Preparation method of hand feeling agent for extrusion material

Abstract

The invention relates to the technical field of high polymer material synthesis and modification, in particular to a preparation method of a feeling agent for an extrusion material. Comprising the following steps: melting trimethylolpropane and dimethylolpropionic acid, and carrying out gradient heating esterification and vacuum dehydration to obtain a hydroxyl-terminated hyperbranched polyester core; the preparation method comprises the following steps: dropwise adding dry single-terminal hydroxyl polydimethylsiloxane into isophorone diisocyanate, shearing at low temperature, heating and curing to obtain an isocyanate-terminated siloxane prepolymer; and finally, dropwise adding the prepolymer into the core solution for graft copolymerization, and carrying out ethanol end capping, rotary evaporation, precipitation and drying to obtain the hand feeling agent for the extrusion material. According to the invention, an isocyanate-terminated siloxane prepolymer is chemically grafted on the surface of a hydroxyl-terminated hyperbranched polyester core, so that a stable core-shell structure is constructed.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis and modification technology, specifically to a method for preparing extruded materials with a hand-feeling agent. Background Technology

[0002] In existing extrusion materials using hand-feeling agents, directly adding lubricants such as dimethyl silicone oil through physical blending can lead to severe macroscopic phase separation due to the large polarity difference between the silicone oil and the substrate, as well as the lack of chemical anchoring. This thermodynamic incompatibility causes the silicone oil to rapidly migrate to the surface during the extrusion thermal process, resulting in severe oiliness and a greasy feel initially. Furthermore, the smooth surface effect cannot be maintained after aging, posing serious problems of poor migration resistance and contamination risk. In addition, when using linear polymers as modifiers, the lack of a spherical topology leads to easy molecular chain entanglement and high melt viscosity, resulting in uneven dispersion in the substrate. This causes crystal points to easily appear on the surface of the parts, resulting in a dry feel and failing to create a silky smooth feel similar to molecular beads. Furthermore, during the synthesis of silicone-containing modifiers, improper reaction kinetic control, such as the failure to use a low-temperature, high-shear process, can easily lead to excessively high local concentrations, causing nucleo-nucleochemical crosslinking initiated by free isocyanates, generating micron-sized gel particles. This results in a rough surface with numerous crystal points, significantly increasing the coefficient of friction and losing the expected lubrication function. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing extruded materials with a hand-feeling agent, avoiding the migration, precipitation, and surface oiling of traditional organosilicon additives during extrusion, and imparting to the material a long-lasting dry, silky feel and excellent aging resistance; specifically, the technical solution of this invention is as follows: A method for preparing an extruded material with a hand-feeling agent includes the following steps: The hydroxyl-terminated hyperbranched polyester core was dissolved in a solvent and ultrasonically dispersed to obtain a core solution. Under heating and stirring conditions, an isocyanate-terminated siloxane prepolymer solution was added dropwise to the core solution to carry out a graft copolymerization reaction. After the reaction was completed, anhydrous ethanol was added for end-capping, the solvent was removed by rotary evaporation, the residue was precipitated in a precipitant, centrifuged, and dried to obtain the extruded material with a hand feel. The preparation of the hydroxyl-terminated hyperbranched polyester core includes the following steps: Trimethylolpropane and dimethylolpropionic acid were added to a reaction vessel and melt-mixed; a catalyst was added and a gradient temperature esterification reaction was carried out; in the later stage of the reaction, vacuum dehydration, cooling, and pulverization were performed to obtain a hydroxyl-terminated hyperbranched polyester core. The preparation of isocyanate-terminated siloxane prepolymers includes the following steps: Step (1) Dehydrate and dry the single-hydroxyl-terminated polydimethylsiloxane under vacuum conditions; Step (2) Mix isophorone diisocyanate and solvent at a cutting rate ≥2000 s. -1 Under high shear and low temperature conditions of -10℃ to 5℃, a dried single-hydroxyl-terminated polydimethylsiloxane solution was added dropwise. After the addition was completed, the low temperature and high shear were maintained. This process was carried out using a high-speed shear dispersion emulsifier. Then, the process was switched to ordinary mechanical stirring mode and the temperature was naturally raised. A catalyst was added and the mixture was heated to mature, resulting in an isocyanate-terminated siloxane prepolymer solution.

[0004] Preferably, the mass ratio of the hydroxyl-terminated hyperbranched polyester core, solvent, isocyanate-based end-capped siloxane prepolymer solution, and anhydrous ethanol is (10):(20-40):(50-100):(1-3); the mass ratio of the hydroxyl-terminated hyperbranched polyester core to the isocyanate-based end-capped siloxane prepolymer solution is 1:5 to 1:10.

[0005] Preferably, the molar ratio of trimethylolpropane to dimethylolpropionic acid is 1:4 to 1:6; the catalyst is p-toluenesulfonic acid, and its amount is 0.05-0.2 parts of the total mass of trimethylolpropane and dimethylolpropionic acid.

[0006] Preferably, the gradient heating esterification reaction specifically involves: first heating to 135-145℃ to melt the raw material, and then heating to 170-190℃ at a rate of 2-5℃ / min; the vacuum dehydration is carried out at 170-190℃ and -0.08MPa to -0.1MPa for 1-3 hours.

[0007] Preferably, the ratio of hydroxyl-terminated polydimethylsiloxane, isophorone diisocyanate, and solvent satisfies that the molar ratio of isocyanate groups to hydroxyl groups is 2.0:1 to 3.0:1; the solvent is toluene, and the amount used is 40-60 parts (relative to 100 parts of hydroxyl-terminated polydimethylsiloxane).

