Flexible lens and preparation method thereof

Abstract

The invention discloses a flexible lens and a preparation method thereof, and belongs to the field of optical materials. The material comprises the following raw materials in parts by mass: 80-100 parts of thermoplastic polyurethane (TPU), 5-15 parts of a flame retardant, 2-8 parts of an antifogging agent, 0.5-3 parts of a light stabilizer and 0.5-2 parts of an antioxidant. The flexible lens has prominent flexibility, and can be bent for 10000 times under the conditions that the bending angle reaches 180 degrees and the left edge and the right edge are in contact, and the lens is free of cracks and damage; the optical property is excellent, the light transmittance is not less than 85%, and the haze is less than 2%; the excellent flame retardant property is realized, and the UL94 V-0 level can be reached; the anti-fogging coating has good anti-fogging performance, and can meet the requirement of no fogging within at least 8 seconds under the condition of GB 32166.1-2016; the anti-yellowing performance is good, and the anti-yellowing performance can reach grade 4-5.

Description

Technical Field

[0001] The present invention relates to the field of optical materials, and particularly to a flexible lens made of thermoplastic polyurethane (TPU) and a preparation method thereof. Background Art

[0002] With the development of technology, people's requirements for the performance of lenses are becoming more and more diverse. Traditional rigid lenses have limitations in some specific scenarios. For example, in the fields of wearable devices, sports protection, gas masks, etc., due to their hard texture, rigid lenses may cause discomfort to users when worn or are easily broken when impacted by external forces, and also make it inconvenient to fold or carry the equipment.

[0003] As a new type of polymer material, thermoplastic polyurethane (TPU) has excellent flexibility, weather resistance, chemical corrosion resistance and optical properties, making it an ideal material for preparing flexible lenses. However, in the current preparation process of existing TPU flexible lenses, there are problems such as complex processes, high costs, and poor optical properties, which limit the wide application of TPU flexible lenses. Summary of the Invention

[0004] The purpose of the present invention is to provide a flexible lens and a preparation method thereof to solve the problems of poor flexibility and optical properties, yellowing resistance, lack of flame retardancy and anti-fogging properties of existing TPU flexible lenses. By modifying the TPU material, a flexible lens with excellent yellowing resistance, flame retardancy and anti-fogging properties, while maintaining good flexibility and optical properties, is prepared.

[0005] The flexible lens of the present invention is mainly composed of the following raw materials in parts by mass: 80 - 100 parts of thermoplastic polyurethane (TPU), 5 - 15 parts of flame retardant, 2 - 8 parts of anti-fogging agent, 0.5 - 3 parts of light stabilizer, and 0.5 - 2 parts of antioxidant.

[0006] The thermoplastic polyurethane (TPU) is polyether-based TPU, with a hardness range of Shore A80 - A100, and has good elasticity and flexibility.

[0007] The flame retardant is a phosphorus-nitrogen type composite flame retardant, which plays a flame retardant role through the charring and gas-phase flame retardant mechanisms. The anti-fogging agent is INTECHEM-06, INTECHEM-07, INTECHEM-08, INTECHEM-10.

[0008] The anti-fogging agent is a fluorocarbon-based non-ionic surfactant, which has good hydrophilicity and surface activity, and can form a uniform water film on the surface of the lens to prevent water vapor from condensing into fog droplets, thereby achieving anti-fogging performance. At the same time, it has good compatibility with the TPU resin and can improve the optical properties and flexibility of the lens to a certain extent. The above anti-fogging agent The light stabilizer is a hindered amine light stabilizer (HALS), which can preferentially absorb ultraviolet light, inhibit the photo-oxidative degradation of thermoplastic polyurethane (TPU) molecules, prevent it from aging and yellowing due to light, and improve the weather resistance of the lens.

[0009] The antioxidant is dilauryl thiodipropionate (DLTP), which can prevent the performance of thermoplastic polyurethane (TPU) from decreasing due to oxidation during processing and use.

[0010] The preparation method of the above-mentioned flexible lens includes the following steps: Step 1: Raw material pretreatment Use a dehumidifying dryer to dry the TPU resin at a temperature of 80°C to 110°C for 4 to 6 hours to remove moisture and prevent bubbles from being generated during processing; crush the flame retardant, anti-fog agent, light stabilizer, and antioxidant respectively, and pass through a 100-200 mesh sieve to make their particle sizes uniform, facilitating subsequent uniform mixing.

