FIG. 3 is the nuclear magnetic carbon spectrograms of unmodified lignin and modified lignin 3.
Detailed Description
The invention provides a preparation method of modified lignin, which comprises the following steps:
and mixing the lignin and the gluconic acid solution, and carrying out esterification reaction to obtain the modified lignin.
In the present invention, the lignin is preferably an organosolv lignin; the lignin is preferably in particulate form; the particle size of the lignin is preferably 0.3-1.2 μm.
In the invention, the concentration of the gluconic acid solution is preferably 30-60 wt%, and more preferably 49-53 wt%; the solvent of the gluconic acid solution is preferably water.
In the present invention, the ratio of the lignin to the gluconic acid solution is preferably 1 g: 15-25 mL, more preferably 1 g: 20 mL.
In the invention, the temperature of the esterification reaction is preferably 120-160 ℃, and more preferably 130-150 ℃; the time of the esterification reaction is preferably 12-48 h, and more preferably 24-48 h. In the present invention, the esterification reaction is preferably carried out in an oil bath. In the present invention, the esterification reaction is preferably carried out under stirring conditions; the stirring speed is preferably 300-500 rpm. In the esterification reaction process, the hydroxyl of lignin and the carboxyl of gluconic acid are combined through ester bonds.
According to the invention, preferably, after the esterification reaction, the obtained system is sequentially subjected to precipitation, washing and drying to obtain the modified lignin. In the present invention, the precipitation is preferably ice water precipitation. In the present invention, the washing is preferably water washing, more preferably deionized water washing. In the present invention, the drying temperature is preferably 65 ℃ and the time is preferably 12 hours.
The invention provides the modified lignin prepared by the preparation method in the technical scheme.
The invention also provides a preparation method of the modified lignin reinforced polyvinyl alcohol fiber, which comprises the following steps:
mixing the modified lignin, the polyvinyl alcohol and the solvent to obtain spinning solution;
extruding the spinning dope into a coagulation bath to form gel fibers;
and sequentially carrying out air drafting and hot drafting on the gel fiber to obtain the modified lignin reinforced polyvinyl alcohol fiber.
The invention mixes the modified lignin, the polyvinyl alcohol and the solvent to obtain the spinning solution. In the invention, the mass ratio of the modified lignin to the polyvinyl alcohol is preferably 0.5-5: 10, and more preferably 0.5:10, 1:10, 2:10, 3:10, 4:10 or 5: 10. In the invention, the mass fraction of the polyvinyl alcohol in the spinning solution is preferably 7-50%, and more preferably 10%.
In the invention, the molecular weight of the polyvinyl alcohol is preferably 5000-186000 g/mol, more preferably 146000-186000 g/mol; the alcoholysis degree of the polyvinyl alcohol is preferably 87-99%, and more preferably 97-99%. The polyvinyl alcohol fiber has the advantages of high molecular weight, narrow molecular weight distribution, less formed fiber defects, and contribution to forming a more perfect fiber structure, thereby improving the mechanical property of the polyvinyl alcohol fiber.
In the present invention, the solvent is preferably one or more of ethylene glycol, glycerol, dimethyl sulfoxide and water, and more preferably dimethyl sulfoxide. The solvent can enable the modified lignin and the polyvinyl alcohol to be mutually soluble.
In the invention, the mixing temperature of the modified lignin, the polyvinyl alcohol and the solvent is preferably 80-100 ℃, and more preferably 85-90 ℃.
After the spinning solution is obtained, the spinning solution is extruded into a coagulating bath to form the gel fiber.
In the present invention, the spinning dope is preferably extruded through an injection needle. In the invention, the coagulating bath is preferably one or more of acetone, methanol, ethanol and butanol, and more preferably a mixed solution of acetone and methanol; the volume ratio of acetone to methanol in the mixed solution of acetone and methanol is preferably 85: 15. in the present invention, the temperature of the coagulation bath is preferably room temperature or lower, more preferably 10 ℃ or lower, and still more preferably 0 ℃.
In the present invention, the diameter of the gel fiber is preferably 10 to 80 μm, and more preferably 30 to 50 μm.
