Method for preparing fibrilia through microwave-assisted seawater degumming

Abstract

The invention discloses a method for preparing fibrilia by microwave-assisted seawater degumming, which comprises the following steps: (1) putting fibrilia into seawater according to the bath ratio of the fibrilia to the seawater of 1: (5-20), then putting into a microwave digestion container, carrying out microwave heating at the microwave heating temperature of 80-120 DEG C for 5-20 minutes under the microwave power of 400-600W, and taking out the fibrilia after the degumming is completed; and (2) washing, filtering and drying the fibrilia taken out after degumming in the step (1) to obtain the degummed fibrilia. The degumming method disclosed by the invention is simple to operate, degumming can be carried out by immersing the fibrilia into seawater and carrying out microwave heating, the use amount of fresh water is reduced, strong base and other chemical reagents do not need to be added, only two times of water washing is needed during degumming water washing, the discharge amount of wastewater is small, and the environmental pollution caused by degumming wastewater is small; the degumming method is high in degumming efficiency, low in energy consumption, mild in degumming condition and small in damage to the fibrilia.

Description

Technical Field

[0001] The present invention relates to the technical field of degumming of hemp fibers, and particularly relates to a method for preparing hemp fibers by microwave-assisted seawater degumming. Background Art

[0002] Hemp fiber is a high-end textile material with high strength, fast moisture absorption, moisture release and air permeability. Raw hemp contains LCC, also known as colloidal complex (25-30%), which is mainly composed of hemicellulose and lignin, etc. Before spinning and preparing textiles, it is necessary to degum the hemp to obtain soft and slender spinning hemp fibers. At present, for the degumming of hemp fibers, the most commonly used traditional alkali cooking chemical degumming has relatively stable degumming and a wide range of applications. However, it requires a large amount of fresh water in the degumming process. Calculated by producing one ton of scutched hemp, 450 tons of fresh water will be consumed, and the amount of degumming wastewater discharged annually is about 3 million tons, and the CODcr emission is about 7,500 tons. This not only causes environmental pollution, but also wastes fresh water resources, and the energy consumption is also high. Especially at present, the shortage of global fresh water resources is a major challenge. Especially in areas facing drought and water resource pressure, climate change and population growth will bring pressure on fresh water resources. Industries that rely heavily on a large amount of fresh water are facing pressure to adopt sustainable alternative solutions. Based on this, a method for preparing hemp fibers by microwave-assisted seawater degumming is proposed. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a method for preparing hemp fibers by microwave-assisted seawater degumming, which is environmentally friendly, economical, has good degumming effect and high degumming efficiency.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for preparing hemp fibers by microwave-assisted seawater degumming, comprising the steps of:

[0006] (1) Put the hemp fibers into seawater, then put them into a microwave digestion container, carry out microwave heating, and take them out after the degumming is completed;

[0007] (2) Wash, filter and dry the hemp fibers taken out after degumming in step (1) to obtain degummed hemp fibers.

[0008] Further, the bath ratio of the hemp fibers to seawater in step (1) is 1:5 to 20.

[0009] Further, the microwave heating temperature in step (1) is 80-120°C, and the microwave heating time is 5-20 min.

[0010] Further, the microwave power in step (1) is 400-600 W.

[0011] Further, in the step (1), the seawater is natural seawater.

[0012] Further, in the step (2), when washing with water, clean water is used for cleaning.

[0013] Further, in the step (2), the drying temperature is 90 - 110 °C.

[0014] Further, before putting the hemp fiber into the seawater, the hemp fiber is cut into a certain length and carded.

[0015] Further, the cutting length of the hemp fiber is 10 - 20 cm.

[0016] Further, the hemp fiber is one of ramie, cannabis, apocynum venetum, kenaf or jute.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The method for preparing hemp fiber by microwave-assisted seawater degumming provided by the present invention is simple in operation. The hemp fiber can be degummed by immersing it in seawater and performing microwave heating, reducing the fresh water consumption. Moreover, no strong alkali and other chemical reagents need to be added. Only 2 times of water washing are required during degumming and water washing, with a small wastewater discharge, and the degumming wastewater has little environmental pollution.

[0019] (2) The method for preparing hemp fiber by microwave-assisted seawater degumming provided by the present invention uses microwave for heating, and a good degumming effect can be achieved by microwave heating for 5 - 20 min. The degumming efficiency is high, and the energy consumption is less.

