Preparation method of non-bleached pulp NMMO (N-methylmorpholine-N-oxide) system regenerated ultraviolet shielding film
Through mechanical and enzyme treatment of unflooded pulp, combined with the dissolution and solidification bath regeneration technology of NMMO aqueous solution, an efficient lignocellulose film was prepared, solving the problem of waste of lignin and hemicellulose resources and poor compatibility of traditional ultraviolet shielding agents. , achieving efficient utilization and good mechanical properties and ultraviolet shielding effect.
Patent Information
- Application Number
- CN202411048389.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-01
- Publication Date
- 2024-12-20
AI Technical Summary
The prior art ignores the potential value of lignin and hemicellulose when utilizing lignocellulose, resulting in waste of resources. The compatibility of traditional ultraviolet shielding agents with biomass materials is poor, making it difficult to achieve efficient utilization.
Mechanical treatment and enzyme treatment were performed using unbleached slurry, and cellulose was dissolved using NMMO aqueous solution to prepare a regenerated ultraviolet shielding film containing lignin. Through mechanical, enzyme treatment and freeze-drying, the moisturization of propyl gallate and NMMO aqueous solution was combined with the moisturization of propyl gallate and NMMO aqueous solution. Swelling and vacuuming treatment to form a highly efficient lignocellulose solution and regenerate the film in a solidification bath.
It has achieved the preparation of a green and environmentally friendly lignocellulose film, with good mechanical properties and ultraviolet shielding properties, and can effectively utilize various lignocellulose components, and is suitable for food packaging and ultraviolet protection fields.
Smart Images
Figure CN119161609A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of material science, and in particular relates to a method for preparing an unbleached pulp NMMO system regenerated ultraviolet shielding film. Background Art
[0002] As one of the most abundant natural resources on earth, lignocellulose has the advantages of sustainability, degradability and renewability. Its application fields are extremely wide, covering textiles, papermaking, medicine and other fields, and it is expected to gradually replace traditional petrochemical resources in the future. The raw materials of lignocellulose are mainly cotton, wood, wheat straw, bamboo, reed, etc., and its chemical composition is mainly composed of cellulose, hemicellulose and lignin. The structural characteristics of its components are closely connected, which makes the process of separating cellulose or extracting lignin more complicated and time-consuming. These factors have greatly limited the efficient utilization of lignocellulose. Dissolution regeneration is one of the ways to achieve high-value utilization of lignocellulose. Most of the current processes focus on the extraction and application of cellulose, while ignoring the potential value of lignin and hemicellulose, which has caused a great waste of resources. Therefore, it is particularly important to find a method that can fully utilize the various components of lignocellulose. NMMO has been widely used as a green solvent that can dissolve cellulose. The accessibility of lignocellulose is improved by pretreatment, and membranes, gels and other materials are prepared by dissolution regeneration. Lignin in the cell wall of lignocellulose raw materials has excellent mechanical strength and can provide structural support for plants. In addition, lignin is a natural UV shielding agent. Excessive UV radiation can cause biological poisoning, destruction and degradation of organic matter. Compared with commonly used UV shielding agents such as TiO2 and ZnO, degradable and renewable lignin has good compatibility with biomass materials. Summary of the invention
[0003] In order to overcome the shortcomings of the prior art, the present invention provides a method for regenerating an ultraviolet shielding film in an unbleached pulp NMMO system, which is green, environmentally friendly and easy to operate.
[0004] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:
[0005] S1, subjecting the unbleached pulp to mechanical and enzyme treatment and freeze drying;
[0006] S2. Weigh the treated unbleached pulp, a certain amount of propyl gallate, add unconcentrated NMMO aqueous solution, and swell for a certain period of time at room temperature. Then reduce the pressure and evacuate, raise the temperature to remove the water in the NMMO aqueous solution, thereby increasing the concentration to make it suitable for dissolving cellulose, and stir for a period of time to obtain a lignocellulose solution;
[0007] S3. After defoaming, the solution is quantitatively poured onto a glass plate and scraped evenly, and regenerated in a coagulation bath to obtain a thin regenerated film containing lignin, which is washed with deionized water and dried at room temperature.
[0008] Furthermore, the unbleached pulp in step S1 is one or more of bamboo pulp, wood pulp, cotton pulp, straw pulp, and sugarcane pulp.
[0009] Furthermore, the lignin content in the unbleached pulp in step S1 is 5%-15%.
[0010] Furthermore, the mechanical treatment in step S1 is one or more of PFI refining, ball milling, and Wall-E pulping machine.
[0011] Furthermore, the enzyme treatment in step S1 is one or more of cellulase, xylanase, mannanase and laccase.