After the gel fiber is obtained, the gel fiber is subjected to air drafting and hot drafting in sequence to obtain the modified lignin reinforced polyvinyl alcohol fiber. In the present invention, the temperature of the air draft is preferably room temperature; the draft multiple of the air draft is preferably 1.5-10, more preferably 2-8, and further preferably 2.8-3.9. In the invention, the air drafting can reduce the fineness of the gel fiber and improve the mechanical property.
In the present invention, it is preferable that after the air drawing, the drawn fiber is placed in a coagulation bath, subjected to solution substitution, and then subjected to hot drawing. In the invention, the coagulating bath is preferably one or more of acetone, methanol, ethanol and butanol, and more preferably a mixed solution of acetone and methanol; the volume ratio of acetone to methanol in the mixed solution of acetone and methanol is preferably 85: 15. in the present invention, the temperature of the coagulation bath is preferably 0 ℃ or lower, and more preferably-25 ℃; the time of the coagulation bath is preferably 24 h. In the present invention, air draft stretches the fiber by means of the deformation, but the deformation is easily recovered, and the orientation of the stretched fiber is fixed by the coagulation bath, which also facilitates the diffusion of the solvent in the spinning dope into the coagulation bath.
In the invention, the temperature of the hot drawing is preferably 80-240 ℃, and more preferably 120-220 ℃. In the present invention, the heat-drawing is preferably carried out in silicone oil; the hot drawing is preferably performed in one or more passes, more preferably in two or more passes, still more preferably in three or more passes, and particularly preferably in four passes. In the present invention, the drawing ratio of the hot drawing is the maximum drawing ratio that ensures continuous drawing of the fiber at the drawing temperature. In the embodiment of the invention, when the hot drawing is four passes, the hot drawing temperature is 133-154 ℃, 180 ℃, 200 ℃ and 220 ℃ from the first pass to the fourth pass in sequence; the draft multiple is 1.7-2.3 times, 1.4-1.6 times, 1.2-1.4 times and 1.2-1.3 times in sequence.
In the invention, the hot drawing can stretch the macromolecules along the drawing direction, reduce the fiber fineness, enable the macromolecule chains to approach each other, enhance the acting force and improve the mechanical property; the hot drawing can improve the fiber structure, and the solvent is diffused into the silicon oil from the interior of the fiber in the hot drawing process, so that the fiber with better section roundness and compact structure can be easily obtained.
The invention provides the modified lignin reinforced polyvinyl alcohol fiber prepared by the preparation method of the technical scheme.
The invention also provides the application of the modified lignin reinforced polyvinyl alcohol fiber in the textile field or the building field, and the modified lignin reinforced polyvinyl alcohol fiber is preferably applied to fiber reinforced composite materials, precursor fibers of carbon fibers and textiles; the textile preferably comprises a conveyor belt, cord, fishing net or canvas.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Example 1
Sequentially adding 1g of lignin and 20mL of gluconic acid solution (with the mass concentration of 50 wt%) into a stirrer at 120 ℃, and stirring and reacting for 12 hours in an oil bath; and after the reaction is finished, precipitating the product by using ice water, washing by using deionized water, filtering to remove the excessive gluconic acid solution, and then placing the filter cake in an oven for drying for 12 hours at 65 ℃ to obtain modified lignin, wherein the label of the modified lignin is modified lignin 1.
Adding polyvinyl alcohol (with the molecular weight of 146000-186000 g/mol and the alcoholysis degree of 99%) and the modified lignin 1 into a dimethyl sulfoxide solvent, and uniformly mixing to form a spinning stock solution; the dissolving temperature of the spinning solution is 85 ℃, the mass fraction of polyvinyl alcohol is 10%, and the mass of the modified lignin 1 is 5% of that of the polyvinyl alcohol;
extruding the spinning stock solution into an acetone/methanol (v: v, 85/15) coagulating bath at 0 ℃ through an injection needle, and coagulating the spinning stock solution into gel fibers at low temperature;
carrying out 1 air drafting on the gel fiber at room temperature, wherein the drafting multiple is 3.8 times; soaking the fiber subjected to air drawing in a coagulating bath (acetone/methanol, v: v, 85/15) at the temperature of-25 ℃ for gel aging for 24h, and then carrying out 4 times of hot drawing in silicone oil at the drawing temperatures of 143 ℃, 180 ℃, 200 ℃ and 220 ℃ respectively, wherein the drawing multiples are respectively 2, 1.4, 1.2 and 1.2 times, so as to obtain the modified lignin reinforced polyvinyl alcohol fiber marked as 5% modified lignin 1/polyvinyl alcohol composite fiber.