[0020] (3) The method for preparing hemp fiber by microwave-assisted seawater degumming provided by the present invention has a degumming effect basically the same as that of traditional alkali boiling degumming. And the degumming method of the present invention has less damage to the hemp fiber, and the degummed hemp fiber maintains a relatively high breaking strength. Description of the Drawings

[0021] Figure 1 It is the SEM photograph of hemp fiber. Among them, (a) is the SEM photograph of cannabis bast fiber, (b) is the SEM photograph of the degummed hemp fiber prepared in Comparative Example 1, and (c), (d) are the SEM photographs of the degummed hemp fiber prepared in Example 1. Detailed Embodiments

[0022] The present invention provides a method for preparing hemp fiber by microwave-assisted seawater degumming. To make the purpose, technical solution and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0023] The present invention provides a method for preparing hemp fibers by microwave-assisted seawater degumming, comprising the steps:

[0024] (1) Cut the hemp fibers into lengths of 10 - 20 cm, card them, then put the hemp fibers into natural seawater, with the bath ratio of hemp fibers to natural seawater being 1:5 - 20, and then put them together into a microwave digestion container for microwave heating. The microwave heating temperature is 80 - 120 °C, the microwave heating time is 5 - 20 min, and the microwave power is 400 - 600 W. After degumming is completed, take them out.

[0025] (2) Wash the hemp fibers taken out after degumming in step (1) twice with clear water and filter them, and then dry them at 90 - 110 °C to obtain degummed hemp fibers.

[0026] In order to reduce wastewater discharge and energy consumption, the present invention uses seawater instead of fresh water and combines microwave radiation heating technology to degum hemp fibers. Seawater contains various minerals (such as sodium chloride, iron chloride, and magnesium chloride, etc.), which can act as natural catalysts to promote gum removal without the need for additional chemical additives. However, using only seawater for degumming hemp bast fibers has poor effect, mainly due to poor removal effect on lignin and hemicellulose in hemp bast fibers. Therefore, we combine seawater with microwave irradiation for degumming. When microwave is applied, the molecular oscillation induced by microwave, driven by dielectric polarization, can activate the catalytic effect of minerals in seawater, realizing the catalytic degradation of non-cellulose substances such as lignin and hemicellulose in hemp bast, and decomposing biological macromolecules into simpler molecules; at the same time, the cavitation effect of microwave makes the structure of hemp bast expand and break, thus further enhancing the catalytic degradation of gum. In addition, due to the rapid thermal effect of microwave, this method has a short degumming time, mild conditions, high degumming efficiency, less energy consumption, and little damage to hemp fibers. In addition, microwave radiation heating can not only improve the degumming efficiency, but also has a modification and regulation effect on the structures of lignin gum and cellulose. This is because microwave radiation heating has both thermal effect and non-thermal effect. The non-thermal effect of microwave radiation can effectively reduce the modification time of hemp fibers, improve the modification degree of hemp fibers, and correspondingly increase the properties of hemp fibers; and microwave has a promoting effect on fiber activation, increasing fiber accessibility, thus facilitating the entry of minerals in seawater into the fiber interior to react with active groups, making it easier to remove lignin and hemicellulose.

[0027] Example 1

[0028] This example provides a method for preparing hemp fibers by microwave-assisted seawater degumming, comprising the steps:

[0029] (1) Cut 100 g of hemp bast fibers into lengths of 15 cm, card them, then put the hemp bast fibers into natural seawater. The bath ratio of hemp bast fibers to natural seawater is 1:15. Then put them together into a microwave digestion container and carry out microwave heating. The microwave heating temperature is 100 °C, the microwave heating time is 10 min, and the microwave power is 600 W. After degumming is completed, take out the hemp fibers;

[0030] (2) Wash the hemp fibers taken out after degumming in step (1) twice with clear water and filter them, and then dry them at 105 °C to obtain degummed hemp fibers.

[0031] Example 2

[0032] This example provides a method for preparing hemp fibers by microwave-assisted seawater degumming, including the steps:

[0033] (1) Cut 100 g of hemp bast fibers into lengths of 15 cm, card them, then put the hemp bast fibers into natural seawater. The bath ratio of hemp bast fibers to natural seawater is 1:10. Then put them together into a microwave digestion container and carry out microwave heating. The microwave heating temperature is 120 °C, the microwave heating time is 8 min, and the microwave power is 600 W. After degumming is completed, take out the hemp fibers;

[0034] (2) Wash the hemp fibers taken out after degumming in step (1) twice with clear water and filter them, and then dry them at 100 °C to obtain degummed hemp fibers.

