Super-hydrophobic paper-based coating as well as preparation method and application thereof
The preparation of esterified lignin superhydrophobic coating by modifying sulfate lignin by acid chloride has solved the problem of insufficient barrier performance of paper products, achieved efficient utilization of biomass resources and improved superhydrophobic performance, and is suitable for packaging materials.
Patent Information
- Application Number
- CN202510664583.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-22
- Publication Date
- 2025-08-08
AI Technical Summary
Existing paper products have insufficient performance in blocking water, grease and gases, and petroleum-based synthetic polymer coatings reduce their biodegradability and recyclability, and it is necessary to develop a safe and environmentally friendly modification method to improve the hydrophobic properties of lignin.
Acid chloride is used to modify the sulfate lignin. By reacting with acid chlorides of different carbon chain lengths in anhydrous pyridine solvent, esterified lignin is prepared and sprayed on the surface of the paper to form a superhydrophobic coating.
It has achieved efficient utilization of biomass resources and prepared a superhydrophobic paper-based coating with excellent water-blocking properties. It is suitable for existing paper production lines and meets the hydrophobic performance requirements of different application scenarios.
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Figure CN120443507A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of preparation of super-hydrophobic paper-based barrier materials, and in particular relates to a super-hydrophobic paper-based coating, a preparation method thereof, and an application thereof. Background Art
[0002] Packaging materials play a vital role in protecting products from the external environment. Currently, packaging materials mostly rely on petrochemical-derived plastics, which offer advantages such as light weight, low price, corrosion resistance, and excellent mechanical properties. However, these plastics are non-biodegradable, non-renewable, and difficult to recycle, contributing to global climate change. Furthermore, as plastics degrade into microplastics and enter the food chain, they pose a significant threat to the environment and human health. Therefore, developing new plastic alternatives that are biocompatible, biodegradable, environmentally friendly, and low-cost is key to reducing the packaging industry's carbon footprint and achieving sustainable packaging applications.
[0003] Paper products, a traditional packaging material based on wood cellulose, have become an alternative to plastic packaging due to their excellent biodegradability, low cost, and scalable production. However, due to the porous structure and hydrophilic surface of paper, cellulose paper still faces significant challenges in terms of barrier properties against water, grease, and gases, which seriously hinders the application of cellulose paper products in packaging materials. Currently, many packaging materials use petroleum-based synthetic polymers as paper coatings. While these coatings offer lower costs and superior barrier properties, they also reduce the biodegradability and recyclability of the paper-based materials.
[0004] Superhydrophobic surfaces, due to their self-cleaning, anti-corrosion, anti-fog, and anti-fouling properties, have great application potential in aerospace, defense, biomedicine, energy, and other fields. In recent years, biomass materials have gained increasing attention for the preparation of superhydrophobic surfaces due to their environmentally friendly and recyclable properties. Lignin, the second-largest renewable polymer in nature, possesses hydrophobic benzene rings, hydroxyl groups that can be modified, and functional properties such as UV resistance and antibacterial properties, making it an ideal material for the development of high-value-added products.
[0005] However, due to the limited hydrophobicity of lignin itself, chemical modification is required. Chemical modification of lignin enhances its properties by introducing new functional groups or changing its molecular structure, thereby broadening its application in biomaterials. Modification methods mainly include oxidation, reduction, sulfonation, methylation, acetylation, and graft copolymerization. These methods can improve lignin's hydrophobicity, solubility, reactivity, weatherability, and mechanical properties.
[0006] Therefore, we modified kraft lignin by adding acyl chlorides with different carbon chain lengths from 6 to 18 to make it superhydrophobic. Summary of the Invention
[0007] Technical problems to be solved: In view of the above-mentioned problems existing in the prior art, the first technical problem to be solved by the present invention is to provide a method for modifying lignin. The method is simple and convenient, reduces the use of chemical reagents in the preparation process, and is safe and environmentally friendly. The second technical problem to be solved by the present invention is to provide a modified lignin, which has excellent water-blocking properties. The third technical problem to be solved by the present invention is to provide a lignin-based multifunctional barrier paper prepared from modified lignin, which has the functions of blocking water and reducing water vapor permeability. The fourth technical problem to be solved by the present invention is to provide a method for preparing lignin-based super-hydrophobic barrier paper. The method is simple and convenient, and the prepared super-hydrophobic barrier paper can be used for product packaging. The fifth technical problem to be solved by the present invention is to provide the application of lignin-based super-hydrophobic barrier paper in product packaging.
