Single-component solvent-free polyurethane hot melt adhesive for functional fabric coating and preparation method of single-component solvent-free polyurethane hot melt adhesive

Abstract

The invention provides a single-component solvent-free polyurethane hot melt adhesive for a functional fabric coating and a preparation method thereof, the hot melt adhesive comprises the following components by weight: 60%-80% of a polyether or polyester soft segment, 10%-20% of a diisocyanate hard segment, 3%-8% of a cross-linking agent and 1%-3% of a stabilizer compound; the curing agent is an isocyanate-terminated prepolymer and is cured by absorbing environmental moisture. According to the invention, a traditional cloth-film-adhesive multilayer physical compounding process is abandoned, and a functional coating with a micro-phase separation structure is generated in situ on the surface of the base cloth through a direct coating and chemical bonding mechanism of the single-component PUR adhesive, so that the problems that the fabric is easy to delaminate and blister and has plastic feeling are thoroughly solved; according to the present invention, the excellent waterproof gas permeation performance and the extremely soft degree are achieved, the whole process is free of solvent volatilization, the manufacturing cost is substantially reduced, and the extremely high environmental protection and industrial application value is provided.

Description

Technical Field

[0001] This invention relates to the field of functional textile fabrics and polymer coating materials, and in particular to a single-component solvent-free polyurethane hot melt adhesive for functional fabric coating and its preparation method. Background Technology

[0002] In the manufacturing of functional fabrics (mainly covering high-end outdoor sportswear, special medical protective clothing, high-tech home textiles, etc.), the fabrics are required to have both high-level waterproof and windproof performance and excellent moisture permeability and breathability. For a long time, the industry has generally adopted a multi-layer physical composite process of "fabric-film-adhesive-fabric" or "fabric-film-adhesive".

[0003] However, with the increasing complexity of end-user scenarios and the continuous upgrading of consumers' demands for wearing experience, this traditional physical composite technology has gradually exposed multiple inherent defects that are difficult to overcome: 1. Delamination and blistering failure caused by physical interface stress imbalance: Traditional processes are essentially physical stacking of heterogeneous materials. Due to the significant differences in tensile modulus, shrinkage rate, and coefficient of thermal expansion between the fabric base, adhesive, and functional film, when clothing is subjected to extreme outdoor temperature fluctuations or mechanical stretching caused by strenuous human movement, especially after multiple daily or industrial washes, extreme interfacial shear stress will be generated between the layers of materials. Traditional physical adhesives cannot withstand this stress tearing for a long time, which can easily lead to irreversible interfacial delamination, local blistering, wrinkling, and edge curling, resulting in fatal quality defects and causing the fabric's protective function to completely fail.

[0004] 2. Comfort bottleneck (strong "plastic feel" and decreased breathability): Because functional films themselves have a certain degree of rigidity, and multi-layer composites increase the overall thickness and stiffness of the fabric, the final product severely loses the original drape and softness of textiles, resulting in a strong "plastic stiffness" when worn, and easily generating noticeable noise when rubbed. In addition, the breathability mechanism of mainstream microporous films (such as ePTFE) relies on the micron-sized pores on the film surface. In actual wear, sebum and sweat secreted by the human body, external dust particles, and detergent residues are very likely to clog these micropores, causing the fabric's moisture permeability and breathability (MVTR) to drop sharply in a short period of time, resulting in a severe stuffy feeling.

[0005] 3. Creating a lengthy process and environmental compliance crisis: Traditional film lamination processes are extremely lengthy (film preparation → adhesive coating → high-temperature hot-pressing → curing and storage), resulting in large equipment investments, high energy consumption, and the generation of large amounts of non-biodegradable waste film scraps during the cutting and lamination process. Even more concerning is the use of solvent-based adhesives containing high levels of volatile organic compounds (VOCs) (such as those containing DMF and toluene), which not only poses a threat to the health of production workers but also fails to meet the increasingly stringent environmental standards of the current international textile market.

