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CN-122011740-A - Brightening aliphatic TPU (thermoplastic polyurethane) base film for invisible vehicle clothing and preparation method thereof

CN122011740ACN 122011740 ACN122011740 ACN 122011740ACN-122011740-A

Abstract

The application relates to a brightening aliphatic TPU base film for invisible vehicle clothing and a preparation method thereof. The base film comprises 100 parts by weight of aliphatic TPU, 0.5-3 parts by weight of optical modifier, 1-5 parts by weight of polyester polyol-siloxane copolymer compatibilizer and brightening agent, and an anti-hydrolysis stabilizer, an ultraviolet absorber and a hindered amine light stabilizer, wherein the modifier is nano SiO 2 and/or nano Al 2 O 3 treated by aminosilane with the average particle size of 10-50 nm, and the refractive index difference between the modifier and the TPU is less than or equal to 0.02. In the preparation, the nano particles are dispersed in an alcohol solvent, a silane coupling agent is dripped at 40-60 ℃ and is subjected to water supplementing in-situ hydrolysis, coupling and curing grafting are completed under the condition of pH4-5, and then the mixture is subjected to melt blending, filtering and tape casting and stretching to form a film. The base film provided by the application has the advantages of high light transmittance, low haze and brightening effect, and improves hydrolysis resistance, weather resistance stability and batch stability.

Inventors

  • Liang Laigen
  • JIANG GUOWEI
  • LUO DAN
  • YANG HU
  • YU LIFENG

Assignees

  • 浙江安布雷拉新材料制造有限公司

Dates

Publication Date
20260512
Application Date
20260316

Claims (10)