[0008] Preferably, the low temperature condition is -10℃ to 5℃; the high shear is achieved using a high shear emulsifier or homogenizer, with a high shear rate ≥2000s. -1 The heating and curing temperature is 55-65℃, and the holding time is 2-4 hours.

[0009] Preferably, the number average molecular weight of the single-hydroxyl-terminated polydimethylsiloxane is 3000-8000; the dehydration drying conditions in step (1) are 100-110℃ and -0.09MPa.

[0010] Preferably, the solvent of the core solution is anhydrous N,N-dimethylformamide; the temperature of the graft copolymerization reaction is 65-85℃, and the dropping rate is strictly controlled during the reaction until the system exhibits a stable micelle dispersion state and the Tyndall effect is observed; the end-capping reaction time is 20-40 minutes.

[0011] Preferably, the rotary evaporation is carried out at 70-90℃ and -0.09MPa; the precipitant is a mixture of methanol and water in a volume ratio of 1:1; and the drying is carried out in a vacuum oven at 55-65℃ for 24 hours.

[0012] Compared with the prior art, the present invention has the following improvements and advantages: 1. This invention constructs a robust core-shell structure by chemically grafting isocyanate-terminated siloxane prepolymer onto the surface of a hydroxyl-terminated hyperbranched polyester core. This chemical bonding significantly enhances the anchoring ability of organosilicon segments in the substrate, effectively limiting their free migration during thermal aging or long-term use. Compared with the technique of directly adding dimethyl silicone oil, the feel agent prepared by this invention exhibits significantly improved surface hydrophobic angle retention after high-temperature aging tests, and no oil precipitation occurs, overcoming the defects of traditional techniques such as initial greasiness, later failure, and packaging contamination. 2. In preparing isocyanate-terminated siloxane prepolymers, this invention employs a specific process combining low temperature and high shear rate, effectively controlling reaction kinetics and avoiding isocyanate double-end reactions and subsequent nucleo-nucleochemical crosslinking caused by excessively high local concentrations. This innovative process eliminates the formation of micron-sized hard gel particles, ensuring high purity and uniformity of the product. Compared to ordinary stirring processes, extruded products using the tactile agent of this invention have no rough crystal points on the surface, and the dynamic friction coefficient is significantly reduced, ensuring a delicate and smooth tactile experience.

[0013] 3. This invention uses hydroxyl-terminated hyperbranched polyester as a rigid core, which is different from traditional linear polymer modifiers. This unique spherical three-dimensional topology effectively reduces the entanglement between molecular chains and significantly reduces the melt viscosity. During the extrusion process, the spherical molecules can play the role of rolling lubrication of molecular balls like micro-bearings, thereby giving the product surface excellent smoothness and fineness, solving the problem of dryness and stickiness caused by molecular chain entanglement in linear structure modifiers. 4. The hand-feeling agent prepared in this invention combines polyurethane hard segments compatible with polar substrates and low-surface-energy polysiloxane soft segments. By strictly controlling the dropping rate, the reaction system exhibits the Tyndall effect, promoting the self-assembly of the graft copolymer in the solvent to form a stable micelle dispersion. This amphiphilic structure enables the hand-feeling agent to form a uniform nanoscale island structure in thermoplastic polyurethane and other substrates, ensuring both good interfacial bonding and efficient enrichment of the organosilicon component on the surface. Thus, excellent lubrication modification effects can be obtained at extremely low addition levels. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0015] Example 1: This embodiment provides a method for preparing a hand-feeling agent for extruded materials, including the following steps: dissolving a hydroxyl-terminated hyperbranched polyester core in anhydrous N,N-dimethylformamide solvent and ultrasonically dispersing it for 30 minutes to obtain a core solution; under heating at 75°C and stirring at 300 rpm, adding an isocyanate-terminated siloxane prepolymer solution dropwise to the core solution to carry out a graft copolymerization reaction, strictly controlling the dropwise addition rate until the system exhibits a significant blue Tyndall effect, indicating that the graft copolymer has self-assembled in the solvent to form a stable micelle dispersion; after maintaining the reaction temperature for 4 hours, adding anhydrous ethanol to react... End-capping should be performed within 30 minutes. Solvent removal is achieved by rotary evaporation at 75°C and -0.09 MPa. The residue is precipitated in a 1:1 volume ratio of methanol and water as a precipitant, centrifuged, and dried in a vacuum oven at 60°C for 24 hours to obtain the extruded material with a hand-feeling effect. The mass ratio of the hydroxyl-terminated hyperbranched polyester core, solvent, isocyanate-based end-capped siloxane prepolymer solution, and anhydrous ethanol is 10:30:80:2. The mass ratio of the hydroxyl-terminated hyperbranched polyester core to the isocyanate-based end-capped siloxane prepolymer solution is 1:8. The preparation of the hydroxyl-terminated hyperbranched polyester core includes the following steps: Trimethylolpropane and dimethylolpropionic acid were added to a reaction vessel and melt-mixed at 140°C. Toluenesulfonic acid catalyst was added, and a gradient temperature esterification reaction was carried out, first heating to 180°C at a rate of 3°C / min. In the later stage of the reaction, vacuum dehydration was performed at 180°C and -0.09 MPa for 2 hours, followed by cooling to 100°C and pulverization to obtain a hydroxyl-terminated hyperbranched polyester core. The molar ratio of trimethylolpropane to dimethylolpropionic acid was 1:5. The amount of toluenesulfonic acid catalyst was 0.1 parts of the total mass of trimethylolpropane and dimethylolpropionic acid. The preparation of the isocyanate-terminated siloxane prepolymer included the following steps: Step (1) Dehydrate and dry single-hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 5000 at 105℃ and -0.09MPa vacuum for 2 hours; Step (2) Mix isophorone diisocyanate and toluene solvent, and dry at a shear rate of 2500s. -1 Under high shear and -5°C conditions, a dried hydroxyl-terminated polydimethylsiloxane solution was added dropwise. After the addition was complete, the solution was maintained at low temperature and high shear for 30 minutes. Then, the stirring mode was switched and the temperature was naturally raised to room temperature. Dibutyltin dilaurate catalyst was added, and the solution was heated to 60°C for aging for 3 hours to obtain an isocyanate-terminated siloxane prepolymer solution. The ratio of hydroxyl-terminated polydimethylsiloxane, isophorone diisocyanate, and solvent was such that the molar ratio of isocyanate groups to hydroxyl groups was 2.1:1. The solvent was toluene, and the amount used was 50 parts.

