Long-chain fat modified chitosan, preparation method and application thereof, high-hydrophobicity textile and preparation method thereof

Abstract

The invention relates to long-chain fat modified chitosan, a preparation method and application thereof, a high-hydrophobicity textile and a preparation method thereof, and belongs to the technical field of functional material and textile treatment. The method comprises the following steps: in the presence of a protective atmosphere and an organic solvent, enabling chitosan to react with long-chain fatty acyl chloride, and sequentially purifying and freeze-drying an obtained crude product, thereby obtaining the long-chain fatty acyl chloride, the number of carbon atoms in the long-chain fatty acyl chloride is greater than or equal to 12. The long-chain fat modified chitosan provided by the invention not only is a super-hydrophobic finishing agent which does not contain perfluorinated and polyfluoroalkyl substances and organic silicon completely, fundamentally solves the problems of environmental persistent pollution and health risk caused by a traditional fluorine-containing finishing agent, but also is a finishing technology which can endow textiles with excellent super-hydrophobic performance and good wearing comfort; furthermore, the long-chain fat modified chitosan can be biodegraded, so that accumulative pollution to the environment is avoided.

Description

Technical Field

[0001] This invention relates to a long-chain fatty acid-modified chitosan and its preparation method and application, as well as a highly hydrophobic textile and its preparation method, belonging to the field of functional materials and textile treatment technology. Background Technology

[0002] The development of hydrophobic finishing agents for textiles has evolved from traditional hydrophobic agents such as paraffin and metallic soaps to high-performance products such as organosilicon, long-chain fluorocarbons (PFAS), and fluoropolymers. Among these, PFAS-based finishing agents dominated for decades due to their extremely low surface energy and excellent durability. However, in recent years, PFAS substances have been shown to have extremely high environmental persistence, bioaccumulation, and potential biotoxicity, thus becoming targets of strict restrictions and even bans by global regulatory agencies. This has forced the entire textile industry to urgently seek an alternative technology that can meet high-performance requirements while being environmentally friendly, safe, and sustainable.

[0003] Currently, the PFAS alternative technologies available on the market mainly fall into the following categories:

[0004] Organosilicon finishing agents impart hydrophobicity to fabrics through the siloxane backbone and organic side chains. They have poor biodegradability and may generate small siloxane molecules during degradation, posing new environmental risks. Furthermore, these finishing agents typically require solvent processing and may cause fabrics to become stiff or yellow.

[0005] Hydrocarbon wax-based finishing agents: Derived from natural animal and plant waxes or petrochemical waxes, they have good safety and biodegradability. However, waxes have low melting points, poor thermal stability, and generally insufficient abrasion resistance and washability. To improve performance, they are often compounded with synthetic polymers such as polyurethane, which introduces non-degradable components and may cause phase separation, affecting the uniformity and durability of the finishing effect.

[0006] Fluoropolymer-free polymers (such as acrylic resins): These finishing agents provide water repellency by forming a film on the fiber surface. However, their main drawback is that they significantly alter the original style of the fabric, resulting in a stiff feel, reduced breathability, and severely impacting wearing comfort.

[0007] Chitosan, a natural cationic polysaccharide, has attracted widespread attention in the field of functional finishing of textiles due to its biocompatibility, biodegradability, antibacterial properties, and excellent film-forming ability. While academia and industry have conducted extensive research, existing chitosan-based finishing agent patents and technical solutions still have several significant shortcomings: firstly, their functions are limited, making it difficult to achieve high-performance superhydrophobicity; secondly, the processes are complex, requiring solvents and raising concerns about environmental friendliness; thirdly, they are difficult to form continuous, dense films, sacrificing the comfort of the fabric; and fourthly, their biodegradability is limited.

[0008] Therefore, there is an urgent need to develop a new hydrophobic finishing agent for textiles. Summary of the Invention

[0009] To address the problems existing in the prior art, one of the objectives of this invention is to provide a method for preparing long-chain fatty modified chitosan. This method involves reacting chitosan with long-chain fatty acyl chlorides, and grafting the acyl groups onto the hydroxyl and amino groups of chitosan through esterification and amidation reactions to generate long-chain fatty modified chitosan. This preparation method is simple and convenient for industrial production.

[0010] The second objective of this invention is to provide a long-chain fatty acid-modified chitosan. The long-chain fatty acid-modified chitosan provided by this invention is not only completely free of PFAS (per- and polyfluoroalkyl substances) and organosilicon superhydrophobic finishing agents, fundamentally solving the problems of persistent environmental pollution and health risks caused by traditional fluorinated finishing agents, but also endows textiles with excellent superhydrophobic properties and good wearing comfort. Furthermore, this long-chain fatty acid-modified chitosan can also be biodegraded, avoiding cumulative environmental pollution.

