A method for preparing hemp fiber based on combined degumming by photocatalysis and organic acid treatment

Abstract

This invention discloses a method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming, comprising the following steps: (1) placing hemp bast fibers into a reactor, adding a weak acid reagent for pretreatment, washing the hemp fibers until neutral after pretreatment, and drying them; (2) adding a photocatalyst into a glass reactor to prepare a degumming solution, and placing the hemp fibers pretreated with the weak acid into the degumming solution for phototreatment, and removing the hemp fibers after phototreatment; (3) washing and drying the hemp fibers obtained in step (2) to obtain degummed hemp fibers. This invention utilizes a photocatalyst and organic acid to remove pectin, lignin, and other non-cellulose gum components from hemp fibers. The degumming conditions are mild, causing little damage to the hemp fibers, and the organic acid can be recycled, resulting in less waste liquid and less environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of textile processing technology, specifically to a method for preparing hemp fibers based on a combination of photocatalysis and organic acid treatment for degumming. Background Technology

[0002] Hemp is a natural bast fiber. As a high-quality natural cellulose resource, hemp fiber is multifunctional. End products made from hemp can be applied in many areas, such as textiles, construction, papermaking, medicine, biofuels, food, and biocomposite materials. Hemp fiber has a bast fiber structure, consisting of individual cellulose protofibrils bound together by a gum substance, mainly composed of hemicellulose, pectin, waxes, water-soluble materials, and lignin. Because a large amount of gum substance increases the toughness and yellowing of hemp fibers, directly limiting further utilization, it is essential to extract high-quality hemp fiber from hemp without sacrificing the physical properties or chemical structure of cellulose. Therefore, hemp should be degummed before spinning and textile production to obtain soft and fine spun hemp fibers.

[0003] Currently, degumming methods for hemp mainly include physical degumming, traditional alkaline boiling degumming, biological degumming, organic solvent degumming, and combined degumming methods. Among them, physical degumming methods are often used as pretreatment because they are incomplete. Traditional alkaline boiling degumming is relatively stable and widely used, but it is energy-intensive and causes serious pollution. Biological enzymatic degumming can significantly reduce pollution emissions, but the degumming enzymes have a single function and require chemical reagents. Organic solvent degumming can recover the degumming liquid, but the solvent cost is extremely high, wastewater requires further treatment, and the degumming effect of organic solvents is limited, also suffering from incomplete degumming. Therefore, there is an urgent need to develop a degumming method that is mild, has low environmental pollution, and provides good degumming effect. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing hemp fibers based on a combination of photocatalysis and organic acid treatment for degumming. This method features mild reaction conditions, minimal environmental pollution, good degumming effect, and minimal damage to the hemp fibers.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming includes the following steps:

[0007] (1) Place the bast fibers of hemp into a reactor, add a weak acid reagent for pretreatment, wash the hemp fibers until neutral after pretreatment, and dry them.

[0008] (2) Add the photocatalyst to the glass reactor to prepare the degumming solution, and put the hemp fiber pretreated with weak acid into the degumming solution for phototreatment. After the phototreatment is completed, take out the hemp fiber.

[0009] (3) The hemp fibers obtained in step (2) are washed and dried to obtain degummed hemp fibers.

[0010] Furthermore, in step (1), the solid-liquid ratio of hemp bast fibers to weak acid reagent is 1:10 to 30.

[0011] Furthermore, the mass concentration of the weak acid reagent in step (1) is 10-30%.

[0012] Furthermore, the weak acid reagent in step (1) is at least one of glycolic acid and lactic acid.

[0013] Furthermore, in step (1), the weak acid pretreatment temperature is 80-100℃ and the pretreatment time is 2-6h.

[0014] Furthermore, in step (2), the photocatalyst is a catalyst that can be excited in the visible light wavelength range, and the amount of photocatalyst used is 2 to 6 g / kg of hemp fiber.

[0015] In the above technical solution, the photocatalyst is a catalyst that can be excited in the visible light wavelength range. Specifically, TiO2-CQDs, ZnO-CQDs, ZnIn2S4 or other photocatalysts can be selected. This type of photocatalyst can be excited in the visible light wavelength range, and visible light accounts for 45% of the total solar energy. It has high light utilization rate, thereby improving the degumming effect.

