A method for improving the degumming effect of DES on hemp / hemp loose fibers by using cysteine

Abstract

The present invention discloses a method for improving the degumming effect of DES on hemp / hemuff fiber by using cysteine, and belongs to the technical field of natural fiber extraction and utilization. The method for improving the degumming effect of DES on hemp / hemuff fiber by using cysteine ​​is specifically to mix cysteine ​​with a low eutectic solvent DES to prepare a degumming solution; then immerse the hemp / hemuff fiber in the prepared degumming solution, degumming the hemp / hemuff fiber by heating drive or electric drive, and washing and drying after the degumming is completed. This method not only improves the selective removal of lignin, but also reduces the damage to the fiber strength, thereby achieving a better degumming effect.

Description

Technical Field

[0001] The invention relates to a method for improving the degumming effect of DES on hemp / hemp loose fibers by utilizing cysteine, and belongs to the technical field of natural fiber extraction and utilization. Background Art

[0002] Cotton-type hemp fiber fabrics have been welcomed by major linen textile companies and consumers in recent years due to their low cost and good wrinkle resistance; hemp second coarse and machine noil (collectively known as hemp bulk fiber) are the main raw materials for preparing cotton-type linen spinning. Hemp bulk fiber is mainly composed of cellulose and its accompanying substances (hemicellulose, lignin, pectin, etc.). The degumming process to remove some of the cellulose accompanying substances is a necessary step to obtain high-quality cotton-type hemp fiber.

[0003] In recent years, deep eutectic solvent (DES) hemp degumming has attracted extensive attention from researchers due to its low water consumption and low pollution discharge; however, the current DES pretreatment technology has the problem of poor selectivity. That is, alkaline DES pretreatment basically does not cause cellulose degradation and can remove most pectin and hemicellulose, but its lignin removal rate is low (<50%); acidic DES pretreatment can achieve a higher lignin removal rate (70% and above), but it will cause a large amount of cellulose degradation, which in turn leads to a decrease in fiber strength and elongation properties.

[0004] Therefore, at present, DES degumming has a good effect on hemp fibers with extremely low lignin content (<1.5%) such as ramie; but it has a poor degumming effect on hemp fibers with higher lignin content such as ramie and hemp, and often requires other degumming methods (such as alkaline oxygen post-treatment, ultrasonic assisted treatment, etc.) to complete the degumming; but these auxiliary methods usually cause damage to cellulose. Summary of the invention

[0005] [Technical issues]

[0006] The existing DES hemp / hemp loose fiber degumming method has the problems of insufficient selectivity, damage to cellulose, and low lignin removal effect and efficiency.

[0007] [Technical solution]

[0008] In view of the above technical problems, the present invention provides a method for improving the degumming effect of DES hemp / hemphic fiber bulk by utilizing cysteine; during the degumming process of hemp / hemphic fiber bulk, since lignin is easily condensed (the lignin units that have been removed and dissolved in the pretreatment liquid are re-bonded with the lignin units remaining on the hemp fiber by CC bonds), it is re-deposited on the surface of the hemp fiber, which leads to unsatisfactory degumming effect of the hemp / hemphic fiber bulk; by adding cysteine ​​to the DES solution and then degumming the hemp / hemphic fiber bulk, not only the selective removal of lignin is improved, but also the damage to the fiber strength can be reduced, thereby achieving a better degumming effect.

[0009] The object of the present invention is to provide a method for improving the degumming effect of DES on hemp / hemp bulk fibers by utilizing cysteine, the method comprising the following steps:

[0010] (1) mixing cysteine ​​with a low eutectic solvent DES to prepare a degumming solution;

[0011] (2) Immersing the hemp / hemf bulk fibers in the degumming solution prepared in step (1), degumming the hemp / hemf bulk fibers by heating or electric driving, and washing and drying the fibers after degumming.

[0012] In one embodiment, the low eutectic solvent in step (1) is prepared by mixing a hydrogen bond donor and a hydrogen bond acceptor, heating and stirring; the hydrogen bond donor includes one or more of urea, thiourea, carboxylic acid, polyol, amino acid, aminosulfonic acid, glucose, fructose, and trifluoroacetamide; and the hydrogen bond acceptor is choline chloride or betaine.

[0013] In one embodiment, the carboxylic acid comprises one or more of phenylacetic acid, malic acid, citric acid, and succinic acid.

[0014] In one embodiment, the polyol includes one or more of ethylene glycol, glycerol, butylene glycol, and xylitol.

