Crosslinked fluororesin, preparation method and application

Abstract

The invention discloses cross-linked fluororesin, a preparation method and application, and belongs to the technical field of fluorine-containing polymers. The cross-linked fluororesin is composed of a fluorine-containing copolymer A and a cross-linking agent B. The tensile strength of the cross-linked fluororesin is larger than or equal to 30 MPa, the elongation at break is larger than or equal to 150%, and the transparency is larger than or equal to 85% when the thickness is 0.1 mm. The fluorine-containing copolymer A is a copolymer formed by copolymerization of perfluoro-2, 2-dimethyl-1, 3-dioxole PDD, hexafluoropropylene and perfluoroalkyl vinyl ether containing two double bonds, and the fluorine-containing copolymer A is a copolymer formed by copolymerization of perfluoro-2, 2-dimethyl-1, 3-dioxole PDD, hexafluoropropylene and perfluoroalkyl vinyl ether containing two double bonds. The cross-linked fluororesin prepared by the invention has the advantages of high strength, high toughness, high transparency and the like, and the performance boundary and the application field of the fluororesin are expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorine-containing polymers, and in particular relates to a cross-linked fluorine resin, a preparation method and an application thereof. Background Art

[0002] Fluoropolymers, due to their unique chemical structure (high bond energy and low surface energy of the C-F bond), possess excellent weather resistance, chemical resistance, and non-stick properties. They can adapt to extreme environments, integrate multiple functionalities, and exhibit long-term durability. They hold enormous potential for application in optics and display technology, electrical and electronic fields, special protective equipment, and smart surfaces. However, traditional fluoropolymers have limitations in their optical and mechanical properties. As modern technology evolves toward high-precision, multifunctional, and extreme-environment applications, the development of fluoropolymers that combine high transparency, strength, and toughness has become a key trend in the materials field. In the optical field, the combination of high transparency, high strength and high toughness with the low refractive index properties of fluoropolymers can replace bulky and fragile glass materials, meeting the dual needs of lightweight and high clarity in flexible displays, photovoltaic modules, AR / VR optical devices, etc. In the medical field, the combination of high transparency, high strength and high toughness with the biocompatibility and high chemical stability of fluoropolymers makes them suitable for implantable medical devices and in vitro diagnostic equipment. In special applications, the combination of high transparency and high strength and high toughness, coupled with the inherent high and low temperature resistance (-200℃ to 260℃), UV resistance and radiation resistance of fluoropolymers, makes them irreplaceable in extreme environments such as aerospace (spacecraft windows) and the nuclear industry (radiation monitoring windows). Therefore, the development of high-transparency, high-strength and high-toughness fluoropolymers is not only the key to breaking through the performance bottleneck of traditional materials, but also the core foundation for supporting the upgrading of strategic industries such as semiconductor manufacturing, new energy, and high-end equipment.

[0003] Most fluororesins have relatively flexible molecular chains and low glass transition temperatures, and thus exhibit high strength only at high crystallinity. However, at high crystallinity, the crystals scatter light, significantly reducing the transparency and toughness of the fluororesin. This makes it difficult for most commercial fluororesins to achieve high strength, high toughness, and high transparency. Therefore, developing fluororesins that combine high strength, high toughness, and high transparency remains a significant challenge. Summary of the Invention

[0004] To address the problems encountered in the prior art, the present invention provides a cross-linked fluororesin, preparation method, and application. First, a fluororesin containing an appropriate amount of rigid heterocyclic structure and a suitable amount of side-chain vinyl groups is prepared by copolymerization. Then, based on click chemistry between mercapto groups and side-chain vinyl groups at high temperatures, the synthesized fluororesin is cross-linked using a multifunctional mercaptoacrylate, thereby producing a fluororesin with high strength, high toughness, and high transparency. Because the cross-linked structure is dynamically reversible, it can be opened at high temperatures and reconstructed at low temperatures. Therefore, the cross-linked fluororesin also has excellent reprocessing performance.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A cross-linked fluororesin is composed of a fluorine-containing copolymer A and a cross-linking agent B. The cross-linked fluororesin has a tensile strength of ≥30 MPa, an elongation at break of ≥150%, and a transparency of ≥85% when the thickness is 0.1 mm.

[0007] Furthermore, the fluorinated copolymer A is a copolymer formed by copolymerizing perfluoro-2,2-dimethyl-1,3-dioxole (PDD), hexafluoropropylene, and a perfluoroalkyl vinyl ether containing two double bonds, wherein the molar content of PDD is 10-35%, the molar content of hexafluoropropylene is 40-60%, and the molar content of the perfluoroalkyl vinyl ether containing two double bonds is 10-30%. The perfluoroalkyl vinyl ether containing two double bonds is one of CF2=CFOCF2CF=CF2 and CF2=CFOCF2CF2CF=CF2, or a combination of the two.