[0008] Technical solution: A method for preparing a super-hydrophobic paper-based coating comprises the following steps: (1) extracting sulfate lignin from papermaking black liquor: filtering the papermaking black liquor and heating it to 40-80°C, adding sulfuric acid to adjust the pH to 2-6, centrifuging and washing with acidic deionized water, and drying to obtain sulfate lignin; (2) esterification modification: reacting the sulfate lignin obtained in step (1) with an acyl chloride with a carbon chain length of C6-C18 in anhydrous pyridine solvent, the reaction temperature is 80-110°C, the stirring rate is 300 rpm, and the reaction time is 3-6 hours to obtain esterified lignin; (3) coating: dissolving the esterified lignin in acetone and spraying it on the paper surface, and controlling the coating amount to 2-7 g / m².
[0009] In step (1), the black liquor heating temperature is controlled at 40-80°C and the pH is adjusted to 2-6.
[0010] The acyl chloride in step (2) can be selected from acyl chlorides with different carbon chain lengths, including acetyl chloride, octanoyl chloride, lauroyl chloride or stearoyl chloride.
[0011] In step (2), the reaction temperature is 80-110°C and the reaction time is 3-6 hours.
[0012] In step (3), the spraying distance is controlled to be 10 cm and the coating amount is 2~7 g / m 2 .
[0013] The esterified lignin-based super-hydrophobic paper-based coating is prepared by the above method.
[0014] A super-hydrophobic barrier paper comprises a paper substrate and the esterified lignin-based super-hydrophobic coating, wherein the coating has a contact angle of 135° to 162° and a Cobb value (60 s) of 5 to 45 g / m².
[0015] The above-mentioned superhydrophobic barrier paper is used in the fields of food packaging, moisture-proofing of electronic products or packaging of medical materials.
[0016] Beneficial effects: (1) Efficient utilization of biomass resources: Using industrial lignin extracted from papermaking black liquor as raw material, high-value utilization of waste resources is achieved, which is in line with the concept of green chemistry. (2) Synergistic effect: By combining esterification modification with physical spraying, micro-nano rough structures are constructed and low surface energy substances are introduced, synergistically improving hydrophobicity. (3) Wide process adaptability: The atmospheric pressure spraying process is adopted, which does not require complex equipment and is suitable for the transformation of existing papermaking production lines. Single-side treatment can reduce raw material consumption (saving more than 30% of the treatment agent dosage). (4) Strong performance controllability: By adjusting the carbon chain length of the acyl chloride (C6-C18), the surface free energy can be precisely controlled, and the contact angle control range is 135°-162°, meeting the needs of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 The figure is a flow chart of a specific embodiment of the process for preparing a paper-based membrane according to the present invention. DETAILED DESCRIPTION
[0018] The present invention will be further described below with reference to specific embodiments.
[0019] The kraft lignin black liquor and unsized cellulose paper used in the following examples were sourced from Jindong Paper Co., Ltd.; the sulfuric acid was sourced from Nanjing Chemical Reagent Co., Ltd. Example 1
[0020] 1. The preparation steps of esterified lignin-based super-hydrophobic barrier paper are as follows: 1) First, filter the papermaking black liquor, heat it to 45℃, add sulfuric acid dropwise and stir continuously, adjust the pH to 3, centrifuge the precipitate, wash it with acidic deionized water, collect the precipitate and centrifuge and dry it to obtain sulfate lignin.
[0021] 2) Graft acetyl chloride onto the kraft lignin molecules to esterify them. Add 15 mL of acetyl chloride dropwise and react at 60°C for 6 h.
[0022] 3) Add 1 g of lignin to 30 mL of acetone, heat to 80 °C in an oil bath, and stir continuously (300 rpm).
[0023] 4) Use spraying method until the coating amount reaches 7 g / m 2 .
[0024] 2. Performance test of esterified lignin-based super-hydrophobic barrier paper The prepared paper was tested for Cobb value.