[0016] Furthermore, the light treatment time in step (2) is 20 to 60 hours.

[0017] Furthermore, the light source used in the illumination process in step (2) is sunlight or simulated sunlight, and simulated sunlight is a light-emitting diode or a xenon lamp.

[0018] Furthermore, in step (2), the solid bath ratio of hemp fiber to degumming solution is 1:10 to 100.

[0019] Furthermore, the bast fiber of the hemp is one of ramie, hemp, apocynum venetum, kenaf, or jute.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention provides a method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming. The method utilizes weak acid pretreatment and photocatalysis to remove waxy, pectin, lignin, hemicellulose and other gum components from hemp bast fibers. The operation process is simple, the degumming conditions are mild, the degumming effect is good, and the damage to hemp fibers is small. Moreover, the organic acid can be recycled, resulting in less waste liquid and less environmental pollution. Attached Figure Description

[0022] To clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 SEM image of raw hemp before degumming treatment;

[0024] Figure 2 SEM image of hemp fibers treated with TiO2-CQDs and acid combined with light irradiation as provided in Example 1. Detailed Implementation

[0025] This invention provides a method for preparing hemp fiber based on a combination of photocatalysis and organic acid treatment for degumming. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] The present invention will now be described in detail with reference to the accompanying drawings.

[0027] Example 1

[0028] This embodiment provides a method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming, including the following steps:

[0029] (1) Place the hemp bast fiber into a reactor and add glycolic acid reagent with a mass concentration of 20% for pretreatment. The solid-liquid ratio of hemp bast fiber to glycolic acid reagent is 1:20. Heat the fiber at 100°C for 4 hours. After the pretreatment is completed, wash the hemp fiber until it is neutral and put it in an oven to dry until the fiber weight no longer changes.

[0030] (2) Add 400ml of 5g / L TiO2 2-CQDs suspension was added to a 30L glass reactor to prepare a degumming solution. 1000g of hemp fiber that had been pretreated with weak acid and dried was placed in the degumming solution. Water was added to make the solid-bath ratio of hemp fiber to degumming solution 1:20. The solution was placed under sunlight for 4 days, specifically 12 hours of light treatment followed by 12 hours of darkness treatment, and this process was repeated for 4 days. After the light treatment was completed, the hemp fiber was removed.

[0031] (3) The hemp fibers obtained in step (2) are washed and dried to obtain degummed hemp fibers.

[0032] Example 2

[0033] This embodiment provides a method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming, including the following steps:

[0034] (1) Place the hemp bast fiber into a reactor and add glycolic acid reagent with a mass concentration of 10% for pretreatment. The solid-liquid ratio of hemp bast fiber to glycolic acid reagent is 1:30. Heat the fiber at 80°C for 5 hours. After the pretreatment is completed, wash the hemp fiber until it is neutral and put it in an oven to dry until the fiber weight no longer changes.

[0035] (2) Add 500ml of 8g / L ZnIn2S4 suspension to a 30L glass reactor to prepare a degumming solution, and put 1000g of hemp fiber pretreated with weak acid into the degumming solution. Add water to make the solid bath ratio of hemp fiber to degumming solution 1:60. Treat with LED light for 20h. After the light treatment is completed, take out the hemp fiber.

[0036] (3) The hemp fibers obtained in step (2) are washed and dried to obtain degummed hemp fibers.

[0037] Comparative Example 1

[0038] This comparative example provides a method for degumming hemp fibers using a photocatalyst, including the following steps:

[0039] (1) Add 400ml of 5g / L TiO2-CQDs suspension to a 30L glass reactor to prepare a degumming solution, and put 1000g of hemp bast fiber into the degumming solution. Add water to make the solid bath ratio of hemp bast fiber to solution 1:20, and treat in the dark for 4 days. Then take out the hemp fiber.

[0040] (2) Wash and dry the hemp fiber to obtain degummed hemp fiber.

