A static-free and powder-avoiding DTF transfer film and a preparation method thereof

Abstract

The present application belongs to the technical field of digital printing heat transfer material, and particularly relates to a DTF transfer film without static electricity and powder scattering and a preparation method thereof; aiming at the contradictory problem among the anti-static function, ink adsorption and peeling strength of the current DTF transfer film; the present application disperses the polymer microcapsule coated ionic liquid antistatic agent in the water-based resin adhesive to form a lower anti-static network structure layer; at the same time, the crystalline polyester hot melt adhesive resin with the bio-based 2,5-furan dicarboxylic acid as the rigid component, and the surface modified boron nitride nanosheet to regulate the crystallization behavior, uses the phase separation curing process to make the anti-static network stably exist in the lower part of the coating, and the hot melt adhesive resin microcrystal selectively enriches in the surface of the coating to form a thermal phase change adhesive layer, so as to realize the static electricity and powder scattering in the printing and powder scattering process.

Description

Technical Field

[0001] This invention belongs to the field of digital printing heat transfer materials technology, specifically relating to an electrostatic powder-free DTF transfer film and its preparation method. Background Technology

[0002] DTF transfer printing is an emerging digital printing transfer process. It involves first printing the design onto a PET film using specialized ink, then applying hot melt adhesive powder, baking the film, and finally heat-pressing the design onto a substrate such as fabric. Compared to traditional DTG or offset printing processes, DTF transfer printing offers advantages such as simpler process, wider applicability to various fabrics, and more vibrant colors in the finished product.

[0003] However, static electricity poses challenges to powder handling and printing quality during the use of DTF transfer films (CN120003178A). Because PET substrates and coatings easily accumulate static electricity in dry environments, powder splattering and adhesion to non-patterned areas often occur during printing and powder application, resulting in excess powder residue around the finished pattern. When the environment is dry and the equipment grounding is poor, the accumulated static charge on the film surface attracts hot melt adhesive powder, preventing excess powder from being completely shaken off. To mitigate the "powder sticking" problem caused by static electricity, some transfer film products on the market have incorporated anti-static treatments into the base film or coating. However, these anti-static measures mostly rely on adding traditional anti-static agents to the coating or applying an anti-static coating to the back of the film. Traditional anti-static agents are susceptible to environmental humidity and have poor durability, often weakening in effectiveness over time or after friction. Especially when DTF films are repeatedly subjected to curling, friction, and long storage periods, the initial anti-static effect may be difficult to maintain.

[0004] On the other hand, the DTF process requires applying hot melt adhesive powder to the printed pattern to achieve adhesion to the fabric. While commonly used hot melt adhesive powders offer high bonding strength and are washable, the powder preparation process increases complexity and can lead to uneven powder distribution due to static electricity. Furthermore, the relatively coarse powder particles result in a thicker adhesive layer after melting, potentially affecting the soft feel of the transferred pattern.

[0005] In summary, existing technologies still require improvement in the antistatic, anti-powder, and adhesive properties of DTF transfer films. How to integrate highly efficient and durable antistatic properties into the transfer film coating, while simultaneously considering ink absorption performance and easy release characteristics of the coating, and providing sufficient adhesive strength without compromising the soft feel of the finished product, has become a pressing problem for those skilled in the art. Summary of the Invention

[0006] This invention provides an antistatic powder-repellent DTF transfer film and its preparation method, which can persistently and stably integrate antistatic components in the film layer, eliminating powder scattering and residue caused by static electricity, while ensuring excellent ink adsorption capacity and coating release performance, ensuring that the pattern after heat transfer to the fabric has a soft feel and strong adhesion.

[0007] The specific technical solution is as follows:

[0008] An electrostatic powder-repellent DTF transfer film and its preparation method are as follows:

[0009] S1: Preparation of crystalline polyester hot melt adhesive resin.

[0010] S11: 2,5-furandicarboxylic acid, adipic acid and 1,4-butanediol were dried and mixed. The mixture was heated and stirred under nitrogen protection throughout the process. After stirring, tetrabutyl titanate catalyst was added. The temperature was continued to rise and the system pressure was gradually reduced to 60 Pa. Then, boron nitride nanosheets modified with KH-550 were added, stirred, cooled and granulated to obtain resin chips.

[0011] S12: The resin slices prepared in S11 are placed in a liquid nitrogen environment for cryogenic embrittlement, crushed, and sieved to obtain crystalline polyester hot melt adhesive micro powder.

[0012] S2: Dispersion preparation.

[0013] S21: Add polyvinyl alcohol to deionized water, stir at 90°C, and cool to room temperature to obtain an aqueous solution.

[0014] S22: Mix 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and toluene diisocyanate, stir, and prepare an oil phase solution.

