Preparation method of pomace cellulose nanocrystal gel with high redispersibility

Abstract

The invention relates to a preparation method of high-redispersibility pomace cellulose nanocrystal gel, which comprises the following steps of: dispersing prepared pomace cellulose nanocrystal latex under the action of ultrasonic waves, and performing pre-shearing mixing treatment on the pomace cellulose nanocrystal latex and sodium lignosulfonate powder by using a high-speed shearing machine to obtain a primary emulsion of pomace cellulose nanocrystal-sodium lignosulfonate; performing high-pressure homogenization treatment on the primary emulsion through a homogenizer, dropwise adding an aqueous solution of alkali lignin at a sample inlet of a feed liquid circulating pump, and performing continuous homogenization treatment for 3-3.5 minutes to prepare the pomace cellulose nanocrystal gel with high redispersibility. According to the invention, sodium lignosulfonate and alkali lignin are used as a natural surface treating agent and an interface screening agent for the first time, so that the pomace cellulose nanocrystal gel can still be completely dispersed in an aqueous solvent after being dehydrated and dried.

Description

Technical Field

[0001] This invention belongs to the field of daily necessities and chemical gel additives. It relates to daily-use gels, antibacterial hand sanitizers, disinfectants, as well as thickeners, preservatives, or other types of functional gel additives used in chemical industrial processes, all of which fall under the technical field of this invention's highly redispersible fruit pomace cellulose nanocrystalline gel. Background Technology

[0002] Cellulose nanocrystals, as an emerging natural polymer nanomaterial, have been widely used in scientific research and industry. However, due to the abundant hydroxyl groups on their surface, conventional cellulose nanocrystals easily aggregate during dehydration or drying through intermolecular hydrogen bonding, forming large particles that lead to demulsification and stratification in colloidal systems. Furthermore, the hydrogen bonds formed during this aggregation process often fail to break completely upon rewetting, resulting in incomplete dispersion. This also makes it difficult to redisperse dried cellulose nanocrystals in solvent systems. This phenomenon is particularly prominent in practical applications; for example, in the preparation of high-concentration dispersions or dry materials, dehydrated cellulose nanocrystal solid particles and films are difficult to redisperse uniformly in a liquid polymer matrix. To address the poor redispersibility of cellulose nanocrystals, researchers have made numerous attempts at improvement, including using ultrasound-assisted redispersibility; surface activation of cellulose nanocrystals to improve the compatibility of the particle-nonpolar polymer interface; chemical modification to introduce hydrophobic or ionic groups to reduce hydrogen bonding between hydroxyl groups; and using biomimetic materials to form a protective layer on the surface of cellulose nanocrystals to inhibit aggregation. However, these measures generally face many challenges, such as high cost, making large-scale application difficult; or limited effectiveness in improving the redispersibility of cellulose nanocrystals, with the dispersion still exhibiting flow birefringence and aggregation. Recently, CN118271469A disclosed a method for preparing redispersible cellulose nanocrystal powder. This method involves hydrolyzing cellulose raw materials with concentrated sulfuric acid to obtain a cellulose nanocrystal suspension, then adding maltodextrin and a debonding agent, followed by drying and grinding to produce redispersible cellulose nanocrystal powder. The redispersible powder of this invention is mainly obtained through grinding, and the debonding agent used is a mixture of cationic and nonionic surfactants. CN202311135821.1 discloses a redispersible nanocellulose composite material, its preparation method, and its application. The nanocellulose composite material mainly consists of a water-soluble thiocate compound and nanocellulose, which are mixed in an aqueous solution and then dehydrated and dried. The nanocellulose composite material prepared by this invention has controllable properties, and all components are green bio-based compounds, making it safe and non-toxic. This invention represents a significant innovation in its implementation concept and methods, resulting in a more natural and environmentally friendly formulation. However, compared to industrial-grade natural lignin derivatives, the application of thiocate compounds is relatively less widespread. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel method for preparing highly redispersible fruit pomace cellulose nanocrystal gel. By adding naturally sourced sodium lignin sulfonate and alkali lignin as interfacial barrier agents during dehydration and drying, the method effectively prevents the formation of dense hydrogen bonds between cellulose nanocrystal particles, improves the overall physical stability of the gel, and enhances the redispersibility of the dried product in solvents.