[0006] Therefore, the technical problem that urgently needs to be solved in this field is: How can we break away from the traditional technological path of "functional film + physical bonding" and develop a polymer coating material that can be directly formed on the fabric surface in one step, has self-breathing and breathability, and is soft to the touch? At the same time, this material can form a deep molecular-level chemical bond with the base fabric. Furthermore, its preparation and forming process must be solvent-free, so as to meet the mass production needs of a new generation of functional fabrics that are efficient, green, and cost-effective. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a single-component solvent-free polyurethane hot melt adhesive for functional fabric coating and its preparation method, which solves the problems of easy delamination and wrinkling, stiff hand feel and loss of fabric properties, and cumbersome and inefficient multiple production processes in the prior art when physical bonding of multiple layers of fabrics is used.

[0008] To achieve the above and other related objectives, the present invention provides a one-component solvent-free polyurethane hot melt adhesive for functional fabric coating, wherein, by weight percentage, the composition of the one-component solvent-free polyurethane hot melt adhesive comprises: The soft segment polymer, comprising 60% to 80% by mass, is selected from one or more mixtures of polyether polyols or polyester polyols; Hard segment isocyanate, accounting for 10% to 20% by mass, is a polyfunctional diisocyanate; Crosslinking agent, accounting for 3% to 8% by mass; The stabilizing system additives, comprising 1% to 3% by mass, include antioxidants and UV stabilizers; The polyurethane hot melt adhesive is a 100% solids content, single-component, moisture-curing adhesive. Its terminal highly active isocyanate groups are configured to undergo cross-linking polymerization with the active oxygen-containing groups on the surface of the base fabric and water molecules in the environment, so as to construct an elastic microporous film that is chemically bonded to the fiber in situ on the surface of the fabric substrate.

[0009] By adopting the above technical solution and strictly limiting the ratio of 60%-80% soft segments to 10%-20% hard segments, the colloid is endowed with an excellent microphase separation structure. Unlike traditional adhesives, the PUR prepolymer of this invention has 100% solid content and no solvent evaporation. Its terminal -NCO groups can chemically covalently bond with the active hydrogen on the surface of the base fabric fibers during curing. This design breaks the structure of traditional "fabric-film" physical bonding and achieves chemical anchoring, which makes the peel strength jump to ≥1.5N / 25mm, which can solve stubborn problems such as delamination, wrinkling, and edge curling. In addition, this component does not require any plastic film material, directly eliminating the plastic feel of the fabric and giving the finished product excellent drape and soft hand feel.

[0010] In one embodiment of the present invention, the soft segment polymer is a mixture of polytetrahydrofuran ether diol and polyadipate diol ester with a number average molecular weight between 2000 and 4000 g / mol; the hard segment isocyanate is selected from any one or a mixture of 4,4'-diphenylmethane diisocyanate or isophorone diisocyanate.

[0011] In one embodiment of the present invention, when the polyurethane hot melt adhesive is used specifically for coating high waterproof fabrics, the mass percentage of the hard segment isocyanate is adjusted to 18% to 20%, and the composition further contains 0.5% to 2.0% of a hydrophobic modifier, which is a polydimethylsiloxane-modified leveling agent. The hydrostatic pressure resistance of the polyurethane hot melt adhesive after complete curing is greater than or equal to 50 kPa.

[0012] In one embodiment of the present invention, when the polyurethane hot melt adhesive is used specifically for coating highly breathable and soft functional fabrics, the soft segment polymer is pure polyether polyol and its mass percentage is increased to 75% to 80%, the use of crystalline polyester polyol is excluded in the composition, the Shore A hardness of the adhesive layer is maintained between 30° and 45° after the polyurethane hot melt adhesive is fully cured, and the moisture permeability and air permeability of the adhesive layer is greater than or equal to 100g / m²·24h.

[0013] In one embodiment of the present invention, the internal cross-linking network density of the fully cross-linked and cured polyurethane hot melt adhesive is greater than or equal to 1.2 mmol / cm³, the peel strength between the adhesive layer and the substrate fabric is greater than or equal to 1.5 N / 25 mm, the elongation at break of the system is greater than or equal to 150%, and it does not contain any volatile organic solvents. The volatile organic compound (VOC) content of the system is less than or equal to 50 g / L.