[0025] Prepare about 30 cm 2A circular sample is placed with the coated surface facing up under a Cobb cylinder. A certain amount of water is then poured into the cylinder. After the water has been in contact for 1 minute, the water is completely poured out and the sample is blot-dried to remove any excess water. The sample paper is then weighed, and the Cobb value is determined based on the weight difference.
[0026] After testing, the contact angle of the functional barrier packaging paper is: 128°±2°, and the Cobb value (60 s) is: 45 g / m². Example 2
[0027] Raw material ratio: octanoyl chloride (C8) modified lignin 1. The preparation steps of esterified lignin-based super-hydrophobic barrier paper are as follows: 1) First, filter the papermaking black liquor, heat it to 45℃, add sulfuric acid dropwise and stir continuously, adjust the pH to 3, centrifuge the precipitate, wash it with acidic deionized water, collect the precipitate and centrifuge and dry it to obtain sulfate lignin.
[0028] 2) Graft octanoyl chloride onto the kraft lignin molecule to esterify it. Add 12 mL of octanoyl chloride dropwise and react at 60°C for 6 h.
[0029] 3) Add 1 g of lignin to 30 mL of acetone, heat to 90 °C in an oil bath, and stir continuously (300 rpm).
[0030] 4) Use spraying method until the coating amount reaches 7 g / m 2 .
[0031] 2. Performance test of esterified lignin-based super-hydrophobic barrier paper The prepared paper was subjected to Cobb value test.
[0032] Prepare about 30 cm 2 A circular sample is placed with the coated surface facing up under a Cobb cylinder. A certain amount of water is then poured into the cylinder. After the water has been in contact for 1 minute, the water is completely poured out and the sample is blot-dried to remove any excess water. The sample paper is then weighed, and the Cobb value is determined based on the weight difference.
[0033] After testing, the contact angle of the functional barrier packaging paper is: 143°±1.5°, and the Cobb value (60s): 28 g / m².
[0034] Example 3 1. The preparation steps of esterified lignin-based super-hydrophobic barrier paper are as follows: 1) First, filter the papermaking black liquor, heat it to 60 ℃, add sulfuric acid dropwise and stir continuously, adjust the pH to 5, centrifuge the precipitate, wash it with acidic deionized water, collect the precipitate and centrifuge and dry it to obtain sulfate lignin.
[0035] 2) Grafting lauroyl chloride onto the kraft lignin molecules to esterify them. Add 12 mL of lauroyl chloride dropwise and react at 70°C for 8 h.
[0036] 3) Add 1 g of lignin to 30 mL of acetone, heat to 90 °C in an oil bath, and stir continuously (300 rpm).
[0037] 4) Apply by spraying until the coating amount reaches 7 g / m².
[0038] 2. Performance test of esterified lignin-based super-hydrophobic barrier paper The prepared paper was subjected to Cobb value test.
[0039] Prepare about 30 cm 2 A circular sample is placed with the coated surface facing up under a Cobb cylinder. A certain amount of water is then poured into the cylinder. After the water has been in contact for 1 minute, the water is completely poured out and the sample is blot-dried to remove any excess water. The sample paper is then weighed, and the Cobb value is determined based on the weight difference.
[0040] After testing, the contact angle of the functional barrier packaging paper is: 152°±1.2°, and the Cobb value (60 s) is: 15 g / m².
[0041] Example 4 Raw material ratio: stearyl chloride (C18) modified lignin 1. The preparation steps of esterified lignin-based super-hydrophobic barrier paper are as follows: 1) First, filter the papermaking black liquor, heat it to 60 ℃, add sulfuric acid dropwise and stir continuously, adjust the pH to 5, centrifuge the precipitate, wash it with acidic deionized water, collect the precipitate and centrifuge and dry it to obtain sulfate lignin.
[0042] 2) Grafting stearoyl chloride onto the kraft lignin molecules to esterify them. 12 mL of stearoyl chloride was added dropwise, and a pre-activation step was added: the lignin was pretreated with 0.5 mol / L NaOH for 2 h.
[0043] 3) Add 1 g of lignin to 30 mL of acetone, heat to 85°C in an oil bath, and react at 70°C for 8 h under nitrogen atmosphere. Stir continuously (300 rpm).
[0044] 4) Apply by spraying until the coating amount reaches 7 g / m².