[0008] Furthermore, the crosslinking agent B is one or a combination of pentaerythritol tetrakis(3-mercaptopropionate) and trimethylolpropane tris(3-mercaptopropionate).

[0009] Furthermore, in parts by mass, the mass content of the fluorinated copolymer A in the cross-linked fluororesin is 100 parts, and the mass content of the cross-linking agent is 4 to 10 parts.

[0010] A method for preparing a cross-linked fluororesin, comprising the following steps:

[0011] (1) plasticizing the fluorinated copolymer A in an internal mixer;

[0012] (2) adding the crosslinking agent B into an internal mixer and uniformly blending it with the fluoropolymer A;

[0013] (3) The blend of the fluorinated copolymer A and the crosslinking agent B is hot pressed to complete crosslinking and molding.

[0014] Furthermore, the preparation method of the fluorinated copolymer A is as follows: solvent 1,1,2-trichlorotrifluoroethane, PDD, perfluoroalkyl vinyl ether containing two double bonds and catalyst diisopropyl peroxydicarbonate are added in sequence to a high-pressure reactor pre-cooled to 0°C, and stirred and mixed evenly; nitrogen is used for replacement several times to make the oxygen content in the reactor lower than 5ppm, and then hexafluoropropylene is slowly added; the reaction is carried out at 40-60°C for 5-7 hours, and the obtained blend solution is poured into methanol to flocculate the prepared fluorinated polymer, and the flocculent is washed with methanol. The washed product is dried in an oven at 70-90°C to constant weight to obtain fluorinated polymer A.

[0015] Furthermore, the plasticizing temperature in step (1) is 100-140° C., the time is 3-5 minutes, and the rotation speed is 60-100 rpm;

[0016] Furthermore, the blending temperature and speed in step (2) are the same as the plasticizing temperature and speed in step (1), and the blending time is 6 to 8 minutes until the torque equilibrium position is reached;

[0017] Furthermore, the hot pressing temperature in step (3) is 140-180° C., and the hot pressing time is 10-20 minutes.

[0018] The invention discloses an application of a cross-linked fluororesin, wherein the cross-linked fluororesin is used for optical lenses, optical windows, packaging materials of electronic components, flexible circuit boards, surgical instrument housings, vascular stents, and battery separators.

[0019] Those skilled in the art may also add other optional additives as needed to obtain better performance. These additives may be selected from transmittance enhancers, transmittance enhancer layers, enhancers, plasticizers, anti-aging agents, pigments, etc., and may be added simultaneously or separately.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention combines an appropriate rigid structure with a thermally reversible cross-linked structure, providing a new approach to the structural design of fluororesins.

[0022] (2) The cross-linked fluororesin prepared by the present invention has the advantages of high strength, high toughness and high transparency, which expands the performance boundaries and application fields of fluororesin. DETAILED DESCRIPTION

[0023] The present invention will be further explained below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. If technicians in this field make some non-essential adjustments and improvements to the present invention based on the above content of the present invention, they still fall within the scope of protection of the present invention.

[0024] Example 1:

[0025] A method for preparing a cross-linked fluororesin comprises the following steps:

[0026] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 12.8 g of PDD, 34.2 g of CF2=CFOCF2CF=CF2 and 0.46 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to make the oxygen content in the autoclave lower than 5 ppm, and then 45 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0027] (2) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 100° C. for 3 minutes at a speed of 60 rpm;

[0028] (3) 5 g of the crosslinking agent pentaerythritol tetrakis(3-mercaptopropionate) was added to an internal mixer and blended evenly with the fluoropolymer A at a temperature of 100° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0029] (4) The above blend of A and B was hot-pressed at 140°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0030] Example 2:

[0031] A method for preparing a cross-linked fluororesin comprises the following steps:

[0032] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 25.6 g of PDD, 34.2 g of CF2=CFOCF2CF=CF2 and 0.49 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to reduce the oxygen content in the autoclave to less than 5 ppm, and then 37.5 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0033] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 120° C. for 4 minutes at a speed of 60 rpm;

[0034] (2) 5 g of the crosslinking agent pentaerythritol tetrakis(3-mercaptopropionate) was added to an internal mixer and uniformly blended with the fluoropolymer A at a temperature of 120° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0035] (3) The blend of A and B was hot-pressed at 160°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0036] Example 3:

[0037] A method for preparing a cross-linked fluororesin comprises the following steps:

[0038] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 38.4 g of PDD, 34.2 g of CF2=CFOCF2CF=CF2 and 0.51 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to reduce the oxygen content in the autoclave to less than 5 ppm, and then 30 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculate was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0039] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 140°C for 5 minutes at a speed of 60 rpm;

[0040] (2) 5 g of the crosslinking agent pentaerythritol tetrakis(3-mercaptopropionate) was added to an internal mixer and uniformly blended with the fluoropolymer A at a temperature of 140° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0041] (3) The blend of A and B was hot-pressed at 180°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0042] Example 4:

[0043] A method for preparing a cross-linked fluororesin comprises the following steps:

[0044] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 25.6 g of PDD, 22.8 g of CF2=CFOCF2CF=CF2 and 0.47 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to make the oxygen content in the autoclave lower than 5 ppm, and then 45 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0045] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 140° C. for 4 minutes at a speed of 80 rpm;

[0046] (2) 5 g of the crosslinking agent pentaerythritol tetrakis(3-mercaptopropionate) was added to an internal mixer and uniformly blended with the fluoropolymer A at a temperature of 140° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0047] (3) The blend of A and B was hot-pressed at 180°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0048] Example 5:

[0049] A method for preparing a cross-linked fluororesin comprises the following steps:

[0050] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 25.6 g of PDD, 22.8 g of CF2=CFOCF2CF=CF2 and 0.47 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to reduce the oxygen content in the autoclave to less than 5 ppm, and then 45 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0051] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 140° C. for 4 minutes at a speed of 80 rpm;

[0052] (2) 4 g of the crosslinking agent pentaerythritol tetrakis(3-mercaptopropionate) was added to an internal mixer and uniformly blended with the fluoropolymer A at a temperature of 140° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0053] (3) The blend of A and B was hot-pressed at 180°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0054] Example 6:

[0055] A method for preparing a cross-linked fluororesin comprises the following steps:

[0056] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 25.6 g of PDD, 22.8 g of CF2=CFOCF2CF=CF2 and 0.47 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to reduce the oxygen content in the autoclave to less than 5 ppm, and then 45 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0057] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 140° C. for 4 minutes at a speed of 80 rpm;

[0058] (2) adding 2 g of the crosslinking agent pentaerythritol tetrakis(3-mercaptopropionate) into an internal mixer and blending it evenly with the fluoropolymer A at a temperature of 140° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0059] (3) The blend of A and B was hot-pressed at 180°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0060] Example 7:

[0061] A method for preparing a cross-linked fluororesin comprises the following steps:

[0062] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 25.6 g of PDD, 22.8 g of CF2=CFOCF2CF=CF2 and 0.47 g of diisopropyl peroxydicarbonate were added in sequence to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to reduce the oxygen content in the autoclave to less than 5 ppm, and then 45 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0063] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 140° C. for 4 minutes at a speed of 80 rpm;

[0064] (2) 4 g of the crosslinking agent trimethylolpropane tris(3-mercaptopropionate) was added to an internal mixer and uniformly blended with the fluoropolymer A at a temperature of 140° C., a rotation speed of 60 rpm, and a blending time of 6 minutes;

[0065] (3) The blend of A and B was hot-pressed at 180°C for 10 minutes to obtain a sheet-like cross-linked resin with a thickness of 0.1 mm.

[0066] Comparative Example 1:

[0067] A method for preparing an uncrosslinked fluororesin, comprising the following steps:

[0068] (1) 400 ml of 1,1,2-trichlorotrifluoroethane, 25.6 g of PDD, 22.8 g of a perfluoroalkyl vinyl ether containing two double bonds, and 0.47 g of diisopropyl peroxydicarbonate were added sequentially to an autoclave precooled to 0°C, and stirred at a speed of 200 rpm for 15 minutes to mix them evenly; nitrogen was used for replacement several times to reduce the oxygen content in the autoclave to less than 5 ppm, and then 45 g of hexafluoropropylene was slowly added through a flow meter; the speed was adjusted to 300 rpm, and after reacting at 50°C for 6 hours, the blend solution was poured into methanol to flocculate the prepared fluoropolymer, and the flocculent was washed with methanol three times. The washed product was dried in an oven at 80°C to constant weight to obtain fluoropolymer A.

[0069] (1) 50 g of fluorinated copolymer A was plasticized in an internal mixer at 140° C. for 4 minutes at a speed of 80 rpm;

[0070] (2) continuing to plasticize the fluoropolymer A at a temperature of 140° C., a rotation speed of 60 rpm, and a stirring time of 6 minutes;

[0071] (3) The plasticized fluoropolymer A was hot-pressed at 180°C for 10 minutes to obtain a fluororesin sheet having a thickness of 0.1 mm.

