Hydrophilic modification method and application of expanded polytetrafluoroethylene

Abstract

The invention relates to the technical field of polytetrafluoroethylene modification, in particular to a hydrophilic modification method and application of expanded polytetrafluoroethylene. The invention provides a hydrophilic modification method of expanded polytetrafluoroethylene, which comprises the following steps: S1, soaking expanded polytetrafluoroethylene in a photoinitiator solution to obtain soaked expanded polytetrafluoroethylene; s2, coating the surface of the soaked expanded polytetrafluoroethylene with a surfactant solution to obtain coated expanded polytetrafluoroethylene; and S3, carrying out ultraviolet irradiation on the coated expanded polytetrafluoroethylene to obtain the hydrophilic modified expanded polytetrafluoroethylene. According to the hydrophilic modification method of the expanded polytetrafluoroethylene, plasma pretreatment or treatment in a specific atmosphere environment is not needed, the steps are simple, conditions are easy to realize, a few reagents are needed, the three-dimensional structure of the expanded polytetrafluoroethylene cannot be damaged, the water contact angle is obviously reduced, the surface energy is increased, and the adhesive property is improved.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene modification, in particular to a hydrophilic modification method and application of expanded polytetrafluoroethylene. Background Art

[0002] Expanded polytetrafluoroethylene membrane has stable chemical properties, excellent corrosion resistance and environmental resistance, and is widely used in petrochemical, aerospace, electronics and other fields. However, these excellent properties also lead to poor wettability and adhesion. Strong hydrophobicity and non-polarity limit its application in surface areas. For this reason, a large number of methods for hydrophilic modification of expanded polytetrafluoroethylene membranes have been developed to increase surface energy and thus improve adhesion.

[0003] Commonly used hydrophilic modification methods, such as plasma treatment, have poor timeliness and low practicality; high-energy radiation grafting modification can easily change the membrane structure and the radiation is harmful to the human body; wet chemical methods are highly toxic and cause serious environmental pollution; atomic deposition or in-situ polymerization can easily discolor the membrane surface. However, UV grafting modification has strong operability, high grafting efficiency, fast reaction speed, and is easy to operate continuously; the reaction is carried out on the membrane surface or sub-surface, and it is easy to control the thickness and reaction depth of the grafted layer, and the performance of the matrix body is not changed. In addition, the equipment required for UV grafting is small and low in cost, which is convenient for large-scale industrial application. The UV grafting method is a free radical polymerization reaction. During the modification, free radicals are generated on the membrane surface through ultraviolet light irradiation, which triggers a free radical polymerization reaction. The reaction is easy to control, the cost is low, and the product is pure, which has attracted more and more attention.

[0004] At present, the UV grafting modification of expanded polytetrafluoroethylene membrane includes the following methods:

[0005] By placing the expanded polytetrafluoroethylene film in a UV-ozone treatment device, without the need for a vacuum environment, the hydrophilic expanded polytetrafluoroethylene film can be obtained by adjusting the UV lamp power, irradiation treatment time, test distance, and controlling the oxygen concentration, thereby improving the surface energy of the expanded polytetrafluoroethylene film. However, this method requires multiple treatments with different UV-irradiation devices, and the oxygen concentration must be controlled to achieve modification, which places strict requirements on the treatment conditions.

[0006] First, the membrane is pretreated by suction grafting with acetone, and the grafted modified membrane is immersed in the grafting modification liquid in the light chamber in an inert gas environment, and then watered by the water spraying device in the chamber and enters the ultraviolet irradiation chamber. The hydrochloric acid solution of the rare earth metal in the modification liquid is used to convert the photo-oxidation and strong oxidization of itself under light to generate free radicals. After ultraviolet light irradiation for a period of time, the expanded polytetrafluoroethylene hydrophilic modified membrane is obtained. However, this method requires a specific gas atmosphere, introduces rare earth metal elements, has high equipment requirements, and has harsh experimental conditions.

[0007] In view of this, this invention is proposed. Summary of the invention

[0008] The first object of the present invention is to provide a method for hydrophilic modification of expanded polytetrafluoroethylene, which has simple steps, does not destroy the three-dimensional structure of expanded polytetrafluoroethylene, significantly reduces the surface water contact angle, increases the surface energy, and improves the bonding performance.

