CN108587086B

CN108587086B - Preparation method for preparing foaming material by using banana nanofiber

Info

Publication number: CN108587086B
Application number: CN201810069998.9A
Authority: CN
Inventors: 孙健; 辛明; 李昌宝; 何雪梅; 周主贵; 零东宁; 李丽; 盛金凤; 郑凤锦; 李志春; 唐雅园; 李杰民; 刘国明
Original assignee: Guangxi Zhuang Nationality Autonomous Region Academy of Agricultural Sciences
Current assignee: Guangxi Zhuang Nationality Autonomous Region Academy of Agricultural Sciences
Priority date: 2018-01-24
Filing date: 2018-01-24
Publication date: 2020-09-29
Anticipated expiration: 2038-01-24
Also published as: CN108587086A

Abstract

The invention relates to the technical field of processing of foaming materials, in particular to a preparation method for preparing a foaming material by using banana nanofibers, which comprises the steps of preparing banana fibers, preparing the banana nanofibers and preparing the foaming material, wherein when the banana fibers are prepared, the banana fibers are subjected to puffing treatment, oxidation treatment, acid treatment, biological enzyme treatment, enzyme inactivation treatment, dehydration, oil supply and drying to carry out pretreatment on the banana hemp in a combined manner, so that colloid, lignin and hemicellulose in the banana hemp are effectively removed, impurity removal is realized, the fiber content is improved, and the compatibility of the foaming material is improved; this application uses banana fiber processing nanofiber and potato starch, polylactic acid, sodium silicate to prepare the expanded material can effectively improve expanded material's foaming efficiency, improves expanded material's quality.

Description

Preparation method for preparing foaming material by using banana nanofiber

[ technical field ] A method for producing a semiconductor device

The invention relates to the technical field of processing of foam materials, in particular to a preparation method for preparing a foam material by using banana nanofibers.

[ background of the invention ]

The foaming material has the advantages of light weight, heat resistance, low price and the like, is widely applied to industry, agriculture, packaging industry, transportation industry and the like, and is mainly concentrated on polystyrene foaming materials, polypropylene foaming materials, polyurethane foaming materials and polyethylene foaming materials in China. The traditional foaming material is not easy to degrade in the environment and causes certain pollution to the environment. Since the problem of "white pollution" caused by the conventional foamed plastic wastes is receiving increasing attention from countries of the world, many countries have legislation that prohibits the production of foam products that are difficult to degrade. At present, some researches on plant fiber foaming materials are also carried out, and the plant fiber foaming materials are prepared by adding starch, plant fibers (waste newspapers, wheat straws, other plant fibers and the like) and auxiliary agents through a foaming process. The main raw materials of the product are starch and plant fiber, which can not cause pollution to the environment, thereby effectively solving the contradiction between economic growth and resource shortage and environmental pollution.

However, the plant fiber raw material is an internal cross-linked structure formed by hydrogen bond connection on the fiber surface, and large gaps exist among fiber molecules, which is not beneficial to the storage of gas in the foaming process; the fiber macromolecules have uneven length and size and more impurities, and like waste paper fibers contain chemicals added in the papermaking process and ink remained on the surfaces of the fibers in the printing process; moreover, the plant fiber is a hydrophilic substance and has a technical defect of high hygroscopicity. At present, domestic reports on the preparation of the foaming material by using the plant fiber mainly refer to fiber materials with larger fiber particle sizes such as straw, waste paper and the like, and reports on the application of banana fiber to the foaming material are not provided, banana stems, stems and leaves contain rich fiber components, if the banana stems, stems and leaves can be used for producing the foaming material, the foaming performance of the foaming material can be further improved, bananas contain abundant cellulose and a large amount of colloid, lignin, and the colloid and lignin can improve the heat resistance of the foaming material, but the lignin and the colloid have a phase separation phenomenon and have lower biocompatibility, so that the foaming material is easy to have the phase separation phenomenon, and therefore, how to pretreat the banana fiber and improve the compatibility of the foaming material is a technical problem to be solved when the banana fiber is used for producing the foaming material.

[ summary of the invention ]

In view of the above, there is a need to produce a nanofiber foam material with high foaming performance, which further improves the utilization field and value of banana waste, and improves the added value of banana waste.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method for preparing a foaming material by using banana nanofibers comprises the following steps:

preparing banana fiber:

(1) pretreatment of raw materials: cutting banana peel, leaf or stem into sections, then breaking and tearing into slices with the thickness of 0.5-2 mm, squeezing, scraping impurities and drying to obtain rough ramie;

(2) degumming treatment: sequentially carrying out puffing treatment, oxidation treatment, acid treatment, biological enzyme treatment, enzyme inactivation treatment, dehydration, oil feeding and drying on the coarse ramie obtained in the step (1) to obtain coarse fibers;

the processing method of the puffing treatment comprises the following steps: mixing crude hemp with a sodium hydroxide solution with the mass concentration of 2g/L-4g/L according to the solid-liquid mass ratio of 1:17-22, quickly heating to 95-100 ℃, decocting at constant temperature for 20min-30min, draining the sodium hydroxide solution, fishing out the crude hemp, putting the crude hemp into hot water with the pressure condition of 7MPa-8MPa and the temperature of 90-95 ℃ for 10min-15min, draining the hot water, putting the crude hemp into cold water with the pressure condition of 2MPa-3MPa and the temperature of 0-5 ℃ for 10min-15min, filtering and airing to finish the bulking treatment process;

the treatment method of the oxidation treatment comprises the following steps: mixing the bulked crude ramie with an oxidant solution according to a solid-liquid mass ratio of 1:20-25, then rapidly heating to 95-100 ℃, decocting at a constant temperature for 15-20 min, draining the oxidant solution, putting the crude ramie into hot water at a temperature of 90-95 ℃, keeping the constant temperature for 5-10 min, then putting the crude ramie into cold water at a temperature of 0-5 ℃, keeping the constant temperature for 5-10 min, filtering, and airing to finish the oxidation treatment process;