[0016] The extrusion material prepared in this embodiment is used as a feel agent in the extrusion production of TPU mobile phone cases. The product surface exhibits a dry and smooth feel, the dynamic coefficient of friction (COF) is reduced to 0.08, and the surface water contact angle retention rate is high after aging test at 80℃, with no obvious grease precipitation. This indicates that the core-shell structure achieves good migration resistance while ensuring lubricity.

[0017] Example 2: This embodiment provides a method for preparing a hand-feeling agent for extruded materials, comprising the following steps: dissolving a hydroxyl-terminated hyperbranched polyester core in anhydrous N,N-dimethylformamide solvent and ultrasonically dispersing it for 40 minutes to obtain a core solution; under heating conditions of 85°C and stirring at 400 rpm, adding an isocyanate-terminated siloxane prepolymer solution dropwise to the core solution to carry out a graft copolymerization reaction, strictly controlling the dropwise addition rate until the system exhibits a significant blue Tyndall effect, indicating that the graft copolymer has self-assembled in the solvent to form a stable micelle dispersion; after maintaining the reaction temperature for 5 hours, adding anhydrous ethanol for further reaction. End-capping was performed for 40 minutes, followed by solvent removal via rotary evaporation at 90°C and -0.09 MPa. The residue was precipitated in a 1:1 (v / v) methanol-water mixture, centrifuged, and dried in a vacuum oven at 65°C for 24 hours to obtain the extruded material with a hand-feeling agent. The mass ratio of the hydroxyl-terminated hyperbranched polyester core, solvent, isocyanate-based end-capped siloxane prepolymer solution, and anhydrous ethanol was 10:40:100:3; the mass ratio of the hydroxyl-terminated hyperbranched polyester core to the isocyanate-based end-capped siloxane prepolymer solution was 1:10. The preparation of the hydroxyl-terminated hyperbranched polyester core included the following steps: Trimethylolpropane and dimethylolpropionic acid were added to a reaction vessel and melt-mixed at 145°C. Toluenesulfonic acid catalyst was added, and a gradient temperature esterification reaction was carried out, first heating to 190°C at a rate of 5°C / min. In the later stage of the reaction, vacuum dehydration was performed at 190°C and -0.1 MPa for 3 hours, followed by cooling to 100°C and pulverization to obtain a hydroxyl-terminated hyperbranched polyester core. The molar ratio of trimethylolpropane to dimethylolpropionic acid was 1:6. The amount of toluenesulfonic acid catalyst was 0.2 parts of the total mass of trimethylolpropane and dimethylolpropionic acid. The preparation of the isocyanate-terminated siloxane prepolymer included the following steps: Step (1) Dehydrate and dry single-hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 8000 at 110℃ and -0.09MPa vacuum for 3 hours; Step (2) Mix isophorone diisocyanate and toluene solvent, and dry at a shear rate of 3000s. -1Under high shear and low temperature conditions of 5°C, a dried single-hydroxyl-terminated polydimethylsiloxane solution was added dropwise. After the addition was complete, the low temperature and high shear were maintained for 40 minutes. Then, the stirring mode was switched and the temperature was naturally raised to room temperature. Dibutyltin dilaurate catalyst was added, and the temperature was raised to 65°C for aging for 4 hours to obtain an isocyanate-terminated siloxane prepolymer solution. The ratio of single-hydroxyl-terminated polydimethylsiloxane, isophorone diisocyanate, and solvent met the requirement that the molar ratio of isocyanate groups to hydroxyl groups was 2.5:1. The solvent was toluene, and the amount used was 60 parts. The extruded material prepared in this embodiment is a hand-feeling agent. Due to the use of a high core-shell ratio and a high molecular weight soft segment, the surface has an extremely smooth initial feel when applied to electronic product protective cases, with a dynamic friction coefficient as low as 0.07. It is suitable for scenarios with extremely high requirements for initial tactile feel. However, the contact angle retention rate after aging is slightly lower than that in Example 1.