[0015] S23: Under medium-speed stirring, the oil phase solution prepared in S22 is added dropwise to the aqueous phase solution prepared in S21, and then shear emulsified to obtain a primary emulsion.

[0016] S24: Add a 5% ethylenediamine aqueous solution to the primary emulsion prepared in S23, stir, cool to room temperature, adjust the pH to 7, filter, and obtain an antistatic microcapsule dispersion.

[0017] S3: Preparation of composite coating liquid.

[0018] S31: Add wetting and dispersing agent and part of defoamer to deionized water, stir at low speed, then add crystalline polyester hot melt adhesive micro powder prepared in S12, stir at high speed, cool to room temperature, then add waterborne polyurethane dispersion and acrylate emulsion, stir to form a mixed resin emulsion matrix.

[0019] S32: Add the antistatic microcapsule dispersion prepared in S24 to the mixed resin emulsion matrix prepared in S31, stir for 10 min, then add leveling agent and the remaining defoamer, then add deionized water to prepare a coating liquid with a solid content of 25-35%, filter, mature and stand to obtain a composite coating liquid.

[0020] S4: Prepare the transfer film by coating the composite coating liquid prepared in S32 onto the PET release base film, then perform gradient curing, rapidly cool to below 50°C, wind up, and cure to obtain the DTF transfer film.

[0021] Furthermore, the molar ratio of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol described in S11 is (6-9):(4-1):(1.05-1.25).

[0022] The heating and stirring described in S11 has the following parameters: temperature 180~210℃, rotation speed 120~200rpm, and duration 2~4h.

[0023] The tetrabutyl titanate catalyst described in S11 is used in an amount of 0.03 to 0.08% of the total mass of 2,5-furandicarboxylic acid, adipic acid and 1,4-butanediol.

[0024] The boron nitride nanosheets described in S11 are used in an amount of 0.5 to 2% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol.

[0025] The stirring described in S11 has the following parameters: rotation speed 80-120 rpm, duration 30-45 min.

[0026] Furthermore, the 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt described in S22 has a mass ratio of 1:1 to 1:2.5 with toluene diisocyanate.

[0027] The medium-speed stirring described in S23 has the following parameter settings: rotation speed 300-500 rpm.

[0028] The shear emulsification described in S23 has the following parameter settings: rotation speed 8000~12000rpm, duration 5~10min.

[0029] The ethylenediamine described in S24 has a mass ratio of 1:1 to 1.2:1 with toluene diisocyanate.

[0030] The stirring described in S24 has the following parameters: temperature 30-35℃, speed 300-400rpm, and duration 2-4h.

[0031] Furthermore, the amount of the defoamer described in S31 is 50% of the total amount of defoamer added.

[0032] The low-speed stirring described in S31 has the following parameter settings: rotation speed 200-400 rpm, duration 5-10 min.

[0033] The high-speed stirring described in S31 has the following parameter settings: rotation speed 1500~2500rpm, duration 15~25min.

[0034] The stirring described in S31 has the following parameters: rotation speed 400-600 rpm, duration 10-15 min.

[0035] The composite coating liquid described in S32 has the following mass ratio of each raw material in the dry film: 35-55% aqueous polyurethane dispersion, 10-20% acrylate emulsion, 5-15% antistatic microcapsule dispersion based on capsule dry weight, 20-35% crystalline polyester hot melt adhesive powder, 0.5-2% wetting and dispersing agent, 0.1-0.5% defoamer, and 0.1-0.5% leveling agent.

[0036] Furthermore, the gradient curing described in S4 has the following parameter settings: first stage temperature 65-80℃, duration 25-40s; second stage temperature 90-110℃, duration 40-60s; and third stage temperature 120-140℃, duration 10-30s.

[0037] The curing process described in S4 has the following parameters: temperature 20-25℃, humidity 45-55%, and duration 24-48h.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention uses microencapsulated ionic liquids fixed in a polymer network, resulting in a long-lasting and stable antistatic effect, thus solving the problems of electrostatic dust attraction and "powder removal" during production and use.

[0040] 2. The present invention ensures good adsorption of water-based inks and appropriate release force through the lower water-based resin network, and the surface-enriched crystalline hot melt adhesive layer provides reliable thermal adhesion. Attached Figure Description

[0041] Figure 1 This is a process flow diagram for the preparation of a non-electrostatic powder-repellent DTF transfer film.

[0042] Figure 2 These are water contact angle diagrams of the DTF transfer films finally prepared in Examples 1-4 and Comparative Examples 1-2.