[0004] The technical solution adopted by this invention to solve the technical problem is: A method for preparing highly redispersible fruit pomace cellulose nanocrystalline gel, comprising the following steps: (1) Preparation of fruit pomace cellulose nanocrystal emulsion: Weigh 50-55 g of fruit pomace cellulose nanocrystal emulsion and dilute it with 1.55-1.6 times its weight of deionized water; (2) Dispersion treatment under the action of ultrasound: the frequency of ultrasound is 75-79 kHz and the time is 10-12 min; (3) Use a high-speed shearing machine to mix and shear the fruit pomace cellulose nanocrystal emulsion and sodium lignosulfonate powder: Add 0.22-0.23 g of sodium lignosulfonate powder to the fruit pomace cellulose nanocrystal emulsion that has been dispersed in step (2) in three batches at a ratio of 1:2:3. Use a high-speed shearing machine at a speed of 6600-6700 r / min for 12-13 min to fully mix the fruit pomace cellulose nanocrystal particles with sodium lignosulfonate. (4) The mixture of fruit pomace cellulose nanocrystals and sodium lignin sulfonate prepared in step (3) is subjected to high-pressure homogenization by a homogenizer. After circulating at 40 MPa for 6 times, the pressure is reduced to 13-15 MPa. An aqueous solution of alkali lignin is added dropwise to the inlet of the feed circulation pump. After the addition is completed, the pressure is increased to 50-52 MPa and the homogenization is continued for 3-3.5 min to obtain highly redispersible fruit pomace cellulose nanocrystal gel.

[0005] Moreover, the specific ultrasonic frequency mentioned in step (2) is 75-79 kHz, and the duration is 10-12 min.

[0006] Moreover, the sodium lignosulfonate powder mentioned in step (3) is derived from commercial sodium lignosulfonate powder or sodium lignosulfonate extracted from sulfite pulp waste liquor.

[0007] Moreover, the alkali lignin aqueous solution described in step (4) is derived from commercial alkali lignin.

[0008] Moreover, the dripping rate of the alkali lignin aqueous solution in step (4) is 200-210 mg / min.

[0009] The advantages and beneficial effects of this invention are: This invention pioneered the use of naturally derived sodium lignosulfonate and alkali lignin as interfacial nanobarriers to inhibit hydrogen bonds formed between hydroxyl groups on the surface of cellulose nanocrystals. While preserving the nanoparticle properties of cellulose crystals, it effectively utilizes the hydrogen bond shielding effect of sodium lignosulfonate and alkali lignin to improve the overall physicochemical stability of the gel and the redispersibility of the dried product in solvents. All materials used in this invention are bio-based natural components, possessing advantages such as being environmentally friendly, having high yield, low cost, and controllable performance. This can effectively expand the application scale of cellulose nanocrystal gels in daily necessities and chemical gel additives. Detailed Implementation

[0010] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0011] The fruit pomace cellulose nanocrystal raw material used in this invention is in a colloidal emulsion state, and its mass concentration is measured to be 9.7% (w / w).

[0012] Example 1

[0013] A method for preparing a highly redispersible fruit pomace cellulose nanocrystalline gel, comprising the following steps: (1) Weigh 50 g of fruit pomace cellulose nanocrystal emulsion and dilute it with 1.55 times its weight of deionized water; (2) Dispersion treatment was carried out under the action of ultrasound, with a frequency of 75 kHz and a duration of 12 min; (3) Use a high-speed shearing machine to mix and shear the fruit pomace cellulose nanocrystal emulsion and sodium lignosulfonate powder. Add 0.22% sodium lignosulfonate powder to the fruit pomace cellulose nanocrystal emulsion that has been dispersed in step (2) in three batches at a ratio of 1:2:3. Use a high-speed shearing machine at a speed of 6600 r / min for 13 min to fully mix the fruit pomace cellulose nanocrystal particles with sodium lignosulfonate. (4) The mixture of fruit pomace cellulose nanocrystals and sodium lignin sulfonate prepared in step (3) was subjected to high-pressure homogenization by a homogenizer. After circulating for 6 times at 40 MPa, the pressure was reduced to 13 MPa. An aqueous solution of alkali lignin was added dropwise at the inlet of the feed circulation pump (dropping rate 200 mg / min). After the dropping was completed, the pressure was increased to 50 MPa and the homogenization was continued for 3.5 min to obtain highly redispersible fruit pomace cellulose nanocrystal gel.