[0018] Example 3: This embodiment provides a method for preparing a hand-feeling agent for extruded materials, including the following steps: dissolving a hydroxyl-terminated hyperbranched polyester core in anhydrous N,N-dimethylformamide solvent and ultrasonically dispersing it for 20 minutes to obtain a core solution; under heating conditions of 65°C and stirring at 200 rpm, adding an isocyanate-terminated siloxane prepolymer solution dropwise to the core solution to carry out a graft copolymerization reaction, strictly controlling the dropwise addition rate until the system exhibits a significant blue Tyndall effect, indicating that the graft copolymer has self-assembled in the solvent to form a stable micelle dispersion; after maintaining the reaction temperature for 3 hours, adding anhydrous ethanol to react... End-capping should be performed within 20 minutes. Solvent removal is achieved by rotary evaporation at 70°C and -0.09 MPa. The residue is precipitated in a 1:1 (v / v) methanol-water mixture as a precipitant, centrifuged, and dried in a vacuum oven at 55°C for 24 hours to obtain the extruded material with a hand-feeling effect. The mass ratio of the hydroxyl-terminated hyperbranched polyester core, solvent, isocyanate-based end-capped siloxane prepolymer solution, and anhydrous ethanol is 10:20:50:1. The mass ratio of the hydroxyl-terminated hyperbranched polyester core to the isocyanate-based end-capped siloxane prepolymer solution is 1:5. The preparation of the hydroxyl-terminated hyperbranched polyester core includes the following steps: Trimethylolpropane and dimethylolpropionic acid were added to a reaction vessel and melt-mixed at 135°C. Toluenesulfonic acid catalyst was added, and a gradient temperature esterification reaction was carried out, first heating to 170°C at a rate of 2°C / min. In the later stage of the reaction, vacuum dehydration was performed at 170°C and -0.08 MPa for 1 hour, followed by cooling to 100°C and pulverization to obtain a hydroxyl-terminated hyperbranched polyester core. The molar ratio of trimethylolpropane to dimethylolpropionic acid was 1:4. The amount of toluenesulfonic acid catalyst was 0.05 parts of the total mass of trimethylolpropane and dimethylolpropionic acid. The preparation of the isocyanate-terminated siloxane prepolymer included the following steps: Step (1) Dehydrate and dry single-hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 3000 at 100℃ and -0.09MPa vacuum for 1 hour; Step (2) Mix isophorone diisocyanate and toluene solvent, and dry at a shear rate of 2000s. -1 Under high shear and -10°C conditions, a dried hydroxyl-terminated polydimethylsiloxane solution was added dropwise. After the addition was complete, the solution was maintained at low temperature and high shear for 20 minutes. Then, the stirring mode was switched and the temperature was naturally raised to room temperature. Dibutyltin dilaurate catalyst was added, and the solution was heated to 55°C for aging for 2 hours to obtain an isocyanate-terminated siloxane prepolymer solution. The ratio of hydroxyl-terminated polydimethylsiloxane, isophorone diisocyanate, and solvent was such that the molar ratio of isocyanate groups to hydroxyl groups was 3:1. The solvent was toluene, and the amount used was 40 parts.

[0019] The extrusion material prepared in this embodiment is a hand-feeling agent with a relatively low proportion of active silicone shell and a small molecular weight. It has excellent anchoring properties in TPU substrate and a high contact angle retention rate in aging tests. Although its coefficient of friction is 0.12 and its slipperiness is slightly inferior to that of Example 1, its surface is dry and oil-free, making it suitable for industrial extrusion parts with high requirements for wear resistance and long-term stability.

[0020] Example 4: This embodiment provides a method for preparing a hand-feeling agent for extruded materials, including the following steps: dissolving a hydroxyl-terminated hyperbranched polyester core in anhydrous N,N-dimethylformamide solvent and ultrasonically dispersing it for 25 minutes to obtain a core solution; under heating at 70°C and stirring at 250 rpm, adding an isocyanate-terminated siloxane prepolymer solution dropwise to the core solution to carry out a graft copolymerization reaction, strictly controlling the dropwise addition rate until the system exhibits a significant blue Tyndall effect, indicating that the graft copolymer has self-assembled in the solvent to form a stable micelle dispersion; after maintaining the reaction temperature for 3.5 hours, adding anhydrous ethanol to react... End-capping should be performed within 25 minutes. Solvent removal is achieved by rotary evaporation at 80°C and -0.09 MPa. The residue is precipitated in a 1:1 volume ratio of methanol and water as a precipitant, centrifuged, and dried in a vacuum oven at 58°C for 24 hours to obtain the extruded material with a hand-feeling agent. The mass ratio of the hydroxyl-terminated hyperbranched polyester core, solvent, isocyanate-based end-capped siloxane prepolymer solution, and anhydrous ethanol is 10:25:60:1.5; the mass ratio of the hydroxyl-terminated hyperbranched polyester core to the isocyanate-based end-capped siloxane prepolymer solution is 1:6. The preparation of the hydroxyl-terminated hyperbranched polyester core includes the following steps: Trimethylolpropane and dimethylolpropionic acid were added to a reaction vessel and melt-mixed at 138°C. Toluenesulfonic acid catalyst was added, and a gradient temperature esterification reaction was carried out, first heating to 175°C at a rate of 2.5°C / min; in the later stage of the reaction, vacuum dehydration was performed at 175°C and -0.085 MPa for 1.5 hours, followed by cooling to 100°C and pulverization to obtain a hydroxyl-terminated hyperbranched polyester core. The molar ratio of trimethylolpropane to dimethylolpropionic acid was 1:4.5; the amount of toluenesulfonic acid catalyst was 0.12 parts of the total mass of trimethylolpropane and dimethylolpropionic acid. The preparation of the isocyanate-terminated siloxane prepolymer included the following steps: Step (1) Dehydrate and dry single-hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 4000 at 102℃ and -0.09MPa vacuum for 1.5 hours; Step (2) Mix isophorone diisocyanate and toluene solvent, and dry at a shear rate of 2200s. -1 Under high shear and -2°C conditions, a dried hydroxyl-terminated polydimethylsiloxane solution was added dropwise. After the addition was complete, the solution was maintained at low temperature and high shear for 25 minutes. Then, the stirring mode was switched and the temperature was naturally raised to room temperature. Dibutyltin dilaurate catalyst was added, and the solution was heated to 58°C for aging for 2.5 hours to obtain an isocyanate-terminated siloxane prepolymer solution. The ratio of hydroxyl-terminated polydimethylsiloxane, isophorone diisocyanate, and solvent was such that the molar ratio of isocyanate groups to hydroxyl groups was 4:1. The solvent was toluene, and the amount used was 45 parts.