the acid treatment method comprises the following steps: mixing the oxidized crude ramie with a sulfuric acid solution with the mass concentration of 1g/L-3g/L according to the solid-liquid mass ratio of 1:15-20, then rapidly heating to 95-100 ℃, decocting at constant temperature for 15min-20min, taking out the crude ramie, putting the crude ramie into hot water with the temperature of 90-95 ℃ for washing for 5min, then putting the crude ramie into cold water with the temperature of 0-5 ℃ for washing for 10min, and then airing to finish the acid treatment process;

the treatment method of the biological enzyme treatment comprises the following steps: mixing the acid-treated crude ramie with a biological enzyme solution according to a solid-liquid mass ratio of 1:18-23, keeping the temperature at 30-40 ℃ for 20-25 min, taking out the crude ramie, and putting the crude ramie into cold water at 0-5 ℃ for washing for 10 min; finishing the biological enzyme treatment process;

the treatment method of the enzyme inactivation treatment comprises the following steps: putting the crude ramie treated by the biological enzyme into hot water with the temperature of 85-90 ℃, and decocting for 30-35 min at constant temperature; completing the enzyme inactivation treatment process;

the dehydration treatment method comprises the following steps: putting the enzyme-inactivated crude ramie into a vacuum diatomite filter press with the vacuum degree of 0.01MPa-0.1MPa for vacuum filter pressing to complete the dehydration treatment process;

the oil feeding treatment method comprises the following steps: uniformly spraying a layer of tea seed oil on the dehydrated rough ramie to finish the oil feeding treatment process;

the drying treatment method comprises the following steps: placing the oiled crude ramie into a hot air dryer at the temperature of 50-60 ℃ until the water content of the crude ramie is 3-5% to obtain banana fiber;

(II) preparing banana nanofiber:

(3) mixing the crude fiber obtained in the step (2) with a cellulose binary system to obtain a banana fiber dissolving solution; preparing the polylactic-co-glycolic acid powder into spinning solution; mixing the banana fiber dissolving solution, the aloe extract, the chitosan and the spinning solution according to the mass ratio of 2-4:1-3:1-3:1, removing bubbles by using ultrasonic waves, and processing by using an electrostatic spinning process to obtain banana nanofibers;

(III) preparing a foaming material:

(4) pretreatment of banana nanofibers: mixing the banana nanofibers obtained in the step (3) with a sodium hydroxide solution with the mass concentration of 1g/L-3g/L according to the mass ratio of 1:16-20, uniformly stirring, soaking in ice water at the temperature of-2-0 ℃ for 2h-4h, heating to 90-95 ℃, soaking at a constant temperature for 3h-5h, filtering to obtain filter residue, washing the filter residue with clear water to be neutral, and then drying the filter residue in a vacuum drying oven at the temperature of 50-55 ℃ until the water content is 5%, thereby completing the pretreatment process;

(5) preparing a foaming material: mixing the banana nanofibers, polylactic acid, potato starch and sodium silicate pretreated in the step (1) according to the mass ratio of 1:10-15:3-5:1-3, then carrying out magnetic stirring for 3h-5h at 40-50 ℃ to obtain a mixed solution, putting the mixed solution into an internal mixer for carrying out honey refining to remove gas in the mixed solution, carrying out hot pressing on the mixed solution after gas removal to form a film, balancing the film material with carbon dioxide at the temperature of 30-40 ℃ and the pressure of 15-30 MPa, and then carrying out pressure relief, foaming and molding to obtain the foaming material.

Further, the oxidant solution in the step (2) is prepared by mixing hydrogen peroxide, methyl orange, a salix populi extract and water according to the mass ratio of 3-5:1-3:6-9: 30-35.

Further, the biological enzyme solution in the step (2) is prepared by mixing pectinase, hemicellulase, lignin degrading enzyme, barbaloin and water according to the mass ratio of 2-4:2-4:1-3:5-9: 30-35.

Further, the cellulose binary system in the step (3) comprises a lithium chloride/dimethylacetamide system or an ammonia/ammonium thiocyanate system.

Further, the lithium chloride/dimethylacetamide system is prepared by mixing lithium chloride, dimethylacetamide and water according to a mass ratio of 4-6:1: 10-15.

Further, the ammonia/ammonium thiocyanate system is prepared by mixing ammonium thiocyanate, ammonia and water according to the mass ratio of 65-75:25-30: 1.

Further, the preparation method of the spinning solution in the step (3) comprises the following steps: mixing tetrahydrofuran and dimethylformamide according to the volume ratio of 3-4:1 to obtain a mixed solvent; mixing the polylactic glycolic acid powder with the mixed solvent according to the mass ratio of 1:10-15, and standing overnight at the temperature of 1-4 ℃.

Further, the electrostatic spinning process in the step (3) has the following process conditions: the positive voltage is 10kV to 20kV, the negative voltage is 1kV to 3kV, the propelling flow rate is 1mL/h to 1.5mL/h, and the receiving distance is 15cm to 25cm, and the electrostatic spinning process has the following process conditions: the positive voltage is 10kV to 20kV, the negative voltage is 1kV to 3kV, the propelling flow rate is 1mL/h to 1.5mL/h, and the receiving distance is 15cm to 25 cm.

Further, the temperature of the internal mixer in the step (5) is 160-170 ℃, and the time of the internal mixer is 6-10 min; the hot pressing temperature is 160-170 ℃, and the hot pressing pressure is 17-20 Mpa; the flow rate of carbon dioxide in the carbon dioxide equilibrium process is 1-2 mL/h.