[0011] Step 2: Mixing and batching According to the above formula ratio, add the dried TPU resin and the pretreated flame retardant, anti-fog agent, light stabilizer, and antioxidant to a high-speed mixer, and mix at a temperature of 80°C to 100°C and a rotation speed of 1000-1500 r / min for 10 to 15 minutes to make all raw materials fully and uniformly mixed.

[0012] Step 3: Melting and extrusion Add the mixed material to a twin-screw extruder for melting and extrusion. The temperature of the extruder is set as follows: zone 1 is 160°C to 180°C, zone 2 is 180°C to 200°C, zone 3 is 200°C to 220°C, zone 4 is 220°C to 240°C, and the head temperature is 230°C to 250°C. Through melting and extrusion, each component is further uniformly dispersed at high temperature, and certain physical and chemical reactions occur to form a stable blend system. The extruded material is cooled by water, drawn into strips, and pelletized to obtain TPU composite particles.

[0013] Step 4: Secondary drying Dry the TPU composite particles again at a temperature of 80°C to 110°C for 4 to 6 hours to remove moisture and prevent bubbles from being generated during processing, which may affect the appearance and performance of the lens.

[0014] Step 5: Injection molding Add the dried TPU composite particles into an injection molding machine for injection molding to prepare flexible lenses. The temperature of the injection molding machine is set as follows: the first zone of the barrel is 180°C - 190°C, the second zone is 190°C - 200°C, the third zone is 200°C - 210°C, and the nozzle temperature is 200°C - 220°C. The injection pressure is 60 - 100 MPa, the holding pressure is 30 - 60 MPa, the holding time is 5 - 10 s, and the cooling time is 10 - 15 s. By precisely controlling the injection process parameters, the molding quality and dimensional accuracy of the lenses are ensured.

[0015] Step Six: Post-treatment of the finished product Open the mold to take out the flexible lens, and place it in an oven at a temperature of 80°C - 100°C for heat treatment for 2 - 4 hours to eliminate the residual stress inside the lens and improve the optical uniformity and dimensional stability of the lens.

[0016] The flexible lens of the present invention has excellent flexibility, optical properties, flame retardant properties, anti-fog properties, and yellowing resistance.

[0017] The preparation method of the flexible lens of the present invention has a simple process, is easy to operate, has high production efficiency, and can effectively ensure the quality and performance stability of the lens by reasonably controlling the process parameters, and is suitable for large-scale industrial production. At the same time, the preparation method has a low cost, can reduce the production cost of the flexible lens, and improve the market competitiveness. Description of the drawings

[0018] Figure 1 It is a flow chart of the preparation method of the flexible lens in the embodiment of the present invention. Specific implementation manners

[0019] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples.

[0020] This embodiment provides a flexible lens and its preparation method to solve the problems of poor flexibility and optical properties, lack of yellowing resistance, and lack of flame retardant and anti-fog properties of existing TPU flexible lenses. Through the modification of the TPU material, a flexible lens with yellowing resistance, good flame retardant and anti-fog properties, and excellent flexibility and optical properties is prepared.

[0021] Example 1 1. Raw material preparation Weigh 100 parts of TPU resin, dry it at 90°C for 4 hours using a dehumidifying dryer, and weigh 10 parts of UZR-6 phosphazene-based composite flame retardant, 4 parts of INTECHEM-06, 1 part of hindered amine light stabilizer, and 1 part of antioxidant dilauryl thiodipropionate, and respectively crush them through a 150-mesh sieve.

[0022] 2. Raw material mixing Add the dried TPU resin, the above-mentioned pretreated flame retardant, INTECHEM-06, light stabilizer and antioxidant into a high-speed mixer, and stir at a speed of 1200 r / min for 12 minutes to fully mix and homogenize all components.

[0023] 3. Melting and Extrusion Add the mixed materials into a twin-screw extruder for melting and extrusion. The temperature of the extruder is set as follows: zone 1 at 160 °C, zone 2 at 180 °C, zone 3 at 200 °C, zone 4 at 220 °C, and the head temperature at 230 °C. The extruded materials are cooled by water, drawn into strips and pelletized to obtain TPU composite particles.