The SEM photograph of the 5% modified lignin 1/polyvinyl alcohol composite fiber prepared in this example is shown in fig. 1 (b), and it can be seen that the modified lignin-reinforced polyvinyl alcohol fiber prepared in the present invention has a circular cross section, a complete and uniform fiber structure, no pores, and fibrils oriented along the fiber axis and tightly stacked.
Example 2
Sequentially adding 1g of lignin and 20mL of gluconic acid solution (with the mass concentration of 50 wt%) into a stirrer at the temperature of 120 ℃, and stirring and reacting in an oil bath for 24 hours; and after the reaction is finished, precipitating the product by using ice water, washing by using deionized water, filtering to remove the excessive gluconic acid solution, and then placing the filter cake in an oven for drying for 12 hours at 65 ℃ to obtain modified lignin, wherein the label of the modified lignin is modified lignin 2.
Adding polyvinyl alcohol (with the molecular weight of 146000-186000 g/mol and the alcoholysis degree of 99%) and the modified lignin 2 into a dimethyl sulfoxide solvent, and uniformly mixing to form a spinning stock solution; the dissolving temperature of the spinning solution is 85 ℃, the mass fraction of polyvinyl alcohol is 10%, and the mass of the modified lignin 2 is 5% of that of the polyvinyl alcohol;
extruding the spinning stock solution into an acetone/methanol (v: v, 85/15) coagulating bath at 0 ℃ through an injection needle, and coagulating the spinning stock solution into gel fibers at low temperature;
carrying out 1 air drafting on the gel fiber at room temperature, wherein the drafting multiple is 3.8 times; soaking the fiber subjected to air drawing in a coagulating bath (acetone/methanol, v: v, 85/15) at the temperature of-25 ℃ for gel aging for 24 hours, and then performing 4 times of hot drawing in silicone oil at the drawing temperatures of 133 ℃, 180 ℃, 200 ℃ and 220 ℃ respectively, wherein the drawing multiples are respectively 1.7, 1.6, 1.4 and 1.2 times, so as to obtain the modified lignin reinforced polyvinyl alcohol fiber which is marked as 5% modified lignin 2/polyvinyl alcohol composite fiber.
The SEM photograph of the 5% modified lignin 2/polyvinyl alcohol composite fiber prepared in this example is shown in fig. 1 (c), and it can be seen that the modified lignin-reinforced polyvinyl alcohol fiber prepared in the present invention has a circular cross section, a complete and uniform fiber structure, no pores, and fibrils oriented along the fiber axis and tightly stacked.
Example 3
Sequentially adding 1g of lignin and 20mL of gluconic acid solution (with the mass concentration of 50 wt%) into a stirrer at 120 ℃, and stirring in an oil bath for reacting for 48 hours; and after the reaction is finished, precipitating the product by using ice water, washing by using deionized water, filtering to remove the excessive gluconic acid solution, and then placing the filter cake in an oven for drying for 12 hours at 65 ℃ to obtain modified lignin, wherein the label of the modified lignin is modified lignin 3.