  1. 1. The brightening aliphatic TPU base film for the invisible car cover is characterized by comprising, by weight, 100 parts of aliphatic thermoplastic polyurethane particles, 0.5-3 parts of optical-grade modifier, 0.3-1.5 parts of anti-hydrolysis stabilizer, 0.5-2 parts of ultraviolet absorber and 0.3-1.5 parts of light stabilizer, wherein the optical-grade modifier is nano silicon dioxide and/or nano aluminum oxide which are subjected to surface treatment and have an average particle size of 10nm-50 nm, the absolute value of the refractive index difference between the optical-grade modifier and the refractive index of the aliphatic TPU base film is not more than 0.02, 1-5 parts of high-molecular-weight compatibilizer brightening agent is polyester polyol-siloxane copolymer with the number average molecular weight of 5000g/mol-20000 g/mol.
  2. 2. The brightness enhancing aliphatic TPU based film for invisible car covers according to claim 1, wherein the aliphatic thermoplastic polyurethane is a polycaprolactone-type or polycarbonate-type thermoplastic polyurethane.
  3. 3. The brightness enhancing aliphatic TPU base film for invisible car covers according to claim 2, wherein the polycaprolactone-type aliphatic thermoplastic polyurethane is one or more of a PCL-type TPU based on hexamethylene diisocyanate, a PCL-type TPU based on hydrogenated diphenylmethane diisocyanate, a PCL-type TPU based on isophorone diisocyanate.
  4. 4. The brightness enhancing aliphatic TPU base film for invisible automotive coating according to claim 2, wherein the polycarbonate type thermoplastic polyurethane is a thermoplastic polyurethane using a polycarbonate diol as a soft segment, and the polycarbonate diol is one of a polycarbonate diol prepared from a linear aliphatic diol, a polycarbonate diol prepared from a branched aliphatic diol, a polycarbonate diol prepared from a diol having a ring structure, a polycarbonate diol prepared from an aromatic diol or a hydrogenated diol thereof, or a copolymerized polycarbonate diol prepared by copolymerizing two or more diols; The straight-chain aliphatic dihydric alcohol comprises one or more of 1,4 butanediol, 1,5 pentanediol, 1,6 hexanediol and 1,8 octanediol; The branched aliphatic diol comprises one or more of neopentyl glycol, 2 methyl 1,3 propylene glycol and 2,2 dimethyl 1,3 propylene glycol; The dihydric alcohol containing the ring structure comprises one or more of 1,4 cyclohexanedimethanol, cyclohexanediol and bisphenol cyclohexanediol; the aromatic diol or the hydrogenated derivative diol thereof comprises one or more of bisphenol A diol and hydrogenated derivative diol of bisphenol A; The dihydric alcohol is any combination of any of the dihydric alcohols.
  5. 5. The brightness enhancing aliphatic TPU base film for invisible automotive coatings according to claim 1, wherein the surface treatment agent of the optical grade modifier is an aminosilane coupling agent, and the aminosilane coupling agent is one or more of 3-aminopropyl triethoxysilane, N- (β -aminoethyl) - γ -aminopropyl trimethoxysilane, and 3-aminopropyl trimethoxysilane.
  6. 6. The brightness enhancing aliphatic TPU based film for invisible automotive covers according to claim 5, wherein the preparation method of the optical grade modifier comprises the steps of: P1, proportioning water and an alcohol solvent according to a volume ratio of 1:9, and uniformly stirring to form the alcohol solvent, wherein the alcohol is one or more of absolute ethyl alcohol, isopropyl alcohol or n-propyl alcohol; p2, mixing nano silicon dioxide and/or nano aluminum oxide powder with the average particle size of 10nm-50nm with the alcohol solvent according to the volume of 50% -90% of the total volume of the mixture, performing ultrasonic dispersion under the conditions of ultrasonic frequency of 20kHz-40kHz, ultrasonic power density of 200W/L-800W/L and ultrasonic time of 10min-30min, and matching with high-speed shearing dispersion, wherein the high-speed shearing rotation speed is 3000rpm-10000rpm, and the shearing time is 5min-20min, so as to obtain stable primary nano suspension; p3, carrying out heat preservation and stirring on the primary nano suspension at the speed of 300rpm-800rpm and the temperature of 40-60 ℃, dropwise adding an aminosilane coupling agent into the primary nano suspension under the condition of heat preservation and stirring, synchronously adding deionized water to carry out in-situ hydrolysis on the aminosilane coupling agent to form silanol, adding deionized water to enable the molar ratio of water to the silane coupling agent to be 13:1-25:1, wherein the dosage of the silane coupling agent is 1-10% of the weight of the nano silicon dioxide and/or nano aluminum oxide powder, regulating the pH value of the mixture to 4-5, and carrying out hydrolysis and preliminary coupling reaction for 1-3 hours; P4, after the hydrolysis and preliminary coupling reaction in the step P3 are finished, continuously heating the mixture to 70-85 ℃, and carrying out heat preservation stirring at the speed of 200-600 rpm at the temperature after heating, so that the mixture is further cured for 2-6 hours, and silanol after the full hydrolysis of the silane coupling agent is subjected to condensation reaction with hydroxyl groups on the surfaces of the nano silicon dioxide and/or nano aluminum oxide powder to complete surface grafting; And P5, after the reaction is finished, centrifugally separating the product, repeatedly washing the precipitate by using the alcohol solvent with the concentration configured in the step P1, and finally, vacuum-drying the washed solid at the temperature of 60-80 ℃ for 6-12 hours, wherein the vacuum degree of the vacuum drying in the step P5 is-0.08 MPa to-0.095 MPa, so as to obtain the optical grade modifier.
  7. 7. The brightening aliphatic TPU base film for invisible car covers according to claim 1, wherein the polyester polyol-siloxane copolymer is one of polybutylene adipate-polydimethylsiloxane block copolymer, polycaprolactone-polydimethylsiloxane block copolymer, polybutylene carbonate-polydimethylsiloxane block copolymer or polybutylene terephthalate-polyether modified siloxane copolymer, the hydrolysis resistant stabilizer is one of polycarbodiimide, monocarbodiimide, oxazoline compound or epoxy compound, the ultraviolet absorber is one of benzotriazole, triazine, benzophenone or cyanoacrylate ultraviolet absorber, and the light stabilizer is hindered amine light stabilizer.
  8. 8. A process for preparing a brightness enhancing aliphatic TPU based film for invisible automotive covers according to any one of claims 1 to 7, comprising the steps of: S1, vacuum drying the raw material components at 75-85 ℃ until the moisture content is lower than 100 ppm, wherein the vacuum degree of the vacuum drying in the step S1 is-0.10 MPa to-0.12 MPa; S2, mixing all the dried components at a high speed under the protection of inert gas to obtain a premix, wherein the high-speed mixing speed is 500-1500 rpm, and the mixing time is 3-10 min; S3, after the premix is melted and blended by a double-screw extruder, filtering a melt by a precise filter with the aperture of 5-15 mu m, wherein the barrel temperature of the double-screw extruder is 160-220 ℃, the screw rotating speed is 150-400 rpm, the melt residence time is 1-3 min, vacuum exhaust is applied to an exhaust section of the extruder, the vacuum degree is-0.09 MPa to-0.11 MPa, the precise filter is a melt filter screen or a candle filter, the filtering temperature of the precise filter is consistent with the melt temperature, the melt pressure at a filtering inlet is 5-20 MPa, and the filtering pressure difference is controlled to be 0.2-2.0 MPa; s4, granulating the filtered melt after water cooling bracing or underwater granulating to obtain composite granules, and performing secondary vacuum drying, wherein the secondary vacuum drying temperature is 70-90 ℃, the vacuum degree is-0.085 MPa to-0.095 MPa, and the drying time is 4-10 h; s5, extruding and casting the composite granules after secondary drying into a molten sheet, and then carrying out biaxial stretching, wherein the total stretching multiplying power is 2.5-4.0 times, the extrusion temperature of extrusion casting is 170-230 ℃, the die head temperature is 180-230 ℃, the casting cooling roller temperature is 20-40 ℃, and the casting linear speed is 5-25 m/min; s6, performing heat setting on the stretched membrane, and then performing programmed cooling and slow cooling; S7, rolling the slowly cooled membrane into a roll under the constant tension condition, wherein the rolling tension is 5N-25N, the rolling speed is 5m/min-30m/min, and after the rolling is finished, the membrane roll is placed in an environment of 40-60 ℃ and then cured for 24-72 h so as to release internal stress and stabilize the size and optical performance.
  9. 9. The method according to claim 8, wherein in the step S5, the biaxial stretching is stepwise biaxial stretching or synchronous biaxial stretching, the stretching temperature is 10 ℃ to 20 ℃ higher than the softening point of the aliphatic thermoplastic polyurethane used, the stretching rate is 50%/sec to 200%/sec, and the stepwise biaxial stretching is longitudinal and transverse or transverse and longitudinal.
  10. 10. The method according to claim 8, wherein in the step S6, the heat setting temperature is 5 ℃ to 15 ℃ higher than the stretching temperature, the heat setting time is 10 seconds to 30 seconds, the program cooling slow cooling is a multi-stage gradient cooling, the multi-stage is 3-5 stages, the set temperature difference between two adjacent stages is 10 ℃ to 20 ℃, the constant temperature holding time of each stage is 30 seconds to 120 seconds, and finally the film is rolled after being reduced to 25 ℃ to 35 ℃.