[0043] Figure 3 This is a comparison chart of the peel strength and water contact angle data of the DTF transfer films finally prepared in Examples 1-4 and Comparative Examples 1-2. Detailed Implementation

[0044] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0045] This invention proposes an electrostatic-free powder-repellent DTF transfer film and its preparation method. The method involves dispersing an ionic liquid antistatic agent encapsulated in polymer microcapsules into an aqueous resin adhesive to form a lower antistatic network structure layer. Simultaneously, a crystalline polyester hot melt adhesive resin with bio-based 2,5-furandicarboxylic acid as a rigid component is synthesized, and its crystallization behavior is controlled by surface-modified boron nitride nanosheets. (See attached image) Figure 1 The image shows an electrostatic powder-repellent DTF transfer film and its preparation method. The detailed technical solution is as follows:

[0046] 1. Preparation of crystalline polyester hot melt adhesive resin

[0047] 2,5-furandicarboxylic acid (FDCA), adipic acid, and 1,4-butanediol were dried and mixed. The mixture was heated and stirred under nitrogen protection throughout the process. After stirring, tetrabutyl titanate catalyst was added, the temperature was increased, and the system pressure was gradually reduced. Then, boron nitride nanosheets modified with KH-550 were added, stirred, cooled, and granulated to obtain resin chips. Finally, the chips were placed in a liquid nitrogen environment for cryogenic embrittlement, pulverized, and sieved to obtain crystalline polyester hot melt adhesive micro powder.

[0048] FDCA possesses a rigid aromatic structure (furan ring) similar to terephthalic acid, providing a high melting point and strength. Adipic acid, as a comonomer, disrupts the excessive regularity of the FDCA homopolymer, increasing molecular chain flexibility, thereby improving resin toughness, reducing brittleness, and moderately regulating the melting point. The addition of surface-modified boron nitride (BN) nanosheets as a heterogeneous nucleating agent in the later stages of polymerization increases the crystallization rate of the copolyester, reduces crystal size, and improves crystallization uniformity. This ensures that after a brief high-temperature curing process, the hot melt adhesive can rapidly form a fine, uniform surface crystalline layer. A slight excess of 1,4-butanediol (5–25%) is used to drive the reaction, ensuring complete carboxyl group reaction and increasing molecular weight.

[0049] 2. Preparation of Dispersion

[0050] Polyvinyl alcohol was added to deionized water and stirred at 90°C. The mixture was then cooled to room temperature to obtain an aqueous solution. 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and toluene diisocyanate were mixed and stirred to prepare an oil phase solution. The oil phase solution was added dropwise to the aqueous solution under medium-speed stirring, followed by shear emulsification to obtain a primary emulsion. A 5% ethylenediamine aqueous solution was then added and stirred. The mixture was cooled to room temperature, the pH was adjusted to 7, and the solution was filtered to obtain an antistatic microcapsule dispersion.

[0051] Ionic liquids, composed of organic cations and inorganic / organic anions, are natural liquid ionic conductors. When a thin film generates electrostatic charge due to friction, the ionic liquid enriched in the coating (even when encapsulated) provides mobile ions. As charge (electrons) accumulates on the material surface, it induces dipole interactions, driving ion rearrangement or trace migration within the microcapsule or near the micropores of the microcapsule wall material. This forms a local conductive pathway, thereby conducting, neutralizing, or dissipating the accumulated electrostatic charge and preventing charge buildup. Imidazole salt ionic liquids are hygroscopic, absorbing trace amounts of moisture from the environment. These water molecules can form hydrogen bond networks with the ionic liquid, further enhancing ionic conductivity. This mechanism can assist in antistatic effects even in relatively dry environments. The semi-permeable wall material of polymer microcapsules allows ions to respond to charges through electrostatic interactions while physically locking the ionic liquid bulk, slowing down performance degradation caused by physical loss, chemical reactions, or excessive migration into the coating, thus achieving a durable and stable antistatic effect.

[0052] Interfacial polymerization was used to disperse a hydrophobic ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt) and a polymerizable monomer (toluene diisocyanate) in water to form tiny oil droplets. Subsequently, another monomer, ethylenediamine, in the aqueous phase diffused to the oil droplet interface and underwent a rapid polymerization reaction with the monomer on the oil droplet surface, forming a dense, insoluble polymer shell on the oil droplet surface, thereby encapsulating the ionic liquid within. The reaction temperature was controlled at 30–35°C because if the temperature was too high, the side reaction between isocyanate and water would intensify, generating CO2 bubbles and potentially causing emulsion demulsification.