[0014] A film-free lamination process for a single-component solvent-free polyurethane hot melt adhesive for functional fabric coating as described above specifically includes the following steps: S1. Substrate pretreatment: The functional textile substrate is subjected to surface plasma high-energy activation treatment or corona discharge treatment to remove surface adsorbed oil and impurities, and induce fiber molecular chain breakage to generate a large number of highly active oxygen-containing free radicals. S2, Melting and Precision Coating: The single-component solvent-free polyurethane hot melt adhesive is added to the adhesive supply system and heated to melt into a fluid adhesive liquid. Then, the adhesive liquid is directly and uniformly coated in situ onto the base fabric surface that has been activated in step S1 using a precision coating device. S3, Temperature and Humidity Controlled Chemical Crosslinking Curing: The semi-finished base fabric that has completed the coating operation is pulled and sent into a curing chamber with a precise environmental control system. The humidity in the environment is used to trigger and maintain the deep hydrolysis and polyurea crosslinking polymerization reaction of the isocyanate groups in the adhesive layer. S4. Finishing and shaping process: After the adhesive layer is fully cross-linked and cured, the fabric is subjected to low-temperature shaping, edge trimming and surface electrostatic dust removal to directly obtain an integrated membrane-free fabric product that combines elasticity and functionality.

[0015] By adopting the above technical solution In one embodiment of the present invention, in step S2, the precision coating equipment adopts a precision adjustable doctor blade coating machine or a screw extrusion hot melt coating machine, the temperature of the glue tank of the glue supply system is precisely controlled between 120 degrees Celsius and 150 degrees Celsius; the amount of glue coated per unit area is precisely controlled within the range of 5 to 50 g / m², and the belt coating speed of the equipment is adapted and controlled between 10 and 50 m / min.

[0016] By adopting the above technical solution In one embodiment of the present invention, in step S2, the mechanical gap of the adjustable doctor blade is adjusted to 0.05 to 0.5 mm by the coordinated control of the servo motor, and the physical pressure of the back pressure roller is adjusted to 0.3 to 0.8 MPa, thereby strictly controlling the uniformity deviation of the adhesive layer thickness of the large-area coating within a range of less than or equal to ±5%, effectively avoiding the occurrence of macroscopic local over-adhesion or microscopic under-adhesion.

[0017] In one embodiment of the present invention, in step S3, the environmental control system in the curing chamber sets and keeps the curing reaction temperature constant in the range of 20 degrees Celsius to 35 degrees Celsius, while strictly controlling the relative humidity in the space within the effective reaction range of 40% to 70%; under the standard natural curing mode, the curing time to complete deep cross-linking is 24 to 48 hours.

[0018] In one embodiment of the present invention, the curing process in step S3 further includes an accelerated curing operation mode, namely, by using an optional ultrasonic high-frequency humidity control system, nano-level atomized water vapor is continuously and uniformly introduced into the curing chamber to forcibly maintain a high humidity microenvironment in the local space. In this mode, the time for complete cross-linking curing can be significantly shortened to 8 to 12 hours without deteriorating the physical and mechanical properties of the adhesive film. During the cross-linking curing process in step S3, the surface coated with the high-activity adhesive layer is covered with anti-stick release paper for isolation and protection. The temperature of the low-temperature setting process in step S4 is set to 60 to 80 degrees Celsius, and the setting time is 10 to 15 minutes.

[0019] As described above, the single-component solvent-free polyurethane hot melt adhesive for functional fabric coating and its preparation method of the present invention have the following beneficial effects: 1. Significantly improved product performance stability: The adhesive layer and the base fabric form an integrated structure through chemical bonding, with a peel strength ≥1.5N / 25mm, solving defects such as delamination, bubbles, wrinkling, and edge curling in traditional film bonding processes; Through formula control, it can precisely achieve functions such as waterproof (hydrostatic pressure resistance ≥50kPa), breathable (breathability ≥100g / m²·24h), and washable (no damage after 50 washes), and the finished product's softness (Shore A 30-45°) is suitable for the use needs of clothing, home textiles and other scenarios.

[0020] 2. Outstanding optimization of production process and cost: Eliminates processes such as film material procurement, slitting, storage and hot pressing lamination, shortening the production cycle by more than 30%; reduces energy consumption of hot pressing equipment, reduces material loss rate to ≤2%, and reduces overall production cost by 15%-20%; coating speed can be flexibly adjusted between 10-50m / min to meet the needs of large-scale mass production.

[0021] 3. Environmental protection and compliance: It completely replaces plastic film materials, reducing plastic waste emissions; the single-component moisture-curing PUR adhesive has no solvent volatilization and a VOC content of ≤50g / L, meeting Bluesign green production standards and ISO9001 quality control requirements, thus enhancing the product's market access competitiveness.

