White high-temperature-resistant TPU film and preparation method thereof

Abstract

The invention relates to a white high-temperature-resistant TPU film and a preparation method thereof.The white high-temperature-resistant TPU film comprises polyurethane matrix resin, a high-temperature-resistant white system and other auxiliaries, and the polyurethane matrix resin comprises, by mass, 50-70 parts of polyester polyol, 20-30 parts of isocyanate and 5-10 parts of a chain extender; the polyester polyol comprises any one of or a mixture of two of polycaprolactone diol and polycarbonate diol, the isocyanate comprises any one of aliphatic isocyanate or ring isocyanate, and the chain extender comprises any one of 1, 4-butanediol or a chain extender containing a heat-resistant group. The TPU film has the effect of improving the high temperature resistance of the TPU film.

Description

Technical Field

[0001] The present application relates to the field of TPU films, and in particular to a white, high-temperature-resistant TPU film and a preparation method thereof. Background Art

[0002] TPU film is made from TPU granules through special processes such as calendering, cast film, blown film, and coating. Due to its good elasticity, excellent physical properties, and excellent mechanical strength, it is widely used in processing methods such as injection, extrusion, calendering, and dissolving into solution-type resins. It is a plastic material frequently used by plastic processing industries, and its products cover a range of industrial applications and civilian necessities.

[0003] Traditional TPU films are prone to yellowing and mechanical property degradation at high temperatures (>120°C). White TPU films are prone to color migration and loss of whiteness under high temperatures or UV exposure. Existing high-temperature resistant TPU films mostly use dark formulations (such as those with added carbon black), which makes it difficult to meet the white appearance requirements. Summary of the Invention

[0004] In order to further improve the high temperature resistance of the white TPU film, the present application provides a white high temperature resistant TPU film and a preparation method thereof.

[0005] The present application provides a white high-temperature resistant TPU film and a preparation method thereof using the following technical solutions: In the first aspect, the present application provides a white high-temperature resistant TPU film, which adopts the following technical solution: A white, high-temperature-resistant TPU film comprises a polyurethane matrix resin, a high-temperature-resistant white system, and other additives. The polyurethane matrix resin comprises the following components in parts by mass: 50-70 parts of a polyester polyol, 20-30 parts of an isocyanate, and 5-10 parts of a chain extender. The polyester polyol comprises any one of polycaprolactone diol and polycarbonate diol, or a mixture of the two. The isocyanate comprises any one of an aliphatic isocyanate or a cyclic isocyanate. The chain extender comprises any one of 1,4-butanediol or a chain extender containing a heat-resistant group.

[0006] By adopting the above technical solution, a polyester polyol with a hydroxyl value of 40-60 mgKOH / g is used as the base material. The main chains of the polycaprolactone diol and carbonate diol contain a rigid ring structure, which can further increase the heat deformation temperature of the film. The isocyanate uses aliphatic isocyanate or cyclic isocyanate to replace the traditional aromatic isocyanate that is easy to turn yellow, eliminating the root cause of yellowing caused by high-temperature oxidation from the molecular structure, thereby reducing the yellowing phenomenon of the prepared white TPU film and improving the high-temperature resistance of the system.

[0007] Preferably, the high temperature resistant white system comprises the following components in parts by mass: 10-15 parts of silane modified titanium dioxide and 1-3 parts of composite heat stabilizer.

[0008] By adopting the above technical solution, the compatibility of silane-modified titanium dioxide is improved, while the agglomeration of nano-titanium dioxide in the system is reduced. The bonding performance between silane-modified titanium dioxide and TPU matrix is improved, further improving the stability of the system.

[0009] Preferably, the composite heat stabilizer includes a hindered phenol antioxidant and a phosphite antioxidant.

[0010] By adopting the above technical solution, under the synergistic effect of the hindered phenol antioxidant and the phosphite antioxidant, the high-temperature oxidation chain reaction can be continuously carried out, thereby delaying the attenuation of whiteness.

[0011] Preferably, the other additives include the following components in parts by mass: 0.5-1 part of ultraviolet absorber, and 0.2-0.5 part of lubricant.

[0012] By adopting the above technical solution, the ultraviolet absorber absorbs ultraviolet rays, thereby further reducing the aging phenomenon of the product, and the lubricant can play a dispersing role, thereby improving the stability of the system.