[0011] The third objective of this invention is to provide an application of long-chain fatty acid-modified chitosan as a hydrophobic finishing agent for textiles.

[0012] The fourth objective of this invention is to provide a method for preparing highly hydrophobic textiles, in which no organic solvents are required, thereby reducing the environmental impact and safety hazards during the production process.

[0013] The fifth objective of this invention is to provide a highly hydrophobic textile that effectively combines superhydrophobicity with core performance characteristics such as softness and breathability.

[0014] To achieve the above objectives, a first aspect of the present invention provides a method for preparing long-chain fatty acid-modified chitosan, the method comprising:

[0015] Chitosan was reacted with long-chain fatty acyl chloride in the presence of a protective atmosphere and organic solvent. The crude product was then purified and freeze-dried to obtain the final product.

[0016] The long-chain fatty acyl chloride has ≥12 carbon atoms;

[0017] The volume of the long-chain fatty acyl chloride used is 8-16 mL relative to 1 g of the chitosan.

[0018] This invention achieves 100% bio-based, PFAS-free superhydrophobicity by precisely chemically modifying the chitosan molecule (grafting long-chain alkyl groups) to generate long-chain aliphatic modified chitosan through esterification and amidation reactions. This allows the chitosan itself to become the source of hydrophobicity, without relying on any external fluorinated or silicone resins. The long-chain aliphatic modification, by grafting long-chain alkanes onto the chitosan molecular chain, significantly reduces the surface energy of the chitosan, providing the chemical basis for its hydrophobicity. Furthermore, the freeze-dried modified chitosan powder possesses a porous structure, allowing for the formation of discrete "island-like" coating spots on subsequent fabric fibers, further enhancing hydrophobicity.

[0019] As a preferred embodiment, the reaction temperature of chitosan with long-chain fatty acyl chloride is 105~125℃, and the reaction time is 4~6h.

[0020] As a preferred embodiment, the long-chain fatty acyl chloride has 16 to 22 carbon atoms.

[0021] As a preferred embodiment, the chitosan has a degree of deacetylation of 75-85% and a molecular weight of 200-250 kDa.

[0022] As a preferred embodiment, the purification process includes: adding the crude product to glacial ethanol, dissolving the obtained solid in dichloromethane after solid-liquid separation, and then adding the resulting solution to glacial ethanol to precipitate the solid.

[0023] As a preferred embodiment, the organic solvent is pyridine.

[0024] It should be noted that the present invention does not have any special requirements on the amount of the organic solvent used, and any solvent known in the art may be used.

[0025] A second aspect of the present invention is to provide a long-chain fatty acid-modified chitosan prepared by the preparation method described in the first aspect above.

[0026] A third aspect of the present invention is to provide the application of the long-chain fatty acid-modified chitosan described in the second aspect above as a hydrophobic finishing agent for textiles.

[0027] A fourth aspect of the present invention is to provide a method for preparing a highly hydrophobic textile, the method comprising:

[0028] Long-chain fatty acid-modified chitosan is evenly spread onto the surface of the fabric, and then the fabric with the long-chain fatty acid-modified chitosan is heat-treated to obtain the product.

[0029] The long-chain fatty acid-modified chitosan is the long-chain fatty acid-modified chitosan described in the second aspect above.

[0030] This invention employs a core process of "modification followed by dry coating." Although solvents are used in the modification step of long-chain fatty acid-modified chitosan, the final coating deposition process is a completely solvent-free dry heat treatment process. This significantly reduces VOC emissions and wastewater generation in the final production stage, better meeting the requirements of green chemicals and clean production.

[0031] Furthermore, during the heat treatment process, the long-chain fatty acid-modified chitosan powder melts and, through its own reactive groups (amino and hydroxyl groups), undergoes physical anchoring and possible chemical bonding with the fabric fiber surface, thus firmly adhering to the fiber and forming a discontinuous "island-like" coating with a micron-scale rough structure on the surface, rather than a closed continuous film. This combination of dual roughness structure and low surface energy chemical composition conforms to the Cassie-Baxter model and is key to generating superhydrophobicity.

[0032] Furthermore, this invention considers the entire life cycle of materials from the design stage. The modified chitosan backbone retains its biodegradable properties, which has been fully verified through BOD testing. This ensures that the coated textiles can be degraded by microorganisms in the natural environment after disposal, avoiding permanent pollution like PFAS or plastics, and truly conforming to the principles of a circular economy.