[0022] 4. Significantly expanded application scenarios: By customizing the adhesive layer formula and process parameters, the finished fabric can cover multiple fields such as outdoor functional clothing, medical protective fabrics, and high-end home textiles, breaking through the performance and scenario limitations of traditional membrane composite fabrics. Attached Figure Description

[0023] Figure 1 The diagram shown is a schematic representation of the overall process disclosed in Embodiment 2 of the present invention. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0025] Please see Figure 1 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation. Example

[0026] This embodiment provides a one-component solvent-free polyurethane hot melt adhesive for functional fabric coating. The composition of the one-component solvent-free polyurethane hot melt adhesive comprises, by weight percentage: The soft segment polymer, comprising 60% to 80% by mass, is selected from one or more mixtures of polyether polyols or polyester polyols; Hard segment isocyanate, accounting for 10% to 20% by mass, is a polyfunctional diisocyanate; Crosslinking agent, accounting for 3% to 8% by mass; The stabilizing system additives, comprising 1% to 3% by mass, include antioxidants and UV stabilizers; Polyurethane hot melt adhesive is a 100% solids content, single-component, moisture-curing adhesive. Its highly active isocyanate groups at the ends are configured to undergo cross-linking polymerization with active oxygen-containing groups on the surface of the base fabric and water molecules in the environment, so as to construct an elastic microporous film that is chemically bonded to the fiber in situ on the surface of the fabric substrate.

[0027] The soft segment polymer is a mixture of polytetrahydrofuran ether diol and polyadipate diol ester with a number average molecular weight between 2000 and 4000 g / mol; the hard segment isocyanate is selected from any one or a mixture of 4,4'-diphenylmethane diisocyanate or isophorone diisocyanate.

[0028] When polyurethane hot melt adhesive is used specifically for coating high-water-resistance fabrics, the mass percentage of hard segment isocyanate is adjusted to 18% to 20%, and the composition is further supplemented with a hydrophobic modifier of 0.5% to 2.0% by mass. The hydrophobic modifier is a polydimethylsiloxane-modified leveling agent. The hydrostatic pressure resistance of the polyurethane hot melt adhesive after complete curing is greater than or equal to 50 kPa.

[0029] When polyurethane hot melt adhesive is used specifically for coating highly breathable and soft functional fabrics, the soft segment polymer is made of pure polyether polyol and its mass percentage is increased to 75% to 80%. The use of crystalline polyester polyol is excluded from the composition. After the polyurethane hot melt adhesive is fully cured, the Shore A hardness of the adhesive layer is maintained between 30° and 45°, and the moisture permeability and air permeability of the adhesive layer is greater than or equal to 100g / m²·24h.

[0030] The internal cross-linking network density of the fully cross-linked polyurethane hot melt adhesive after curing is greater than or equal to 1.2 mmol / cm³, the peel strength between the adhesive layer and the substrate fabric is greater than or equal to 1.5 N / 25 mm, the elongation at break of the system is greater than or equal to 150%, and it does not contain any volatile organic solvents. The volatile organic compound (VOC) content of the system is less than or equal to 50 g / L. Example

[0031] like Figure 1 As shown, this embodiment provides a film-free lamination process for a single-component solvent-free polyurethane hot melt adhesive for functional fabric coating as described in Embodiment 1, specifically including the following steps: S0. Raw material preparation: Before coating, each component is precisely measured according to the formula (60%-80% polyether / polyester soft segment, 10%-20% diisocyanate hard segment, 3%-8% crosslinking agent, 1%-3% antioxidant / UV stabilizer), and a prepolymerization reaction is carried out in a reactor to prepare a one-component moisture-curing polyurethane hot melt adhesive (PUR) containing highly active terminal isocyanate groups (-NCO). It is stored in a sealed and moisture-proof glue container for later use, ensuring that the adhesive material has both flexibility and extremely high reactivity.