[0024] 4. Secondary Drying Use a dehumidifying dryer to dry the TPU composite particles again at a temperature of 80 °C for 6 hours to remove moisture and prevent bubbles from being generated during processing, which may affect the appearance and performance of the lens.

[0025] 5. Injection Molding Add the dried TPU composite particles into an injection molding machine for injection molding to prepare flexible lenses. The temperature of the injection molding machine is set as follows: barrel zone 1 at 180 °C, zone 2 at 190 °C, zone 3 at 200 °C, and the nozzle temperature at 210 °C. The injection pressure is 60 MPa, the holding pressure is 30 MPa, the holding time is 7 s, and the cooling time is 10 s.

[0026] 6. Post-treatment of Finished Products Open the mold to take out the flexible lenses, and place them in an oven at a temperature of 80 °C for heat treatment for 2 hours to eliminate the residual stress inside the lenses and improve the optical uniformity and dimensional stability of the lenses.

[0027] Example 2 1. Raw Material Preparation Weigh 100 parts of TPU resin, and use a dehumidifying dryer to dry it at 100 °C for 5 hours. Weigh 12 parts of UZR-6 phosphazene-based composite flame retardant, 6 parts of INTECHEM-08, 1.5 parts of hindered amine light stabilizer, and 1.5 parts of antioxidant dilauryl thiodipropionate, and respectively crush them through a 180-mesh sieve.

[0028] 2. Raw Material Mixing Add the dried TPU resin, the above-mentioned pretreated flame retardant, INTECHEM-08, light stabilizer and antioxidant into a high-speed mixer, and stir at a speed of 1300 r / min for 13 minutes to fully mix and homogenize all components.

[0029] 3. Melting and Extrusion Add the mixed materials into a twin-screw extruder for melt extrusion. The temperatures of the extruder are set as follows: zone 1 at 170 °C, zone 2 at 190 °C, zone 3 at 210 °C, zone 4 at 230 °C, and the head temperature at 240 °C. The extruded materials are cooled by water, drawn into strips, and pelletized to obtain TPU composite particles.

[0030] 4. Secondary drying Use a dehumidifying dryer to dry the TPU composite particles again at a temperature of 90 °C for 5 hours to remove moisture and prevent the generation of bubbles during processing, which may affect the appearance and performance of the lens.

[0031] 5. Injection molding Add the dried TPU composite particles into an injection molding machine for injection molding to prepare flexible lenses. The temperatures of the injection molding machine are set as follows: barrel zone 1 at 185 °C, zone 2 at 195 °C, zone 3 at 205 °C, and the nozzle temperature at 210 °C. The injection pressure is 80 MPa, the holding pressure is 45 MPa, the holding time is 8 s, and the cooling time is 12 s.

[0032] 6. Post-treatment of finished products Open the mold to take out the flexible lenses and place them in an oven at a temperature of 90 °C for 3 hours of heat treatment to eliminate the residual stress inside the lenses and improve the optical uniformity and dimensional stability of the lenses.

[0033] Example 3 1. Raw material preparation Weigh 100 parts of TPU resin and dry it using a dehumidifying dryer at 110 °C for 6 hours. Weigh 15 parts of UZR-6 phosphorus-nitrogen type composite flame retardant, 8 parts of INTECHEM-10, 2 parts of hindered amine light stabilizer, and 2 parts of antioxidant dilauryl thiodipropionate, and respectively crush them through a 200-mesh sieve.

[0034] 2. Raw material mixing Add the dried TPU resin and the above-mentioned pretreated flame retardant, INTECHEM-10, light stabilizer, and antioxidant into a high-speed mixer and stir at a speed of 1500 r / min for 15 minutes to make each component fully and evenly mixed.

[0035] 3. Melt extrusion Add the mixed materials into a twin-screw extruder for melt extrusion. The temperatures of the extruder are set as follows: zone 1 at 180 °C, zone 2 at 200 °C, zone 3 at 220 °C, zone 4 at 240 °C, and the head temperature at 250 °C. The extruded materials are cooled by water, drawn into strips, and pelletized to obtain TPU composite particles.

[0036] 4. Secondary drying The TPU composite material particles were dried again at 110°C for 4 hours using a dehumidifying dryer to remove moisture and prevent bubbles from being generated during processing, which would affect the appearance and performance of the lens.