[0033] As a preferred embodiment, the heat treatment conditions are as follows: in an air atmosphere, the temperature is increased from room temperature to 140-160°C at a heating rate of 8-12°C / min, and then held at 140-160°C for 8-15 minutes.

[0034] The particle size of the long-chain fatty modified chitosan is <100μm.

[0035] This invention constructs a discontinuous "island-like" dot-like coating on the fiber surface by controlling the particle size of modified chitosan powder and the heat treatment process. This structure creates roughness at the micron scale to achieve superhydrophobicity, while preserving the original porosity and structure of the fabric to the maximum extent at the macro scale, thus excellently balancing superhydrophobicity with the fabric's core performance characteristics such as softness and breathability.

[0036] As a preferred embodiment, the density of the long-chain fatty acid-modified chitosan sprinkled on the fabric surface is 1~2.5 mg / cm². This preferred configuration ensures the fabric's durability and breathability. If the density is too high, the fabric's durability will be reduced; if the density is too low, the fabric's feel will be affected, causing it to stiffen.

[0037] The present invention does not have special requirements for the material of the fabric, which can be a hydrophilic cellulose fabric and / or a hydrophobic polyester.

[0038] A fifth aspect of the present invention is to provide a highly hydrophobic textile prepared by the preparation method described in the fourth aspect above.

[0039] Compared with the prior art, the present invention has at least the following advantages:

[0040] (1) Compared with the prior art, the present invention is not a simple formulation improvement or process adjustment, but a systematic and original solution from molecular design, synthesis route, application process to performance evaluation. It successfully solves the core pain points of the prior art such as "difficulty in balancing function and environmental protection", "contradiction between performance and comfort", and "neither production nor waste is green", and provides a high-performance superhydrophobic finishing technology for textiles that truly meets the requirements of future sustainable development, with significant progressiveness and outstanding substantive features.

[0041] (2) The highly hydrophobic textile provided by the present invention has excellent superhydrophobicity. Droplet impact test shows that the coating can achieve complete droplet rebound and has anti-dynamic wetting ability.

[0042] (3) The highly hydrophobic textile provided by the present invention has excellent acid resistance. After repeated immersion in acidic solution, its superhydrophobic properties can still be maintained, showing chemical stability superior to many wax-based coatings.

[0043] (4) The highly hydrophobic textile provided herein has good environmental compatibility and safety. The material can be degraded by microorganisms and by heat.

[0044] (5) The highly hydrophobic textile provided by the invention can maintain the comfort of the fabric. Its unique “island” coating structure avoids the formation of a continuous film, thereby maximizing the preservation of the original porosity, breathability, moisture permeability and soft hand feel of the fabric, which is an advantage that traditional film-forming finishing agents cannot match.

[0045] (6) This invention provides a long-chain fatty modified chitosan that is completely free of PFAS (per- and polyfluoroalkyl substances) and organosilicon as a superhydrophobic finishing agent. Its hydrophobicity comes from the long carbon chain, which fundamentally solves the problem of persistent environmental pollution and health risks caused by traditional fluorinated finishing agents. Attached Figure Description

[0046] Figure 1 The image shows a SEM image of the long-chain fatty modified chitosan powder prepared in Example 1. It can be seen from the image that the chitosan powder exhibits an irregular porous sheet-like structure, and the lateral size of the sheet-like particles is distributed between 10 and 100 micrometers.

[0047] Figure 2This is a SEM image of the highly hydrophobic textile prepared in Example 1. As can be seen from the image, the coating adheres to the surface of the fabric fibers in a discrete island-like structure. The size of these island-like structures is approximately 50 to 150 micrometers, and their coverage area accounts for 40% to 70% of the fiber surface area. This structure allows the porosity between fibers to be retained, thereby ensuring the breathability of the finished fabric. Detailed Implementation

[0048] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0049] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] The preparation examples of the present invention are used to prepare long-chain fatty acid-modified chitosan.