[0009] The second object of the present invention is to provide the application of the hydrophilic modification method of expanded polytetrafluoroethylene as described above in improving the adhesiveness of expanded polytetrafluoroethylene, thereby solving the problem that expanded polytetrafluoroethylene is difficult to bond and composite with other materials.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] The present invention provides a method for hydrophilic modification of expanded polytetrafluoroethylene, comprising the following steps:

[0012] S1, soaking expanded polytetrafluoroethylene in a photoinitiator solution to obtain soaked expanded polytetrafluoroethylene;

[0013] S2, coating the surface of the soaked expanded polytetrafluoroethylene with a surfactant solution to obtain a coated expanded polytetrafluoroethylene;

[0014] S3, irradiating the coated expanded polytetrafluoroethylene with ultraviolet light to obtain hydrophilically modified expanded polytetrafluoroethylene.

[0015] Furthermore, step S1 includes at least one of the following features (1) to (3);

[0016] (1) The photoinitiator solution comprises a photoinitiator and an organic solvent;

[0017] (2) the photoinitiator comprises at least one of α-ketoglutaric acid, α,α-diethoxyacetophenone, α-hydroxyalkylphenone and α-aminoalkylphenone;

[0018] (3) The organic solvent includes at least one of ethanol, acetone and N,N-dimethylformamide.

[0019] Furthermore, in step S1, the content of the photoinitiator in the photoinitiator solution is 0.5 wt% to 5 wt%.

[0020] Furthermore, in step S1, the soaking time is 1 to 6 hours.

[0021] Further, step S2 includes at least one of the following features (1) to (4);

[0022] (1) The surfactant solution comprises a surfactant and water;

[0023] (2) The surfactant includes a sulfonate anionic surfactant and / or a sulfate anionic surfactant;

[0024] (3) The sulfonate anionic surfactant includes sodium alkylbenzene sulfonate;

[0025] (4) The sulfate anionic surfactant includes sodium dodecyl sulfate and / or sodium lauryl sulfate.

[0026] Furthermore, in step S2, the content of the surfactant in the surfactant solution is 2wt% to 7wt%.

[0027] Further, in step S2, the coating includes spraying.

[0028] Furthermore, in step S2, the spraying time is 10 to 1200 seconds.

[0029] Further, step S3 includes at least one of the following features (1) to (4);

[0030] (1) The power of the ultraviolet light irradiation is 10 to 300 W;

[0031] (2) The ultraviolet light wavelength of the ultraviolet light irradiation is 180 to 400 nm;

[0032] (3) The distance of the ultraviolet light irradiation is 5 to 15 cm;

[0033] (4) The ultraviolet light irradiation time is 30 to 900 seconds.

[0034] The present invention also provides application of the hydrophilic modification method of expanded polytetrafluoroethylene in improving the adhesiveness of expanded polytetrafluoroethylene.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The hydrophilic modification method of expanded polytetrafluoroethylene provided by the present invention can successfully realize the hydrophilic modification of expanded polytetrafluoroethylene by loading an initiator in the pore structure of expanded polytetrafluoroethylene, spraying a specific surfactant, and initiating a free radical reaction under ultraviolet light; the method does not require plasma pretreatment or treatment under a specific atmosphere environment, has simple steps, is easy to achieve under conditions, reduces energy consumption and equipment costs, requires less reagents, and the hydrophilic modification occurs on the surface of the expanded polytetrafluoroethylene without destroying the three-dimensional structure of the expanded polytetrafluoroethylene; the water contact angle of the surface of the hydrophilically modified expanded polytetrafluoroethylene is significantly reduced, the surface energy is increased, the bonding performance is excellent, and the bonding effect with other materials such as adhesives is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a schematic diagram of testing the peeling force of the expanded polytetrafluoroethylene film of the present invention.

[0039] Figure 2 The SEM images are of the unmodified expanded polytetrafluoroethylene membrane of the present invention and the hydrophilically modified expanded polytetrafluoroethylene membrane of Example 2. DETAILED DESCRIPTION

[0040] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0041] The following is a detailed description of a hydrophilic modification method and application of expanded polytetrafluoroethylene according to an embodiment of the present invention.

[0042] In some embodiments of the present invention, a method for hydrophilic modification of expanded polytetrafluoroethylene is provided, comprising the following steps:

[0043] S1, soaking expanded polytetrafluoroethylene in a photoinitiator solution to obtain soaked expanded polytetrafluoroethylene;

[0044] S2, coating the surface of the soaked expanded polytetrafluoroethylene with a surfactant solution to obtain coated expanded polytetrafluoroethylene;

[0045] S3, irradiating the coated expanded polytetrafluoroethylene with ultraviolet light to obtain hydrophilically modified expanded polytetrafluoroethylene.