[0014] Example 2

[0015] A method for preparing a highly redispersible fruit pomace cellulose nanocrystalline gel, comprising the following steps: (1) Weigh 55 g of fruit pomace cellulose nanocrystal emulsion and dilute it with 1.6 times its weight of deionized water; (2) Dispersion treatment was carried out under the action of ultrasound, with a frequency of 79 kHz and a duration of 10 min; (3) Use a high-speed shearing machine to mix and shear the fruit pomace cellulose nanocrystal emulsion and sodium lignosulfonate powder. Add 0.23 g of sodium lignosulfonate powder to the fruit pomace cellulose nanocrystal emulsion that has been dispersed in step (2) in three batches at a ratio of 1:2:3. Use a high-speed shearing machine at a speed of 6700 r / min for 12 min to fully mix the fruit pomace cellulose nanocrystal particles with sodium lignosulfonate. (4) The mixture of fruit pomace cellulose nanocrystals and sodium lignin sulfonate prepared in step (3) was subjected to high-pressure homogenization by a homogenizer. After circulating for 6 times at 40 MPa, the pressure was reduced to 15 MPa. An aqueous solution of alkali lignin was added dropwise at the inlet of the feed circulation pump (dropping rate 210 mg / min). After the dropping was completed, the pressure was increased to 52 MPa and the homogenization was continued for 3 min to obtain highly redispersible fruit pomace cellulose nanocrystal gel.

[0016] Example 3

[0017] A method for preparing a highly redispersible fruit pomace cellulose nanocrystalline gel, comprising the following steps: (1) Weigh 52.5 g of fruit pomace cellulose nanocrystal emulsion and dilute it with 1.6 times its weight of deionized water; (2) Dispersion treatment under the action of ultrasound: the frequency of ultrasound is 78 kHz and the time is 11 min; (3) Use a high-speed shearing machine to mix and shear the fruit pomace cellulose nanocrystal emulsion and sodium lignin sulfonate powder. Add 0.22 g of sodium lignin sulfonate powder to the fruit pomace cellulose nanocrystal emulsion that has been dispersed in step (2) in three batches at a ratio of 1:2:3. Use a high-speed shearing machine at a speed of 6650 r / min for 12.5 min to fully mix the fruit pomace cellulose nanocrystal particles with sodium lignin sulfonate. (4) The mixture of fruit pomace cellulose nanocrystals and sodium lignin sulfonate prepared in step (3) was subjected to high-pressure homogenization by a homogenizer. After circulating for 6 times at 40 MPa, the pressure was reduced to 14 MPa. An aqueous solution of alkali lignin was added dropwise at the inlet of the feed circulation pump (dropping rate 205 mg / min). After the dropping was completed, the pressure was increased to 51 MPa and the homogenization was continued for 3.5 min to obtain highly redispersible fruit pomace cellulose nanocrystal gel.

[0018] Example 4

[0019] The preparation process differs from that of Example 1, which uses the same mass of fruit pomace cellulose nanocrystals as the initial raw material. In step (1), the fruit pomace cellulose nanocrystal emulsion is added to 83.2 g of deionized water for dilution. In step (2), the ultrasonic frequency is 77 kHz and the time is 12 min. In step (3), 0.23 g of sodium lignin sulfonate powder is added in three portions at a ratio of 1:2:3 to the dispersed fruit pomace cellulose nanocrystal emulsion. The emulsion is then subjected to high-speed shearing at 6700 r / min for 12.5 min to ensure thorough mixing of all components. In step (4), after six cycles of high-pressure circulation at 40 MPa, the pressure is reduced to 15 MPa. An aqueous solution of alkali lignin is added dropwise (dropping rate 210 mg / min) at the inlet of the liquid circulation pump. After the addition is completed, the pressure is increased to 51 MPa and homogenization is continued for 3 min. The remaining parameters are consistent with those in Example 1, and a highly redispersible fruit pomace cellulose nanocrystal gel is prepared.