[0015] In one embodiment, the mass ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:2 to 2:1, and the heating and stirring temperature is 70 to 90°C.

[0016] In one embodiment, the concentration of cysteine ​​in the degumming solution in step (1) is 0.5-2.0 g / mL.

[0017] In one embodiment, the hemp / hemphragm loose fibers in step (2) are immersed in the degumming solution prepared in step (1) at a bath ratio of 1:18-20.

[0018] In one embodiment, when the degumming is carried out in step (2) by a heating-driven method, the degumming reaction temperature is 60 to 80° C. and the time is 30 to 60 minutes.

[0019] In one embodiment, when degumming is performed in step (2) by electric drive, electrolysis is performed using a three-electrode device consisting of a working electrode, an auxiliary electrode, and a reference electrode; the electrolysis temperature is 25 to 60° C., and the time is 0.5 to 3.5 hours.

[0020] In one embodiment, the scanning voltage of the electric drive is 0-8.0V.

[0021] In one embodiment, the washing and drying in step (2) is specifically washing with clean water until the hemp / hemp bulk fiber is neutral, and drying in an oven at 90-105°C.

[0022] In one embodiment, the working electrode includes, according to the material, an inorganic non-metal electrode, a metal electrode, and a polymer electrode.

[0023] In one embodiment, the inorganic non-metallic electrode includes one or more of glassy carbon, graphite, and diamond.

[0024] In one embodiment, the metal electrode comprises an electrode formed of ruthenium titanium or lead dioxide.

[0025] In one embodiment, the polymer electrode is a polypyrrole electrode.

[0026] In one embodiment, the working electrode includes the following forms: sheet electrode, mesh electrode, disk electrode, foam electrode, gas diffusion electrode.

[0027] In one embodiment, the auxiliary electrode material includes one or more of platinum, nickel, and graphite felt; the auxiliary electrode is in the form of a sheet or foam; and the working area of ​​the auxiliary electrode is larger than that of the working electrode.

[0028] In one embodiment, the reference electrode includes one or more of a calomel electrode, a standard hydrogen electrode, and a silver / silver chloride electrode.

[0029] In one embodiment, the electrolysis method includes any one of cyclic voltammetry, linear sweep voltammetry, and constant current electrolysis.

[0030] In one embodiment, the scanning voltage range of the cyclic voltammetry or linear sweep voltammetry is -6.0 to 8.0V.

[0031] Another object of the present invention is to provide an application of the above method in degumming hemp / hemp bulk fibers.

[0032] Beneficial effects of the present invention:

[0033] (1) The present invention adds cysteine ​​to the DES solution and then degummes the hemp / hemp loose fibers, which not only improves the selective removal of lignin, but also reduces the damage to the fiber strength, thereby achieving a better degumming effect.

[0034] (2) Compared with the method of degumming hemp / hemphic fiber using only DES solution to degumming hemp / hemphic fiber, the degumming solution formed by adding cysteine ​​to DES solution in the present invention significantly improves the lignin removal rate. At the same time, the fiber polymerization degree and bundle fiber strength are also significantly better than the method of degumming hemp / hemphic fiber using DES solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the experimental device of the electric driven degumming of the present invention; wherein 1 is the working electrode, 2 is the auxiliary electrode, 3 is the reference electrode, 4 is the pretreatment liquid, and 5 is the plant fiber raw material. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0037] The test method involved in the present invention is:

[0038] 1. Determination of lignin removal rate

[0039] Lignin is the most necessary and difficult component to remove during hemp degumming. Based on this, this paper uses lignin content as the main evaluation index of residual gum.

[0040] The determination method is as follows: weigh about (0.3±0.005) g of the dry sample to be tested, record the mass m, accurately measure 3 mL of 72% sulfuric acid and add it to the system, stir and react at a constant temperature of 30°C in a water bath for 1 hour; after the reaction is completed, drain the resulting liquid into a 150 mL conical flask, and add 84 mL of deionized water to adjust the acidity of the solution, and react at 121°C in an autoclave for 1 hour. After the reaction is completed, filter with a G4# sand core funnel and first dry it at 105°C to absolute dryness, cool and weigh m0, then place it in a muffle furnace and set the temperature to 550°C to burn for about 30 hours, then take out and weigh m1, and determine the lignin content by weight loss method. The calculation formula is as follows:

[0041] Y=(m o -m1) / m0

[0042] 2. Determination of fiber polymerization degree

[0043] The polymerization degree of hemp fiber was tested with reference to FZ / T 50010.3-2011 "Determination of viscosity of viscose pulp". Each group of samples was tested 3 times and the results were averaged.