[0046] Expanded polytetrafluoroethylene has low surface energy, high hydrophobicity and stable chemical properties. It is widely used as a sealing material in various fields. Common expanded polytetrafluoroethylene sealing materials include gaskets, sealing strips, O-rings, etc., with many types and a wide range of applications. However, expanded polytetrafluoroethylene has poor bonding properties and is difficult to bond and compound with other materials, which greatly limits its application areas.

[0047] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention comprises the following steps: firstly, the polytetrafluoroethylene is completely immersed in a photoinitiator solution, and the photoinitiator is loaded on the surface and pores of the expanded polytetrafluoroethylene; then, the surface of the expanded polytetrafluoroethylene after the immersion is coated with a surfactant solution; under the action of ultraviolet light, the photoinitiator absorbs light energy and transitions from a ground state to an excited state or even a triplet state, generates free radicals, and initiates a free radical reaction, so that the free radicals are cross-linked with ionic groups of the surfactant coated on the surface, the molecular chain length of the surface of the expanded polytetrafluoroethylene is increased, and the hydrophilic groups are attached to the surface of the expanded polytetrafluoroethylene, so that the surface of the expanded polytetrafluoroethylene has hydrophilicity, and the hydrophilic modification occurs on the surface of the expanded polytetrafluoroethylene, and the three-dimensional structure of the expanded polytetrafluoroethylene is not damaged.

[0048] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention increases the surface hydrophilicity of expanded polytetrafluoroethylene, significantly reduces the surface water contact angle, increases the surface energy, and thus improves the adhesion of expanded polytetrafluoroethylene.

[0049] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention occurs on the surface of the expanded polytetrafluoroethylene and does not change the three-dimensional structure of the expanded polytetrafluoroethylene. The process is simple and easy to expand, providing a new idea for the industrial application of hydrophilic modification of expanded polytetrafluoroethylene.

[0050] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention is simple, the experimental conditions are easy to achieve, it can be completed at room temperature and atmospheric environment, it is easy to realize industrialization, the types of reagents used are small, the concentration is low, and the pressure of reagent treatment on the environment is reduced.

[0051] In the prior art, when the expanded polytetrafluoroethylene is subjected to ultraviolet light treatment, the direct ultraviolet light treatment has a poor effect, and the polytetrafluoroethylene needs to be pre-treated with plasma, corona, etc. to generate free radicals on its surface before ultraviolet grafting. However, the plasma and corona treatment space is limited and the pretreatment cost is increased. The hydrophilic modification method of the expanded polytetrafluoroethylene of the present invention does not require the pretreatment of the polytetrafluoroethylene with an instrument.

[0052] In the prior art, when the expanded polytetrafluoroethylene is directly subjected to ultraviolet light treatment, it is generally necessary to carry out the treatment in an inert atmosphere or an ozone environment, which has high requirements on the environment. In the hydrophilic modification method of the expanded polytetrafluoroethylene of the present invention, no specific atmosphere is required, and the ultraviolet light irradiation modification treatment can be directly carried out in the atmospheric environment.

[0053] In the prior art, a strongly oxidizing ion solution such as a trivalent cerium ion, a tetravalent cerium ion acid solution, etc. is usually added to the modified liquid as a catalyst, and the treatment cost of the waste liquid containing these ions is relatively high; the hydrophilic modification method of expanded polytetrafluoroethylene of the present invention requires fewer types of reagents, and does not need to add a strongly oxidizing ion solution. The waste liquid after hydrophilic modification only needs to be treated according to conventional waste liquid treatment, and the solution can be recycled, and the waste liquid treatment pressure is low.

[0054] In some embodiments of the present invention, in step S1, the expanded polytetrafluoroethylene is an expanded polytetrafluoroethylene membrane; preferably, the thickness of the expanded polytetrafluoroethylene membrane is 0.3 to 2.5 mm; preferably, the expanded polytetrafluoroethylene membrane includes but is not limited to at least one of an expanded polytetrafluoroethylene thin film, an expanded polytetrafluoroethylene flat membrane and an expanded polytetrafluoroethylene hollow fiber membrane.

[0055] The present invention does not impose strict restrictions on the expanded polytetrafluoroethylene membrane, and any conventional expanded polytetrafluoroethylene membrane may be used.

[0056] In some embodiments of the present invention, in step S1, before soaking, the process further includes: washing and drying the expanded polytetrafluoroethylene in sequence.