Adding polyvinyl alcohol (with the molecular weight of 146000-186000 g/mol and the alcoholysis degree of 99%) and the modified lignin 3 into a dimethyl sulfoxide solvent, and uniformly mixing to form a spinning stock solution; the dissolving temperature of the spinning solution is 85 ℃, the mass fraction of polyvinyl alcohol is 10%, and the mass of the modified lignin 3 is 5% of the mass of the polyvinyl alcohol;
extruding the spinning stock solution into an acetone/methanol (v: v, 85/15) coagulating bath at 0 ℃ through an injection needle, and coagulating the spinning stock solution into gel fibers at low temperature;
carrying out 1 air drafting on the gel fiber at room temperature, wherein the drafting multiple is 3.9 times; soaking the fiber subjected to air drawing in a coagulating bath (acetone/methanol, v: v, 85/15) at the temperature of-25 ℃ for gel aging for 24 hours, and then performing 4 times of hot drawing in silicone oil at the drawing temperatures of 133 ℃, 180 ℃, 200 ℃ and 220 ℃ respectively, wherein the drawing multiples are respectively 1.7, 1.6, 1.3 and 1.2 times, so as to obtain the modified lignin reinforced polyvinyl alcohol fiber which is marked as 5% modified lignin 3/polyvinyl alcohol composite fiber.
The SEM photograph of the 5% modified lignin 3/polyvinyl alcohol composite fiber prepared in this example is shown in fig. 1 (d), and it can be seen that the modified lignin-reinforced polyvinyl alcohol fiber prepared in the present invention has a circular cross section, a complete and uniform fiber structure, no pores, and fibrils oriented along the fiber axis and tightly stacked.
Example 4
Sequentially adding 1g of lignin and 20mL of gluconic acid solution (with the mass concentration of 50 wt%) into a stirrer at the temperature of 120 ℃, and stirring and reacting in an oil bath for 48 hours; and after the reaction is finished, precipitating the product by using ice water, washing by using deionized water, filtering to remove the excessive gluconic acid solution, and then placing the filter cake in an oven for drying for 12 hours at 65 ℃ to obtain modified lignin, wherein the label of the modified lignin is modified lignin 3.
Adding polyvinyl alcohol (with the molecular weight of 146000-186000 g/mol and the alcoholysis degree of 99%) and the modified lignin 3 into a dimethyl sulfoxide solvent, and uniformly mixing to form a spinning stock solution; the dissolving temperature of the spinning solution is 85 ℃, the mass fraction of the polyvinyl alcohol is 10%, and the mass of the modified lignin 3 is 30% of the mass of the polyvinyl alcohol;
extruding the spinning stock solution into an acetone/methanol (v: v, 85/15) coagulating bath at 0 ℃ through an injection needle, and coagulating the spinning stock solution into gel fibers at low temperature;
carrying out 1 air drafting on the gel fiber at room temperature, wherein the drafting multiple is 2.8 times; soaking the fiber subjected to air drawing in a coagulating bath (acetone/methanol, v: v, 85/15) at the temperature of-25 ℃ for gel aging for 24 hours, and then performing 4 times of hot drawing in silicone oil at the drawing temperatures of 154 ℃, 180 ℃, 200 ℃ and 220 ℃ respectively, wherein the drawing multiples are 2.3 times, 1.5 times, 1.2 times and 1.3 times respectively, so as to obtain the modified lignin reinforced polyvinyl alcohol fiber marked as 30% modified lignin 3/polyvinyl alcohol composite fiber.
Comparative example 1
Essentially the same as in example 1, except that in the preparation of the modified lignin-reinforced polyvinyl alcohol fibers, unmodified lignin was used.
As shown in fig. 1 (a), it can be seen that the cross section of the unmodified lignin/polyvinyl alcohol composite fiber prepared in this comparative example is circular and has a complete structure, and the cross section is coarser than that of the modified lignin/polyvinyl alcohol fiber, and has no morphology of fibrils oriented along the fiber axis.
Comparative example 2
Essentially the same as in example 4, except that in the preparation of the modified lignin-reinforced polyvinyl alcohol fibers, unmodified lignin was used.
Test example 1
The mechanical properties and crystallinity (WAXD) of the modified lignin-reinforced polyvinyl alcohol fibers prepared in examples 1 to 4 were tested and compared with those of comparative examples 1 to 2, and the results are shown in table 1.
