Light-colored kenaf lignin nano-spherical particles and preparation method and application thereof

Abstract

The present invention belongs to the technical field of high-value utilization of woody biomass resources, specifically relating to light-colored kenaf lignin nanoparticles, their preparation method, and applications. The present invention chemically pretreats kenaf xylem to obtain light-colored, stable lignin, which is then further prepared into nanoparticles for use as a natural sunscreen. The remaining fibers are then combined with other fibers to make paper. The preparation method is simple, low-cost, and easy to implement, providing a new strategy for the comprehensive utilization of kenaf biomass resources and possessing excellent practical application value.

Description

Technical Field

[0001] The invention belongs to the technical field of high-value utilization of woody biomass resources, and particularly relates to light-colored kenaf lignin nano-spherical particles, a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Woody biomass, such as wood and straw, is an important biomass resource. Its primary chemical components are cellulose, hemicellulose, and lignin. Lignin is the most abundant natural aromatic polymer on Earth. According to statistics, 50 million tons of industrial lignin are produced annually in the pulping and biomass refining industries, but only approximately 2% is used in the production of composite materials and industrial chemicals. Most of this lignin is burned as a low-value fuel for heat energy, rather than being used for high-value purposes. This leads to a waste of woody biomass resources.

[0004] Lignin is an aromatic compound containing phenolic and ketone groups, making it highly resistant to UV rays. However, in the pulp and paper industry, the intense chemical reactions during delignification lead to severe polycondensation of lignin, forming dark lignin, making it difficult to use in high-value-added products such as sunscreen.

[0005] Kenaf is a short-lived hemp fiber crop with a physical structure consisting of phloem and xylem. The phloem is widely used in the textile industry, while the xylem is typically discarded or incinerated, preventing the comprehensive utilization of kenaf biomass resources. Summary of the Invention

[0006] To address the shortcomings of the aforementioned prior art, the inventors, after extensive technical and practical exploration, have developed a light-colored kenaf lignin nanoparticle, a preparation method, and applications thereof. This invention utilizes chemical pretreatment of kenaf xylem to obtain light-colored, stable lignin, which is then further prepared into nanoparticles for use as a natural sunscreen. The remaining fibers are then combined with other fibers to make paper, thereby providing a new strategy for the comprehensive utilization of kenaf biomass resources. This invention is based on these research findings.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a method for preparing light-colored kenaf lignin nano-spherical particles, the preparation method comprising:

[0009] S1. crushing kenaf stalks and washing them with water to remove impurities to obtain kenaf powder particles;

[0010] S2, placing the kenaf powder particles obtained in step S1 in a formaldehyde / p-toluenesulfonic acid aqueous solution, stirring at room temperature, and then heating and stirring and steaming;

[0011] S3, performing solid-liquid separation on the material after cooking in step S2, washing the solid portion with water until neutral to obtain kenaf fiber for standby use, and adding water to the filtrate to obtain kenaf crude lignin;

[0012] S4, washing the crude kenaf lignin obtained in step S3 with water until neutral, and drying to obtain kenaf lignin;

[0013] S5. Dissolve the kenaf lignin prepared in step S4 in a γ-valerolactone solution, dialyze in water, and then dry to obtain light-colored kenaf lignin nano-spherical particles.

[0014] The second aspect of the present invention provides light-colored kenaf lignin nano-spherical particles and / or kenaf fibers produced by the above-mentioned preparation method.

[0015] The third aspect of the present invention provides the application of the above preparation method in any one or more of the following:

[0016] (a) UV protection or the preparation of sunscreen products.

[0017] (b) Papermaking.

[0018] Compared with the existing technical solutions, the above one or more technical solutions have the following beneficial effects:

[0019] (1) The above technical solution provides a light-colored ramie lignin nano-spherical particle, which has a regular spherical shape and a small particle size, and exhibits excellent ultraviolet protection performance when mixed with commercial sunscreen lotion.

[0020] (2) The kenaf stalk biomass raw material used in the above technical solution is agricultural and forestry waste, which is pretreated with formaldehyde / p-toluenesulfonic acid solution. The process is simple to operate, has a short reaction time, and mild conditions; p-toluenesulfonic acid can be recycled using recycling technology.

[0021] (3) The above technical solution provides that the combination of kenaf stalk fiber and coniferous wood pulp for papermaking can reduce the cost of paper production and improve some paper properties to a certain extent, so it has good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 is a SEM image of light-colored spherical nanoparticles of kenaf lignin prepared in Example 1 of the present invention;

[0024] Figure 2 This is an appearance diagram of the mixed sunscreen lotion prepared in Example 1 of the present invention;

[0025] Figure 3 This is a test chart of the ultraviolet transmittance of different sunscreen lotions containing light-colored kenaf lignin nano-spherical particles in different proportions in Example 1 of the present invention;

[0026] Figure 4 This is a measurement chart of the sun protection factor (SPF) of the mixed sunscreen lotion in Example 1 of the present invention.