[0057] In some embodiments of the present invention, in step S1, the cleaning agent includes but is not limited to ethanol and / or acetone.

[0058] In some embodiments of the present invention, in step S1, the drying temperature is 25-50°C.

[0059] In some embodiments of the present invention, in step S1, the photoinitiator solution includes a photoinitiator and an organic solvent.

[0060] In some embodiments of the present invention, in step S1, the photoinitiator in the photoinitiator solution includes at least one of α-ketoglutaric acid, α,α-diethoxyacetophenone, α-hydroxyalkylphenone and α-aminoalkylphenone.

[0061] In some embodiments of the present invention, in step S1, the organic solvent in the photoinitiator solution includes at least one of ethanol, acetone and N,N-dimethylformamide.

[0062] The present invention dissolves the photoinitiator in an organic solvent, and the organic solvent can completely soak the expanded polytetrafluoroethylene. Through the action of the organic solvent, the photoinitiator can be fully loaded on the surface and pores of the expanded polytetrafluoroethylene after soaking for a certain period of time.

[0063] In some embodiments of the present invention, in step S1, the content of photoinitiator in the photoinitiator solution is 0.5wt% to 5wt%; typically but not limitatively, for example, in step S1, the content of photoinitiator in the photoinitiator solution can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or a range of any two thereof.

[0064] In some embodiments of the present invention, in step S1, the soaking time is 1 to 6 hours; typically but not limitatively, for example, in step S1, the soaking time can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours or a range of any two thereof.

[0065] In some embodiments of the present invention, in step S1, after immersion, the sample is taken out and sequentially cleaned and dried; preferably, the cleaning agent comprises ethanol and / or acetone; and the drying temperature is 25-50°C.

[0066] In some embodiments of the present invention, in step S2, the surfactant solution includes a surfactant and water.

[0067] In some embodiments of the present invention, in step S2, the surfactant in the surfactant solution includes a sulfonate anionic surfactant and / or a sulfate anionic surfactant.

[0068] In some embodiments of the present invention, in step S2, the sulfonate anionic surfactant includes sodium alkylbenzene sulfonate; preferably, the sodium alkylbenzene sulfonate includes sodium dodecylbenzene sulfonate.

[0069] In some embodiments of the present invention, in step S2, the sulfate anionic surfactant includes sodium dodecyl sulfate and / or sodium lauryl sulfate.

[0070] The surfactant of the present invention adopts water-soluble sodium alkylbenzene sulfonate and / or water-soluble fatty alcohol sulfate; sulfonate / sulfate ions are typical hydrophilic ions with good water solubility, low cost and easy to obtain.

[0071] In some embodiments of the present invention, in step S2, the content of the surfactant in the surfactant solution is 2wt% to 7wt%; typically but not limitatively, for example, in step S2, the content of the surfactant in the surfactant solution can be 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt% or a range of any two thereof.

[0072] In some embodiments of the present invention, in step S2, coating includes at least one of spray coating, spin coating and scraping coating; preferably, coating includes spray coating.

[0073] In some embodiments of the present invention, in step S2, the spraying time is 10 to 1200 s; typically but not limitatively, for example, in step S2, the spraying time can be 10 s, 20 s, 30 s, 50 s, 80 s, 100 s, 150 s, 200 s, 250 s, 300 s, 350 s, 400 s, 450 s, 500 s, 550 s, 600 s, 700 s, 800 s, 900 s, 1000 s, 1100 s, 1200 s or a range consisting of any two of them.

[0074] The present invention sprays the surfactant aqueous solution on the surface of the expanded polytetrafluoroethylene film. Since the surfactant aqueous solution will not penetrate downward within a certain period of time, it can ensure that the surfactant and the initiator react on the surface of the expanded polytetrafluoroethylene film.

[0075] In some embodiments of the present invention, in step S2, a surfactant solution is coated on one side of the surface of the soaked expanded polytetrafluoroethylene membrane.

[0076] In some embodiments of the present invention, in step S3, a UV lamp is used to irradiate the surface of the expanded polytetrafluoroethylene coated with the surfactant solution with UV light.

[0077] In some embodiments of the present invention, in step S3, the power of ultraviolet light irradiation is 10 to 300 W; typically but not limitatively, for example, in step S3, the power of ultraviolet light irradiation can be 10 W, 20 W, 40 W, 60 W, 80 W, 100 W, 120 W, 140 W, 160 W, 180 W, 200 W, 220 W, 240 W, 260 W, 280 W, 300 W or a range of any two thereof.