[0021] The extruded material prepared in this embodiment, by adjusting the core-shell ratio and molecular weight to a medium range, exhibits balanced performance in TPU cable sheath applications. It has a delicate surface feel, a stable coefficient of friction of around 0.1, and maintains good hydrophobicity and smoothness after multiple bends.

[0022] Example 5: This embodiment provides a method for preparing a hand-feeling agent for extruded materials, including the following steps: dissolving a hydroxyl-terminated hyperbranched polyester core in anhydrous N,N-dimethylformamide solvent and ultrasonically dispersing it for 35 minutes to obtain a core solution; under heating at 80°C and stirring at 350 rpm, adding an isocyanate-terminated siloxane prepolymer solution dropwise to the core solution to carry out a graft copolymerization reaction, strictly controlling the dropwise addition rate until the system exhibits a significant blue Tyndall effect, indicating that the graft copolymer has self-assembled in the solvent to form a stable micelle dispersion; after maintaining the reaction temperature for 4.5 hours, adding anhydrous ethanol to react... End-capping should be performed within 35 minutes. Solvent removal is achieved by rotary evaporation at 85°C and -0.09 MPa. The residue is precipitated in a 1:1 volume ratio of methanol and water as a precipitant, centrifuged, and dried in a vacuum oven at 62°C for 24 hours to obtain the extruded material with a hand-feeling agent. The mass ratio of the hydroxyl-terminated hyperbranched polyester core, solvent, isocyanate-based end-capped siloxane prepolymer solution, and anhydrous ethanol is 10:35:90:2.5. The mass ratio of the hydroxyl-terminated hyperbranched polyester core to the isocyanate-based end-capped siloxane prepolymer solution is 1:9. The preparation of the hydroxyl-terminated hyperbranched polyester core includes the following steps: Trimethylolpropane and dimethylolpropionic acid were added to a reaction vessel and melt-mixed at 142°C. Toluenesulfonic acid catalyst was added, and a gradient temperature esterification reaction was carried out, first heating to 185°C at a rate of 4°C / min; in the later stage of the reaction, vacuum dehydration was performed at 185°C and -0.095 MPa for 2.5 hours, followed by cooling to 100°C and pulverization to obtain a hydroxyl-terminated hyperbranched polyester core. The molar ratio of trimethylolpropane to dimethylolpropionic acid was 1:5.5; the amount of toluenesulfonic acid catalyst was 0.15 parts of the total mass of trimethylolpropane and dimethylolpropionic acid. The preparation of the isocyanate-terminated siloxane prepolymer included the following steps: Step (1) Dehydrate and dry single-hydroxyl-terminated polydimethylsiloxane with a number average molecular weight of 6000 at 108℃ and -0.09MPa vacuum for 2.5 hours; Step (2) Mix isophorone diisocyanate and toluene solvent, and dry at a shear rate of 2800s. -1 Under high shear and low temperature conditions of 2°C, a dried single-hydroxyl-terminated polydimethylsiloxane solution was added dropwise. After the addition was complete, the solution was maintained at low temperature and high shear for 35 minutes. Then, the stirring mode was switched and the temperature was naturally raised to room temperature. Dibutyltin dilaurate catalyst was added, and the solution was heated to 62°C for aging for 3.5 hours to obtain an isocyanate-terminated siloxane prepolymer solution. The ratio of single-hydroxyl-terminated polydimethylsiloxane, isophorone diisocyanate, and solvent was such that the molar ratio of isocyanate groups to hydroxyl groups was 5:1. The solvent was toluene, and the amount used was 55 parts.

[0023] The extrusion material prepared in this embodiment has a high grafting density and exhibits excellent initial smoothness and good surface flatness in the extrusion test of TPU smartwatch strap. It can effectively improve the stickiness of the material surface and meet the surface feel requirements of high-end wearable devices.

[0024] Comparative Example 1: This comparative example provides a method for using a hand-feeling agent in extruded materials. The difference lies in the direct use of dimethyl silicone oil with a number-average molecular weight of 5000 as the hand-feeling agent, without the synthesis of terminally hydroxyl hyperbranched polyester cores or graft copolymerization. Specifically, dimethyl silicone oil and TPU resin particles are physically mixed at a ratio of 2 wt% and extruded in a twin-screw extruder at 200°C. The samples prepared in this comparative example exhibit severe macroscopic phase separation due to the significant polarity difference and lack of chemical anchoring between the dimethyl silicone oil and the TPU substrate. During the extrusion thermal process, the silicone oil rapidly migrates to the surface, resulting in severe initial oiliness and a greasy feel. Furthermore, after aging at 80°C, the surface contact angle decreases significantly, the slippery effect cannot be maintained for long, and there is a risk of contaminating the packaging.