[0013] In a second aspect, the present application provides a method for preparing a white high-temperature resistant TPU film, which adopts the following technical solution: A method for preparing a white high-temperature resistant TPU film comprises the following steps: S1. Raw material pretreatment: heating the polyester polyol and then dehydrating it to obtain dehydrated polyester polyol; treating the surface of nano titanium dioxide with a silane coupling agent to obtain silane-modified titanium dioxide; S2. Prepolymer synthesis: mixing the dehydrated polyester polyol with isocyanate, and reacting at elevated temperature to obtain an isoterminal cyanate prepolymer; S3, chain extension and mixing: adding a chain extender, silane-modified titanium dioxide, and a composite heat stabilizer to the isoterminal cyanate-based prepolymer, and mixing at a high speed to obtain a mixture; S4. Melting and extrusion: The mixture is extruded through a twin-screw extruder to prepare a TPU film by casting or blow molding; after aging the prepared TPU film at 150° C. for 500 hours, the whiteness (CIE L*) is ≥88 and the tensile strength retention is ≥85%.

[0014] By adopting the above technical solution, the terminal isocyanate prepolymer is first synthesized and then the chain is extended, which can further improve the regularity of the molecular chain and enhance the mechanical stability of the film.

[0015] Preferably, in step S1, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0016] Preferably, in the step S2, the molar ratio of the isocyanate group to the hydroxyl group in the dehydrated polyester polyol and the isocyanate added is (1.05-1.1):1.

[0017] By adopting the above technical solution, the molar ratio between the isocyanate and the hydroxyl group in the dehydrated polyester polyol and the isocyanate is preferably within the above range, which can further improve the overall stability of the prepared system.

[0018] Preferably, in step S4, the twin-screw extruder adopts segmented temperature control: zone 1: 160-170°C; zone 2: 180-190°C; zone 3: 190-200°C; and die head temperature: 185-195°C.

[0019] By adopting the above technical solution, the zone temperature of the twin-screw extruder is preferably within the above range, which can reduce the occurrence of material degradation caused by shearing under high temperature conditions and enable the modified titanium dioxide to be evenly dispersed in the system.

[0020] In summary, this application includes at least one of the following beneficial technical effects: 1. By adding heat-resistant additives, the high-temperature resistance of the prepared TPU film is significantly improved. The TPU film is not easy to stick in high-temperature environments and can maintain good physical properties. The selection of white pigment and the control of the amount of white pigment make the color of the prepared film more stable and reduce the occurrence of fading. The raw materials selected in this application all meet environmental requirements, are non-toxic and harmless, and can be widely used in food packaging and medical fields. 2. Polyester polyol is used as the base material. The main chains of polycaprolactone diol and carbonate diol both contain rigid ring structures, which can further increase the heat deformation temperature of the film. Aliphatic isocyanate or cyclic isocyanate is used as the isocyanate, replacing the traditional aromatic isocyanate that is prone to yellowing. The molecular structure reduces the occurrence of high-temperature oxidation yellowing, thereby reducing the yellowing of the prepared white silk TPU film and improving the high-temperature resistance of the system. 3. By treating the surface of nano titanium dioxide with a coupling agent, the compatibility and bonding performance between silane-modified titanium dioxide and the TPU matrix are improved, while reducing the agglomeration of nano titanium dioxide in the system, further improving the overall stability of the system; 4. First synthesize the terminal isocyanate prepolymer and then extend the chain to improve the regularity of the molecular chain, thereby improving the mechanical stability of the TPU film. DETAILED DESCRIPTION

[0021] The TPU film prepared in this application can be applied to the fields of automotive interior, LED heat dissipation film, high-temperature sterilization medical packaging, etc.

[0022] The present application is further described in detail below with reference to the embodiments: Raw materials: All raw materials in the examples are commercially available; among them, the titanium dioxide is nano-grade rutile titanium dioxide, the ultraviolet absorber is Tinuvin 326, and the lubricant is calcium stearate.