[0032] S1. Substrate pretreatment: The functional textile substrate is subjected to surface plasma high-energy activation treatment or corona discharge treatment to remove surface adsorbed oil and impurities, and induce fiber molecular chain breakage to generate a large number of highly active oxygen-containing free radicals. S2, Melting and Precision Coating: The single-component solvent-free polyurethane hot melt adhesive is added to the adhesive supply system and heated to melt into a fluid adhesive liquid. Then, the adhesive liquid is directly and uniformly coated in situ onto the base fabric surface that has been activated in step S1 using a precision coating device. S3, Temperature and Humidity Controlled Chemical Crosslinking Curing: The semi-finished base fabric that has completed the coating operation is pulled and sent into a curing chamber with a precise environmental control system. The humidity in the environment is used to trigger and maintain the deep hydrolysis and polyurea crosslinking polymerization reaction of the isocyanate groups in the adhesive layer. S4. Finishing and shaping process: After the adhesive layer is fully cross-linked and cured, the fabric is subjected to low-temperature shaping, edge trimming and surface electrostatic dust removal to directly obtain an integrated membrane-free fabric product that combines elasticity and functionality.

[0033] In step S2, the precision coating equipment adopts a precision adjustable doctor blade coating machine or a screw extrusion hot melt coating machine. The temperature of the glue tank in the glue supply system is precisely controlled between 120 degrees Celsius and 150 degrees Celsius. The amount of glue coated per unit area is precisely controlled between 5 and 50 g / m². The belt coating speed of the equipment is adapted and controlled between 10 and 50 m / min.

[0034] In step S2, the mechanical gap of the adjustable doctor blade is adjusted to 0.05 to 0.5 mm by the servo motor, and the physical pressure of the back pressure roller is adjusted to 0.3 to 0.8 MPa. This strictly controls the uniformity deviation of the adhesive layer thickness of the large-area coating to within a range of less than or equal to ±5%, effectively avoiding macroscopic local over-adhesion or microscopic under-adhesion.

[0035] In step S3, the environmental control system in the curing chamber sets and keeps the curing reaction temperature constant between 20 degrees Celsius and 35 degrees Celsius, while strictly controlling the relative humidity in the space within the effective reaction range of 40% to 70%. Under the standard natural curing mode, the curing time to complete deep cross-linking is 24 to 48 hours.

[0036] The curing process in step S3 also includes an accelerated curing operation mode, which uses an optional ultrasonic high-frequency humidity control system to continuously and uniformly introduce nano-level atomized water vapor into the curing chamber, forcibly maintaining a high humidity microenvironment in the local space. In this mode, the time for complete cross-linking and curing can be significantly shortened to 8 to 12 hours without deteriorating the physical and mechanical properties of the adhesive film. During the cross-linking and curing process in step S3, the side surface coated with the highly active adhesive layer is covered with release paper for isolation and protection. In step S4, the temperature of the low-temperature setting process is set to 60 to 80 degrees Celsius, and the setting time is 20 to 30 minutes. Example

[0037] This embodiment provides a versatile functional fabric that combines everyday water repellency and windproof breathability. The formula is precisely calculated by weight percentage as follows: High molecular weight polymeric alcohols serving as the soft segment backbone: 70.0% (using high-purity polytetrahydrofuran ether diol PTMEG with a number average molecular weight of 3000 g / mol to ensure high-frequency free mobility of molecular chain segments at low temperatures); Diisocyanate as support for the crosslinked hard phase network: 15.0% (selected 4,4'-diphenylmethane diisocyanate MDI to provide excellent hydrogen bond strength). Small and medium molecular chain extender and crosslinker: 10.0% (1,4-butanediol and trace amounts of trifunctional chain extender compounded in a specific ratio, used to weave the initial three-dimensional network nodes). Reaction control and stabilizing agent system: 3.0% (including special tackifying resins that promote interfacial affinity and hindered phenolic antioxidants that resist photothermal oxidation); Composite catalyst system: 2.0% (organic bismuth-based environmentally friendly catalyst, designed to precisely tune the nucleophilic reaction rate of hydroxyl groups and -NCO).

[0038] Detailed explanation of the process preparation steps: S1. High-energy activation of textile substrate: A standard polyester base fabric with uniform weight distribution was selected and laid flat and pulled through a plasma surface processor under specific tension (RF discharge power stabilized at 2.5kW, and high-energy plasma cloud bombardment residence time precisely controlled at 2.0 seconds). This step removed the extremely weak boundary layer (WBL) on the fiber surface and measured that the surface tension of the substrate soared from the conventional 35 dynes to over 52 dynes, successfully inducing a dense matrix of reactive oxygen species.