[0027] Figure 5 This is a graph showing the physical properties of paper obtained by testing papermaking using different ratios of kenaf fiber and softwood pulp in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] As mentioned earlier, kenaf is a short-lived hemp fiber crop whose physical structure is divided into phloem and xylem. The phloem is widely used in the textile industry, while the xylem is usually discarded or incinerated, preventing the comprehensive utilization of kenaf biomass resources.

[0031] In view of this, the present invention uses agricultural and forestry waste kenaf stalks as raw materials and utilizes formaldehyde / p-toluenesulfonic acid aqueous solution as pretreatment reagents. During the pretreatment process, formaldehyde stabilizes lignin, reduces the degree of condensation, and reduces color. The entire process is simple to operate, has a short reaction time, mild conditions, and p-toluenesulfonic acid can be recycled. The obtained lignin is further prepared into nano-spherical particles using the green solvent γ-valerolactone and applied to sunscreen lotion, showing good sunscreen effect and can be used as a sunscreen additive. The remaining solids are ultrasonically dispersed into fibers and further mixed with coniferous wood pulp for papermaking, which can effectively improve the ring crush strength index and tensile index of the paper, which can not only reduce papermaking costs, but also achieve efficient utilization of agricultural and forestry waste.

[0032] Specifically, in a typical embodiment of the present invention, a method for preparing light-colored kenaf lignin nano-spherical particles is provided, the preparation method comprising:

[0033] S1. crushing kenaf stalks and washing them with water to remove impurities to obtain kenaf powder particles;

[0034] S2, placing the kenaf powder particles obtained in step S1 in a formaldehyde / p-toluenesulfonic acid aqueous solution, stirring at room temperature, and then heating and stirring and steaming;

[0035] S3, performing solid-liquid separation on the material after cooking in step S2, washing the solid portion with water until neutral to obtain kenaf fiber for standby use, and adding water to the filtrate to obtain kenaf crude lignin;

[0036] S4, washing the crude kenaf lignin obtained in step S3 with water until neutral, and drying to obtain kenaf lignin;

[0037] S5. Dissolve the kenaf lignin prepared in step S4 in a γ-valerolactone solution, dialyze in water, and then dry to obtain light-colored kenaf lignin nano-spherical particles.

[0038] In another embodiment of the present invention,

[0039] In step S1, the kenaf stalks are peeled kenaf stalks;

[0040] The particle size of the particles obtained after the crushing is 20-40 meshes.

[0041] In another embodiment of the present invention,

[0042] In step S2, the formaldehyde / p-toluenesulfonic acid aqueous solution is controlled to have a formaldehyde concentration of 1.0-3.0 wt% (preferably 1.5 wt%) and a p-toluenesulfonic acid concentration of 45-65 wt% (preferably 50 wt%). Furthermore, the p-toluenesulfonic acid can be recycled and reused through recycling technology. The present invention utilizes the formaldehyde / p-toluenesulfonic acid aqueous solution as a pretreatment reagent. During the pretreatment process, formaldehyde stabilizes lignin, reduces condensation, and reduces color.

[0043] The mass volume ratio of the kenaf powder particles to the formaldehyde / p-toluenesulfonic acid aqueous solution is 1-10 g:50 mL, preferably 3 g:50 mL.

[0044] The stirring treatment at room temperature and then heating for stirring and cooking treatment is specifically a stirring treatment at room temperature for 10-60 minutes, preferably 30 minutes, and then a heating and stirring treatment at 60-80° C. (preferably 70° C.) for 10-60 minutes, preferably 30 minutes.

[0045] In another embodiment of the present invention,

[0046] In step S3, the water addition and sedimentation treatment time is not less than 24 hours. The sedimentation treatment for a certain period of time allows the crude lignin of kenaf to be deposited.

[0047] In another embodiment of the present invention,

[0048] In step S5, the γ-valerolactone solution is a high-concentration γ-valerolactone solution, such as a 98% γ-valerolactone solution, and the concentration of the kenaf lignin in the solution is controlled to be 0.2-0.8 mg / mL (preferably 0.4 mg / mL). By controlling the addition concentration, the particle size of the finally prepared light-colored kenaf lignin nano-spherical particles is uniform.