[0041] Comparative Example 2

[0042] This comparative example provides a method for degumming hemp fibers using a photocatalyst, including the following steps:

[0043] (1) Add 400ml of 5g / L TiO2-CQDs suspension to a 30L glass reactor to prepare a degumming solution, and put 1000g of hemp fiber into the degumming solution. Add water to make the solid bath ratio of hemp fiber to solution 1:20, and perform sunlight treatment for 4 days. Specifically, after 12 hours of light treatment, the solution is dark for 12 hours. Repeat this process for 4 days. After the light treatment is completed, take out the hemp fiber.

[0044] (2) Wash and dry the hemp fiber to obtain degummed hemp fiber.

[0045] Comparative Example 3

[0046] This comparative example provides a method for degumming hemp fibers using acid treatment, including the following steps:

[0047] (1) Place the hemp bast fiber into a reactor and add glycolic acid reagent with a mass concentration of 20% for pretreatment. The solid-liquid ratio of hemp bast fiber to glycolic acid reagent is 1:20. Heat the fiber at 100°C for 4 hours. After the pretreatment is completed, wash the hemp fiber until it is neutral and put it in an oven to dry until the fiber weight no longer changes.

[0048] (2) Take 1000g of hemp fiber pretreated with weak acid and put it into a 30L glass reactor, add water, the solid bath ratio of hemp fiber to solution is 1:20, and perform dark treatment for 4 days, and then take out the hemp fiber.

[0049] (3) Wash and dry the hemp fiber to obtain degummed hemp fiber.

[0050] Comparative Example 4

[0051] This comparative example provides a method for degumming hemp fibers using acid treatment, including the following steps:

[0052] (1) Place the hemp bast fiber into a reactor and add glycolic acid reagent with a mass concentration of 20% for pretreatment. The solid-liquid ratio of hemp bast fiber to glycolic acid reagent is 1:20. Heat the fiber at 100°C for 4 hours. After the pretreatment is completed, wash the hemp fiber until it is neutral and put it in an oven to dry until the fiber weight no longer changes.

[0053] (2) Take 1000g of hemp fiber pretreated with weak acid and put it into a 30L glass reactor and add water. The solid bath ratio of hemp fiber to solution is 1:20. Then, it is subjected to sunlight treatment for 4 days. Specifically, it is subjected to sunlight treatment for 12 hours and then to darkness treatment for 12 hours. This process is repeated for 4 days. Then, the hemp fiber is taken out.

[0054] (3) Wash and dry the hemp fiber to obtain degummed hemp fiber.

[0055] Comparative Example 5

[0056] This comparative example provides a method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming, including the following steps:

[0057] (1) Place the hemp bast fiber into a reactor and add glycolic acid reagent with a mass concentration of 20% for pretreatment. The solid-liquid ratio of hemp bast fiber to glycolic acid reagent is 1:20. Heat the fiber at 100°C for 4 hours. After the pretreatment is completed, wash the hemp fiber until it is neutral and put it in an oven to dry until the fiber weight no longer changes.

[0058] (2) Add 400ml of 5g / L TiO2 2- CQDs suspension was added to a 30L glass reactor to prepare a degumming solution. 1000g of hemp fiber pretreated with weak acid was placed in the degumming solution. Water was added to make the solid bath ratio of hemp fiber to degumming solution 1:20. The solution was treated in the dark for 4 days. After the treatment was completed, the hemp fiber was taken out.

[0059] (3) The hemp fibers obtained in step (2) are washed and dried to obtain degummed hemp fibers.

[0060] Scanning electron microscopy was used to test the hemp bast fibers before degumming treatment and the degummed hemp fibers from Example 1 above. Figure 1 , 2 .from Figure 1 It can be seen that the surface of the raw hemp fibers before degumming is rough, covered with a thick layer of gum, and the fibers aggregate to form bundles; from Figure 2 As can be seen, after combined photocatalysis with acid treatment and light irradiation, the hemp fibers are separated into individual fibers, and the fiber surface is relatively smooth with low gum content.

[0061] In addition, the chemical composition of the degummed hemp fiber and the undegummed hemp bast fiber prepared in Example 1 and Comparative Examples 1-5 were tested, and the test results are shown in Table 1. The physical properties of the hemp bast fiber and the degummed hemp fiber prepared in Example 1 were also tested, and the test results are shown in Table 2.