The invention has the following beneficial effects:

1. the banana nanofiber processing method comprises the steps of carrying out puffing treatment, oxidation treatment, acid treatment, biological enzyme treatment, enzyme inactivation treatment, dehydration, oil supply and drying on banana hemp, wherein the pretreatment is carried out on the banana hemp by combining the steps of the puffing treatment, the oxidation treatment, the acid treatment, the biological enzyme treatment, the enzyme inactivation treatment, the dehydration, the oil supply and the drying, the colloid and the impurity removal in the banana hemp can be effectively removed, so that the fiber content is increased, the puffing treatment is carried out on the hemp by soaking the hemp in high-temperature alkali liquor, the acting force among the colloids can be effectively weakened, the lignin is dissolved, then the puffing is carried out on the hemp by firstly heating and pressurizing and then quickly reducing the pressure, the hydrogen bond breakage among the colloids is accelerated, the colloid macromolecules are scattered, the; although the rough ramie is subjected to the swelling treatment, the colloid and lignin components in the rough ramie cannot be dissolved and separated, and further treatment is needed, the swelling treatment is carried out on the rough ramie and an oxidant (prepared by hydrogen peroxide, methyl orange, a salix populi extract and water) to effectively remove the induction force among the colloids, the colloid and the lignin are more effectively dissolved, the hydrogen peroxide has strong oxidizing property, but the structure of cellulose can be damaged by using excessive hydrogen peroxide, and the inventor researches and discovers that when the hydrogen peroxide is matched with the methyl orange and the salix populi extract according to a certain amount, the decomposition capability of the colloid and the lignin can be effectively improved, and the strength of the cellulose can be effectively maintained; after the swelling and oxidation treatment, the fiber can not meet the requirement of producing the nanofiber, the acid treatment is carried out by a sulfuric acid solution, the fiber is rapidly cooled after being heated by the acid treatment, the toughness of the fiber can be effectively improved, and the fineness of the nanofiber can be conveniently improved in the later-stage production of the nanofiber; however, although the banana fiber is subjected to puffing, oxidation and acid treatment, part of the pectin, lignin and hemicellulose decomposed into small molecules after puffing are still attached to the cellulose, and in order to further purify the fiber content of the banana fiber, a corresponding biological enzyme solution (pectinase, hemicellulase, lignin degrading enzyme, barbaloin and water) is prepared according to the characteristics of the components of the pectin to specifically decompose the pectin, lignin and hemicellulose, so that impurities are effectively removed, the fiber content is improved, and preparation is made for next-step production of the nanofiber; after the pretreatment of puffing, oxidation, acidification and biological enzyme, the cellulose content of the banana fiber is relatively pure, and then the banana fiber is sprayed by using tea seed oil, so that the fiber components can be effectively protected, the unsaturated acid content of the fiber can be improved, the electrolytic capacity of the banana fiber spinning solution is improved, and the thinner nanometer banana fiber can be produced; the application also uses the electrostatic spinning process to prepare the nano banana fiber, the process can effectively improve the yield of the nano banana fiber, can effectively remove impurities and produce the nano banana fiber with finer fineness, therefore, the method for producing the nano banana fiber can effectively improve the fineness of the banana fiber, remove the impurities and further improve the quality of the banana nano fiber.

2. The application uses banana nanofibers to prepare the foam material, after the banana fibers are processed to be nano-scale, intermolecular inductive force is reduced, and the cells of the foam material cannot be damaged, but because the banana nanofiber has too small particle size, the entanglement effect of fiber particles and an adhesive can be weakened by using the conventional adhesive, and the conventional adhesive is not beneficial to gas storage, therefore, the application also adds potato starch which has large molecular size and viscosity and can firmly adsorb the banana nanofibers in the starch, but the viscosity of the starch is still insufficient to support the cells of the foam material, the applicant finds through research that the addition of the polylactic acid powder can not only effectively improve the molecular particle size of the foam raw material, so that the adhesive viscosity of the foam base material is stronger and beneficial to foaming, and the molecular weight can effectively improve the mechanical property of the foam material, and improve the compression resistance and bending resistance, because the molecular structure of the polylactic acid powder is larger, if the polylactic acid powder can be successfully foamed, a certain amount of foaming agent needs to be added, therefore, the applicant adds the sodium silicate, the foaming efficiency can be effectively improved, meanwhile, the shape of the foam cells of the foaming material cannot be damaged, the larger the foam cells of the foaming material are, the lighter the material is, and the more convenient the application is.

[ detailed description ] embodiments

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

Any feature disclosed in this specification (including any accompanying claims, abstract) is merely an example of a generic series of equivalent or similar features, unless explicitly described as such.

Example 1:

preparing banana fiber:

(1) pretreatment of raw materials: cutting banana peel, leaf or stem into sections, then breaking and tearing into slices with the thickness of 0.5mm, squeezing, scraping impurities and drying to obtain rough ramie;

the processing method of the puffing treatment comprises the following steps: mixing crude hemp with a sodium hydroxide solution with the mass concentration of 2g/L according to the solid-liquid mass ratio of 1:17, then rapidly heating to 95 ℃, boiling at constant temperature for 20min, draining the sodium hydroxide solution, fishing out the crude hemp, putting the crude hemp into hot water with the pressure condition of 7MPa and the temperature of 90 ℃ for constant temperature keeping for 10min, then draining the hot water, putting the crude hemp into cold water with the pressure condition of 2MPa and the temperature of 0 ℃ for constant temperature keeping for 10min, filtering and airing to finish the swelling treatment process;

the treatment method of the oxidation treatment comprises the following steps: mixing the bulked crude ramie with an oxidant solution according to a solid-liquid mass ratio of 1:20, rapidly heating to 95 ℃, decocting at a constant temperature for 15min, draining the oxidant solution, putting the crude ramie into hot water at a temperature of 90 ℃, keeping the constant temperature for 5min, putting the crude ramie into cold water at a temperature of 0 ℃, keeping the constant temperature for 5min, filtering, and airing to finish an oxidation treatment process;