[0012] Furthermore, in step S2, the pulp concentration is 1%-5%, and the amount of propyl gallate added is 1%-3% (based on absolute dry pulp).
[0013] Furthermore, in step S2, the swelling time is 2-6 hours, and the swelling concentration of the NMMO aqueous solution is 50%-70%.
[0014] Furthermore, in step S2, the dissolution temperature is 90-110° C., the dissolution time is 2-5 hours, and the dissolution concentration of the NMMO aqueous solution is 83%-87%.
[0015] Furthermore, the coagulation bath in step S3 is one or more of distilled water, ethanol, propanol, methanol, and ethylene glycol.
[0016] Furthermore, the immersion time in the coagulation bath in step S3 is 24-72 hours, during which the coagulation bath is changed every 2-5 hours.
[0017] Furthermore, the defoaming in step S3 is one or more of static defoaming, ultrasonic defoaming, and vacuum defoaming.
[0018] An ultraviolet shielding film prepared by the above preparation method.
[0019] The present invention uses NMMO as a solvent to dissolve cellulose, which is recyclable, non-toxic, and does not pollute the environment, and is in line with the modern green and environmental protection concept.
[0020] The invention uses unbleached pulp as raw material, undergoes mechanical treatment and enzyme treatment, and uses NMMO aqueous solution to prepare a lignin-containing cellulose film. The film has good mechanical properties and ultraviolet shielding properties, and has good application prospects in the fields of food packaging, ultraviolet protection, etc. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 is a digital photograph of the lignocellulose film of the present invention;
[0022] Figure 2 SEM images of the lignocellulose films in the examples and comparative examples of the present invention (a is from Example 1; b is from Example 2; c is from Example 3; d is from Comparative Example 1);
[0023] Figure 3 Infrared images of the lignocellulose films in the examples and comparative examples of the present invention (a is from Example 1; b is from Example 2; c is from Example 3; d is from Comparative Example 1);
[0024] Figure 4 1 and 2 are stress-strain diagrams of the lignocellulose films in the examples and comparative examples of the present invention (a is from Example 1; b is from Example 2; c is from Example 3; d is from Comparative Example 1). DETAILED DESCRIPTION
[0025] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.
[0026] Example 1
[0027] The unbleached pulp is subjected to a ball milling mechanical treatment, and then washed and the moisture is balanced for use. The pulp after grinding is treated with cellulase, washed and freeze-dried. Weigh the treated pulp, a certain amount of propyl gallate, add a 50% NMMO aqueous solution by mass, and swell at room temperature for 6 hours. Then vacuum heat to 86% NMMO, slowly heat to 100°C, stir for about 2 hours to dissolve it, and obtain a 1wt% lignocellulose solution. After ultrasonic defoaming, the uniform solution is quantitatively poured onto a glass plate and scraped with a film scraper, regenerated in distilled water for 24 hours, and dried at room temperature. As can be seen from the data in Table 1, the transmittance of the lignocellulose film is 67%, the UVA ultraviolet shielding rate is about 83%, and the UVB ultraviolet shielding rate is about 87%. Figure 1 Digital photos of lignocellulose films. Figure 2 a is an electron microscope image of the lignocellulose membrane in Example 1, and its surface is relatively smooth, indicating that lignin is well dispersed in the solution. Figure 3 For infrared analysis of lignocellulose membranes. Figure 4 It can be seen that the film has a breaking strength of 22 MPa and a breaking elongation of 2.4% in a dry state.
[0028] Example 2
[0029] The unbleached pulp is subjected to PFI refining treatment, then washed and the moisture is balanced for later use. The pulp after refining is treated with polyxylanase, washed and freeze-dried. Weigh the treated pulp, a certain amount of propyl gallate, put into a 100mL flask, add a 55% NMMO aqueous solution by mass, and swell at room temperature for 4 hours. Then vacuum heat to 85% NMMO, slowly heat to 105°C, stir for about 3 hours to dissolve it, and obtain a 2wt% lignocellulose solution. After standing and defoaming, pour the uniform lignocellulose solution quantitatively onto a glass plate and use a film scraper to scrape the film, regenerate in ethanol for 48 hours, wash with deionized water, and dry at room temperature. As can be seen from the data in Table 1, the transmittance of the cellulose film is 63%, the UVA ultraviolet shielding rate is about 89%, and the UVB ultraviolet shielding rate is about 91%. Figure 2 b is the electron microscopy analysis of the lignocellulose membrane in Example 1. Figure 3 For infrared analysis of lignocellulose membranes. Figure 4 It can be seen that the breaking strength of the film in the dry state is 35 MPa and the breaking elongation is 2.6%.