[0039] S2. Fluid rheology control and precise coating: Place the strictly dehumidified and sealed single-component PUR hot melt adhesive in a screw-type hot melt coating machine system that prevents air backflow, and turn on the progressive heating to keep the temperature of the dispensing tank constant at 135 degrees Celsius. At this time, the adhesive exhibits excellent non-Newtonian fluid pseudoplasticity.

[0040] Start the fabric traction drive and set the conveyor belt speed to a medium speed of 30 m / min. The servo hydraulic system controls the precision doctor blade system (the doctor blade gap is precisely locked at 0.2 mm, and the physical support pressure of the back pressure polyurethane roller is 0.5 MPa) to scrape and extrude the molten PUR adhesive into the surface layer of the base fabric fibers. The online thickness gauge controls the coating surface density in a closed loop to accurately maintain the target value of 25 g / m².

[0041] S3. Diffusion-Reaction Kinetic Steady-State Curing: Immediately after the fabric coating is completed, a layer of low-peel-stretch silicone release paper is applied online to its surface to isolate dust and prevent layering and adhesion. It is then placed in a large, temperature- and humidity-controlled chamber. The chamber's microcomputer temperature control system maintains the temperature at the collision activity point of 28 degrees Celsius, while the ultrasonic humidification component maintains a constant relative humidity (RH) of 60%. During this 36-hour static curing period, external water molecules orderly trigger macromolecular chain extension and deep cross-linking reactions, steadily generating a three-dimensional network.

[0042] S4. Residual Thermodynamic Stress Release and Finishing: Remove the temporary release paper from the surface, and feed the cross-linked fabric into the tension release setting machine. Baking is carried out at a gentle high temperature of 75 degrees Celsius for 12 minutes to eliminate the internal stress of the polymer chains accumulated during the manufacturing process. Then, high-precision photoelectric edge cutting and constant tension winding are performed to complete the preparation of high-end membrane-free integrated finished fabric rolls.

[0043] In summary, this invention, through specific formula customization and a precise coating and curing closed-loop process, breaks through the limitations of traditional multi-layer physical composites, achieving a comprehensive breakthrough in feel, performance, environmental protection, and production efficiency. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0044] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A one-component solvent-free polyurethane hot melt adhesive for functional fabric coating, characterized in that, The composition of the one-component solvent-free polyurethane hot melt adhesive, by weight percentage, comprises: The soft segment polymer, comprising 60% to 80% by mass, is selected from one or more mixtures of polyether polyols or polyester polyols; Hard segment isocyanate, accounting for 10% to 20% by mass, is a polyfunctional diisocyanate; Crosslinking agent, accounting for 3% to 8% by mass; The stabilizing system additives, comprising 1% to 3% by mass, include antioxidants and UV stabilizers; The polyurethane hot melt adhesive is a 100% solids content, single-component, moisture-curing adhesive. Its terminal highly active isocyanate groups are configured to undergo cross-linking polymerization with the active oxygen-containing groups on the surface of the base fabric and water molecules in the environment, so as to construct an elastic microporous film that is chemically bonded to the fiber in situ on the surface of the fabric substrate.

2. The single-component solvent-free polyurethane hot melt adhesive for functional fabric coating according to claim 1, characterized in that: The soft segment polymer is a mixture of polytetrahydrofuran ether diol and polyadipate diol ester with a number average molecular weight between 2000 and 4000 g / mol; the hard segment isocyanate is selected from any one or a mixture of 4,4'-diphenylmethane diisocyanate or isophorone diisocyanate.

3. The single-component solvent-free polyurethane hot melt adhesive for functional fabric coating according to claim 1, characterized in that: When the polyurethane hot melt adhesive is used specifically for coating high-water-resistance fabrics, the mass percentage of the hard segment isocyanate is adjusted to 18% to 20%, and the composition further contains 0.5% to 2.0% of a hydrophobic modifier, which is a polydimethylsiloxane-modified leveling agent. The hydrostatic pressure resistance of the polyurethane hot melt adhesive after complete curing is greater than or equal to 50 kPa.