[0035] Example 3

[0036] This example provides a method for preparing hemp fibers by microwave-assisted seawater degumming, including the steps:

[0037] (1) Cut 100 g of hemp bast fibers into lengths of 15 cm, card them, then put the hemp bast fibers into natural seawater. The bath ratio of hemp bast fibers to natural seawater is 1:20. Then put them together into a microwave digestion container and carry out microwave heating. The microwave heating temperature is 80 °C, the microwave heating time is 20 min, and the microwave power is 400 W. After degumming is completed, take out the hemp fibers;

[0038] (2) Wash the hemp fibers taken out after degumming in step (1) twice with clear water and filter them, and then dry them at 105 °C to obtain degummed hemp fibers.

[0039] Comparative Example 1

[0040] This comparative example provides a method for preparing hemp fibers by microwave-assisted fresh water degumming, including the steps:

[0041] (1) Cut 100 g of hemp bast fibers into lengths of 15 cm, and card them. Then put the hemp bast fibers into deionized water with a bath ratio of hemp bast fibers to water of 1:15. Then put them together into a microwave digestion container and conduct microwave heating at a temperature of 100 °C for 10 min with a microwave power of 600 W. After degumming is completed, take out the hemp fibers;

[0042] (2) Wash the hemp fibers taken out after degumming in step (1) twice with clear water and filter them, and then dry them at 105 °C to obtain degummed hemp fibers.

[0043] Comparative Example 2

[0044] This comparative example provides a method for preparing hemp fibers by seawater cooking and degumming, including the steps:

[0045] (1) Cut 100 g of hemp bast fibers into lengths of 15 cm, and card them. Then put the hemp bast fibers into natural seawater with a bath ratio of hemp bast fibers to natural seawater of 1:15. Then put them together into a reaction kettle and boil at high temperature for 2 h. After degumming is completed, take out the hemp fibers;

[0046] (2) Wash the hemp fibers taken out after degumming in step (1) twice with clear water and filter them, and then dry them at 105 °C to obtain degummed hemp fibers.

[0047] Comparative Example 3

[0048] This comparative example provides a method for preparing hemp fibers by traditional alkali cooking and degumming, including the steps:

[0049] (1) Cut 100 g of hemp bast fibers into lengths of 15 cm, and card them;

[0050] (2) Immerse the hemp bast fibers in a sulfuric acid solution with a concentration of 1 g / L with a bath ratio of hemp bast fibers to sulfuric acid solution of 1:15, soak at 50 °C for 1 h, and then wash twice with clear water;

[0051] (3) Take out the washed hemp fibers and immerse them in an alkali solution composed of 6.5 wt% sodium hydroxide, 3 wt% sodium silicate, 4 wt% sodium sulfite, and 2 wt% penetrant (fatty alcohol polyoxyethylene ether) with a bath ratio of hemp fibers to alkali solution of 1:15, and conduct alkali cooking at 100 °C for 2 h. After degumming is completed, take out the hemp fibers;

[0052] (4) Conduct pickling once, wash five times with water and filter the degummed hemp fibers taken out, and then dry them at 105 °C to obtain degummed hemp fibers.

[0053] The hemp bast fibers used in the above Examples 1-3 and Comparative Examples 1-3 are of the same batch.

[0054] SEM photos obtained by detecting the degummed hemp fibers prepared from the above-mentioned hemp bast fibers, Example 1 and Comparative Example 1 using a scanning electron microscope are as Figure 1 shown. Among them, (a) is the SEM photo of the hemp bast fibers, (b) is the SEM photo of the degummed hemp fibers prepared in Comparative Example 1, and (c) and (d) are the SEM photos of the degummed hemp fibers prepared in Example 1, and (d) is the SEM photo of a single degummed hemp fiber.

[0055] From the above Figure 1 it can be seen that: The hemp bast fibers before degumming show a rough surface, and the hemp fibers are bonded together due to the surface gum. After degumming with deionized water and microwave heating in Comparative Example 1, part of the gum on the surface of the hemp fibers is removed, showing a relatively clean surface, but the surface of the hemp fibers is still relatively rough and not completely separated into individual fibers. After degumming with seawater and microwave heating in Example 1, the gum on the surface of the hemp fibers is basically removed, showing a clean and smooth surface, with a uniform diameter, and basically separated into individual fibers.

[0056] The degummed hemp fibers prepared from the above-mentioned hemp bast fibers, Examples 1-3 and Comparative Examples 1-3 were tested for chemical composition and physical properties according to the following methods:

[0057] Test method for chemical composition: Refer to GB 5889–1986 "Quantitative Analysis Method for Chemical Composition of Ramie" to test the residual gum rate of degummed hemp fibers;

[0058] Test method for fineness: Refer to GB / T 6100–2007 "Mid-section Weighing Method for Test Method of Cotton Fiber Linear Density" to test the fineness of degummed hemp fibers;

[0059] Test method for bundle fiber strength: Refer to GB / T 5882–1986 "Test Method for Breaking Strength of Ramie Bundle Fibers" to test the strength of degummed hemp fibers.