[0045] 2. Performance test of esterified lignin-based super-hydrophobic barrier paper The prepared paper was tested for Cobb value.
[0046] Prepare about 30 cm 2 A circular sample is placed with the coated surface facing up under a Cobb cylinder. A certain amount of water is then poured into the cylinder. After the water has been in contact for 1 minute, the water is completely poured out and the sample is blot-dried to remove any excess water. The sample paper is then weighed, and the Cobb value is determined based on the weight difference.
[0047] After testing, the contact angle of the functional barrier packaging paper is: 162°±0.8°, and the Cobb value (60 s) is: 5 g / m².
[0048] Example 5 1. The preparation steps of esterified lignin-based super-hydrophobic barrier paper with different coating amounts are as follows: 1) First, filter the papermaking black liquor, heat it to 60 ℃, add sulfuric acid dropwise and stir continuously, adjust the pH to 5, centrifuge the precipitate, wash it with acidic deionized water, collect the precipitate and centrifuge and dry it to obtain sulfate lignin.
[0049] 2) Grafting stearoyl chloride onto the kraft lignin molecules to esterify them. 12 mL of stearoyl chloride was added dropwise, and a pre-activation step was added: the lignin was pretreated with 0.5 mol / L NaOH for 2 h.
[0050] 3) Add 1 g of lignin to 30 mL of acetone, heat to 85°C in an oil bath, and react at 70°C for 8 h under nitrogen protection. Stir continuously (300 rpm).
[0051] 4) Apply by spraying until the coating amount reaches 3 g / m².
[0052] 2. Performance test of esterified lignin-based super-hydrophobic barrier paper The prepared paper was tested for Cobb value.
[0053] Prepare about 30 cm 2 A circular sample is placed with the coated surface facing up under a Cobb cylinder. A certain amount of water is then poured into the cylinder. After the water has been in contact for 1 minute, the water is completely poured out and the sample is blot-dried to remove any excess water. The sample paper is then weighed, and the Cobb value is determined based on the weight difference.
[0054] Testing showed that the functional barrier packaging paper had a contact angle of 158°±1.0° and a Cobb value (60 s) of 10 g / m² (showing excellent durability, with the contact angle remaining at 152° after durability testing).
[0055] The above examples are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.
Claims
1. A method for preparing a super-hydrophobic paper-based coating, characterized in that, The method comprises the following steps: (1) extracting sulfate lignin from papermaking black liquor: filtering the papermaking black liquor and heating it to 40-80°C, adding sulfuric acid to adjust the pH to 2-6, centrifuging and washing with acidic deionized water, and drying to obtain sulfate lignin; (2) esterification modification: reacting the sulfate lignin obtained in step (1) with an acyl chloride with a carbon chain length of C6-C18 in anhydrous pyridine solvent, the reaction temperature is 80-110°C, the stirring rate is 300 rpm, and the reaction time is 3-6 hours to obtain esterified lignin; (3) coating: dissolving the esterified lignin in acetone and spraying it on the surface of paper, and controlling the coating amount to be 2-7 g / m².
2. The method according to claim 1, characterized in that In step (1), the black liquor heating temperature is controlled at 40-80°C and the pH is adjusted to 2-6.
3. The method according to claim 1, characterized in that The acyl chloride in step (2) can be selected from acyl chlorides with different carbon chain lengths, including acetyl chloride, octanoyl chloride, lauroyl chloride or stearoyl chloride.
4. The method according to claim 1, wherein In step (2), the reaction temperature is 80-110°C and the reaction time is 3-6 hours.
5. The method according to claim 1, wherein In step (3), the spraying distance is controlled to be 10 cm and the coating amount is 2~7 g / m 2 .
6. An esterified lignin-based super-hydrophobic paper-based coating prepared by the method according to any one of claims 1 to 5.
7. A super hydrophobic barrier paper, characterized in that: The invention comprises a paper substrate and the esterified lignin-based super-hydrophobic coating according to claim 6, wherein the coating has a contact angle of 135° to 162° and a Cobb value (60 s) of 5 to 45 g / m².
8. Use of the super-hydrophobic barrier paper according to claim 6 or 7 in the fields of food packaging, moisture-proofing of electronic products, or packaging of medical materials.