[0030] Example 3
[0031] The unbleached pulp was beaten with a Wall-E pulper, then washed and the water content was balanced for later use. The pulp after refining was pretreated with cellulase, washed and freeze-dried. Weigh the treated pulp, a certain amount of propyl gallate, put into a 100mL flask, add a 60% NMMO aqueous solution by mass, and swell at room temperature for 5 hours. Then vacuum and heat to 87% NMMO, slowly heat to 110°C, stir for about 3 hours, and obtain a 3wt% lignocellulose solution. After vacuum defoaming, pour the uniform solution quantitatively onto a glass plate and use a film scraper to scrape the film, regenerate in distilled water for 72 hours, and dry at room temperature. It can be seen from the data in Table 1 that the transmittance of the lignocellulose film is 60%, the UVA ultraviolet shielding rate is about 95%, and the UVB ultraviolet shielding rate is about 96%. Figure 2 c is the electron microscopy analysis of the wood cellulose membrane in Example 3, and its surface is relatively smooth. Figure 3 For infrared analysis of lignocellulose membranes. Figure 4 It can be seen that the breaking strength of the film in the dry state is 42 MPa and the breaking elongation is 5.2%.
[0032] Comparative Example 1
[0033] Weigh unbleached pulp, a certain amount of propyl gallate, add an aqueous solution with a mass concentration of 86% NMMO, slowly heat to 100°C, stir for about 4 hours to dissolve it, and obtain a 2wt% lignocellulose solution. After ultrasonic defoaming, pour the uniform solution quantitatively onto a glass plate and use a film scraper to scrape the film, regenerate in ethylene glycol for 24 hours, wash with dedistilled water, and dry at room temperature. From the data in Table 1, it can be seen that the light transmittance of the lignocellulose film is 51%, the UVA ultraviolet shielding rate is about 70%, and the UVB ultraviolet shielding rate is about 76%. Figure 2 d is the electron microscopy analysis of the wood cellulose membrane material of comparative example 1. Figure 3 For infrared analysis of lignocellulose membranes. Figure 4 It can be seen that the breaking strength of the film in the dry state is 20 MPa and the breaking elongation is 2.1%.
[0034] Performance Testing
[0035] Table 1 Light transmittance and UV shielding rate of lignocellulose films in Examples and Comparative Examples
[0036]
[0037] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.
Claims
1. A method for preparing an unbleached pulp NMMO system regenerated ultraviolet shielding film, the main steps of which are: S1, subjecting the unbleached pulp to mechanical and enzyme treatment and freeze drying; S2. Weigh the treated unbleached pulp, a certain amount of propyl gallate, add unconcentrated NMMO aqueous solution, and swell for a certain period of time at room temperature. Then reduce the pressure and evacuate, raise the temperature to remove the water in the NMMO aqueous solution, thereby increasing the concentration. Make it suitable for dissolving cellulose, and stir for a period of time to obtain a lignocellulose solution; S3. After defoaming, the solution is quantitatively poured onto a glass plate and scraped with a film scraper, and then regenerated in a coagulation bath to obtain a thin regenerated film containing lignin, which is washed with deionized water and dried at room temperature.
2. The method for regenerating UV shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: The unbleached pulp in step 1 is one or more of bamboo pulp, wood pulp, cotton pulp, straw pulp and sugarcane pulp, and the lignin content is 3%-15%.
3. The method for regenerating UV shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: In the step 1, the mechanical treatment is one or more of PFI refining, ball milling, and Wall-E pulping machine, and the enzyme treatment is one or more of cellulase, xylanase, mannanase, and laccase.
4. The method for regenerating UV shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: In step 2, the pulp concentration is 1%-5%, and the addition amount of propyl gallate is 1%-3% (based on absolute dry pulp).
5. The method for regenerating ultraviolet shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: In step 2, the swelling time is 2-6 hours, and the swelling concentration of the NMMO aqueous solution is 50%-70%.
6. The method for regenerating UV shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: In step 2, the dissolution temperature is 90-110° C., the dissolution time is 2-5 hours, and the dissolution concentration of the NMMO aqueous solution is 83%-87%.
7. The method for regenerating UV shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: In step 3, the coagulation bath is one or more of distilled water, ethanol, propanol, methanol, and ethylene glycol. The immersion time in the coagulation bath is 24-72 hours, and the coagulation bath is changed every 2-5 hours.
8. The method for regenerating UV shielding film from unbleached pulp NMMO system according to claim 1, characterized in that: The defoaming in step 3 is one or more of static defoaming, ultrasonic defoaming, and vacuum defoaming.