[0052] Preparation Example 1

[0053] In a 250 mL three-necked round-bottom flask equipped with a reflux condenser, accurately weigh 1.00 g of chitosan powder (acetylation 80%, MW 230 kDa). Add 60 mL of pyridine to the flask and mechanically stir until the chitosan is fully dispersed. Then, slowly add 13.2 mL of stearoyl chloride dropwise using a constant-pressure dropping funnel, controlling the dropping rate to avoid an overly vigorous reaction. Heat the reaction system in an oil bath to 115°C and, under nitrogen protection, continuously stir and reflux for 5 hours. During the reaction, the system gradually changes from a suspension to a homogeneous phase, eventually becoming a pale yellow to brownish-yellow viscous liquid. After the reaction is complete, cool to room temperature. Slowly pour the reaction mixture into 400 mL of ice-cold ethanol while stirring vigorously; a large amount of pale yellow solid precipitates. Collect the solid by filtration through a Buchner funnel. Completely dissolve the crude product in 100 mL of dichloromethane (DCM). Then, while stirring, slowly add the DCM solution to 100 mL of anhydrous ethanol; solid precipitates again. This "dissolve-reprecipitate" purification process was repeated three times to ensure complete removal of impurities such as pyridine hydrochloride and unreacted stearoyl chloride. The final purified product was freeze-dried (-50°C, 0.1 mbar, 48 hours) to obtain a fluffy, pale yellow porous solid. The solid was passed through a standard sieve with a 100 μm pore size using a vibrating sieve separator, and the undersize material was collected to obtain long-chain fatty acid-modified chitosan powder, which was then sealed and stored for later use.

[0054] Preparation Example 2

[0055] This preparation example was carried out using a method similar to that of Preparation Example 1, except that stearyl chloride was replaced with an equal volume of dodecyl chloride.

[0056] Preparation Example D1

[0057] This preparation example was carried out using a method similar to that of Preparation Example 1, except that the amount of stearoyl chloride was adjusted to 6.6 mL.

[0058] Preparation Example D2

[0059] This preparation example was carried out using a method similar to that of Preparation Example 1, except that the amount of stearoyl chloride was adjusted to 19.8 mL.

[0060] Preparation Example D3

[0061] This preparation example was carried out using a method similar to that of Preparation Example 1, except that stearoyl chloride was replaced with an equal volume of hexanoyl chloride.

[0062] The embodiments of the present invention are used to prepare highly hydrophobic textiles.

[0063] Example 1

[0064] Cut cellulose fabric (hydrophilic) into 2.5 cm × 2.5 cm pieces, ultrasonically clean with ethanol for 10 minutes to remove surface contaminants, and then dry thoroughly in a 60°C oven. Lay the dried fabric flat.

[0065] A certain mass of long-chain fatty acid-modified chitosan powder (prepared in Preparation Example 1) was weighed using a precision balance, with a coating amount of 1.6 mg / cm². The powder was carefully and evenly sprinkled onto the fabric surface using a fine-mesh sieve or manually. The powder-coated fabric was then transferred to a programmable temperature oven. Under air atmosphere, the temperature was increased from room temperature to 150°C at a rate of 10°C / min and held at 150°C for 10 minutes. Subsequently, it was allowed to cool naturally to room temperature. The treated fabric was removed, and any loosely bonded powder was gently blown away with an airflow to obtain a highly hydrophobic textile.

[0066] Example 2

[0067] This embodiment is carried out using a method similar to that of Example 1, except that the coating amount of the long-chain fatty modified chitosan powder is adjusted to 0.8 mg / cm².

[0068] Example 3

[0069] This embodiment is carried out using a method similar to that of Example 1, except that the coating amount of the long-chain fatty acid modified chitosan powder is adjusted to 3.2 mg / cm².

[0070] Example 4

[0071] This embodiment is carried out using a method similar to that of Example 1, except that the long-chain fatty acid modified chitosan powder is prepared by Preparation Example 2, and its coating amount remains unchanged.

[0072] Comparative Example 1

[0073] This comparative example was conducted using a method similar to that of Example 1, except that the long-chain fatty acid-modified chitosan powder was prepared using Preparation Example D1, while maintaining the same coating amount.

[0074] Comparative Example 2

[0075] This comparative example was conducted using a method similar to that of Example 1, except that the long-chain fatty modified chitosan powder was prepared using Preparation Example D2, while maintaining the same coating amount.

[0076] Comparative Example 3

[0077] This comparative example was conducted using a method similar to that of Example 1, except that the long-chain fatty modified chitosan powder was prepared using Preparation Example D3, while maintaining the same coating amount.

[0078] Test case

[0079] The hydrophobicity, durability, and fabric feel of the highly hydrophobic textiles prepared in the above examples were tested, and the specific results are shown in Table 1.

[0080] Hydrophobicity testing method: Static contact angle test: Using a contact angle analyzer and the seated drop method, measure the contact angle of a 3 μL deionized water droplet on the sample surface at room temperature. Measure at least 5 different locations randomly selected for each sample and take the average value.

[0081] Durability: Acid Washing Resistance Test: The finished fabric sample was immersed in an aqueous solution adjusted to pH 4 with hydrochloric acid and continuously magnetically stirred at room temperature for 2 hours. After removal, it was rinsed thoroughly with deionized water until neutral, and then dried in an oven at 45°C for 2 hours. This process is defined as one cycle. After each cycle, the water contact angle was measured.