[0044] 3. Determination of bundle fiber strength

[0045] With reference to GB / T13783 "Determination of the specific breaking strength of cotton fibers - Flat bundle method", the strength of hemp fiber was tested using the YG011N bundle fiber strength tester (Stroh instrument).

[0046] Example 1

[0047] A method for improving the effect of DES on flax degumming by using cysteine, comprising the following steps:

[0048] (1) Preparation of DES solvent: Choline chloride and urea in a molar ratio of 2:1 were mixed at 80° C. to prepare a DES solution, and cysteine ​​was added thereto to prepare a degumming solution. The concentration of cysteine ​​in the degumming solution was 0.5 g / mL;

[0049] (2) Degumming by heating: immerse the flax fiber in the degumming solution prepared in step (1) at a bath ratio of 1:20, and react at 125°C for 2.5 hours; after the reaction, take out the flax fiber, wash it with clean water until the pH value of the flax fiber is 7, and dry it in an oven at 105°C.

[0050] Example 2

[0051] A method for improving the effect of DES on flax degumming by using cysteine, comprising the following steps:

[0052] (1) Preparation of DES solvent: Choline chloride and lactic acid in a molar ratio of 2:1 were mixed at 80° C. to prepare a DES solution, and cysteine ​​was added thereto to prepare a degumming solution. The concentration of cysteine ​​in the degumming solution was 0.8 g / mL;

[0053] (2) Degumming by heating: immersing the flax fiber in the degumming solution prepared in step (1) at a bath ratio of 1:20, and reacting at 65°C for 40 minutes; after the reaction, taking out the flax fiber, washing it with clean water until the pH value of the flax fiber is 7, and drying it in an oven at 105°C.

[0054] Example 3

[0055] A method for improving the degumming effect of DES on hemp machine-fallen fibers by using cysteine ​​comprises the following steps:

[0056] (1) Preparation of DES solvent: Choline chloride and urea in a molar ratio of 2:1 were mixed at 80° C. to prepare a DES solution, and cysteine ​​was added thereto to prepare a degumming solution. The concentration of cysteine ​​in the degumming solution was 0.8 g / mL;

[0057] (2) Electrochemical degumming (device structure diagram as shown in the figure) Figure 1 As shown): 3×3cm 2 The graphite plate is used as the working electrode, 4×4cm 2 An electrolytic device is formed by using a platinum sheet electrode as an auxiliary electrode and a calomel electrode as a reference electrode; the degumming solution prepared in step (1) and hemp residue are placed into the reaction device at a bath ratio of 1:20; an electrolytic pretreatment is performed at 35°C using a cyclic voltammetry method (scanning voltage 0-8.0V) for 1.0h; after the treatment, the mixture is washed and dried.

[0058] Example 4

[0059] A method for improving the degumming effect of DES on hemp machine-fallen fibers by using cysteine ​​comprises the following steps:

[0060] (1) Preparation of DES solvent: Choline chloride and lactic acid in a molar ratio of 2:1 were mixed at 80° C. to prepare a DES solution, and cysteine ​​was added thereto to prepare a degumming solution. The concentration of cysteine ​​in the degumming solution was 0.9 g / mL;

[0061] (2) Electrochemical degumming: 3×3cm 2 The graphite plate is used as the working electrode, 4×4cm 2 An electrolytic device is formed by using a platinum sheet electrode as an auxiliary electrode and a calomel electrode as a reference electrode; the degumming solution prepared in step (1) and hemp residue are added into the reaction device at a bath ratio of 1:20; an electrolytic pretreatment is carried out at 25° C. under a voltage of cyclic voltammetry (scanning voltage 0-8.0 V) for 0.5 h; after the treatment, the mixture is washed and dried.

[0062] Comparative Example 1

[0063] (1) Preparation of DES solvent: Choline chloride and urea in a molar ratio of 2:1 are mixed at 80° C. to prepare a DES solution, which is then prepared into a degumming solution;

[0064] (2) Degumming by heating: immerse the flax fiber in the degumming solution prepared in step (1) at a bath ratio of 1:20, and react at 150°C for 4 hours; after the reaction, take out the flax fiber, wash it with clean water until the pH value of the flax fiber is 7, and dry it in an oven at 105°C.

