Preparation method of polytetrafluoroethylene waterproof breathable film for car lamp

Abstract

The preparation method comprises the following steps: S1, material mixing: weighing polytetrafluoroethylene, polyvinylidene fluoride and pullulan according to a mass ratio of 100: (5-20): (10-30), uniformly blending, and putting the mixture into a drying box to dry moisture; and S2, sintering: filling the mixed powder dried in the S1 into a mold, pre-pressing the mixed powder into blocks, then carrying out vacuum hot pressing sintering molding under the conditions that the vacuum degree of a sintering environment is 0.1-100 Pa, the sintering temperature is 340-380 DEG C, the heating speed is 10-15 DEG C / min, the pressure is 10-15 MPa, when the temperature is increased to 180-200 DEG C, heat preservation is carried out for 1-2 hours, when the temperature is increased to the sintering temperature, the heat preservation time is 3-5 hours, natural cooling is carried out to room temperature, and turning is carried out to obtain the composite film. The polytetrafluoroethylene waterproof and breathable film prepared by the invention has excellent waterproof, breathable and tensile properties.

Description

Technical Field

[0001] This invention relates to the field of polytetrafluoroethylene (PTFE) membrane technology, and specifically to a method for preparing a PTFE waterproof and breathable membrane for automotive lights. Background Technology

[0002] As an essential electrical device for nighttime driving, automotive lighting systems primarily illuminate the road ahead and provide safety signals, playing a crucial role in ensuring driving safety at night or in rainy or foggy weather. During daily driving, headlights face constantly changing environmental conditions. Whether it's ordinary halogen headlights, headlights with LED lights, or xenon headlights, they must be protected from dust, dirt, deposits, and condensation to consistently provide the driver with clear visibility. Ensuring reliable protection for headlights by preventing condensation and blocking dirt and water from entering while simultaneously balancing the pressure inside the lens has long been a challenge for automakers and suppliers.

[0003] The main sources of moisture in car headlights are: (1) condensation caused by temperature difference, which accounts for about 80% of the moisture in the headlights; (2) infiltration, where external water vapor diffuses through plastic over a long period of time and enters the interior of the outer shell; and (3) the waterproof and breathable product itself, through which moisture enters and exits the headlights.

[0004] The PTFE waterproof and breathable membrane used in automotive lights allows for rapid air exchange when subjected to pressure differences caused by temperature changes within the lamp, effectively ensuring airflow inside the lamp and removing moisture through convection or diffusion. It balances the internal temperature of the lamp, reduces the convection of hot and cold gases, and eliminates condensation caused by temperature differences. Furthermore, it possesses extremely high temperature resistance, chemical resistance, and excellent hydrophobic and oleophobic properties. It prevents dust, dirt, deposits, wash water, rainwater, oil, lubricants, detergents, and other fluids from entering the lamp, ensuring both aesthetics and safety.

[0005] Existing PTFE waterproof and breathable membranes still have room for improvement in terms of waterproof and breathable performance. Therefore, this application provides a method for preparing a PTFE waterproof and breathable membrane for automotive lights. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights. Technical solution

[0007] A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights includes the following steps: S1. Mixing: Weigh polytetrafluoroethylene, polyvinylidene fluoride and pullulan polysaccharide according to the mass ratio of 100:5-20:10-30, mix them evenly and place them in a drying oven to dry the moisture. S2: Sintering: The dried mixed powder of S1 is filled into a mold, pre-pressed into a block, and then vacuum hot-pressed and sintered. The vacuum degree of the sintering environment is 0.1-100 Pa, the sintering temperature is 340-380℃, the heating rate is 10-15℃ / min, the pressure is 10-15 MPa, when the temperature is raised to 180-200℃, it is held for 1-2 hours, when the temperature is raised to the sintering temperature, it is held for 3-5 hours, and then naturally cooled to room temperature. The composite film is then machined. S3: The composite membrane is immersed in clean water and ultrasonically cleaned three times. After cleaning, it is placed in a drying oven to dry and obtain a microporous membrane.

[0008] Furthermore, the polytetrafluoroethylene, polyvinylidene fluoride and pullulan in S1 are mixed using a planetary ball mill at a speed of 200-400 r / min for 6-8 h.

[0009] Furthermore, the drying temperature in S1 is 110-120℃, and the drying time is 3-5 h.