[0049] The dialysis time is controlled to be no less than 48 hours. In another specific embodiment of the present invention, the dialysis time is 48 hours.

[0050] In another embodiment of the present invention,

[0051] In steps S4 and S5, the drying process is preferably freeze drying. To avoid the introduction of impurities, the water used in the preparation method is pure water.

[0052] In another embodiment of the present invention, light-colored kenaf lignin nano-spherical particles and / or kenaf fibers prepared by the above-mentioned preparation method are provided.

[0053] In another embodiment of the present invention, the application of the above preparation method in any one or more of the following is provided:

[0054] (a) UV protection or the preparation of sunscreen products.

[0055] (b) Papermaking.

[0056] Specifically, in application (a), the sunscreen product can be made by adding the aforementioned light-colored kenaf lignin nanoparticles to an existing sunscreen product. The added mass fraction of the light-colored kenaf lignin nanoparticles is controlled to be 1-4%, such as 1%, 2%, 3%, or 4%. Research has shown that adding a small amount of light-colored kenaf lignin nanoparticles can significantly enhance the sunscreen product's effectiveness.

[0057] The known existing product may be any known sunscreen cream, sunscreen lotion, or sunscreen lotion, etc. In one embodiment of the present invention, the known existing product includes but is not limited to commercial sunscreen lotions with SPF10, SPF30, and SPF50.

[0058] In the application (b), the papermaking may specifically be a process of mixing the kenaf fiber and coniferous wood pulp to make paper.

[0059] The kenaf fiber addition rate is controlled at 1-20%, such as 1%, 5%, 10%, 15%, and 20%. The present invention has found that when the kenaf fiber addition rate is 5%, the paper's ring crush index increases from 5.7 N·m / g to 5.8 N·m / g, and its tensile index increases from 14.5 N·m / g to 16.0 N·m / g, while its tear index decreases. Therefore, adding an appropriate amount of kenaf fiber to softwood pulp can effectively improve the paper's ring crush index and tensile index, reducing papermaking costs while achieving efficient utilization of agricultural waste.

[0060] The present invention will be further described below with reference to specific examples. The following examples are only for the purpose of explaining the present invention and are not intended to limit its content. Any simple modifications, equivalent changes and modifications made to the embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

[0061] Example 1

[0062] A method for preparing light-colored kenaf lignin nano-spherical particles, comprising:

[0063] (1) The peeled kenaf stalks are used as raw materials and further processed into powder particles. The powder particles of 20-30 mesh are taken and washed with water to remove impurities.

[0064] (2) Prepare a mixed aqueous solution with a formaldehyde concentration of 1.5 wt% and a p-toluenesulfonic acid concentration of 50 wt%, measure 50 mL into a round-bottom flask, add 3 g of the powdered material in step (1), stir at room temperature for 30 min, and then place in an oil bath at 70°C and stir for 30 min.

[0065] (3) After the cooking is completed, the material in step (2) is subjected to solid-liquid separation using a suction filtration device, the filtrate is transferred to a beaker, distilled water is added to precipitate the kenaf crude lignin, the solid part is washed with distilled water until neutral, and placed in an ultrasonic instrument for ultrasonic dispersion for 30 minutes to obtain kenaf fiber.

[0066] (4) washing the lignin obtained in step (3) with distilled water until neutral, and freeze-drying the lignin to obtain light-colored kenaf lignin.

[0067] (5) The lignin in step (4) was dissolved in 98% γ-valerolactone solution at a concentration of 0.4 mg / mL, dialyzed in distilled water for 48 h at room temperature, and then freeze-dried to obtain light-colored kenaf lignin nano-spherical particles, labeled as ESL-LNPs. Figure 1 As shown, the light-colored kenaf lignin is in the form of regular spherical nanoparticles.

[0068] The light-colored linalool nanoparticles (ESL-LNPs) prepared in this example were mixed with a commercial sunscreen lotion with SPF10 at a mass fraction of 1%, 2%, 3% and 4%, respectively, and mixed with a commercial sunscreen lotion with SPF30 at a mass fraction of 2%, and stirred at room temperature in the dark for 24 hours. The resulting mixed emulsions were as follows: Figure 2 As shown in the figure, it can be seen that the appearance of the mixed sunscreen lotion is light yellow.