[0053] 3. Preparation of composite coating liquid

[0054] Wetting and dispersing agents and part of the defoamer were added to deionized water and stirred at low speed. Then, crystalline polyester hot melt adhesive powder was added and stirred at high speed. After cooling to room temperature, aqueous polyurethane dispersion and acrylate emulsion were added and stirred to form a mixed resin emulsion matrix. Antistatic microcapsule dispersion was added to the mixed resin emulsion matrix and stirred. Then, leveling agent and the remaining defoamer were added, followed by deionized water. The mixture was filtered, allowed to mature and stand, and the composite coating liquid was obtained.

[0055] Utilizing the water-based resin itself as a dispersion medium and protective colloid, mechanical shear force is used to uniformly disperse the resilient hot melt adhesive powder, antistatic microcapsules encapsulated by polymer wall material, and other additives into a homogeneous and stable suspension. The water-based polyurethane dispersion provides the main framework of the coating; the acrylic emulsion provides rigidity and hardness, improving the coating drying speed. High-speed dispersion ensures sufficient depolymerization and wetting of the hot melt adhesive powder; insufficient rotation speed or too short a time will lead to powder agglomeration and defects in the coating.

[0056] Preparation and application: The composite coating liquid is applied to the PET release film, then gradient curing is performed, the film is rapidly cooled to below 50°C, wound up, and cured to obtain the DTF transfer film.

[0057] Due to their high density and strong hydrophilicity, ionic liquid microcapsules tend to remain in the lower part of the coating; while the hydrophobic crystalline polyester resin gradually migrates to the surface and crystallizes and deposits. During the evaporation of water and the increase in temperature, the hot melt adhesive particles melt and spontaneously migrate towards the air interface (coating surface) to reduce the system's free energy. By controlling the temperature and rate of each drying stage, this migration and phase separation process can be precisely controlled: the low-temperature stage allows the aqueous resin to initially form a film and fix the underlying structure; the medium-temperature stage allows the resin to fully cross-link and "lock" the microcapsules at the bottom; the high-temperature stage provides sufficient migration kinetic energy and crystallization driving force for the hot melt adhesive, causing it to accumulate on the surface and crystallize rapidly, ultimately forming a gradient coating with "antistatic bottom and thermal adhesion top".

[0058] The gradient coating is formed through an integrated coating process, and its layering is spontaneously formed. Therefore, the concentration difference between the thermal adhesive layer (crystalline polyester resin) and the antistatic layer is not as significant as in step-coating. Because the crystalline polyester resin is relatively hard and has a smooth surface with low surface free energy, it can effectively disperse powder. Furthermore, since the spontaneously enriched concentration is limited, it does not form a barrier layer, allowing the ink to wet well. This enables the ink to be adsorbed and fixed by the network structure composed of water-based polyurethane and acrylic resin in the antistatic layer. The antistatic capsules are located in the lower layer, making them less susceptible to damage during use. (On the one hand, during hot pressing, the outermost thermally induced phase change adhesive layer melts first, absorbing most of the direct heat and transferring pressure and heat evenly and gently to the lower layer; on the other hand, the microcapsules are embedded and fixed in a fully cross-linked three-dimensional network, which withstands the main mechanical pressure, protecting the internal microcapsules from direct crushing.) This also provides excellent sustained-release properties.

[0059] Example 1

[0060] An electrostatic powder-repellent DTF transfer film and its preparation method are as follows:

[0061] Table 1 Main Raw Materials

[0062]

[0063] S1: Preparation of crystalline polyester hot melt adhesive resin.

[0064] S11: 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol were dried and mixed. The mixture was heated and stirred under nitrogen protection throughout the process. After stirring, tetrabutyl titanate catalyst was added, and the temperature was continued to rise while the system pressure was gradually reduced to 60 Pa. Then, KH-550-modified boron nitride nanosheets were added, and the mixture was stirred at 100 rpm for 38 min. After cooling, the mixture was granulated to obtain resin chips. The molar ratio of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol was 7.5:2.5:1.15. The stirring temperature was 195℃, the stirring speed was 160 rpm, and the stirring time was 3 h. The amount of tetrabutyl titanate catalyst was 0.06% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; the amount of boron nitride nanosheets was 1.3% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol.

[0065] S12: The resin slices prepared in S11 are placed in a liquid nitrogen environment for cryogenic embrittlement, crushed, and sieved to obtain crystalline polyester hot melt adhesive micro powder.

[0066] S2: Dispersion preparation.

[0067] S21: Add polyvinyl alcohol to deionized water, stir at 90°C, and cool to room temperature to obtain an aqueous solution.

[0068] S22: Mix 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and toluene diisocyanate, and stir to prepare an oil phase solution. The mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to toluene diisocyanate is 1:1.8.

[0069] S23: Under medium-speed stirring, the oil phase solution prepared in S22 is added dropwise to the aqueous phase solution prepared in S21, followed by shear emulsification to obtain a primary emulsion. The medium-speed stirring parameters are set to 400 rpm; the shear emulsification parameters are set to 10000 rpm for 8 minutes.