[0078] In some embodiments of the present invention, in step S3, the wavelength of ultraviolet light for ultraviolet light irradiation is 180-400nm; typically but not limitatively, for example, in step S3, the wavelength of ultraviolet light for ultraviolet light irradiation can be 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, 400nm or a range of any two thereof.

[0079] In some embodiments of the present invention, in step S3, the distance of ultraviolet light irradiation is 5 to 15 cm; typically but not limiting, for example, in step S3, the distance of ultraviolet light irradiation can be 5 cm, 8 cm, 10 cm, 12 cm, 14 cm, 15 cm or a range of any two thereof. The distance of ultraviolet light irradiation is the vertical distance between the ultraviolet light source and the surface of expanded polytetrafluoroethylene.

[0080] In some embodiments of the present invention, in step S3, the time of ultraviolet light irradiation is 30 to 900 s; typically but not limitatively, for example, in step S3, the time of ultraviolet light irradiation can be 30 s, 100 s, 200 s, 300 s, 400 s, 500 s, 600 s, 700 s, 800 s, 900 s or a range value composed of any two of them.

[0081] In some embodiments of the present invention, in step S3, ultraviolet light irradiation is performed in an atmospheric environment.

[0082] The present invention adopts the above-mentioned ultraviolet light irradiation parameters and controls the irradiation time, thereby further ensuring that the hydrophilic modification occurs on the surface of the expanded polytetrafluoroethylene.

[0083] In some embodiments of the present invention, in step S3, after ultraviolet light irradiation, cleaning and drying are performed in sequence; preferably, the cleaning agent includes ethanol and / or acetone; and the drying temperature is 25-50°C.

[0084] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention requires fewer types of reagents, has low concentration, is simple to operate, and has easy-to-satisfy conditions; the surfactant solution and the photoinitiator solution still have hydrophilic modification effects after being placed for 7 days, indicating that the modified liquid can be recycled, reducing environmental pressure and facilitating the realization of industrialization.

[0085] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention utilizes ultraviolet light to initiate free radical reaction for hydrophilic modification. By controlling the concentration of a photoinitiator solution, the immersion time, the concentration of a surfactant solution, the spraying time, the ultraviolet light irradiation conditions, etc., one side of the expanded polytetrafluoroethylene film can be hydrophilically modified without changing the original hydrophobic and antifouling properties of the other side that is not coated. The hydrophilic modification only occurs on the surface of the expanded polytetrafluoroethylene film without changing the three-dimensional structure of the expanded polytetrafluoroethylene film. The expanded polytetrafluoroethylene film will not swell or shrink.

[0086] Since the photoinitiator is loaded on the whole membrane, on this basis, by increasing the concentration of the surfactant solution and the UV irradiation time, the free radical reaction generated by the surfactant and the photoinitiator tends more and more to the inside of the membrane or even the other side of the membrane, and the two sides of the expanded polytetrafluoroethylene membrane can also be hydrophilically modified to lose its hydrophobic properties and be used as a filtration membrane; by controlling the parameters of the hydrophilic modification method of expanded polytetrafluoroethylene, the needs of different applications can be met, and the expanded polytetrafluoroethylene can be modified on one side or both sides according to the needs.

[0087] In the hydrophilic modification method of expanded polytetrafluoroethylene of the present invention, when the immersion time of the initiator solution is 1 to 6 hours, the concentration of the surfactant solution is 2wt% to 7wt%, and the illumination time is 30 to 900 seconds, the three-dimensional structure of the expanded polytetrafluoroethylene film will not be changed, and the expanded polytetrafluoroethylene film will not swell, shrink, or the like.

[0088] When the initiator immersion time is longer than 6 h, the surfactant concentration is higher than 7 wt %, and the illumination time is longer than 20 min, the surface of the expanded polytetrafluoroethylene membrane begins to be penetrated by the solution, and becomes transparent after being penetrated by the solution, losing its hydrophobic properties.