[0062] The methods for testing the above chemical composition and physical properties are as follows:

[0063] Test method for chemical composition: The residual gum rate of degummed hemp fiber was tested according to GB 5889–1986 "Quantitative Analysis Method for Chemical Composition of Ramie".

[0064] Fineness test method: Refer to GB / T 6100–2007 "Test method for linear density of cotton fiber - mid-section weighing method" to test the fineness of degummed hemp fiber.

[0065] Test method for bundle fiber strength: The strength of degummed hemp fiber is tested in accordance with GB / T 5882–1986 "Test method for breaking strength of ramie bundle fiber".

[0066] Table 1

[0067]

[0068] Table 2

[0069] Fineness (dtex) Fracture strength (cN / dtex) Hemp bast fiber 8.42±0.08 4.35±0.98 Example 1 6.71±0.14 4.18±0.86

[0070] As can be seen from Table 1 above, Example 1, which uses weak acid and TiO2-CQDs under light conditions, has the highest removal rate of waxes, pectins, lignin, hemicellulose, and other gums in the prepared hemp fibers. Compared with Example 1, Comparative Example 5, which is treated under dark conditions, has higher contents of waxes, pectins, lignin, and hemicellulose. Comparative Example 1, which is treated under dark conditions with TiO2-CQDs, still has a high content of each gum. Comparative Example 2, which is treated only with TiO2-CQDs under light conditions, still has a high content of each gum, with only a slight decrease in lignin and hemicellulose. Comparative Examples 3 and 4, which are treated with weak acid under dark or light conditions, remove some of the pectin, waxes, lignin, and hemicellulose, but the contents of pectin, lignin, and hemicellulose are still relatively high.

[0071] As can be seen from Table 2 above, Example 1 uses a combined degumming process with weak acid and TiO2-CQDs photocatalyst. After degumming, the fiber fineness is 6.71 dtex and the breaking strength is 4.18 cN / dtex. The degumming effect is good, the amount of glue adhering between the single fibers is reduced, the hemp fiber fineness is finer, and the fiber has better dispersibility. The reaction conditions in Example 1 are mild, causing less damage to the hemp fiber, so that the hemp fiber has good breaking strength, and the breaking strength remains basically unchanged.

[0072] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0073] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing hemp fiber based on combined degumming using photocatalysis and organic acid treatment, characterized in that, Including the following steps: (1) Place the bast fibers of hemp into the reactor, add a weak acid reagent for pretreatment, wash the hemp fibers until neutral after pretreatment, and dry them; (2) Add the photocatalyst into the glass reactor to prepare the degumming solution, and put the hemp fibers pretreated with weak acid into the degumming solution for phototreatment. After the phototreatment is completed, take out the hemp fibers. (3) The hemp fibers obtained in step (2) are washed and dried to obtain degummed hemp fibers; The photocatalyst in step (2) is TiO2-CQDs, ZnO-CQDs, or ZnIn2S4.

2. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, In step (1), the solid-liquid ratio of hemp bast fibers to weak acid reagent is 1:10~30.

3. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, The mass concentration of the weak acid reagent in step (1) is 10-30%.

4. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, The weak acid reagent in step (1) is at least one of glycolic acid and lactic acid.

5. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, In step (1), the weak acid pretreatment temperature is 80~100℃ and the pretreatment time is 2~6h.

6. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, In step (2), the photocatalyst is a catalyst that can be excited in the visible light wavelength range, and the amount of photocatalyst used is 2~6g / kg hemp fiber.

7. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, The light treatment time in step (2) is 20~60h.

8. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, The light source used in step (2) during the illumination process is sunlight or simulated sunlight, and simulated sunlight is a light-emitting diode or a xenon lamp.

9. The method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to claim 1, characterized in that, In step (2), the solid bath ratio of hemp fiber to degumming solution is 1:10~100.

10. A method for preparing hemp fiber based on photocatalysis and organic acid treatment for combined degumming according to any one of claims 1-9, characterized in that, The bast fiber of the bast fiber is one of ramie, hemp, apocynum venetum, kenaf, or jute.

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