[0070] S24: Add a 5% ethylenediamine aqueous solution to the primary emulsion prepared in S23, stir, cool to room temperature, adjust the pH to 7, filter, and obtain an antistatic microcapsule dispersion. The mass ratio of ethylenediamine to toluene diisocyanate is 1.1:1. Stirring parameters are set as follows: temperature 33℃, rotation speed 350 rpm, and stirring time 34 h.

[0071] S3: Preparation of composite coating liquid.

[0072] S31: Add the wetting and dispersing agent and a portion (50%) of the defoamer to deionized water, stir at low speed, then add the crystalline polyester hot melt adhesive micropowder prepared in S12, stir at high speed, cool to room temperature, then add the aqueous polyurethane dispersion and acrylate emulsion, stir to form a mixed resin emulsion matrix. The low-speed stirring parameters are set as follows: 300 rpm for 8 min; high-speed stirring parameters are set as follows: 2000 rpm for 20 min; stirring parameters are set as follows: 500 rpm for 13 min.

[0073] S32: The antistatic microcapsule dispersion prepared in S24 is added to the mixed resin emulsion matrix prepared in S31 and stirred for 10 minutes. Then, leveling agent and the remaining (50%) of defoamer are added, followed by deionized water to prepare a coating liquid with a solid content of 30%. The mixture is filtered, allowed to mature and stand, and the composite coating liquid is obtained. The mass ratio of each raw material in the dry film of the composite coating liquid is as follows: waterborne polyurethane dispersion 45%, acrylic emulsion 15%, antistatic microcapsule dispersion 10% (based on capsule dry weight), crystalline polyester hot melt adhesive micropowder 28%, wetting and dispersing agent 1.4%, defoamer 0.3%, and leveling agent 0.3%.

[0074] S4: Preparation of the transfer film. The composite coating liquid prepared in S32 is applied to the PET release film, followed by gradient curing, rapid cooling to below 50℃, winding, and curing to obtain the DTF transfer film. The gradient curing parameters are as follows: first stage temperature 73℃, duration 33s; second stage temperature 100℃, duration 50s; third stage temperature 130℃, duration 20s. The curing parameters are: temperature 23℃, humidity 50%, duration 36h.

[0075] Example 2

[0076] The composition and preparation process are the same as in Example 1, except that:

[0077] In the preparation process, the molar ratio of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol in S11 is 6:4:1.05; the amount of tetrabutyl titanate catalyst is 0.03% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; the amount of boron nitride nanosheets is 0.5% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; and other components are the same.

[0078] In the preparation process S11, the heating and stirring parameters are set as follows: temperature 180℃, rotation speed 120rpm, duration 2h; stirring parameters are set as follows: rotation speed 80rpm, duration 30min, and other steps are the same.

[0079] In the preparation process S22, the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to toluene diisocyanate is 1:1; other components are the same.

[0080] In the preparation process S23, the medium-speed stirring parameters are set as follows: 300 rpm; the shear emulsification parameters are set as follows: 8000 rpm and 5 min. Other steps are the same.

[0081] In the preparation process S24, the mass ratio of ethylenediamine to toluene diisocyanate is 1:1, and other components are the same.

[0082] The stirring parameters in step S24 of the preparation process are set as follows: temperature 30℃, rotation speed 300rpm, duration 2h, and other steps are the same.

[0083] In the preparation process S31, the low-speed stirring parameters were set as follows: 200 rpm for 5 min; the high-speed stirring parameters were set as follows: 1500 rpm for 15 min; and the stirring parameters were set as follows: 400 rpm for 10 min. Other steps were the same.

[0084] The composite coating liquid prepared in process S32 has a solid content of 25%. The mass ratio of each raw material in the dry film is as follows: waterborne polyurethane dispersion 35%, acrylate emulsion 20%, antistatic microcapsule dispersion 15% based on the dry weight of the capsules, crystalline polyester hot melt adhesive micro powder 29.3%, wetting and dispersing agent 0.5%, defoamer 0.1%, leveling agent 0.1%, and other components are the same.

[0085] The gradient curing parameters in step S4 of the preparation process are set as follows: first stage temperature 65℃, duration 25s, second stage temperature 90℃, duration 40s, third stage temperature 120℃, duration 10s; curing parameters are set as follows: temperature 20℃, humidity 45%, duration 24h, and other steps are the same.

[0086] Example 3

[0087] The composition and preparation process are the same as in Example 1, except that:

[0088] In the preparation process, the molar ratio of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol in S11 is 9:1:1.25; the amount of tetrabutyl titanate catalyst is 0.08% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; the amount of boron nitride nanosheets is 2% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; other components are the same.