[0089] In some specific embodiments of the present invention, the hydrophilic modification method of expanded polytetrafluoroethylene membrane comprises the following steps:

[0090] S1, soaking the expanded polytetrafluoroethylene film in a photoinitiator solution to obtain an expanded polytetrafluoroethylene film after soaking; wherein the content of the photoinitiator in the photoinitiator solution is 0.5wt% to 5wt%, and the soaking time is 1 to 6h;

[0091] S2, spraying a surfactant solution on one side of the surface of the soaked expanded polytetrafluoroethylene membrane to obtain a sprayed expanded polytetrafluoroethylene membrane; wherein the content of the surfactant in the surfactant solution is 2wt% to 7wt%, and the spraying time is 10 to 1200s;

[0092] S3. The coated expanded polytetrafluoroethylene membrane is irradiated with ultraviolet light to obtain a hydrophilically modified expanded polytetrafluoroethylene membrane; wherein the parameters of the ultraviolet light irradiation are as follows: power of 10 to 300 W, ultraviolet light wavelength of 180 to 400 nm, distance of 5 to 15 cm, and time of 30 to 900 s.

[0093] The hydrophilic modification method of the expanded polytetrafluoroethylene membrane of the present invention adopts the above parameter range to perform hydrophilic modification on one side of the expanded polytetrafluoroethylene membrane without changing the original performance of the other uncoated side. The hydrophilic modification only occurs on the surface of the expanded polytetrafluoroethylene membrane without changing the three-dimensional structure of the expanded polytetrafluoroethylene membrane.

[0094] In some embodiments of the present invention, in step S3, the water contact angle of the hydrophilically modified expanded polytetrafluoroethylene is 40° to 90°.

[0095] In some embodiments of the present invention, in step S3, the water contact angle of the hydrophilically modified expanded polytetrafluoroethylene changes by 5° to 10° before and after being placed for 20 days.

[0096] In some embodiments of the present invention, in step S3, the peel force of the hydrophilically modified expanded polytetrafluoroethylene is greater than 0.2 kN / m; preferably, in step S3, the peel force of the hydrophilically modified expanded polytetrafluoroethylene is 0.2-1.5 kN / m, and the peel force test standard is GB / T2792-2014.

[0097] The invention also provides application of the hydrophilic modification method of expanded polytetrafluoroethylene in improving the adhesiveness of the expanded polytetrafluoroethylene.

[0098] After the expanded polytetrafluoroethylene is modified by the hydrophilic modification method of the present invention, the water contact angle on the surface of the expanded polytetrafluoroethylene is significantly reduced, the surface energy is increased, and the expanded polytetrafluoroethylene is easy to bond, which significantly improves the adhesion of the expanded polytetrafluoroethylene. In addition, the hydrophilic modification has a long time effect and can fully meet the time requirement of subsequent bonding.

[0099] The hydrophilic modification method of expanded polytetrafluoroethylene of the present invention is used to improve the adhesiveness of expanded polytetrafluoroethylene, thereby solving the problem that expanded polytetrafluoroethylene is difficult to bond and compound with other materials. The expanded polytetrafluoroethylene after hydrophilic modification has excellent adhesiveness, good bonding effect with adhesive, and can be used for a long time without falling off.

[0100] The features and properties of the present invention are further described in detail below in conjunction with examples and comparative examples.

[0101] Examples 1 to 10

[0102] The hydrophilic modification method of expanded polytetrafluoroethylene provided in Examples 1 to 10 comprises the following steps:

[0103] S1. After washing the expanded polytetrafluoroethylene membrane with ethanol, drying it at 45° C., immersing it in a photoinitiator solution (the photoinitiator is α-ketoglutaric acid, and the organic solvent is ethanol), taking it out, washing it with ethanol, and drying it at 45° C. to obtain the immersed expanded polytetrafluoroethylene membrane;

[0104] S2, spraying an aqueous solution of a surfactant (sodium dodecylbenzene sulfonate) on one side of the surface of the soaked expanded polytetrafluoroethylene membrane to obtain a sprayed expanded polytetrafluoroethylene membrane;

[0105] S3. Using an ultraviolet lamp to irradiate the surface of the sprayed expanded polytetrafluoroethylene film (the surface on the side sprayed with the aqueous solution of the surfactant) with ultraviolet light to obtain a single-sided hydrophilic-modified expanded polytetrafluoroethylene film.

[0106] In Examples 1 to 10, the parameters of each step are shown in Table 1.

[0107] Table 1

[0108]

[0109]

[0110] Embodiment 11

[0111] The hydrophilic modification method of expanded polytetrafluoroethylene provided in this embodiment refers to Example 4, except that the photoinitiator is α-hydroxyalkyl phenone and the surfactant is sodium dodecyl sulfonate.