Description

Brightening aliphatic TPU (thermoplastic polyurethane) base film for invisible vehicle clothing and preparation method thereof Technical Field The application belongs to the technical field of high molecular functional films and automobile surface protection materials, and particularly relates to a brightening aliphatic TPU (thermoplastic polyurethane) base film for invisible automobile clothing and a preparation method thereof. Background As an important material for protecting the paint surface of an automobile, a base film is generally required to have high light transmittance, low haze, high surface gloss and good imaging definition, and to maintain yellowing resistance, hydrolysis resistance and ultraviolet aging resistance under outdoor long-term use conditions. Aliphatic TPU is widely used for a car cover base film because of relatively excellent yellowing resistance, but still faces the problem that multiple targets are difficult to consider in practical application, on one hand, in order to improve the visual effects of brightening, deep-looking and the like after car cover, functional components capable of improving interface compatibility and optical uniformity are often required to be introduced, on the other hand, nano inorganic particles can be used for improving the wear resistance and stability of a film, but have larger difficulty in dispersing and interface matching in a TPU system, and if the particles are aggregated or have too large refractive index difference with a matrix, light scattering enhancement is easily caused, so that haze is increased, light transmittance is reduced and imaging definition is deteriorated. In addition, the invisible car cover is easy to generate aging behaviors such as soft segment hydrolysis, photooxidation, segment fracture and the like in environments such as high temperature, high humidity, ultraviolet irradiation and the like, so that the film material is yellow, foggy, gloss is attenuated or mechanical property is reduced. In the prior art, chinese patent application with publication number of CN118578620A provides a preparation method of a car cover protective film, which comprises the steps of premixing TPU master batch with an antioxidant and an ultraviolet absorber, drying and dehumidifying, melting and plasticizing by a screw, sieving out melt impurities, adding extinction powder into the melt, uniformly mixing, extruding and casting to form a film, and then cooling by cold pressing, regulating thickness by a roller, trimming and rolling to finish a finished product. The technical concept is that the matte surface of the film layer is frosted by using the matting powder to reduce reflection, and the uniformity of film thickness and the uniformity of size are improved by cold pressing and rolling thickness adjustment in combination with trimming procedures. The Chinese patent with the publication number of CN 118599462B discloses a TPU hot melt adhesive for invisible vehicle covers with high yellowing resistance and high viscosity, a preparation method and application thereof. According to the technical scheme, the TPU hot melt adhesive for the invisible car cover is prepared by taking polymer dihydric alcohol and aliphatic diisocyanate as main bodies, introducing a curing system formed by small molecular dihydric alcohol small molecular dioxime and trimethylolpropane according to a set molar ratio, a plasticizer and the like, and the technical scheme is that oxime urethane bonds are embedded into a structure by using dioxime, so that the oxime urethane bonds of the material are gradually dissociated and viscosity is reduced when the temperature is higher than 90 ℃, the viscosity of the system is further reduced by matching with the plasticizer so as to facilitate coating and film pasting operation, and yellowing resistance and bonding strength are simultaneously considered through the design of aliphatic isocyanate, TMP and the like. Therefore, the prior art is mainly improved from an adhesive layer material system or a base film forming process, for example, viscosity regulation and yellowing resistance under an attached temperature window are realized through hot melt adhesive formula design, or appearance consistency and surface reflection performance are improved through drying and dehumidification, melt screening and extinction powder introduction in the TPU melt extrusion casting process, but if the system control on the surface chemical state of nano particles, refractive index matching with TPU and filtration and impurity removal in the melt processing process is lacked, the problems of large fluctuation of optical indexes, insufficient batch stability, non-ideal long-term weather resistance and the like still can occur. Therefore, there is a need for an aliphatic TPU based film technology that is synergistically optimized in material formulation and nanoparticle surface modification processes, and melt blending and precision filtration fil