the acid treatment method comprises the following steps: mixing the oxidized crude ramie with a sulfuric acid solution with the mass concentration of 1g/L according to the solid-liquid mass ratio of 1:15, then rapidly heating to 95 ℃, decocting at constant temperature for 15min, taking out the crude ramie, putting the crude ramie into hot water with the temperature of 90 ℃ for washing for 5min, then putting the crude ramie into cold water with the temperature of 0 ℃ for washing for 10min, and then airing to finish the acid treatment process;

the treatment method of the biological enzyme treatment comprises the following steps: mixing the acid-treated crude hemp with a biological enzyme solution according to a solid-liquid mass ratio of 1:18-23, keeping the temperature at 30 ℃ for 20min, taking out the crude hemp, and washing the crude hemp in cold water at 0 ℃ for 10 min; finishing the biological enzyme treatment process;

the treatment method of the enzyme inactivation treatment comprises the following steps: putting the crude hemp after the biological enzyme treatment into hot water of 85 ℃, and decocting for 30min at constant temperature; completing the enzyme inactivation treatment process;

the dehydration treatment method comprises the following steps: putting the enzyme-inactivated crude ramie into a vacuum diatomite filter press with the vacuum degree of 0.01MPa for vacuum filter pressing to complete the dehydration treatment process;

the drying treatment method comprises the following steps: putting the oiled crude ramie into a hot air dryer at 50 ℃ until the water content of the crude ramie is 3% to obtain crude fiber;

(II) preparing banana nanofiber:

(3) preparing nano fibers: mixing the crude fiber obtained in the step (2) with a cellulose binary system to obtain a banana fiber dissolving solution; preparing the polylactic-co-glycolic acid powder into spinning solution; mixing the banana fiber dissolving solution, the aloe extract, the chitosan and the spinning solution according to a mass ratio of 2:1:1, mixing, removing bubbles by using ultrasound, and performing electrostatic spinning process treatment to obtain the banana nanofiber, wherein the process conditions of the electrostatic spinning process treatment are as follows: the positive voltage is 10kV, the negative voltage is 1kV, the propelling flow rate is 1mL/h, and the receiving distance is 15 cm;

(III) preparing a foaming material:

(4) pretreatment of banana nanofibers: mixing the banana nanofibers obtained in the step (3) with a sodium hydroxide solution with the mass concentration of 1g/L according to the mass ratio of 1:16, uniformly stirring, soaking in ice water at the temperature of-2 ℃ for 2 hours, heating to 90 ℃, soaking at the constant temperature for 3 hours, filtering to obtain filter residues, washing the filter residues with clear water to be neutral, then putting the filter residues into a vacuum drying oven at the temperature of 50 ℃ for drying until the moisture content is 5%, and finishing the pretreatment process;

(5) preparing a foaming material: mixing the banana nanofiber pretreated in the step (1), polylactic acid, potato starch and sodium silicate according to the mass ratio of 1:10:3:1, then carrying out magnetic stirring for 3 hours at 40 ℃ to obtain a mixed solution, and putting the mixed solution into an internal mixer for honey refining to remove gas in the mixed solution, wherein the honey refining temperature of the internal mixer is 160 ℃, and the honey refining time is 6 min; hot-pressing the mixed solution after the gas is removed by the honey into a film at the temperature of 160 ℃ and the pressure of 17Mpa, balancing the film material with carbon dioxide at the temperature of 30 ℃ and the pressure of 15Mpa at the flow rate of 1mL/h, and finally decompressing, foaming and molding to obtain the foaming material.

Wherein the oxidant solution is prepared by mixing hydrogen peroxide, methyl orange, salix populi extract and water according to the mass ratio of 3:1:6: 30.

In the oxidant solution, the extraction method of the salix populi extract comprises the following steps: drying poplar bark and then crushing the dried poplar bark into 300 meshes, mixing the powder with 75% ethanol solution by volume according to a solid-to-liquid ratio of 1:5, putting the mixture into an ultrasonic extractor, and performing intermittent ultrasonic extraction at a power of 400w, wherein the total extraction time of the intermittent extraction is 2 hours, namely ultrasonic extraction for 2min, stopping the ultrasonic extraction for 10s and ultrasonic extraction for 2 min; performing ultrasonic extraction, placing the mixture into a reflux extractor, performing constant temperature extraction at 150 deg.C for 12h, and performing rotary evaporation and concentration on the extractive solution until the water content is 5% to obtain Salix babylonica extract with Salix babylonica glycoside content of 98.09 mg/g; the content of sodium salicylate is 146.09 mg/g.

Wherein the biological enzyme solution is prepared by mixing pectinase, hemicellulase, lignin degrading enzyme, barbaloin and water according to the mass ratio of 2:2:1:5: 30.

In the biological enzyme solution, the enzyme activity of the pectinase is 1000U/g: the enzyme activity of the hemicellulase is 800U/g, and the enzyme activity of the lignin degrading enzyme is 1200U/g.

Wherein the cellulose binary system is a lithium chloride/dimethylacetamide system or an ammonia/ammonium thiocyanate system.

The lithium chloride/dimethylacetamide system is prepared by mixing lithium chloride, dimethylacetamide and water according to a mass ratio of 4:1: 10.

The preparation method of the spinning solution comprises the following steps: mixing tetrahydrofuran and dimethylformamide according to the volume ratio of 3:1 to obtain a mixed solvent; mixing the polylactic glycolic acid powder with the mixed solvent according to the mass ratio of 1:10, and standing overnight at the temperature of 1 ℃.