[0082] Fabric hand feel: The evaluation standard for the test is the "Guideline for the Evaluation of Fabric Hand Feel" (AATCC EP5-2011).

[0083]

[0084] Note 1: θ A Forward contact angle, θ R This is the retraction contact angle.

[0085] Note 2: In the durability test, "Excellent" means that after 10 acid cycles, the water contact angle of the fabric sample is ≥150°, "Good" means that after 7 acid cycles, the water contact angle of the fabric sample is 145°~150°, "Acceptable" means that after 5 acid cycles, the water contact angle of the fabric sample is 140°~145°, and "Poor" means that within 5 cycles, the water contact angle of the fabric sample is <140°.

[0086] Dynamic droplet impact tests and BOD biodegradability tests were conducted on the highly hydrophobic textiles prepared in Example 1.

[0087] Dynamic droplet impact test: The droplet impact process was recorded using a high-speed camera (Photron Fastcam SA4). 5 μL and 13 μL water droplets were released from different heights (0.5 - 5 cm) and impacted the sample surface at different velocities (U = 0.3 - 1 m / s).

[0088] Droplet impact experiments show that the highly hydrophobic textile prepared in Example 1 can achieve complete droplet bounce and has anti-dynamic wetting ability.

[0089] BOD biodegradability: Measured using an Oxitop® breather system. Approximately 100 mg of powder sample (long-chain fatty acid-modified chitosan powder prepared in Example 1) was accurately weighed and placed in a 510 mL amber glass bottle. 432 mL of natural seawater (containing a natural microbial community) filtered through a 0.22 μm membrane was added as the culture medium. Microcrystalline cellulose was used as a positive control, and polypropylene (PP) as a negative control. The bottle was sealed and placed in the dark, then magnetically stirred at room temperature. Pressure changes within the system were recorded periodically and converted into oxygen consumption.

[0090] BOD biodegradability tests showed that the oxygen consumption reached 9 mg O2 / 100 mg of material within 30 days, proving that it can be effectively degraded by microorganisms.

[0091] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing long-chain fatty acid-modified chitosan, characterized in that: The method includes: Chitosan was reacted with long-chain fatty acyl chloride in the presence of a protective atmosphere and organic solvent. The crude product was then purified and freeze-dried to obtain the final product. The long-chain fatty acyl chloride has ≥12 carbon atoms; The volume of the long-chain fatty acyl chloride used is 8-16 mL relative to 1 g of the chitosan.

2. The method for preparing long-chain fatty acid-modified chitosan according to claim 1, characterized in that: The reaction temperature of chitosan with long-chain fatty acyl chloride is 105~125℃, and the time is 4~6h; And / or, the long-chain fatty acyl chloride has 16 to 22 carbon atoms.

3. A method for preparing long-chain fatty acid-modified chitosan according to claim 1 or 2, characterized in that: The purification process includes: adding the crude product to glacial ethanol, dissolving the obtained solid in dichloromethane after solid-liquid separation, and then adding the resulting solution to glacial ethanol to precipitate the solid.

4. A method for preparing long-chain fatty acid-modified chitosan according to claim 1 or 2, characterized in that: The degree of deacetylation of the chitosan is 75-85%, and the molecular weight is 200-250 kDa.

5. Long-chain fatty acid-modified chitosan prepared by any one of claims 1 to 4.

6. The application of the long-chain fatty acid-modified chitosan according to claim 5 as a hydrophobic finishing agent for textiles.

7. A method for preparing a highly hydrophobic textile, characterized in that: The method includes: Long-chain fatty acid-modified chitosan is evenly spread onto the surface of the fabric, and then the fabric with the long-chain fatty acid-modified chitosan is heat-treated to obtain the product. The long-chain fatty acid-modified chitosan is the long-chain fatty acid-modified chitosan as described in claim 5.

8. The method for preparing a highly hydrophobic textile according to claim 7, characterized in that: The heat treatment conditions are as follows: in an air atmosphere, the temperature is increased from room temperature to 140-160°C at a heating rate of 8-12°C / min, and then held at 140-160°C for 8-15min. The particle size of the long-chain fatty modified chitosan is <100μm.

9. A method for preparing a highly hydrophobic textile according to claim 7 or 8, characterized in that: The density of the long-chain fatty acid-modified chitosan sprinkled on the fabric surface is 1~2.5 mg / cm².

10. A highly hydrophobic textile prepared by any one of claims 7 to 9.

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