[0010] Furthermore, the sintering temperature in S2 is 350-360℃.

[0011] Furthermore, the pressure for S2 pre-compression into blocks is 10-30 MPa.

[0012] Furthermore, the drying temperature in S3 is 60-65℃, and the drying time is 5-10 h.

[0013] Beneficial effects:

[0014] This invention provides a method for preparing a polytetrafluoroethylene (PTFE) waterproof and breathable membrane for automotive lights. A portion of polyvinylidene fluoride (PVDF) and pullulan are blended into PTFE resin. PVDF has a lower melting point than both PTFE and pullulan, and melts first during sintering. Its properties are similar to PTFE, allowing it to adhere to the surface of unmelted PTFE particles, adjusting the interfacial bonding between PTFE particles and initially forming a network structure that surrounds the pullulan. This results in more uniform dispersion of the pullulan, reducing agglomeration, particularly the agglomeration caused by increased fluidity after the pullulan melts. The melting point of pullulan falls between that of PTFE and PTFE. After PTFE melts, it forms an elastomer, which is further processed into a membrane. Pullulan has excellent water solubility and is used as a pore-forming agent. After film formation, it is dissolved in water to form micropores, resulting in a more uniform micropore distribution. These micropores provide the material with waterproof and breathable properties. The addition of PTFE also improves the tensile properties of the PTFE waterproof and breathable membrane. Detailed Implementation

[0015] The present invention will now be described in detail. Example 1:

[0016] A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights includes the following steps: S1. Mixing: Weigh polytetrafluoroethylene, polyvinylidene fluoride and pullulan polysaccharide according to a mass ratio of 100:5:20, add them to a planetary ball mill, and mix at a speed of 220 r / min for 6 h. After mixing evenly, place them in a drying oven to dry the moisture. The drying temperature is 110℃ and the drying time is 4 h. S2: Sintering: The dried mixed powder of S1 is filled into a mold, pre-pressed into a block under a pressure of 10 MPa, and then vacuum hot-pressed and sintered. The vacuum degree of the sintering environment is 0.1-100 Pa, the sintering temperature is 340℃, the heating rate is 10℃ / min, the pressure is 12 MPa, and when the temperature is raised to 180℃ (between the melting points of polyvinylidene fluoride and pullulan), it is held for 2 h. When the temperature is raised to the sintering temperature, it is held for 5 h. After natural cooling to room temperature, the composite film is obtained by turning. S3: The composite membrane is immersed in clean water and ultrasonically cleaned three times. After cleaning, it is placed in a drying oven and dried at 60°C for 6 hours to obtain a microporous membrane. Example 2:

[0017] A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights includes the following steps: S1. Mixing: Weigh polytetrafluoroethylene, polyvinylidene fluoride and pullulan polysaccharide according to a mass ratio of 100:10:30, add them to a planetary ball mill, and mix at a speed of 350 r / min for 7 h. After mixing evenly, place them in a drying oven to dry the moisture. The drying temperature is 120℃ and the drying time is 3 h. S2: Sintering: The dried mixed powder of S1 is filled into a mold, pre-pressed into a block under a pressure of 30 MPa, and then vacuum hot-pressed and sintered. The vacuum degree of the sintering environment is 0.1-100 Pa, the sintering temperature is 350℃, the heating rate is 15℃ / min, the pressure is 15 MPa, when the temperature is raised to 200℃ (between the melting points of polyvinylidene fluoride and pullulan), it is held for 1 h, when the temperature is raised to the sintering temperature, it is held for 4 h, and then naturally cooled to room temperature. The composite film is then machined. S3: The composite membrane was immersed in clean water and ultrasonically cleaned three times. After cleaning, it was placed in a drying oven and dried at 65°C for 10 hours to obtain a microporous membrane. Example 3:

[0018] A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights includes the following steps: S1. Mixing: Weigh polytetrafluoroethylene, polyvinylidene fluoride and pullulan polysaccharide according to the mass ratio of 100:20:10, add them to a planetary ball mill, and mix at a speed of 300 r / min for 8 h. After mixing evenly, place them in a drying oven to dry the moisture. The drying temperature is 110℃ and the drying time is 5 h. S2: Sintering: The dried mixed powder of S1 is filled into a mold, pre-pressed into a block under a pressure of 20 MPa, and then vacuum hot-pressed and sintered. The vacuum degree of the sintering environment is 0.1-100 Pa, the sintering temperature is 360℃, the heating rate is 15℃ / min, the pressure is 10 MPa, and when the temperature is raised to 190℃ (between the melting points of polyvinylidene fluoride and pullulan), it is held for 2 h. When the temperature is raised to the sintering temperature, it is held for 4 h. After natural cooling to room temperature, the composite film is obtained by turning. S3: The composite membrane is immersed in clean water and ultrasonically cleaned three times. After cleaning, it is placed in a drying oven at 65°C for 5 hours to obtain a microporous membrane.

[0019] Examples 4-5: The preparation method is the same as in Example 3, except that the sintering temperatures are 370℃ and 380℃, respectively.

[0020] Comparative Example 1: A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights includes the following steps: S1. Mixing: Weigh polytetrafluoroethylene and pullulan polysaccharide at a mass ratio of 100:10, add them to a planetary ball mill, and mix at a speed of 300 r / min for 8 h. After mixing evenly, place them in a drying oven to dry the moisture. The drying temperature is 110℃ and the drying time is 5 h. S2: Sintering: The dried mixed powder of S1 is filled into a mold, pre-pressed into a block under a pressure of 20 MPa, and then vacuum hot-pressed and sintered. The vacuum degree of the sintering environment is 0.1-100 Pa, the sintering temperature is 360℃, the heating rate is 15℃ / min, the pressure is 10 MPa, and when the temperature is raised to 190℃ (between the melting points of polyvinylidene fluoride and pullulan), it is held for 2 h. When the temperature is raised to the sintering temperature, it is held for 4 h. After natural cooling to room temperature, the composite film is obtained by turning. S3: The composite membrane is immersed in clean water and ultrasonically cleaned three times. After cleaning, it is placed in a drying oven at 65°C for 5 hours to obtain a microporous membrane.

[0021] Performance testing:

[0022] In summary, the polytetrafluoroethylene waterproof and breathable membranes prepared in Examples 1-5 all exhibit excellent waterproof and breathable properties, with uniformly distributed micropores and uniformly high pore size. Compared to Example 3, Comparative Example 1 did not add polyvinylidene fluoride. To eliminate the influence of sintering temperature, the same sintering conditions as in Example 3 were used. As a result, its micropore distribution was uneven, and the pore size varied, with the maximum pore size reaching 1.5 micrometers, and the air permeability was significantly reduced.

[0023] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights, characterized in that, Includes the following steps: S1. Mixing: Weigh polytetrafluoroethylene, polyvinylidene fluoride and pullulan polysaccharide according to the mass ratio of 100:5-20:10-30, mix them evenly and place them in a drying oven to dry the moisture. S2: Sintering: The dried mixed powder of S1 is filled into a mold, pre-pressed into a block, and then vacuum hot-pressed and sintered. The vacuum degree of the sintering environment is 0.1-100 Pa, the sintering temperature is 340-380℃, the heating rate is 10-15℃ / min, the pressure is 10-15 MPa, when the temperature is raised to 180-200℃, it is held for 1-2 hours, when the temperature is raised to the sintering temperature, it is held for 3-5 hours, and then naturally cooled to room temperature. The composite film is then machined. S3: The composite membrane is immersed in clean water and ultrasonically cleaned three times. After cleaning, it is placed in a drying oven to dry and obtain a microporous membrane.

2. The method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights according to claim 1, characterized in that, The polytetrafluoroethylene, polyvinylidene fluoride and pullulan in S1 were mixed using a planetary ball mill at a speed of 200-400 r / min for 6-8 h.

3. The method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights according to claim 1, characterized in that, The drying temperature in S1 is 110-120℃, and the drying time is 3-5 h.

4. The method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights according to claim 1, characterized in that, The sintering temperature in S2 is 350-360℃.

5. A method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights according to any one of claims 1-4, characterized in that, The pressure for S2 pre-compression into blocks is 10-30 MPa.

6. The method for preparing a polytetrafluoroethylene waterproof and breathable membrane for automotive lights according to claim 5, characterized in that, The drying temperature in S3 is 60-65℃, and the drying time is 5-10 h.

Images