[0089] In the preparation process S11, the heating and stirring parameters are set as follows: temperature 210℃, speed 200rpm, duration 4h; stirring parameters are set as follows: speed 120rpm, duration 45min, and other steps are the same.

[0090] In the preparation process S22, the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to toluene diisocyanate is 1:2.5; other components are the same.

[0091] In step S23 of the preparation process, the medium-speed stirring parameters are set as follows: 500 rpm; the shear emulsification parameters are set as follows: 12000 rpm and 10 min. Other steps are the same.

[0092] In the preparation process S24, the mass ratio of ethylenediamine to toluene diisocyanate is 1.2:1, and other components are the same.

[0093] The stirring parameters in step S24 of the preparation process are set as follows: temperature 35℃, rotation speed 400rpm, duration 4h, and other steps are the same.

[0094] In the preparation process S31, the low-speed stirring parameters were set as follows: 400 rpm for 10 min; the high-speed stirring parameters were set as follows: 2500 rpm for 25 min; and the stirring parameters were set as follows: 600 rpm for 15 min. Other steps were the same.

[0095] The composite coating liquid prepared in process S32 has a solid content of 35%. The mass ratio of each raw material in the dry film is as follows: 50% waterborne polyurethane dispersion, 20% acrylate emulsion, 7% antistatic microcapsule dispersion based on the dry weight of the capsules, 20% crystalline polyester hot melt adhesive powder, 2% wetting and dispersing agent, 0.5% defoamer, 0.5% leveling agent, and other components are the same.

[0096] The gradient curing parameters in step S4 of the preparation process are set as follows: first stage temperature 80℃, duration 40s; second stage temperature 110℃, duration 60s; third stage temperature 140℃, duration 30s; curing parameters are set as follows: temperature 25℃, humidity 55%, duration 48h, and other steps are the same.

[0097] Example 4

[0098] The composition and preparation process are the same as in Example 1, except that:

[0099] In the preparation process, the molar ratio of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol in S11 is 8:3:1.11; the amount of tetrabutyl titanate catalyst is 0.04% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; the amount of boron nitride nanosheets is 0.8% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol; and other components are the same.

[0100] In the preparation process S11, the heating and stirring parameters are set as follows: temperature 190℃, rotation speed 140rpm, duration 2.5h; stirring parameters are set as follows: rotation speed 110rpm, duration 42min, and other steps are the same.

[0101] In the preparation process S22, the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to toluene diisocyanate is 1:2; other components are the same.

[0102] In the preparation process S23, the medium-speed stirring parameters are set as follows: 450 rpm; the shear emulsification parameters are set as follows: 9000 rpm and 9 min. Other steps are the same.

[0103] In the preparation process S24, the mass ratio of ethylenediamine to toluene diisocyanate is 1.15:1, and other components are the same.

[0104] The stirring parameters in step S24 of the preparation process are set as follows: temperature 34℃, rotation speed 380rpm, duration 3.5h, and other steps are the same.

[0105] The low-speed stirring parameters for step S31 of the preparation process are set as follows: 260 rpm for 9 min; high-speed stirring parameters are set as follows: 2300 rpm for 22 min; stirring parameters are set as follows: 550 rpm for 11 min. Other steps are the same.

[0106] The composite coating liquid prepared in process S32 has a solid content of 33%. The mass ratio of each raw material in the dry film is as follows: waterborne polyurethane dispersion 47%, acrylate emulsion 16%, antistatic microcapsule dispersion 13% based on capsule dry weight, crystalline polyester hot melt adhesive micro powder 22%, wetting and dispersing agent 1.2%, defoamer 0.4%, leveling agent 0.4%, and other components are the same.

[0107] The gradient curing parameters in step S4 of the preparation process are set as follows: first stage temperature 66℃, duration 36s; second stage temperature 105℃, duration 55s; third stage temperature 133℃, duration 26s; curing parameters are set as follows: temperature 24℃, humidity 52%, duration 40h, and other steps are the same.

[0108] Comparative Example 1

[0109] The composition and preparation process are the same as in Example 1, except that:

[0110] Preparation of S1-removed crystalline polyester hot melt adhesive powder.

[0111] In step S3 of the preparation process, the crystalline polyester hot melt adhesive powder is replaced with low-melting-point ethylene-vinyl acetate copolymer hot melt adhesive powder (EVA), while the other steps remain the same.

[0112] Comparative Example 2

[0113] The composition and preparation process are the same as in Example 1, except that:

[0114] In step S3 of the preparation process, the antistatic microcapsules are replaced with an equal mass of uncoated antistatic agent, while the other steps remain the same.