[0025] Comparative Example 2: This comparative example provides a method for preparing a feel agent for extruded materials. The difference lies in that: when preparing the isocyanate-based end-capped siloxane prepolymer, a low-temperature, high-shear process was not used. Instead, single-hydroxyl-terminated polydimethylsiloxane was added dropwise under normal stirring conditions at room temperature and 300 rpm. Other steps and raw material ratios remained consistent with Example 1. The extruded material prepared in this comparative example, when used as a feel agent, suffered from insufficient contact and reaction between IPDI and single-hydroxyl-terminated polydimethylsiloxane due to excessively high local concentrations during the reaction process. A large number of unreacted free IPDI molecules remained in the system. These free IPDI molecules acted as crosslinking agents in subsequent steps, directly reacting with multiple hydroxyl groups of the end-hydroxyl hyperbranched polyester core, thereby initiating severe nucleo-nucleochemical crosslinking and generating micron-sized gel particles. When applied to TPU extrusion, the product surface was rough, densely covered with crystal points, and the dynamic friction coefficient was as high as 0.35, losing the expected lubrication and feel-improving functions.

[0026] Comparative Example 3: This comparative example provides a method for preparing a tactile agent for extruded materials, the difference being that a linear polyester diol is used to replace the hydroxyl-terminated hyperbranched polyester core, resulting in a linear polyurethane-polysiloxane block copolymer. Other raw materials and process parameters are the same as in Example 1. The tactile agent prepared in this comparative example, due to the lack of a spherical hyperbranched topology, exhibits easy molecular chain entanglement, high melt viscosity, and uneven dispersion in the TPU substrate. The extruded part shows visible microcrystalline points on its surface, has a dynamic coefficient of friction of 0.18, and a relatively dry feel, failing to achieve the silky smooth feel of molecular beads as described in Example 1.

[0027] In Examples 1-5 and Comparative Examples 1-3, trimethylolpropane was sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 77-99-6; dimethylolpropionic acid was sourced from Shanghai Maclean Biochemical Technology Co., Ltd., CAS No.: 4767-03-7; isophorone diisocyanate (IPDI) was sourced from Wanhua Chemical Group Co., Ltd., CAS No.: 4098-71-9; and single-hydroxyl-terminated polydimethylsiloxanes (number-average molecular weights Mn of 3000, 4000, 5000, 6000, and 8000, respectively) were purchased from Anhui Aiyota Silicone Oil Co., Ltd. All were custom-made industrial-grade products. Hydroxyl activity >99%; thermoplastic polyurethane (TPU) resin particles were purchased from BASF (China) Co., Ltd., brand name Elastollan 1185A; dimethyl silicone oil was purchased from Dow Corning, brand name PMX-200, viscosity 1000 cSt; linear polyester diol (polybutylene adipate diol, Mn=2000) was purchased from Wanhua Chemical Group Co., Ltd.; the catalysts p-toluenesulfonic acid, dibutyltin dilaurate, and solvents anhydrous N,N-dimethylformamide, toluene, anhydrous ethanol, etc. were all analytical grade reagents produced by Sinopharm Chemical Reagent Co., Ltd.; all other products were commercially available.

[0028] The extruded materials prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to corresponding performance tests using a hand feel agent.

[0029] Test sample preparation: The hand feel agent prepared in Examples 1-5 and Comparative Examples 1-3 was mixed with thermoplastic polyurethane (TPU) resin particles (brand name: BASFElastollan1185A) at a ratio of 2 wt% in a high-speed mixer until homogeneous; then it was added to a twin-screw extruder, melt-extruded and granulated at a temperature of 200°C, and injection molded into standard test samples (100 mm × 100 mm × 2 mm). The test results are shown below: (1) Surface smoothness and dynamic coefficient of friction (COF) test Test method description: Refer to standard ASTM D1894-14, "Standard Test Methods for Static and Dynamic Coefficients of Friction of Plastic Films and Sheets"; Test equipment: Friction coefficient tester (model: MXD-02, Jinan Langguang Electromechanical Technology Co., Ltd.); Test conditions: Ambient temperature 23±2℃, relative humidity 50±5%. A 200g standard slider was used, the test speed was 150mm / min, and the test stroke was 70mm. Data processing: Each sample group was tested 5 times. The maximum and minimum values ​​were removed and the arithmetic mean was taken, accurate to two decimal places.

[0030] Table 1. Dynamic friction coefficient and initial feel evaluation data for each group of samples.