[0112] Example 12

[0113] The hydrophilic modification method of expanded polytetrafluoroethylene provided in this embodiment refers to Example 4, except that the photoinitiator is α,α-diethoxyacetophenone and the surfactant is sodium lauryl sulfate.

[0114] Example 13

[0115] The hydrophilic modification method of expanded polytetrafluoroethylene provided in this embodiment comprises the following steps:

[0116] S1. After washing the expanded polytetrafluoroethylene membrane with ethanol, drying it at 45° C., immersing it in a photoinitiator solution with a concentration of 1wt% to 5wt% (the photoinitiator is α-ketoglutaric acid, and the organic solvent is ethanol) for at least 12 hours, taking it out, washing it with ethanol, and drying it at 45° C. to obtain the immersed expanded polytetrafluoroethylene membrane;

[0117] S2, spraying an aqueous solution of a surfactant (sodium dodecylbenzene sulfonate) with a concentration greater than 7 wt % on one side of the soaked expanded polytetrafluoroethylene membrane for a spraying time greater than 5 min to obtain a sprayed expanded polytetrafluoroethylene membrane;

[0118] S3. Use an ultraviolet lamp to irradiate the surface of the sprayed expanded polytetrafluoroethylene membrane (the side surface sprayed with the aqueous solution of the surfactant), and the ultraviolet irradiation parameters are: power of 100-300W, wavelength of 390nm, irradiation distance of less than 10cm, irradiation time of more than 20min, to obtain a double-sided hydrophilic modified expanded polytetrafluoroethylene membrane.

[0119] Comparative Examples 1 to 6

[0120] The hydrophilic modification method of expanded polytetrafluoroethylene provided in Comparative Examples 1 to 6 comprises the following steps:

[0121] S1. After washing the expanded polytetrafluoroethylene membrane with ethanol, drying it at 45° C., immersing it in a photoinitiator solution (the photoinitiator is α-ketoglutaric acid, and the organic solvent is ethanol), taking it out, washing it with ethanol, and drying it at 45° C. to obtain the immersed expanded polytetrafluoroethylene membrane;

[0122] S2, spraying an aqueous solution of a surfactant (sodium dodecylbenzene sulfonate) on one side of the surface of the soaked expanded polytetrafluoroethylene membrane to obtain a sprayed expanded polytetrafluoroethylene membrane;

[0123] S3. Using an ultraviolet lamp to irradiate the surface of the sprayed expanded polytetrafluoroethylene membrane (the surface on the side sprayed with the aqueous solution of the surfactant) with ultraviolet light to obtain a hydrophilically modified expanded polytetrafluoroethylene membrane.

[0124] In Comparative Examples 1 to 6, the parameters of each step are shown in Table 2.

[0125] Table 2

[0126]

[0127]

[0128] Comparative Example 7

[0129] The hydrophilic modification method of expanded polytetrafluoroethylene provided in this comparative example comprises the following steps:

[0130] S1. After washing the expanded polytetrafluoroethylene membrane with ethanol, drying it at 45° C., soaking it in a 0.05wt% α-ketoglutaric acid / ethanol solution for 1 hour and a 0.05wt% α-hydroxyalkyl phenone / ethanol solution for 1 hour, taking it out, washing it with ethanol, and drying it at 45° C. to obtain the soaked expanded polytetrafluoroethylene membrane;

[0131] S2, spraying a 2 wt % sodium dodecylbenzene sulfonate aqueous solution and a 2 wt % sodium lauryl sulfate aqueous solution on one side of the soaked expanded polytetrafluoroethylene membrane for 5 min and 5 min, respectively, to obtain a sprayed expanded polytetrafluoroethylene membrane;

[0132] S3. The surface of the sprayed expanded polytetrafluoroethylene membrane (the surface on which the aqueous solution of the surfactant is sprayed) is irradiated with ultraviolet light for 2 minutes with a power of 30 W, a wavelength of 254 nm, and an irradiation distance of 10 cm to obtain a hydrophilically modified expanded polytetrafluoroethylene membrane.

[0133] Test example

[0134] The properties of the hydrophilically modified expanded polytetrafluoroethylene membranes of Examples 1 to 4, the hydrophilically modified expanded polytetrafluoroethylene membrane of Comparative Example 7, and the unmodified expanded polytetrafluoroethylene membrane were tested, and the results are shown in Table 3.

[0135] The peeling force (180°) test diagram of each expanded polytetrafluoroethylene film is shown in FIG. Figure 1 As shown; the peel force test standard is GB / T2792-2014.