[0037] 5. Injection molding The dried TPU composite pellets were placed in an injection molding machine for injection molding to produce flexible lenses. The machine temperature settings were: barrel zone 1: 190°C, zone 2: 200°C, zone 3: 210°C, and nozzle temperature: 220°C. The injection pressure was 100 MPa, the holding pressure was 60 MPa, the holding time was 10 seconds, and the cooling time was 15 seconds.

[0038] 6. Finished product post-processing The mold is opened and the flexible lens is taken out and placed in an oven at 100°C for 4 hours of heat treatment to eliminate the residual stress inside the lens and improve the optical uniformity and dimensional stability of the lens.

[0039] Example 4 1. Raw Materials Preparation Weigh 100 parts of TPU resin and dry them at 90°C for 4 hours in a dehumidifying dryer. Weigh 10 parts of UZR-6 phosphorus-nitrogen composite flame retardant, 4 parts of polyglycerol fatty acid ester, 1 part of hindered amine light stabilizer, and 1 part of antioxidant dilauryl thiodipropionate and grind them through a 150-mesh sieve respectively.

[0040] 2. Raw material mixing The dried TPU resin, the pretreated flame retardant, polyglycerol fatty acid ester, light stabilizer and antioxidant were added into a high-speed mixer and stirred at a speed of 1200 r / min for 12 minutes to fully mix the components.

[0041] 3. Melt extrusion The mixed materials were added to a twin-screw extruder for melt extrusion. The extruder temperature was set to 160°C in zone 1, 180°C in zone 2, 200°C in zone 3, 220°C in zone 4, and a die head temperature of 230°C. The extruded materials were water-cooled, stretched, and pelletized to obtain TPU composite pellets.

[0042] 4. Secondary drying The TPU composite material particles were dried again at 80°C for 6 hours using a dehumidifying dryer to remove moisture and prevent bubbles from being generated during processing, which would affect the appearance and performance of the lens.

[0043] 5. Injection molding Add the dried TPU composite material particles into an injection molding machine for injection molding to prepare flexible lenses. The temperature of the injection molding machine is set as follows: the first zone of the barrel is 180 °C, the second zone is 190 °C, the third zone is 200 °C, and the nozzle temperature is 210 °C. The injection pressure is 60 MPa, the holding pressure is 30 MPa, the holding time is 7 s, and the cooling time is 10 s.

[0044] 6. Post-treatment of the finished product Open the mold to take out the flexible lenses and place them in an oven at 80 °C for 2 hours of heat treatment to eliminate the residual stress inside the lenses and improve the optical uniformity and dimensional stability of the lenses.

[0045] The test results of the product performance parameters of this patent are as follows: 1. Flexibility: When the flexible lenses prepared in Examples 1-4 are bent 10,000 times at a bending angle of 180° and the left and right edges can touch, the lenses have no cracks or damages, indicating that the lenses have good flexibility.

[0046] 2. Optical properties: The transmittance and haze of the flexible lenses prepared in Examples 1-4 are tested according to the method described in GB 14866-2006. The results show that the transmittance of the lenses in Example 1 all reaches more than 95%, and the haze is all less than 1.2%, meeting the optical property requirements. The transmittance of the lenses in Example 2 all reaches more than 96%, and the haze is all less than 1.5%, meeting the optical property requirements. The transmittance of the lenses in Example 3 all reaches more than 94%, and the haze is all less than 0.8%, meeting the optical property requirements. The transmittance of the lenses in Example 4 all reaches more than 85%, and the haze is all less than 2%, basically meeting the optical property requirements.

[0047] 3. Flame retardant properties: The flame retardant properties of the flexible lenses prepared in Examples 1-4 are tested according to the UL94 standard. The test results show that the flame retardant grades of the lenses prepared in the three examples all reach UL94 V-0 level.

[0048] 4. Anti-fogging properties: The anti-fogging properties of the flexible lenses prepared in Examples 1-4 are tested according to the method described in GB 32166.1-2016. The test results show that the lenses in Example 1 do not fog up within 15 s, indicating that the lenses have excellent anti-fogging properties. The lenses in Example 2 do not fog up within 20 s, indicating that the lenses have excellent anti-fogging properties. The lenses in Example 3 do not fog up within 18 s, indicating that the lenses have excellent anti-fogging properties. The lenses in Example do not fog up within 8 s, indicating that the lenses have excellent anti-fogging properties.