4. The single-component solvent-free polyurethane hot melt adhesive for functional fabric coating according to claim 1, characterized in that: When the polyurethane hot melt adhesive is used specifically for coating highly breathable and soft functional fabrics, the soft segment polymer is pure polyether polyol and its mass percentage is increased to 75% to 80%. The use of crystalline polyester polyol is excluded from the composition. After the polyurethane hot melt adhesive is fully cured, the Shore A hardness of the adhesive layer is maintained between 30° and 45°, and the moisture permeability and air permeability of the adhesive layer is greater than or equal to 100 g / m²·24h.

5. The single-component solvent-free polyurethane hot melt adhesive for functional fabric coating according to claim 1, characterized in that: The internal cross-linking network density of the fully cross-linked and cured polyurethane hot melt adhesive is greater than or equal to 1.2 mmol / cm³, the peel strength between the adhesive layer and the substrate fabric is greater than or equal to 1.5 N / 25 mm, the elongation at break of the system is greater than or equal to 150%, and it does not contain any volatile organic solvents. The volatile organic compound (VOC) content of the system is less than or equal to 50 g / L.

6. A method for preparing a one-component solvent-free polyurethane hot melt adhesive for functional fabric coating as described in any one of claims 1 to 5, characterized in that, Specifically, the following steps are included: S1. Substrate pretreatment: The functional textile substrate is subjected to surface plasma high-energy activation treatment or corona discharge treatment to remove surface adsorbed oil and impurities, and induce fiber molecular chain breakage to generate a large number of highly active oxygen-containing free radicals. S2, Melting and Precision Coating: The single-component solvent-free polyurethane hot melt adhesive is added to the adhesive supply system and heated to melt into a fluid adhesive liquid. Then, the adhesive liquid is directly and uniformly coated in situ onto the base fabric surface that has been activated in step S1 using a precision coating device. S3, Temperature and Humidity Controlled Chemical Crosslinking Curing: The semi-finished base fabric that has completed the coating operation is pulled and sent into a curing chamber with a precise environmental control system. The humidity in the environment is used to trigger and maintain the deep hydrolysis and polyurea crosslinking polymerization reaction of the isocyanate groups in the adhesive layer. S4. Finishing and shaping process: After the adhesive layer is fully cross-linked and cured, the fabric is subjected to low-temperature shaping, edge trimming and surface electrostatic dust removal to directly obtain an integrated membrane-free fabric product that combines elasticity and functionality.

7. The method for preparing a single-component solvent-free polyurethane hot melt adhesive for functional fabric coatings according to claim 6, characterized in that: In step S2, the precision coating equipment adopts a precision adjustable doctor blade coating machine or a screw extrusion hot melt coating machine. The temperature of the glue tank in the glue supply system is precisely controlled between 120 degrees Celsius and 150 degrees Celsius. The amount of glue coated per unit area is precisely controlled within the range of 5 to 50 g / m². The belt coating speed of the equipment is adapted and controlled between 10 and 50 m / min.

8. The method for preparing a single-component solvent-free polyurethane hot melt adhesive for functional fabric coatings according to claim 6, characterized in that: In step S2, the mechanical gap of the adjustable scraper is adjusted to 0.05 to 0.5 mm by the servo motor, and the physical pressure of the back pressure roller is adjusted to 0.3 to 0.8 MPa, so that the uniformity deviation of the adhesive layer thickness of the large-area coating is strictly controlled within the range of less than or equal to ±5%, effectively avoiding the occurrence of macroscopic local over-adhesion or microscopic under-adhesion.

9. The method for preparing a single-component solvent-free polyurethane hot melt adhesive for functional fabric coatings according to claim 6, characterized in that: In step S3, the environmental control system in the curing chamber sets and keeps the curing reaction temperature constant between 20 degrees Celsius and 35 degrees Celsius, while strictly controlling the relative humidity in the space within the effective reaction range of 40% to 70%. Under the standard natural curing mode, the curing time to complete deep cross-linking is 24 to 48 hours.

10. The method for preparing a single-component solvent-free polyurethane hot melt adhesive for functional fabric coatings according to claim 6, characterized in that: The curing process in step S3 also includes an accelerated curing operation mode, which is to continuously and uniformly introduce nano-level atomized water vapor into the curing chamber through an optional ultrasonic high-frequency humidity control system, thereby forcibly maintaining a high humidity microenvironment in the local space; the temperature of the low-temperature setting process in step S4 is set to 60 degrees Celsius to 80 degrees Celsius, and the setting time is 20 to 30 minutes.

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