[0136] Table 3

[0137]

[0138]

[0139] It can be seen from Table 3 that the surface water contact angle of the expanded polytetrafluoroethylene membrane without hydrophilic modification is greater than 90°, which is in a hydrophobic state, has a low surface energy, is difficult to bond on the surface, and is easy to fall off after bonding, and the peeling force is less than 0.2 kN / m; the surface water contact angle of the expanded polytetrafluoroethylene membrane after hydrophilic modification is less than 90°, which is in a hydrophilic state. Compared with the hydrophobic state, the surface energy is increased and it is easier to bond. The tested peeling force after bonding is greater than 0.2 kN / m, which meets the use requirements; among them, the peeling forces of the hydrophilically modified expanded polytetrafluoroethylene membranes of Comparative Examples 1 to 7 are all less than 0.2 kN / m.

[0140] The unmodified expanded polytetrafluoroethylene membrane was tested by SEM, and the results are as follows: Figure 2 As shown in a, the hydrophilic modified expanded polytetrafluoroethylene membrane of Example 2 was subjected to SEM testing, and the results are as follows Figure 2 As shown in b.

[0141] from Figure 2 It can be seen that a is the unmodified membrane surface and b is the hydrophilic modified membrane surface. Both have a loose three-dimensional network structure. Compared with a, the surface of b is denser, which is due to the addition of hydrophilic substances on the surface after modification. Apart from this, there is no other obvious change, and it still has a loose three-dimensional network structure.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for hydrophilic modification of expanded polytetrafluoroethylene, characterized in that: The steps include: S1, soaking expanded polytetrafluoroethylene in a photoinitiator solution to obtain soaked expanded polytetrafluoroethylene; S2, coating the surface of the soaked expanded polytetrafluoroethylene with a surfactant solution to obtain a coated expanded polytetrafluoroethylene; S3, irradiating the coated expanded polytetrafluoroethylene with ultraviolet light to obtain hydrophilically modified expanded polytetrafluoroethylene.

2. The hydrophilic modification method of expanded polytetrafluoroethylene according to claim 1, characterized in that: In step S1, at least one of the following features (1) to (3) is included; (1) The photoinitiator solution comprises a photoinitiator and an organic solvent; (2) the photoinitiator comprises at least one of α-ketoglutaric acid, α,α-diethoxyacetophenone, α-hydroxyalkylphenone and α-aminoalkylphenone; (3) The organic solvent includes at least one of ethanol, acetone and N,N-dimethylformamide.

3. The hydrophilic modification method of expanded polytetrafluoroethylene according to claim 2, characterized in that: In step S1, the content of the photoinitiator in the photoinitiator solution is 0.5 wt% to 5 wt%.

4. The method for hydrophilic modification of expanded polytetrafluoroethylene according to claim 3, characterized in that: In step S1, the soaking time is 1 to 6 hours.

5. The method for hydrophilic modification of expanded polytetrafluoroethylene according to claim 4, characterized in that: In step S2, at least one of the following features (1) to (4) is included; (1) The surfactant solution comprises a surfactant and water; (2) The surfactant includes a sulfonate anionic surfactant and / or a sulfate anionic surfactant; (3) The sulfonate anionic surfactant includes sodium alkylbenzene sulfonate; (4) The sulfate anionic surfactant includes sodium dodecyl sulfate and / or sodium lauryl sulfate.

6. The method for hydrophilic modification of expanded polytetrafluoroethylene according to claim 5, characterized in that: In step S2, the content of the surfactant in the surfactant solution is 2 wt% to 7 wt%.

7. The method for hydrophilic modification of expanded polytetrafluoroethylene according to claim 6, characterized in that: In step S2, the coating includes spraying.

8. The method for hydrophilic modification of expanded polytetrafluoroethylene according to claim 7, characterized in that: In step S2, the spraying time is 10 to 1200 seconds.

9. The method for hydrophilic modification of expanded polytetrafluoroethylene according to claim 8, characterized in that: In step S3, at least one of the following features (1) to (4) is included; (1) The power of the ultraviolet light irradiation is 10 to 300 W; (2) The ultraviolet light wavelength of the ultraviolet light irradiation is 180 to 400 nm; (3) The distance of the ultraviolet light irradiation is 5 to 15 cm; (4) The ultraviolet light irradiation time is 30 to 900 seconds.

10. Use of the hydrophilic modification method of expanded polytetrafluoroethylene according to any one of claims 1 to 9 in improving the adhesiveness of expanded polytetrafluoroethylene.

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