[0049] 5. Yellowing resistance: The yellowing resistance of the flexible lenses prepared in Examples 1-4 is tested using a SUNTEST tester. The test results show that the yellowing resistance of the lenses prepared in the four examples all reaches above level 4.

[0050] The flexible lens of the present invention has excellent flexibility, optical properties, flame retardancy, anti-fogging properties and yellowing resistance.

[0051] The preparation method of the flexible lens of the present invention has the advantages of simple process, easy operation and high production efficiency. By reasonably controlling process parameters, the quality and performance stability of the lens can be effectively guaranteed, which is suitable for large-scale industrial production. At the same time, the preparation method has a low cost, can reduce the production cost of the flexible lens and improve the market competitiveness.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flexible lens, characterized in that, The composition ratio of the raw materials of the flexible lens is as follows by mass fraction: 80 - 100 parts of thermoplastic polyurethane, 5 - 15 parts of flame retardant, 2 - 8 parts of anti-fog agent, 0.5 - 3 parts of light stabilizer, and 0.5 - 2 parts of antioxidant.

2. The flexible lens according to claim 1, wherein The thermoplastic polyurethane is polyether-based TPU with a Shore A hardness of 80 - 100.

3. The flexible lens according to claim 1, characterized in that, The flame retardant is a phosphorus-nitrogen type composite halogen-free flame retardant UZR-6.

4. The flexible lens according to claim 1, wherein The anti-fog agent is any one of INTECHEM-06, INTECHEM-07, INTECHEM-08, and INTECHEM-10.

5. The flexible lens according to claim 1, wherein The light stabilizer is a hindered amine light stabilizer, which can effectively absorb ultraviolet light, inhibit the photo-oxidative degradation of TPU molecules, and improve the yellowing resistance of the lens.

6. The flexible lens according to claim 1, characterized in that, The antioxidant is dilauryl thiodipropionate, which can prevent the performance of TPU from decreasing due to oxidation during processing and use.

7. The preparation method of the flexible lens according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1: Raw material pretreatment Use a dehumidifying dryer to dry the TPU resin at a temperature of 80°C - 110°C for 4 - 6 hours to remove moisture; crush the flame retardant, anti-fog agent, light stabilizer, and antioxidant respectively. Step 2: Mixing and batching According to the above formula ratio, add the dried TPU resin and the pretreated flame retardant, anti-fog agent, light stabilizer, and antioxidant to high-speed stirring to make each raw material fully mixed and uniform. Step 3: Melting and extrusion Add the mixed materials into a twin-screw extruder for melting and extrusion to obtain TPU composite particles. Step 4: Secondary drying Dry the TPU composite particles again at a temperature of 80°C - 110°C for 4 - 6 hours to remove moisture. Step 5: Injection molding Add the dried TPU composite particles into an injection molding machine for injection molding to prepare a flexible lens. Step 6: Post-treatment of the finished product Open the mold to take out the flexible lens, put it into an oven with a temperature of 80°C - 100°C, and conduct heat treatment for 2 - 4 hours to obtain a flexible lens.

8. The preparation method of the flexible lens according to claim 7, wherein, In Step 2, mix at a temperature of 80°C - 100°C and a rotation speed of 1000 - 1500 r / min for 10 - 15 minutes to make each raw material fully mixed and uniform.

9. The method for preparing a flexible lens according to claim 7, wherein The temperature settings for the melting and extrusion in Step 3 are as follows: Zone 1: 160°C - 180°C, Zone 2: 180°C - 200°C, Zone 3: 200°C - 220°C, Zone 4: 220°C - 240°C, and the head temperature: 230°C - 250°C.

10. The preparation method of the flexible lens according to claim 7, characterized in that, The temperature settings for the injection molding in Step 5 are as follows: Barrel Zone 1: 180°C - 190°C, Zone 2: 19 °C - 200°C, Zone 3: 200°C - 210°C, Nozzle temperature: 200°C - 220°C, Injection pressure: 60 - 100 MPa, Holding pressure: 30 - 60 MPa, Holding time: 5 - 10 s, Cooling time: 10 - 15 s.

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