[0023] Example 1 Preparation of white high temperature resistant TPU film: S1. Raw material pretreatment: Polycaprolactone diol was selected as the polyester polyol, and 50 parts of the polyester polyol was vacuum dehydrated at 100°C for 4 hours to reduce the moisture content to ≤0.03%, thereby obtaining the dehydrated polyester polyol. Nano-titanium dioxide was surface-modified with KH550 at 80°C to obtain silane-modified titanium dioxide. S2. Prepolymer synthesis: The dehydrated polyester polyol was mixed with 20 parts of isocyanate so that the molar ratio of isocyanate group to hydroxyl group was 1.05:1, and then reacted at 80°C for 2 hours to obtain an isocyanate-terminated prepolymer; wherein the isocyanate was an aliphatic isocyanate hexamethylene diisocyanate; S3, chain expansion and mixing: 5 parts of a chain extender, 10 parts of silane-modified titanium dioxide, and 1 part of a composite thermal stabilizer were added to the above-prepared isocyanate-terminated prepolymer, and the mixture was stirred at a speed of 1000 rpm to mix the system uniformly to obtain a mixture; wherein the chain extender was 1,4-butanediol, and the composite thermal stabilizer was a mixture of a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1, the hindered phenol antioxidant was Irganox 1010, and the phosphite antioxidant was Irgafos 168; S4. Melt extrusion and film forming: The mixture was extruded using a twin-screw extruder. The temperature of zone one, zone two, zone three, and die head were set at 160°C, 180°C, 190°C, and 185°C, respectively. After extrusion, the mixture was formed into a film by casting. The film thickness was 0.01 mm, and a white, high-temperature resistant TPU film was obtained.

[0024] Example 2 Preparation of white high temperature resistant TPU film: S1. Raw material pretreatment: Polycarbonate diol was selected as the polyester polyol, and 70 parts of the polyester polyol was vacuum dehydrated at 120°C for 2 hours to reduce the moisture content to ≤ 0.03%, thereby obtaining the dehydrated polyester polyol. Nano-titanium dioxide was surface-modified with KH550 at 80°C to obtain silane-modified titanium dioxide. S2. Prepolymer synthesis: The dehydrated polyester polyol was mixed with 30 parts of isocyanate so that the molar ratio between the isocyanate group and the hydroxyl group was 1.1:1, and then reacted at 80°C for 2 hours to obtain an isocyanate-terminated prepolymer; wherein the isocyanate was an alicyclic isocyanate 4,4'-dicyclohexylmethane diisocyanate; S3, chain expansion and mixing: 10 parts of a chain extender, 15 parts of silane-modified titanium dioxide, and 3 parts of a composite heat stabilizer were added to the above-prepared isocyanate-terminated prepolymer, and the mixture was stirred at 1000 rpm to uniformly mix the system to obtain a mixture; wherein the chain extender was a heat-resistant group-containing chain extender hydroquinone dihydroxyethyl ether HQEE, and the composite heat stabilizer was a mixture of a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1, the hindered phenol antioxidant was Irganox 1010, and the phosphite antioxidant was Irgafos 168; S4. Melt extrusion and film forming: The mixture was extruded using a twin-screw extruder. The temperature of zone one, zone two, zone three, and die head were set at 170°C, 190°C, and 200°C, respectively. After extrusion, the mixture was formed into a film by casting. The film thickness was 0.08 mm, and a white, high-temperature-resistant TPU film was obtained.

[0025] Example 3 Preparation of white high temperature resistant TPU film: S1. Raw material pretreatment: Polycarbonate diol was selected as the polyester polyol, and 60 parts of the polyester polyol was vacuum dehydrated at 110°C for 3 hours to reduce the moisture content to ≤0.03%, thereby obtaining the dehydrated polyester polyol. Nano-titanium dioxide was surface-modified with KH550 at 80°C to obtain silane-modified titanium dioxide. S2. Prepolymer synthesis: The dehydrated polyester polyol was mixed with 25 parts of isocyanate so that the molar ratio of isocyanate group to hydroxyl group was 1.07:1, and then reacted at 80° C. for 2 hours to obtain an isocyanate-terminated prepolymer; wherein the isocyanate was an aliphatic isocyanate, isophorone diisocyanate; S3, chain expansion and mixing: 7 parts of a chain extender, 12 parts of silane-modified titanium dioxide, and 2 parts of a composite thermal stabilizer were added to the above-prepared isocyanate-terminated prepolymer, and the mixture was stirred at 1000 rpm to uniformly mix the system to obtain a mixture; wherein the chain extender was a heat-resistant group-containing chain extender hydroquinone dihydroxyethyl ether HQEE, and the composite thermal stabilizer was a mixture of a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1, the hindered phenol antioxidant was Irganox 1010, and the phosphite antioxidant was Irgafos 168; S4. Melt extrusion and film forming: The mixture was extruded using a twin-screw extruder. The temperature of zone one, zone two, zone three, and die head were set at 165°C, 185°C, 195°C, and 190°C, respectively. After extrusion, the mixture was formed into a film by casting. The film thickness was 0.05 mm, and a white, high-temperature resistant TPU film was obtained.