[0031] As can be seen from the test data in Table 1, the extruded materials prepared in Examples 1-5 of the present invention can effectively reduce the surface friction coefficient of the TPU substrate by using the feel agent, thus giving the material a good tactile feel. Specifically, Example 1 achieved the optimal performance balance at a core-shell ratio of 1:8 and a soft segment molecular weight of 5000, with a COF as low as 0.08, resulting in a silky smooth feel similar to molecular ball bearings. Example 2, while having the lowest COF (0.07), benefited from a higher proportion of silicone shells and longer PDMS segments, leading to lower surface energy. However, as discussed later, its aging resistance was slightly compromised. Conversely, Example 3, due to its lower amount of active silicon grafting and shorter molecular chains, was unable to form a continuous, dense, flexible capping layer at the micro-interface, resulting in a higher COF. Although Comparative Example 1 exhibits an extremely low coefficient of friction, this is attributed to the uncontrolled migration of free silicone oil on the surface, resulting in a greasy, pseudo-slippery feel that does not meet the requirements of high-end applications. Comparative Example 2 shows the worst performance, with a COF as high as 0.35, which fully demonstrates the necessity of the low-temperature, high-shear process. In Comparative Example 2, due to the lack of control over reaction kinetics, the isocyanate-terminated siloxane prepolymer exhibits double-end sealing, leading to severe chemical crosslinking when reacting with the hydroxyl-terminated hyperbranched polyester core, generating micron-sized gel particles. These hard gel points not only fail to provide lubrication but also significantly increase surface roughness and frictional resistance. Comparative Example 3 uses a linear structure to replace the hyperbranched core. Due to the easy entanglement of molecular chains, high melt viscosity, and uneven dispersion, it cannot form the rolling effect unique to the spherical hyperbranched structure. Therefore, its slippery effect is significantly better than Comparative Example 2 but still inferior to the embodiments of the present invention.

[0032] (2) Aging resistance and contact angle retention test Test method description: The test was conducted according to GB / T24368-2009 "Detection of Hydrophobic Contaminants on Glass Surface - Contact Angle Measurement Method"; Test equipment: Contact angle measuring instrument, model: JC2000D, Shanghai Zhongchen Digital Technology Equipment Co., Ltd.; Testing process: The water contact angle WCA_initial on the sample surface under the initial test conditions was tested. The samples were placed in a constant temperature drying oven at 80℃ for accelerated aging treatment for 168 hours. After removing the sample and cooling it to room temperature, the water contact angle WCA_aged was tested again. Calculate the contact angle retention rate = (WCA_aged / WCA_initial) × 100%; Observation indicators: Visually inspect the surface of the sample after aging to see if there are droplets or powder precipitates.

[0033] Table 2. Changes in contact angle and precipitation in each group of samples before and after aging.

[0034] The data in Table 2 reveals the core advantages of the unique core-shell structure of this invention in solving the migration resistance problem; Example 1 exhibits excellent stability, with a contact angle retention rate of up to 98.5% after aging and no precipitation. This is due to the strong physical anchoring effect formed between the hydroxyl-terminated hyperbranched polyester core and the TPU substrate, and the isocyanate-terminated siloxane prepolymer firmly grafted onto the core surface through chemical bonds, which fundamentally limits the thermal migration of organosilicon segments. In contrast, the retention rate of Example 2 decreased to 88.4%; this was because the excessively high silicon content (core-shell ratio 1:10) and excessively large molecular weight (Mn=8000) led to a significant steric hindrance effect, hindering the grafting reaction between some prepolymers and the core, leaving a small amount of unreacted free components in the system, which migrated at high temperatures. Although Example 3 had an extremely high retention rate, as shown in Table 1, it sacrificed slip properties. The failure was most pronounced in Comparative Example 1, with a contact angle retention rate of only 58.4%. This is because the physical blend of dimethyl silicone oil and TPU has a large polarity difference and is thermodynamically unstable. High temperatures accelerated its migration and loss to the surface, leading to a significant decline in hydrophobicity. The retention rate of Comparative Example 3 was lower than that of Example 1, indicating that the entanglement effect of linear molecules is not as stable as the anchoring effect of the spherical hyperbranched structure, and some low molecular weight segments still have a tendency to migrate. In summary, the process parameters described in Example 1 achieved the best aging resistance performance while ensuring lubricity.

[0035] (3) Microstructure and dispersibility test Test method description: Testing equipment: Field emission scanning electron microscope (SEM, model: Hitachi S-4800) and polarizing microscope; Testing process: The extruded sample was fractured in liquid nitrogen, and its microstructure was observed after gold sputtering treatment on the fracture surface; at the same time, the flatness of the sample surface was directly observed. Table 3. Results of microscopic morphology observation

[0036] Observation of the microstructure further confirms the decisive influence of the synthesis process on the material properties; SEM images of Example 1 show that the hyperbranched polysiloxane-polyurethane feel agent exhibits a uniform nanoscale dispersion in the TPU matrix. This ideal island structure is attributed to the Tyndall effect that occurs during the reaction, indicating that the core-shell particles have formed a stable micelle structure in the solvent, and that the external urethane polar hard segments have excellent compatibility with the TPU substrate, while the internal spherical polyester core provides support. The dispersed phase in Example 3 has the smallest particle size and the most dense distribution, which is consistent with its low silicon grafting amount. Example 5 shows a nanoscale spherical distribution highly similar to Example 1, with a particle size of approximately 60-110 nm. Comparative Example 1 shows a large-area interconnected amorphous oily phase under SEM, with extremely clear interfaces and obvious macroscopic phase separation, confirming that physical blending cannot form a stable microstructure. Conversely, Comparative Example 2 exhibited obvious micron-sized gel particles and phase separation interfaces on its cross-section. This was due to the lack of a low-temperature, high-shear process, which led to uncontrolled reaction and the formation of a cross-linked macromolecular network structure. These gel points could not melt and disperse during extrusion, ultimately forming crystal points on the surface of the product, severely damaging the material's appearance and feel. The linear molecules in Comparative Example 3 tended to align along the flow direction in the extrusion flow field, failing to provide isotropic ball lubrication like the spherical molecules in Example 1, resulting in poor uniformity of feel on a macroscopic scale. The lack of microstructure in Comparative Example 1 was due to the physical addition of silicone oil, which was easily lost or contaminated during liquid nitrogen brittle fracture and vacuum gold sputtering, making it difficult to capture a stable cross-sectional morphology. This also reflects its extremely poor interfacial bonding. In summary, this invention has successfully prepared an extrusion-grade hand feel agent that combines an extremely smooth feel, excellent aging and migration resistance, and good dispersibility by precisely controlling the synthesis of the end-hydroxyl hyperbranched polyester core, the low-temperature high-shear preparation of the isocyanate-terminated siloxane prepolymer, and the in-situ grafting ratio of the two. This solves the problem of not being able to achieve both lubricity and durability in traditional technologies.