[0072] Table 1 Typical properties of Comparative Examples 1 to 4 and Examples 1 to 11

[0073]

[0074] The above results show that: 1) The uncrosslinked ternary copolymer fluororesin (Comparative Example 1) has good toughness, but low transparency and tensile strength, while the crosslinked fluororesin (Examples 1-6) has excellent transparency, tensile strength and toughness. 2) Examples 1-3 show that the rigid structural unit PDD can effectively improve the transparency and strength of the resin, but will significantly reduce the elongation at break; 3) Examples 4-6 show that the crosslinked structure can improve the transparency and strength of the resin, but will slightly reduce the toughness of the crosslinked resin. 4) Examples 5 and 7 show that the higher the functionality of the crosslinking agent, the higher the probability of effective crosslinking, which helps to improve the strength and transparency of the crosslinked fluororesin.

[0075] Those skilled in the art should understand that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cross-linked fluororesin, characterized in that: The cross-linked fluororesin is composed of a fluorine-containing copolymer A and a cross-linking agent B. The cross-linked fluororesin has a tensile strength of ≥30 MPa, an elongation at break of ≥150%, and a transparency of ≥85% when the thickness is 0.1 mm.

2. A cross-linked fluororesin according to claim 1, characterized in that: The fluorine-containing copolymer A is a copolymer formed by copolymerizing perfluoro-2,2-dimethyl-1,3-dioxole PDD, hexafluoropropylene and perfluoroalkyl vinyl ether containing two double bonds, wherein the molar content of PDD is 10-35%, the molar content of hexafluoropropylene is 40-60%, and the molar content of perfluoroalkyl vinyl ether containing two double bonds is 10-30%; the perfluoroalkyl vinyl ether containing two double bonds is one of CF2=CFOCF2CF=CF2 and CF2=CFOCF2CF2CF=CF2, or a combination of two of them.

3. A cross-linked fluororesin according to claim 1, characterized in that: The crosslinking agent B is one or a combination of pentaerythritol tetrakis (3-mercaptopropionate) and trimethylolpropane tris (3-mercaptopropionate).

4. A cross-linked fluororesin according to claim 1, characterized in that: In parts by mass, the mass content of the fluorinated copolymer A in the cross-linked fluororesin is 100 parts, and the mass content of the cross-linking agent is 4 to 10 parts.

5. The method for preparing a cross-linked fluororesin according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: (1) plasticizing the fluorinated copolymer A in an internal mixer; (2) adding the crosslinking agent B into an internal mixer and uniformly blending it with the fluoropolymer A; (3) The blend of the fluorinated copolymer A and the crosslinking agent B is hot pressed to complete crosslinking and molding.

6. The method for preparing a cross-linked fluororesin according to claim 5, characterized in that: The preparation method of the fluorinated copolymer A is as follows: a solvent 1,1,2-trichlorotrifluoroethane, PDD, a perfluoroalkyl vinyl ether containing two double bonds, and a catalyst diisopropyl peroxydicarbonate are sequentially added into a high-pressure reactor precooled to 0° C., and the mixture is stirred and mixed evenly; nitrogen is replaced several times to reduce the oxygen content in the reactor to less than 5 ppm, and hexafluoropropylene is slowly added; the mixture is reacted at 40-60° C. for 5-7 hours, the obtained blend solution is poured into methanol to flocculate the prepared fluorinated polymer, the flocculate is washed with methanol, and the washed product is dried in an oven at 70-90° C. to a constant weight to obtain the fluorinated polymer A.

7. The method for preparing a cross-linked fluororesin according to claim 5, characterized in that: The plasticizing temperature in step (1) is 100-140° C., the time is 3-5 minutes, and the rotation speed is 60-100 rpm.

8. The method for preparing a cross-linked fluororesin according to claim 5, characterized in that: The blending temperature and rotation speed in step (2) are the same as the plasticizing temperature and rotation speed in step (1), and the blending time is 6 to 8 minutes until the torque balance position is reached.

9. The method for preparing a cross-linked fluororesin according to claim 5, characterized in that: The hot pressing temperature in step (3) is 140 to 180° C., and the hot pressing time is 10 to 20 minutes.

10. Use of a cross-linked fluororesin according to any one of claims 1 to 4, or a cross-linked fluororesin prepared by the preparation method according to any one of claims 5 to 9, characterized in that: The cross-linked fluororesin is used for optical lenses, optical windows, packaging materials for electronic components, flexible circuit boards, surgical instrument housings, vascular stents, and battery separators.

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