Example 2:

preparing banana fiber:

(1) pretreatment of raw materials: cutting banana peel, leaf or stem into sections, then breaking and tearing into slices with the thickness of 2mm, squeezing, scraping impurities and drying to obtain rough ramie;

the processing method of the puffing treatment comprises the following steps: mixing the crude ramie with a sodium hydroxide solution with the mass concentration of 4g/L according to the solid-liquid mass ratio of 1:22, then rapidly heating to 100 ℃, decocting at constant temperature for 30min, draining the sodium hydroxide solution, fishing out the crude ramie, putting the crude ramie into hot water with the pressure condition of 8MPa and the temperature of 95 ℃ for constant temperature for 15min, draining the hot water, putting the crude ramie into cold water with the pressure condition of 3MPa and the temperature of 5 ℃ for constant temperature for 15min, filtering and airing to finish the puffing treatment process;

the treatment method of the oxidation treatment comprises the following steps: mixing the bulked crude ramie with an oxidant solution according to a solid-liquid mass ratio of 1:25, quickly heating to 100 ℃, decocting at a constant temperature for 20min, draining the oxidant solution, putting the crude ramie into hot water at a temperature of 95 ℃, keeping the constant temperature for 10min, putting the crude ramie into cold water at a temperature of 5 ℃, keeping the constant temperature for 10min, filtering, and airing to finish an oxidation treatment process;

the acid treatment method comprises the following steps: mixing the oxidized crude ramie with a sulfuric acid solution with the mass concentration of 3g/L according to the solid-liquid mass ratio of 1:20, then rapidly heating to 100 ℃, decocting at constant temperature for 20min, taking out the crude ramie, washing in hot water with the temperature of 95 ℃ for 5min, washing in cold water with the temperature of 5 ℃ for 10min, and then drying in the air to finish the acid treatment process;

the treatment method of the biological enzyme treatment comprises the following steps: mixing the acid-treated crude hemp with a biological enzyme solution according to a solid-liquid mass ratio of 1:23, keeping the temperature at 40 ℃ for 25min, taking out the crude hemp, and putting the crude hemp into cold water at 5 ℃ for washing for 10 min; finishing the biological enzyme treatment process;

the treatment method of the enzyme inactivation treatment comprises the following steps: putting the crude hemp after the biological enzyme treatment into hot water of 90 ℃, and decocting for 35min at constant temperature; completing the enzyme inactivation treatment process;

the dehydration treatment method comprises the following steps: putting the enzyme-inactivated crude ramie into a vacuum diatomite filter press with the vacuum degree of 0.1MPa for vacuum filter pressing to complete the dehydration treatment process;

the drying treatment method comprises the following steps: putting the oiled crude ramie into a hot air dryer at the temperature of 60 ℃ until the moisture content of the crude ramie is 5 percent to obtain crude fiber;

(II) preparing banana nanofiber:

(3) preparing nano fibers: mixing the crude fiber obtained in the step (2) with a cellulose binary system to obtain a banana fiber dissolving solution; preparing the polylactic-co-glycolic acid powder into spinning solution; mixing the banana fiber dissolving solution, the aloe extract, the chitosan and the spinning solution according to the mass ratio of 4:3:3:1, removing bubbles by using ultrasonic waves, and performing electrostatic spinning process treatment to obtain the banana nanofibers, wherein the electrostatic spinning process treatment process conditions are as follows: the positive voltage was 20kV, the negative voltage was 3kV, the flow rate of propulsion was 1.5mL/h, and the reception distance was 25 cm.

(III) preparing a foaming material:

(4) pretreatment of banana nanofibers: mixing the banana nanofibers obtained in the step (3) with a sodium hydroxide solution with the mass concentration of 3g/L according to the mass ratio of 1:20, uniformly stirring, soaking in ice water at 0 ℃ for 4 hours, heating to 95 ℃, soaking at constant temperature for 5 hours, filtering to obtain filter residues, washing the filter residues with clear water to be neutral, then putting the filter residues into a vacuum drying oven at 55 ℃ for drying until the moisture content is 5%, and finishing the pretreatment process;

(5) preparing a foaming material: mixing the banana nanofiber pretreated in the step (1), polylactic acid, potato starch and sodium silicate according to the mass ratio of 1:15:5:3, then carrying out magnetic stirring for 5 hours at 50 ℃ to obtain a mixed solution, and putting the mixed solution into an internal mixer for honey refining to remove gas in the mixed solution, wherein the honey refining temperature of the internal mixer is 170 ℃, and the honey refining time is 10 min; hot-pressing the mixed solution after the gas is removed by the honey into a film at the temperature of 170 ℃ and the pressure of 20Mpa, balancing the film material with carbon dioxide at the temperature of 40 ℃ and the pressure of 30Mpa at the flow rate of 2mL/h, and finally decompressing, foaming and molding to obtain the foaming material.

Wherein the oxidant solution is prepared by mixing hydrogen peroxide, methyl orange, salix populi extract and water according to the mass ratio of 5:3:9: 35.

In the oxidant solution, the extraction method of the salix populi extract is completely consistent with that of example 1.

Wherein the biological enzyme solution is prepared by mixing pectinase, hemicellulase, lignin degrading enzyme, barbaloin and water according to the mass ratio of 4:4:3:9: 35.

In the biological enzyme solution, the enzyme activity of the pectinase is 1500U/g: the enzyme activity of the hemicellulase is 1200U/g, and the enzyme activity of the lignin degrading enzyme is 1000U/g.

Wherein the cellulose binary system is a lithium chloride/dimethylacetamide system.

The lithium chloride/dimethylacetamide system is prepared by mixing lithium chloride, dimethylacetamide and water according to the mass ratio of 6:1: 15.

The preparation method of the spinning solution comprises the following steps: mixing tetrahydrofuran and dimethylformamide according to the volume ratio of 4:1 to obtain a mixed solvent; mixing the polylactic glycolic acid powder with the mixed solvent according to the mass ratio of 1:15, and standing overnight at 4 ℃.