[0020] Example 5

[0021] The preparation process differs from that in Example 2, which uses the same mass of fruit pomace cellulose nanocrystals as the initial raw material. In step (1), the fruit pomace cellulose nanocrystal emulsion is added to 80.6 g of deionized water for dilution. In step (2), the ultrasonic frequency is 76 kHz and the time is 12 min. In step (3), 0.22 g of sodium lignin sulfonate powder is added in three portions at a ratio of 1:2:3 to the dispersed fruit pomace cellulose nanocrystal emulsion. The emulsion is then subjected to high-speed shearing at 6600 r / min for 12 min to ensure thorough mixing of all components. In step (4), after six cycles of high-pressure circulation at 40 MPa, the pressure is reduced to 14 MPa. An aqueous solution of alkali lignin is added dropwise (dropping rate 200 mg / min) at the inlet of the feed pump. After the addition is complete, the pressure is increased to 51 MPa and homogenization is continued for 3.5 min. The remaining parameters are consistent with those in Example 2, and a highly redispersible fruit pomace cellulose nanocrystal gel is prepared.

[0022] Under the embodiments listed above, the novel fruit pomace cellulose nanocrystal gels obtained can all be completely redispersed in an aqueous solvent after dehydration and drying. Measurements using a Brookhaven Instruments 90 Plus particle size analyzer (Holtsville, NY, USA) showed that the average particle size of the cellulose nanocrystals in the original gel was 117 nm, and the average particle size of the redispersed cellulose nanocrystals after drying was 118 nm; the morphology of the two was almost indistinguishable (the temperature of the sample testing platform was set at 25°C, and the wavelength at 658 nm).

[0023] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing high redispersibility pomace cellulose nanocrystal gel, characterized in that: The preparation steps are as follows: (1) Prepare pomace cellulose nanocrystal emulsion: weigh 50-55 g of pomace cellulose nanocrystal emulsion and dilute with 1.55-1.6 times the weight of deionized water; (2) Disperse under the action of ultrasonic waves: the frequency of the ultrasonic waves is 75-79 kHz, and the time is 10-12 min; (3) Mix and shear the pomace cellulose nanocrystal emulsion and sodium lignosulfonate powder using a high-speed shearing machine: add 0.22-0.23 g of sodium lignosulfonate powder in three portions according to a ratio of 1:2:3 to the pomace cellulose nanocrystal emulsion dispersed in step (2), and shear at a speed of 6600-6700 r / min for 12-13 min using a high-speed shearing machine to fully mix the pomace cellulose nanocrystal particles and sodium lignosulfonate; (4) Prepare the pomace cellulose nanocrystal-sodium lignosulfonate mixture in step (3), and perform high-pressure homogenization treatment using a homogenizer: after 6 cycles at 40 MPa, reduce the pressure to 13-15 MPa, add an aqueous alkali lignin solution drop by drop at the sample inlet of the liquid circulating pump, after the addition is complete, increase the pressure to 50-52 MPa and continue the homogenization treatment for 3-3.5 min, and obtain the high redispersibility pomace cellulose nanocrystal gel.

2. The method of claim 1, wherein: The specific ultrasonic frequency in step (2) is 75-79 kHz, and the time is 10-12 min.

3. The method of claim 1, wherein: The sodium lignosulfonate powder in step (3) is derived from commercial sodium lignosulfonate powder or sodium lignosulfonate extracted from sulfite pulp waste liquid.

4. The method of claim 1, wherein: The aqueous alkali lignin solution in step (4) is derived from commercial alkali lignin.

5. The method of claim 1, wherein: The addition rate of the aqueous alkali lignin solution in step (4) is 200-210 mg / min.