[0037] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a hand agent for an extruded material, characterized by, The method comprises the following steps: The step of dissolving the hydroxyl-terminated hyperbranched polyester core in a solvent, ultrasonic dispersion, to obtain a core solution; under the condition of heating and stirring, the isocyanate-terminated siloxane prepolymer solution is added dropwise into the core solution to carry out graft copolymerization reaction; after the reaction is completed, anhydrous ethanol is added to terminate, the solvent is removed by rotary evaporation, the residue is precipitated in a precipitant, centrifugal separation is carried out, and drying is carried out to obtain a hand feel agent for extrusion material; The preparation of the hydroxyl-terminated hyperbranched polyester core comprises the following steps: The trimethylolpropane and dimethylolpropionic acid are added into a reaction kettle and melt-mixed; a catalyst is added to carry out gradient temperature esterification reaction; vacuum dehydration is carried out in the later stage of the reaction, cooling is carried out, and crushing is carried out to obtain the hydroxyl-terminated hyperbranched polyester core; The preparation of the isocyanate-terminated siloxane prepolymer comprises the following steps: Step (1) The monohydroxyl polydimethylsiloxane is dehydrated and dried under vacuum conditions; Step (2) mixing isophorone diisocyanate and solvent, under the condition of high shear rate ≥2000 s -1 dropping the dried monohydroxyl polydimethylsiloxane solution into it under the condition of high shear rate ≥2000 s -10℃ to 5℃; after dropping, maintaining low temperature and high shear rate, using high-speed shear dispersion emulsifier, then switching to ordinary mechanical stirring mode and natural temperature rising, adding catalyst, warming up and curing, obtaining isocyanate group terminated siloxane prepolymer solution.

2. The method of claim 1, wherein the hand agent is prepared by the steps of: The mass ratio of the hydroxyl-terminated hyperbranched polyester core, the solvent, the isocyanate-terminated siloxane prepolymer solution and anhydrous ethanol is (10):(20-40):(50-100):(1-3); the mass ratio of the hydroxyl-terminated hyperbranched polyester core and the isocyanate-terminated siloxane prepolymer solution is 1:5 to 1:

10.

3. The method for preparing a hand-feeling agent for extruded materials according to claim 1, characterized in that, The molar ratio of trimethylolpropane to dimethylolpropionic acid is 1:4 to 1:6; the catalyst is p-toluenesulfonic acid, and the amount of the catalyst is 0.05-0.2 parts based on the total mass of trimethylolpropane and dimethylolpropionic acid.

4. The method of claim 1, wherein the hand agent is prepared by the steps of: The gradient temperature esterification reaction is specifically as follows: first, the temperature is raised to 135-145 DEG C to melt the raw materials, and then the temperature is raised to 170-190 DEG C at a rate of 2-5 DEG C / min; the vacuum dehydration is carried out at 170-190 DEG C, -0.08 MPa to -0.1 MPa for 1-3 hours.

5. The method for preparing a hand-feeling agent for extruded materials according to claim 1, characterized in that, The ratio of the monohydroxyl polydimethylsiloxane, isophorone diisocyanate and solvent satisfies that the molar ratio of isocyanate groups to hydroxyl groups is 2.0:1 to 3.0:1; the solvent is toluene, and the amount of the solvent is 40-60 parts (relative to 100 parts of monohydroxyl polydimethylsiloxane).

6. The method of claim 1, wherein the hand agent is prepared by the steps of: The low temperature condition is -10℃ to 5℃; the high shear is carried out by using a high shear emulsifying machine or a homogenizer, and the shear rate of the high shear is ≥2000s -1 ; the temperature of the temperature increasing ripening is 55-65℃, and the holding time is 2-4 hours.

7. The method for preparing a hand-feeling agent for extruded materials according to claim 1, characterized in that, The number average molecular weight of the monohydroxyl polydimethylsiloxane is 3000-8000; and the dehydrating and drying conditions in step (1) are 100-110 DEG C, -0.09 MPa.

8. The method for preparing a hand-feeling agent for extruded materials according to claim 1, characterized in that, The solvent of the core solution is anhydrous N,N-dimethylformamide; the temperature of the graft copolymerization reaction is 65-85 DEG C, and the dropping speed is strictly controlled during the reaction until the system presents a stable micellar dispersion state and the Tyndall effect is observed; the termination reaction time is 20-40 minutes.

9. The method for preparing a hand-feel agent for extruded materials according to claim 1, characterized in that, The rotary evaporation is carried out at 70-90 DEG C, -0.09 MPa; the precipitant is a mixture of methanol and water with a volume ratio of 1:1; and the drying is carried out in a vacuum oven at 55-65 DEG C for 24 hours.

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