Example 3:

preparing banana fiber:

(1) pretreatment of raw materials: cutting banana peel, leaf or stem into sections, then breaking and tearing into slices with the thickness of 1mm, squeezing, scraping impurities and drying to obtain rough ramie;

the processing method of the puffing treatment comprises the following steps: mixing crude hemp with a sodium hydroxide solution with the mass concentration of 3g/L according to the solid-liquid mass ratio of 1:20, then rapidly heating to 98 ℃, decocting at constant temperature for 25min, draining the sodium hydroxide solution, fishing out the crude hemp, putting the crude hemp into hot water with the pressure condition of 7.5MPa and the temperature of 92 ℃ for constant temperature maintenance for 12min, then draining the hot water, putting the crude hemp into cold water with the pressure condition of 2.5MPa and the temperature of 2 ℃ for constant temperature maintenance for 12min, filtering and airing to finish the bulking treatment process;

the treatment method of the oxidation treatment comprises the following steps: mixing the bulked crude ramie with an oxidant solution according to a solid-liquid mass ratio of 1:22, quickly heating to 98 ℃, decocting at a constant temperature for 17min, draining the oxidant solution, putting the crude ramie into hot water at a temperature of 92 ℃, keeping the constant temperature for 7min, putting the crude ramie into cold water at a temperature of 2 ℃, keeping the constant temperature for 7min, filtering, and airing to finish an oxidation treatment process;

the acid treatment method comprises the following steps: mixing the oxidized crude ramie with a sulfuric acid solution with the mass concentration of 2g/L according to the solid-liquid mass ratio of 1:17, then rapidly heating to 98 ℃, decocting at constant temperature for 18min, taking out the crude ramie, washing in hot water with the temperature of 92 ℃ for 5min, washing in cold water with the temperature of 2 ℃ for 10min, and drying in the air to finish the acid treatment process;

the treatment method of the biological enzyme treatment comprises the following steps: mixing the acid-treated crude hemp with a biological enzyme solution according to a solid-liquid mass ratio of 1:20, keeping the temperature at 35 ℃ for 22min, taking out the crude hemp, and putting the crude hemp into cold water at 3 ℃ for washing for 10 min; finishing the biological enzyme treatment process;

the treatment method of the enzyme inactivation treatment comprises the following steps: putting the crude hemp after the biological enzyme treatment into hot water of 87 ℃, and decocting for 32min at constant temperature; completing the enzyme inactivation treatment process;

the dehydration treatment method comprises the following steps: putting the enzyme-inactivated crude ramie into a vacuum diatomite filter press with the vacuum degree of 0.08MPa for vacuum filter pressing to complete the dehydration treatment process;

the drying treatment method comprises the following steps: putting the oiled crude ramie into a hot air dryer at the temperature of 55 ℃ until the moisture content of the crude ramie is 4% to obtain crude fiber;

(II) preparing banana nanofiber:

(3) preparing nano fibers: mixing the crude fiber obtained in the step (2) with a cellulose binary system to obtain a banana fiber dissolving solution; preparing the polylactic-co-glycolic acid powder into spinning solution; mixing the banana fiber dissolving solution, the aloe extract, the chitosan and the spinning solution according to a mass ratio of 3:2: 1, mixing, removing bubbles by using ultrasound, and performing electrostatic spinning process treatment to obtain the banana nanofiber, wherein the process conditions of the electrostatic spinning process treatment are as follows: the positive voltage was 15kV, the negative voltage was 2kV, the flow rate of propulsion was 1.2mL/h, and the reception distance was 20 cm.

(III) preparing a foaming material:

(4) pretreatment of banana nanofibers: mixing the banana nanofibers obtained in the step (3) with a sodium hydroxide solution with the mass concentration of 2g/L according to the mass ratio of 1:18, uniformly stirring, soaking in ice water at the temperature of-1 ℃ for 3 hours, heating to 92 ℃, soaking at constant temperature for 4 hours, filtering to obtain filter residues, washing the filter residues with clear water to be neutral, then putting the filter residues into a vacuum drying oven at the temperature of 52 ℃ for drying until the moisture content is 5%, and finishing the pretreatment process;

(5) preparing a foaming material: mixing the banana nanofiber pretreated in the step (1), polylactic acid, potato starch and sodium silicate according to the mass ratio of 1:12:4:2, then carrying out magnetic stirring for 4 hours at 45 ℃ to obtain a mixed solution, and putting the mixed solution into an internal mixer for honey refining to remove gas in the mixed solution, wherein the honey refining temperature of the internal mixer is 165 ℃, and the honey refining time is 8 min; hot-pressing the mixed solution after the gas is removed by the honey into a film at the temperature of 165 ℃ and the pressure of 19Mpa, balancing the film material with carbon dioxide at the temperature of 35 ℃ and the pressure of 25Mpa at the flow rate of 1.5mL/h, and finally decompressing, foaming and molding to obtain the foaming material.

Wherein the oxidant solution is prepared by mixing hydrogen peroxide, methyl orange, salix populi extract and water according to the mass ratio of 4:2:7: 33.

Wherein the biological enzyme solution is prepared by mixing pectinase, hemicellulase, lignin degrading enzyme, barbaloin and water according to the mass ratio of 3:3:2:7: 32.

In the biological enzyme solution, the enzyme activity of the pectinase is 1200U/g: the enzyme activity of the hemicellulase is 900U/g, and the enzyme activity of the lignin degrading enzyme is 1300U/g.

The lithium chloride/dimethylacetamide system is prepared by mixing lithium chloride, dimethylacetamide and water according to a mass ratio of 5:1: 13.

The preparation method of the spinning solution comprises the following steps: mixing tetrahydrofuran and dimethylformamide according to the volume ratio of 3.5:1 to obtain a mixed solvent; mixing the polylactic glycolic acid powder with the mixed solvent according to the mass ratio of 1:12, and standing overnight at the temperature of 3 ℃.