[0069] Test the UV transmittance of mixed sunscreen lotion Figure 3 As shown in the figure, as the amount of light-colored kenaf lignin nanoparticles added increases, the UV transmittance of the sunscreen lotion in the UVA (320nm-400nm) and UVB (290nm-320nm) regions decreases significantly, indicating that the prepared light-colored kenaf lignin nanoparticles have excellent UV blocking properties in the sunscreen lotion. In particular, when 2% light-colored kenaf lignin nanoparticles are added to a commercial SPF 30 lotion, its UV transmittance shows a significant decrease in the UVA region compared to the sunscreen lotion without light-colored kenaf lignin nanoparticles, indicating that the prepared light-colored kenaf lignin nanoparticles have excellent broad-spectrum sun protection in the sunscreen lotion.

[0070] The results of calculating the sun protection index (SPF) based on the UV transmittance are as follows: Figure 4As shown, the actual measured SPF values ​​of commercial sunscreen lotions with SPF 10, SPF 30, and SPF 50 are 7.05, 37.16, and 46.4, respectively. Adding 3% of light-colored kenaf lignin nanoparticles to a commercial SPF 10 sunscreen lotion reaches an SPF value of 20.42, meeting the market demand for SPF 15 sunscreen products. Increasing the addition level to 4% increases the SPF value to 27.84, approximately four times that of the original sunscreen lotion and approaching the UV protection requirement of SPF 30 sunscreen products. At a 2% addition level to a commercial SPF 30 sunscreen lotion, the SPF value reaches 67.88, far exceeding the requirement for SPF 30 sunscreen products on the market.

[0071] The kenaf fibers obtained in this example were mixed with softwood pulp at mass fractions of 0%, 5%, 10%, 15% and 20% to make paper, and the physical properties of the obtained paper (including ring crush strength index, tensile index and tear index) were tested. Figure 5 As shown in the figure, adding an appropriate amount of kenaf fiber to softwood pulp improves the physical properties of paper to a certain extent. For example, when the kenaf fiber addition level is 5%, the paper's ring crush index increases from 5.7 N·m / g to 5.8 N·m / g, and the tensile index increases from 14.5 N·m / g to 16.0 N·m / g, while the tear index decreases. Therefore, adding an appropriate amount of kenaf fiber to softwood pulp can effectively improve the paper's ring crush index and tensile index, reducing papermaking costs while achieving efficient utilization of agricultural waste.

[0072] Example 2

[0073] A method for preparing light-colored kenaf lignin nano-spherical particles, comprising:

[0074] (1) The peeled kenaf stalks are used as raw materials and further processed into powder particles. The powder particles of 30-40 mesh are taken and washed with water to remove impurities.

[0075] (2) Prepare a mixed aqueous solution with a formaldehyde concentration of 1.0 wt% and a p-toluenesulfonic acid concentration of 60 wt%, measure 50 mL into a round-bottom flask, add 5 g of the powdered material in step (1), stir at room temperature for 30 min, and then place in an oil bath at 70°C and stir for 30 min.

[0076] (3) After the cooking is completed, the material in step (2) is subjected to solid-liquid separation using a suction filtration device, the filtrate is transferred to a beaker, distilled water is added to precipitate the kenaf crude lignin, the solid part is washed with distilled water until neutral, and placed in an ultrasonic instrument for ultrasonic dispersion for 30 minutes to obtain kenaf fiber.

[0077] (4) washing the lignin obtained in step (3) with distilled water until neutral, and freeze-drying the lignin to obtain light-colored kenaf lignin.

[0078] (5) The lignin in step (4) was dissolved in 98% γ-valerolactone solution at a concentration of 0.3 mg / mL, dialyzed in distilled water at room temperature for 48 h, and then freeze-dried to obtain light-colored kenaf lignin nano-spherical particles.

[0079] The light-colored kenaf lignin nano-spherical particles prepared in this example were mixed with a commercial sunscreen lotion with SPF10 at a mass fraction of 1%, 2%, 3% and 4%, respectively, and were mixed with a commercial sunscreen lotion with SPF30 at a mass fraction of 2%.

[0080] The kenaf fibers obtained in this example were mixed with softwood pulp at mass fractions of 0%, 5%, 10%, 15% and 20% for papermaking.

[0081] Example 3

[0082] A method for preparing light-colored kenaf lignin nano-spherical particles, comprising:

[0083] (1) The peeled kenaf stalks are used as raw materials and further processed into powder particles. 30-40 powder particles are taken and washed with water to remove impurities.

[0084] (2) Prepare a mixed aqueous solution with a formaldehyde concentration of 1.5 wt% and a p-toluenesulfonic acid concentration of 70 wt%, measure 50 mL into a round-bottom flask, add 2 g of the powdered material in step (1), stir at room temperature for 30 min, and then place in an oil bath at 70°C and stir for 30 min.