[0026] Performance testing The following performance tests were performed on the samples of Examples 1-3: High temperature aging performance test: The samples were aged at 150°C for 500 h, and the whiteness and tensile strength of the samples were tested. The tensile strength test was based on GB / T1040.1-2006. Each sample was tested three times, and the average value was taken. The test results were filled in Table 1.

[0027] Table 1 Performance test results of Examples 1-3 Test items Whiteness / CIE L* Tensile strength / % Example 1 89 87 Example 2 88 86 Example 3 90 87 From Table 1, it can be seen that the whiteness of Examples 1-3 is all above 88, and the tensile strength is all above 85%, indicating that the white TPU film prepared in this application has good high temperature resistance and can maintain good whiteness even after high temperature.

[0028] This specific embodiment is merely an explanation of the present application and does not limit the present application. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of the present application. The technical scope of the present application is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A white high-temperature resistant TPU film, characterized by: The invention comprises a polyurethane matrix resin, a high-temperature resistant white system and other additives. The polyurethane matrix resin comprises the following components in parts by mass: 50-70 parts of polyester polyol, 20-30 parts of isocyanate, and 5-10 parts of chain extender. The polyester polyol comprises any one of polycaprolactone diol and polycarbonate diol or a mixture of the two. The isocyanate comprises any one of aliphatic isocyanate or cyclic isocyanate. The chain extender comprises any one of 1,4-butanediol or a chain extender containing a heat-resistant group.

2. The white high-temperature resistant TPU film according to claim 1, characterized in that: The high-temperature resistant white system comprises the following components in parts by mass: 10-15 parts of silane-modified titanium dioxide and 1-3 parts of a composite heat stabilizer.

3. The white high-temperature resistant TPU film according to claim 1, characterized in that: The composite heat stabilizer comprises a hindered phenol antioxidant and a phosphite antioxidant.

4. The white high-temperature resistant TPU film according to claim 3, characterized in that: The other auxiliary agents include the following components in parts by mass: 0.5-1 part of ultraviolet absorber and 0.2-0.5 part of lubricant.

5. A method for preparing the white high-temperature resistant TPU film according to claims 1-4, characterized in that: The steps include: S1. Raw material pretreatment: heating the polyester polyol and then dehydrating it to obtain dehydrated polyester polyol; treating the surface of nano titanium dioxide with a silane coupling agent to obtain silane-modified titanium dioxide; S2. Prepolymer synthesis: mixing the dehydrated polyester polyol with isocyanate, and reacting at elevated temperature to obtain an isoterminal cyanate prepolymer; S3, chain extension and mixing: adding a chain extender, silane-modified titanium dioxide, and a composite heat stabilizer to the isoterminal cyanate-based prepolymer, and mixing at a high speed to obtain a mixture; S4, melting and extrusion: using a twin-screw extruder to extrude the mixture and prepare a TPU film by casting or blow molding; After aging for 500 hours at 150° C., the prepared TPU film has a whiteness (CIE L*) of ≥88 and a tensile strength retention rate of ≥85%.

6. The method for preparing a white high-temperature resistant TPU film according to claim 5, characterized in that: In step S1, the silane coupling agent is γ-aminopropyltriethoxysilane.

7. The method for preparing a white high-temperature resistant TPU film according to claim 5, characterized in that: In the step S2, the molar ratio of the isocyanate group to the hydroxyl group in the dehydrated polyester polyol and the isocyanate added is (1.05-1.1):

1.

8. The method for preparing a white high-temperature resistant TPU film according to claim 5, characterized in that: In step S4, the twin-screw extruder adopts segmented temperature control: zone 1: 160-170°C; zone 2: 180-190°C; zone 3: 190-200°C; and die head temperature: 185-195°C.