Example 4:

the other preparation method of this example is exactly the same as example 1, but the cellulose binary system uses an ammonia/ammonium thiocyanate system. Wherein the ammonia/ammonium thiocyanate system is prepared by mixing ammonium thiocyanate, ammonia and water according to the mass ratio of 65:25: 1.

Example 5:

the other preparation method of this example is exactly the same as example 2, but the cellulose binary system uses an ammonia/ammonium thiocyanate system. Wherein the ammonia/ammonium thiocyanate system is prepared by mixing ammonium thiocyanate, ammonia and water according to the mass ratio of 75:30: 1.

Example 6:

the other preparation method of this example is exactly the same as example 3, but the cellulose binary system uses an ammonia/ammonium thiocyanate system. Wherein the ammonia/ammonium thiocyanate system is prepared by mixing ammonium thiocyanate, ammonia and water according to the mass ratio of 70:28: 1.

Control group 1:

in the comparison group, the banana hemp is pretreated without using puffing treatment in the process of preparing the banana fiber, and other parameters and methods are completely consistent with those of the embodiment 1.

Control group 2:

in the comparison group, the banana hemp is pretreated without oxidation treatment in the process of preparing the banana fiber, and other parameters and methods are completely consistent with those of the embodiment 1.

Control group 3:

the control group does not use acid treatment to pretreat the banana hemp during the preparation of the banana fiber, and other parameters and methods are completely consistent with those of the example 1.

Control group 4:

in the control group, the banana hemp is pretreated without using biological enzyme treatment in the process of preparing the banana fiber, and other parameters and methods are completely consistent with those of the embodiment 1.

Control group 5:

the control group does not use tea seed oil to pretreat the banana fiber in the process of preparing the banana fiber, and other parameters and methods are completely consistent with those of the embodiment 1.

Control group 6:

the banana nanofibers are not used for preparing the foaming material, the crude fibers of the bananas are used for pretreatment and then are directly mixed with polylactic acid, potato starch and sodium silicate to prepare the foaming material, and other parameters and methods are completely consistent with those of example 1.

Control group 7:

the banana nanofibers are not pretreated when the foam material is prepared, namely, the nanofibers prepared in the step (3) are directly mixed with polylactic acid, potato starch and sodium silicate to prepare the foam material, and other parameters and methods are completely consistent with those of the embodiment 1.

Control group 8:

the pretreated banana nanofibers, polylactic acid, potato starch and sodium silicate are mixed to prepare the foaming material, and other parameters and methods are completely consistent with those of example 1.

Control group 9:

the pretreated banana nanofibers, the potato starch and the sodium silicate are mixed to prepare the foaming material, and other parameters and methods are completely consistent with those of example 1.

Control group 10:

the pretreated banana nanofibers, polylactic acid and sodium silicate are mixed to prepare the foaming material, and other parameters and methods are completely consistent with those of example 1.

Control group 11:

the pretreated banana nanofibers, polylactic acid and potato starch are mixed to prepare the foaming material, and other parameters and methods are completely consistent with those of example 1.

Control group 12:

the polylactic acid, the potato starch and the sodium silicate are mixed to prepare the foaming material, and other parameters and methods are completely consistent with example 1.

Test run 1:

after pretreatment of banana fiber, examples 1-6 and control groups 1-5 of the present application were tested for the contents of lipo-waxy, hemicellulose, pectin, water soluble, lignin, cellulose and gum content components, and the results are shown in table 1:

table 1 units: is based on

As can be seen from the above table, after pretreatment of the stems, stalks and leaves of bananas in examples 1 to 6 and control groups 1 to 5, the contents of lipo-waxes, hemicellulose, pectin, water-soluble substances, lignin, cellulose and gum content of examples 1 to 6 and control groups 1 to 5 are substantially the same.

Test run 2:

the banana nanofibers of examples 1-6 and control groups 1-5 were tested for residual gum ratio, residual lignin, fineness, and tenacity, and the test results are shown in table 2:

TABLE 2

Group of	Residual gum ratio (%)	Residual lignin (%)	Average length (μm)	Average diameter (nm)	Strength (cN)
						Example 1	0.23	0.98	465	68	58.36
Example 2	0.21	0.94	451	69	56.21
						Example 3	0.27	0.96	463	61	57.26
Example 4	0.22	0.91	478	59	56.09
						Example 5	0.24	0.97	471	64	57.08
Example 6	0.26	0.99	469	65	56.97
						Control group 1	0.56	2.01	264	231	26.31
Control group 2	0.61	2.03	263	232	23.54
						Control group 3	0.63	2.61	271	236	26.35
Control group 4	0.64	2.74	273	237	23.15
						Control group 5	0.26	1.06	105	361	16.35

As can be seen from the above table, the residual gum content and the residual lignin content of examples 1 to 6 are lower than those of control groups 1 to 4, and are equivalent to that of control group 5; the degumming treatment is carried out by the steps of puffing treatment, oxidation treatment, acid treatment and biological enzyme, the residual gum rate and the residual lignin content of the fiber can be effectively reduced, and the residual gum rate and the residual lignin content of the banana fiber cannot be influenced by the oil feeding treatment of the tea seed oil; the average length of the examples 1 to 6 is longer than that of the control groups 1 to 4 and longer than that of the control group 5, which shows that the degumming treatment of the steps of the swelling treatment, the oxidation treatment, the acid treatment and the biological enzyme can effectively improve the length of the nano fiber, and the oil feeding of the tea seed oil is more beneficial to producing longer nano fiber; the average diameter of the examples 1 to 6 is smaller than that of the control group 1 to 4 and is even smaller than that of the control group 5, which shows that the degumming treatment of the steps of the puffing treatment, the oxidation treatment, the acid treatment and the biological enzyme can effectively reduce the diameter of the nano fiber, the oil feeding of the tea seed oil is more beneficial to producing the nano fiber with a finer diameter and can improve the fineness of the nano fiber; the strength of the examples 1 to 6 is higher than that of the control groups 1 to 4 and higher than that of the control group 5, which shows that the degumming treatment of the steps of the puffing treatment, the oxidation treatment, the acid treatment and the biological enzyme can effectively improve the strength of the nano fiber, and the oil feeding of the tea seed oil is more beneficial to producing the nano fiber with higher strength.