TABLE 1 results of mechanical Properties and crystallinity tests of examples 1 to 4 and comparative examples 1 to 2
As can be seen from Table 1, the modified lignin prepared by the method has a more significant enhancement effect on polyvinyl alcohol than unmodified lignin, and promotes the formation of polyvinyl alcohol fiber crystals. From the results of example 4 and comparative example 2, it can be seen that the effect of the modified lignin-reinforced polyvinyl alcohol fiber is higher than that of the unmodified lignin-reinforced polyvinyl alcohol fiber under the same conditions at a high addition content of 30%.
As can be seen from the detection results of the above examples and comparative examples, the modified lignin-reinforced polyvinyl alcohol fiber prepared by the invention has excellent tensile strength and toughness and good Young modulus, and can meet the requirements of the textile and building fields on high-performance polyvinyl alcohol fibers.
Test example 2
FIG. 2 is an infrared spectrum of unmodified lignin and modified lignin 3, and it can be seen from FIG. 2 that the modified lignin has a characteristic peak of new ester group (1755 cm) compared with the unmodified lignin-1) And a stronger characteristic peak of hydroxyl (3300-3400 cm)-1) It was confirmed that the modified lignin was bonded to gluconic acid via an ester bond.
FIG. 3 is a nuclear magnetic carbon spectrum of unmodified lignin and modified lignin 3. from FIG. 3, it can be seen that the modified lignin has a new ester group signal peak (173-176ppm) and signal peaks (60-80 ppm) of gluconic acid C2-C6, and the successful esterification of gluconic acid and lignin can be inferred.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A preparation method of modified lignin reinforced polyvinyl alcohol fiber comprises the following steps:
mixing the modified lignin, polyvinyl alcohol and a solvent to obtain a spinning solution;
extruding the spinning dope into a coagulation bath to form gel fibers;
sequentially carrying out air drafting and hot drafting on the gel fiber to obtain a modified lignin reinforced polyvinyl alcohol fiber;
the preparation method of the modified lignin comprises the following steps:
mixing lignin and a gluconic acid solution, and carrying out esterification reaction to obtain modified lignin; the concentration of the gluconic acid solution is 30-60 wt%; the dosage ratio of the lignin to the gluconic acid solution is 1 g: 15-25 mL; the temperature of the esterification reaction is 120-160 ℃; the esterification reaction time is 12-48 h.
2. The preparation method according to claim 1, wherein the mass ratio of the modified lignin to the polyvinyl alcohol is 0.5-5: 10; the mass fraction of polyvinyl alcohol in the spinning solution is 7-50%; the molecular weight of the polyvinyl alcohol is 5000-186000 g/mol.
3. The method of claim 1, wherein the coagulating bath is one or more of acetone, methanol, ethanol and butanol.
4. The method according to claim 1, wherein the temperature of the hot drawing is 80 to 240 ℃.
5. The modified lignin-reinforced polyvinyl alcohol fiber prepared by the preparation method of any one of claims 1 to 4.
6. The use of the modified lignin-reinforced polyvinyl alcohol fibers according to claim 5 in the textile or construction field.
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| CN100509891C (en) * | 2005-04-30 | 2009-07-08 | 江苏工业学院 | Process for preparing modified lignocellulose sulfonate graft copolymer |
| CN102604307B (en) * | 2012-03-08 | 2013-10-02 | 华东理工大学 | Polypropylene composite |
| US9340425B2 (en) * | 2012-10-09 | 2016-05-17 | Iowa State University Research Foundation, Inc. | Process of making carbon fibers from compositions including esterified lignin and poly(lactic acid) |
| CN104945573B (en) * | 2015-06-15 | 2018-05-01 | 中国科学院宁波材料技术与工程研究所 | The preparation method of the preparation method and lignin-base carbon fiber of lignin and acrylonitrile copolymer |
| DE102015120377A1 (en) * | 2015-11-25 | 2017-06-01 | Deutsche Institute Für Textil- Und Faserforschung Denkendorf | Process for the preparation of a lignin-based composition |
| EP3409727A1 (en) * | 2017-05-29 | 2018-12-05 | Annikki GmbH | Method for the preparation of a lignin prepolymer |
| DE102017128339A1 (en) * | 2017-11-29 | 2019-05-29 | Deutsche Institute Für Textil- Und Faserforschung Denkendorf | Modified lignin, process for its preparation and use |
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