[0065] Comparative Example 2

[0066] (1) Preparation of DES solvent: choline chloride and lactic acid in a molar ratio of 2:1 are mixed at 80° C. to prepare a DES solution, which is then prepared into a degumming solution;

[0067] (2) Degumming by heating: immerse the flax fiber in the degumming solution prepared in step (1) at a bath ratio of 1:20, and react at 85°C for 1 hour; after the reaction, take out the flax fiber, wash it with clean water until the pH value of the flax fiber is 7, and dry it in an oven at 105°C.

[0068] Comparative Example 3

[0069] (1) Preparation of DES solvent: Choline chloride and urea in a molar ratio of 2:1 are mixed at 80° C. to prepare a DES solution, which is then prepared into a degumming solution;

[0070] (2) Electrochemical degumming: 3×3cm 2 The graphite plate is used as the working electrode, 4×4cm 2 An electrolytic device is formed by using a platinum sheet electrode as an auxiliary electrode and a calomel electrode as a reference electrode; the degumming solution prepared in step (1) and hemp residue are added into the reaction device at a bath ratio of 1:20; an electrolytic pretreatment is carried out at 45°C under a voltage of cyclic voltammetry (scanning voltage 0-8.0V) for 1.5h; after the treatment, the mixture is washed and dried.

[0071] Comparative Example 4

[0072] (1) Preparation of DES solvent: choline chloride and lactic acid in a molar ratio of 2:1 are mixed at 80° C. to prepare a DES solution, which is then prepared into a degumming solution;

[0073] (2) Electrochemical degumming: 3×3cm 2 The graphite plate is used as the working electrode, 4×4cm 2 An electrolytic device is formed by using a platinum sheet electrode as an auxiliary electrode and a calomel electrode as a reference electrode; the degumming solution prepared in step (1) and hemp residue are added into the reaction device at a bath ratio of 1:20; an electrolytic pretreatment is carried out at 25° C. under a voltage of cyclic voltammetry (scanning voltage 0-8.0 V) for 1.5 h; after the treatment, the mixture is washed and dried.

[0074] The properties of the hemp / flax fibers obtained after degumming treatment in Examples 1 to 4 and Comparative Examples 1 to 4 were measured, and the results are shown in Table 1:

[0075] Table 1 Fiber properties after degumming

[0076] Lignin removal rate (%) Degree of Polymerization Bundle fiber strength (cN / dtex) Example 1 60 2103 70.1 Comparative Example 1 18.1 2087 66.5 Example 2 83.2 1544 55.8 Comparative Example 2 55.2 1246 32.1 Example 3 76.8 2178 74.2 Comparative Example 3 65.0 2100 73.0 Example 4 78.6 1680 61.4 Comparative Example 4 63.1 1478 47.6

Claims

1. A method for improving the degumming effect of DES on hemp / hemp bulk fiber by using cysteine, characterized in that: The method comprises the following steps: (1) Mixing cysteine ​​with a low eutectic solvent DES to prepare a degumming solution; (2) immersing the hemp / hemuffluff fibers into the degumming solution prepared in step (1), degumming the hemp / hemuffluff fibers by electric drive, and after degumming, washing and drying the fibers; When degumming hemp / hemp loose fibers by electric drive, a three-electrode device consisting of a working electrode, an auxiliary electrode, and a reference electrode is used for electrolysis; the electrolysis temperature is 25-60°C, and the time is 0.5-3.5 h; the scanning voltage of the electric drive is 0-8.0 V.

2. The method according to claim 1, characterized in that The low eutectic solvent in step (1) is prepared by mixing a hydrogen bond donor and a hydrogen bond acceptor, heating and stirring; the hydrogen bond donor includes one or more of urea, thiourea, carboxylic acid, polyol, amino acid, aminosulfonic acid, glucose, fructose, and trifluoroacetamide; and the hydrogen bond acceptor is choline chloride or betaine.

3. The method according to claim 2, characterized in that The mass ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:2 to 2:1, and the heating and stirring temperature is 70 to 90°C.

4. The method according to claim 1, characterized in that The concentration of cysteine ​​in the degumming solution of step (1) is 0.5-2.0 g / mL.

5. The method according to claim 1, characterized in that In step (2), the hemp / hemphragm loose fibers are immersed in the degumming solution prepared in step (1) at a bath ratio of 1:18-20.

6. The method according to claim 1, characterized in that The washing and drying in step (2) specifically involves washing with clean water until the hemp / hemp loose fibers are neutral, and drying in an oven at 90-105°C.

7. Use of the method according to any one of claims 1 to 6 in degumming hemp / hemp bulk fibers.

Images