Test run 3:

the foamed materials of examples 1 to 6 and comparative examples 1 to 11 were tested for their average cell diameter, cell shape under electron microscope observation, foaming properties (including apparent density and cell density), and mechanical properties (including impact strength, flexural strength and amount of compressed film), and specifically shown in Table 3:

TABLE 3

As can be seen from the above table, the average diameters of the foam pores of examples 1 to 6 are larger than those of the reference groups 1 to 5 and are all spherical, which indicates that the foam pores of the foam material can be larger and the foaming effect is better due to the expanding treatment, the oxidizing treatment, the acid treatment and the biological enzyme degumming of the banana fiber; the average diameter of the cells of the control group 6 is smaller than that of the cells of the examples 1-6, and the shape of the cells is rhombic, which shows that the foam material prepared by using the banana nanofiber has better foaming effect and is finer than the foam material prepared by using the banana coarse fiber; the average diameter of the cells of the control 7 is smaller than that of the examples 1-6, but the shape of the cells is spherical, which shows that the banana nanofibers do not affect the quality of the cells without pretreatment, but affect the expansion effect of the foam; the average diameter of the cells of controls 8-12 was significantly smaller than that of examples 1-6, and the cells were diamond, oval, and elongated irregular in shape, indicating that the present application prepares the starting materials for the foamed material: the lack of one raw material in the preparation of the foaming material from the raw materials of banana nanofiber, polylactic acid, potato starch and sodium silicate can affect the foaming rate and the foam cell quality of the foaming material; while the apparent densities of examples 1-6 are less than those of controls 1-12, and the cell densities of examples 1-6 are greater than those of controls 1-12, indicating that the foamed films of the present application are lighter and more compact than controls 1-12, indicating that examples 1-6 have better foaming efficiencies than controls 1-12; the impact strength, flexural strength and compressive film content of examples 1-6 were all greater than those of controls 1-12, indicating that the mechanical properties of examples 1-6 were better than those of controls 1-12.

In conclusion, the banana nanofibers produced by the method for preparing the foam material can obviously improve the foaming efficiency of the foam material, improve the quality of foam holes and enable the foam material to be lighter, and have stronger impact resistance, bending strength and compression film amount.

The above examples are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A preparation method for preparing a foaming material by using banana nanofibers is characterized by comprising the following steps of:

preparing banana fiber:

the drying treatment method comprises the following steps: placing the oiled crude ramie into a hot air dryer at the temperature of 50-60 ℃ to dry the crude ramie until the water content of the crude ramie is 3-5% to obtain banana fiber;

(II) preparing banana nanofiber:

(III) preparing a foaming material:

(5) preparing a foaming material: mixing the banana nanofibers, polylactic acid, potato starch and sodium silicate pretreated in the step (1) according to a mass ratio of 1:10-15:3-5:1-3, then carrying out magnetic stirring for 3h-5h at 40-50 ℃ to obtain a mixed solution, placing the mixed solution into an internal mixer for milling to remove gas in the mixed solution, carrying out hot pressing on the mixed solution after gas removal to form a film, balancing the film material with carbon dioxide at a temperature of 30-40 ℃ and a pressure of 15MP a-30MP a, and then carrying out pressure relief, foaming and molding to obtain the foaming material;

the oxidant solution in the step (2) is prepared by mixing hydrogen peroxide, methyl orange, salix populi extract and water according to the mass ratio of 3-5:1-3:6-9: 30-35;

the cellulose binary system in the step (3) comprises a lithium chloride/dimethylacetamide system or an ammonia/ammonium thiocyanate system.

2. The method of claim 1, wherein the bio-enzyme solution of step (2) is prepared by mixing pectinase, hemicellulase, lignin degrading enzyme, barbaloin and water at a mass ratio of 2-4:2-4:1-3:5-9: 30-35.

3. The preparation method according to claim 1, wherein the lithium chloride/dimethylacetamide system is prepared by mixing lithium chloride, dimethylacetamide and water in a mass ratio of 4-6:1: 10-15.

4. The method according to claim 1, wherein the ammonia/ammonium thiocyanate system is prepared by mixing ammonium thiocyanate, ammonia and water in a mass ratio of 65-75:25-30: 1.

5. The preparation method according to claim 1, wherein the spinning solution of step (3) is prepared by: mixing tetrahydrofuran and dimethylformamide according to the volume ratio of 3-4:1 to obtain a mixed solvent; mixing the polylactic glycolic acid powder with the mixed solvent according to the mass ratio of 1:10-15, and standing overnight at the temperature of 1-4 ℃.

6. The preparation method according to claim 1, wherein the electrostatic spinning process of step (3) has the following process conditions: the positive voltage is 10kV to 20kV, the negative voltage is 1kV to 3kV, the propelling flow rate is 1mL/h to 1.5mL/h, and the receiving distance is 15cm to 25 cm.

7. The preparation method according to claim 1, characterized in that the banbury mixer of the step (5) has a mixing temperature of 160 ℃ to 170 ℃ and a mixing time of 6min to 10 min; the hot pressing temperature is 160-170 ℃, and the hot pressing pressure is 17MP a-20 MPa; the flow rate of carbon dioxide in the carbon dioxide equilibrium process is 1-2 mL/h.