[0060] After the tests were completed, the test results of the chemical composition were shown in Table 1, and the test results of the physical properties were shown in Table 2 below.

[0061] Table 1 Test Results of Chemical Composition

[0062]

[0063] Table 2 Test Results of Physical Properties

[0064] Fineness (dtex) Breaking strength (cN / dtex) Example 1 4.8±0.12 4.03±0.78 Example 2 4.7±0.33 3.96±0.54 Example 3 4.9±0.09 4.11±0.63 Comparative Example 1 23.4±2.08 2.37±0.99 Comparative Example 2 14.5±0.61 2.76±0.87 Comparative Example 3 4.6±0.23 3.97±0.65

[0065] Analysis of the test results in Table 1 above: In Examples 1-3 of the present invention, the microwave-assisted seawater degumming process is adopted. After degumming, the contents of wax, water-soluble substances, pectin, lignin and hemicellulose are all significantly reduced, and the gum is basically removed. The degumming effect is basically the same as that of the traditional alkali cooking degumming in Comparative Example 3; in Comparative Example 1, microwave-assisted deionized water is used for degumming, and the content of water-soluble substances is significantly reduced, while wax, pectin, lignin and hemicellulose are basically not removed; in Comparative Example 2, seawater cooking degumming is adopted, and the contents of wax, water-soluble substances and pectin are significantly reduced, while the removal of lignin and hemicellulose is relatively less. Through the above comparative analysis: when using seawater cooking alone or using microwave and pure water alone to degum hemp fibers, the degumming effect is relatively poor and the fibers cannot be dispersed; but after using microwave and seawater treatment, the degumming effect is good. Not only the contents of wax, water-soluble substances and pectin are greatly reduced, but also the contents of hemicellulose and lignin are significantly reduced. In particular, microwave-assisted seawater degumming has a good degumming effect on the difficult-to-remove hemicellulose and lignin.

[0066] Analysis of the test results in Table 2 above: In Examples 1-3 of the present invention, the microwave-assisted seawater degumming process is adopted. After degumming, the fiber fineness is 4.8 dtex and the breaking strength is 4.03 cN / dtex. After degumming in Examples 1-3, the fiber fineness is equivalent to that of the traditional alkali cooking degumming, but the breaking strength is slightly higher than that of the traditional alkali cooking degumming, indicating that the degumming effect of the present invention is good, and the breaking strength after degumming is high, and the damage to hemp fibers is small.

[0067] It should be noted that the parts not described in the present invention can be realized by adopting or referring to the existing technologies.

[0068] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the substantial scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing ramie fibers by microwave-assisted seawater degumming, characterized in that, Including the steps: (1) Put the hemp fiber into seawater, then put it into a microwave digestion container, conduct microwave heating, and take it out after degumming is completed; (2) Wash, filter, and dry the hemp fiber taken out after degumming in step (1) to obtain degummed hemp fiber.

2. The method for preparing ramie fiber by microwave-assisted seawater degumming according to claim 1, wherein, In step (1), the bath ratio of the hemp fiber to seawater is 1:5 to 20.

3. A method for preparing ramie fibers by microwave-assisted seawater degumming according to claim 1, characterized in that, In step (1), the microwave heating temperature is 80 to 120 °C, and the microwave heating time is 5 to 20 min.

4. A method for preparing ramie fiber by microwave-assisted seawater degumming according to claim 1, characterized in that, In step (1), the microwave power is 400 to 600 W.

5. A method for preparing ramie fiber by microwave-assisted seawater degumming according to claim 1, characterized in that, In step (1), the seawater is natural seawater.

6. A method for preparing ramie fiber by microwave-assisted seawater degumming according to claim 1, characterized in that, In step (2), clean water is used for washing during the water washing.

7. A method for preparing ramie fiber by microwave-assisted seawater degumming according to claim 1, characterized in that, In step (2), the drying temperature is 90 to 110 °C.

8. A method for preparing ramie fibers by microwave-assisted seawater degumming according to claim 1, characterized in that, It also includes cutting and carding the hemp fiber before putting the hemp fiber into seawater.

9. A method for preparing ramie fibers by microwave-assisted seawater degumming according to claim 8, characterized in that, The cut length of the hemp fiber is 10 to 20 cm.

10. A method for preparing ramie fiber by microwave-assisted seawater degumming according to any one of claims 1-9, characterized in that, The hemp fiber is one of ramie, cannabis, apocynum venetum, kenaf or jute.

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