[0085] (3) After the cooking is completed, the material in step (2) is subjected to solid-liquid separation using a suction filtration device, the filtrate is transferred to a beaker, distilled water is added to precipitate the kenaf crude lignin, the solid part is washed with distilled water until neutral, and placed in an ultrasonic instrument for ultrasonic dispersion for 30 minutes to obtain kenaf fiber.

[0086] (4) washing the lignin obtained in step (3) with distilled water until neutral, and freeze-drying the lignin to obtain light-colored kenaf lignin.

[0087] (5) The lignin in step (4) was dissolved in 98% γ-valerolactone solution at a concentration of 0.5 mg / mL, dialyzed in distilled water at room temperature for 48 h, and then freeze-dried to obtain light-colored kenaf lignin nano-spherical particles.

[0088] The light-colored kenaf lignin nano-spherical particles prepared in this example were mixed with a commercial sunscreen lotion with SPF10 at a mass fraction of 1%, 2%, 3% and 4%, respectively, and were mixed with a commercial sunscreen lotion with SPF30 at a mass fraction of 2%.

[0089] The kenaf fibers obtained in this example were mixed with softwood pulp at mass fractions of 0%, 5%, 10%, 15% and 20% for papermaking.

[0090] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing light-colored kenaf lignin nano-spherical particles, characterized in that: The preparation method comprises: S1. crushing kenaf stalks and washing them with water to remove impurities to obtain kenaf powder particles; S2, placing the kenaf powder particles obtained in step S1 in a formaldehyde / p-toluenesulfonic acid aqueous solution, stirring at room temperature, and then heating and stirring and steaming; In the formaldehyde / p-toluenesulfonic acid aqueous solution, the formaldehyde concentration is controlled to be 1.0-3.0 wt %, and the p-toluenesulfonic acid concentration is controlled to be 45-65 wt %; S3, performing solid-liquid separation on the material after cooking in step S2, washing the solid portion with water until neutral to obtain kenaf fiber for standby use, and adding water to the filtrate to obtain kenaf crude lignin; S4, washing the crude kenaf lignin obtained in step S3 with water until neutral, and drying to obtain kenaf lignin; S5, dissolving the kenaf lignin prepared in step S4 in a γ-valerolactone solution, dialyzing in water, and drying to obtain light-colored kenaf lignin nano-spherical particles; The γ-valerolactone solution is a high-concentration γ-valerolactone solution, including a 98% γ-valerolactone solution. The concentration of the kenaf lignin in the solution is controlled to be 0.2-0.8 mg / mL.

2. The preparation method according to claim 1, wherein In step S1, the kenaf stalks are peeled kenaf stalks; The particle size of the particles obtained after the crushing is 20-40 meshes.

3. The preparation method according to claim 1, wherein In step S2, the mass volume ratio of the kenaf powder particles to the formaldehyde / p-toluenesulfonic acid aqueous solution is 1-10 g:50 mL; The stirring treatment at room temperature and then the heating and stirring cooking treatment are specifically carried out by stirring at room temperature for 10-60 minutes and then heating and stirring at 60-80° C. for 10-60 minutes.

4. The preparation method according to claim 1, wherein In step S2, the mass volume ratio of the kenaf powder particles to the formaldehyde / p-toluenesulfonic acid aqueous solution is 3 g:50 mL.

5. The preparation method according to claim 1, wherein In step S3, the water addition and sedimentation treatment time is not less than 24 hours.

6. The preparation method according to claim 1, wherein In step S5, the dialysis time is controlled to be no less than 48 hours.

7. The preparation method according to claim 1, wherein In steps S4 and S5, the drying process used is freeze drying.

8. Light-colored kenaf lignin nano-spherical particles and / or kenaf fibers obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the preparation method according to any one of claims 1 to 7 in any one or more of the following: (a) UV protection or the preparation of sunscreen products; (b) Papermaking.

10. The use according to claim 9, characterized in that In the application (a), the sunscreen product is specifically prepared by adding the light-colored kenaf lignin nano-spherical particles according to claim 8 to an existing known sunscreen product; the existing known product is any known sunscreen cream, sunscreen lotion or sunscreen lotion.

11. The use according to claim 10, characterized in that In the application (a), the added mass fraction of the light-colored kenaf lignin nano-spherical particles is controlled to be 1-4%; the existing known products include commercial sunscreen lotions with SPF10, SPF30 and SPF50.

12. The use according to claim 9, characterized in that In the application (b), the papermaking is specifically to mix the kenaf fiber according to claim 8 with softwood pulp to make paper; the mass fraction of the kenaf fiber added is controlled to be 1-20%.

13. The use according to claim 12, characterized in that The added mass fraction of the kenaf fiber is controlled to be 5%.

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