[0115] Based on Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared DTF transfer film were taken for initial surface resistance and environmental reliability tests: the samples were treated at a constant temperature and humidity of 25°C and 50% relative humidity for 24 hours, then the electrodes were brought into close contact with the coating surface, a test voltage of 100V was applied, and the surface resistance was recorded. After recording, the samples were placed in an environment of 40°C and 80%RH for 7 days, and then the same test was performed, referring to the standard GB / T 31838.3-2019 "Dielectric and resistive properties of solid insulating materials - Part 3: Resistive properties (DC method) - Surface resistance and surface resistivity".

[0116] Based on Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared DTF transfer film were taken for peel strength testing: the transfer film was hot-pressed onto cotton cloth (160℃, 20s, 0.4MPa). After cooling, it was cut into 25mm wide pieces, and then T-shaped peeling was performed using a universal testing machine at a constant speed (300mm / min). The average force value during the peeling process was recorded, and the peel strength was calculated.

[0117] Combining Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared DTF transfer film were taken for water contact angle testing: at room temperature, water droplets were automatically dropped onto a flat, clean coating surface, and images were captured using a high-speed camera. Figure 2 The water contact angle diagrams for Examples 1-4 and Comparative Examples 1-2 are shown, with reference to standard GB / T 30447-2013 "Method for measuring contact angle of nanofilms".

[0118] Based on Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared DTF transfer film were taken for ink drying time testing: a 6μm thick layer of ink was evenly coated onto the coating using a wire rod, and a stopwatch was immediately started. Every 1 second, the non-edge area of ​​the ink was gently touched with the fingertip until no ink transferred to the fingertip and the area felt dry, at which point the time was recorded.

[0119] The specific test results are shown in Table 2. Figure 2 , Figure 3 As shown:

[0120] Table 2 Comparison of core performance of Examples 1-4 and Comparative Examples 1-2

[0121]

[0122] The comparison results above show that Example 1 has the best overall performance. The optimized furan-adipic acid copolyester ratio, BN nanosheet reinforcement, microcapsule encapsulation of antistatic agent, and gradient curing process demonstrate that Example 1 successfully achieved a balance between antistatic properties, ink adsorption, and adhesive strength in the DTF transfer film. The overall performance of Examples 2 to 4 is slightly lower than that of Example 1, but still maintains a high level, indicating that excellent antistatic effects were still achieved under a wide range of parameter variations. Comparative Example 1 uses ethylene-vinyl acetate copolymer hot melt adhesive powder, which has low polarity and extremely poor compatibility with polar ionic liquids. This results in the antistatic agent not being effectively dispersed in the EVA matrix and even more difficult to migrate to the surface to form a conductive layer, resulting in high surface resistance and low peel strength. Comparative Example 2 does not have an antistatic agent coating, and the ionic liquid migrates directly, resulting in poor antistatic durability (environmental reliability).

[0123] In summary, it is clear from the above embodiments and comparative examples that the DTF transfer film provided by the present invention has significantly better antistatic ability and peel strength than traditional solutions. This is attributed to the optimized furan-adipic acid copolyester ratio, BN nanosheet reinforcement, microcapsule encapsulation of antistatic agent, and gradient curing process, thereby solving the balance problem between antistatic properties, ink adsorption, and adhesive strength of the DTF transfer film.

Claims

1. A non-static powder-repellent DTF transfer film, comprising a PET release film and a composite coating, characterized in that: The composite coating is a functional gradient coating formed in one application, without any boundary interface. The side of the composite coating closest to the PET release film is an antistatic network structure region, which contains an ionic liquid antistatic agent encapsulated in polymer microcapsules and uniformly dispersed in the composite polyester matrix. The side of the composite coating furthest from the PET release film is a thermo-induced phase change adhesive layer, which is enriched with crystalline polyester hot melt adhesive resin. The crystalline polyester hot melt adhesive resin melts during the coating curing process and spontaneously migrates to form enriched areas. The composite coating comprises the following raw materials in the following proportions: 35-55% waterborne polyurethane dispersion, 10-20% acrylate emulsion, 5-15% antistatic microcapsule dispersion based on capsule dry weight, 20-35% crystalline polyester hot melt adhesive powder, 0.5-2% wetting and dispersing agent, 0.1-0.5% defoamer, and 0.1-0.5% leveling agent.

2. The DTF transfer film with electrostatic powder-repellent properties according to claim 1, characterized in that: The crystalline polyester hot melt adhesive micro powder is a crystalline polyester hot melt adhesive resin with bio-based 2,5-furandicarboxylic acid as the rigid component, and is modified with boron nitride nanosheets on the surface.

3. The DTF transfer film with electrostatic powder-repellent properties according to claim 1, characterized in that: The antistatic microcapsule dispersion comprises 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, toluene diisocyanate, and ethylenediamine; the mass ratio of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt to toluene diisocyanate is 1:1 to 1:2.5; and the mass ratio of ethylenediamine to toluene diisocyanate is 1:1 to 1.2:

1.

4. The method for preparing the electrostatic powder-free DTF transfer film according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Preparation of crystalline polyester hot melt adhesive resin; S11: 2,5-furandicarboxylic acid, adipic acid and 1,4-butanediol were dried and mixed. The mixture was heated and stirred under nitrogen protection throughout the process. After stirring, tetrabutyl titanate catalyst was added. The temperature was continued to rise and the system pressure was gradually reduced to 60 Pa. Then, boron nitride nanosheets modified with KH-550 were added, stirred, cooled and granulated to obtain resin chips. S12: The resin chips prepared in S11 are placed in a liquid nitrogen environment for cryogenic embrittlement, crushed, and sieved to obtain crystalline polyester hot melt adhesive micro powder. S2: Dispersion preparation; S21: Add polyvinyl alcohol to deionized water, stir at 90°C, and cool to room temperature to obtain an aqueous solution; S22: Mix 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and toluene diisocyanate, stir, and prepare an oil phase solution; S23: Under medium-speed stirring, the oil phase solution prepared in S22 is added dropwise to the aqueous phase solution prepared in S21, and then shear emulsified to obtain a primary emulsion; S24: Add a 5% ethylenediamine aqueous solution to the primary emulsion prepared in S23, stir, cool to room temperature, adjust the pH to 7, filter, and obtain an antistatic microcapsule dispersion. S3: Preparation of composite coating liquid; S31: Add wetting and dispersing agent and part of defoamer to deionized water, stir at low speed, then add crystalline polyester hot melt adhesive micro powder prepared in S12, stir at high speed, cool to room temperature, then add waterborne polyurethane dispersion and acrylate emulsion, stir to form a mixed resin emulsion matrix. S32: Add the antistatic microcapsule dispersion prepared in S24 to the mixed resin emulsion matrix prepared in S31, stir for 10 min, then add leveling agent and the remaining defoamer, then add deionized water to prepare a coating liquid with a solid content of 25-35%, filter, mature and stand to obtain a composite coating liquid. S4: Prepare the transfer film by coating the composite coating liquid prepared in S32 onto the PET release base film, then perform gradient curing, rapidly cool to below 50°C, wind up, and cure to obtain the DTF transfer film.

5. The method for preparing an electrostatic powder-free DTF transfer film according to claim 4, characterized in that: The molar ratio of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol described in S11 is (6-9):(4-1):(1.05-1.25). The heating and stirring described in S11 has the following parameters: temperature 180~210℃, rotation speed 120~200rpm, duration 2~4h; The tetrabutyl titanate catalyst described in S11 is used in an amount of 0.03 to 0.08% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol. The boron nitride nanosheets described in S11 are used in an amount of 0.5-2% of the total mass of 2,5-furandicarboxylic acid, adipic acid, and 1,4-butanediol. The stirring described in S11 has the following parameters: rotation speed 80-120 rpm, duration 30-45 min.

6. The method for preparing an electrostatic powder-repellent DTF transfer film according to claim 4, characterized in that: The medium-speed stirring described in S23 has the following parameter settings: rotation speed 300-500 rpm; The shear emulsification described in S23 has the following parameter settings: rotation speed 8000~12000rpm, duration 5~10min.

7. The method for preparing an electrostatic powder-free DTF transfer film according to claim 4, characterized in that: The stirring described in S24 has the following parameters: temperature 30-35℃, speed 300-400rpm, and duration 2-4h.

8. The method for preparing an electrostatic powder-free DTF transfer film according to claim 4, characterized in that: The defoamer described in S31 is added in an amount that is 50% of the total amount of defoamer added. The low-speed stirring described in S31 has the following parameter settings: rotation speed 200-400 rpm, duration 5-10 min; The high-speed stirring described in S31 has the following parameter settings: rotation speed 1500~2500rpm, duration 15~25min; The stirring described in S31 has the following parameters: rotation speed 400-600 rpm, duration 10-15 min.

9. The method for preparing an electrostatic powder-free DTF transfer film according to claim 4, characterized in that: The gradient curing described in S4 has the following parameter settings: first stage temperature 65-80℃, duration 25-40s; second stage temperature 90-110℃, duration 40-60s; third stage temperature 120-140℃, duration 10-30s. The curing process described in S4 has the following parameters: temperature 20-25℃, humidity 45-55%, and duration 24-48h.

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