Patent Application
20240425657
The present disclosure relates to the field of polymeric film material, in particular, a gas permeable polytetrafluoroethylene stretched film and a preparation method thereof.
A stretched film is a thermoplastic plastic film that stretches in vertical and horizontal stretching directions of the film during the production process while contracting by heat during the use process. At present, commonly used stretched films can be divided into a PVC film, a polyethylene film, a polycatum film, a polystyrene film, a polypropylene film, a nylon film, etc. The stretched films can be used to pack various products. According to different materials, the stretched films are used in different fields and are widely used in the fields of food, drinks, automobile supplies, daily chemicals, stationery, medicine, etc.
With the improvement demand of consumers for health, environmental protection, green and other aspects, the stretched film develops to be non-toxic, biodegradable, easy to recycle, and high recycling rate. The polyethylene film is commonly used as one of base materials for heat shrinkable film. The polyethylene film has good flexibility, impact resistance, tear resistance, breakage resistance, moisture resistance, and high shrinkage rate. The polyethylene film is widely used in the whole collection of packaging of products such as alcohol, cans, mineral water, a variety of beverages, and cloth. The pvc film, based on the characteristics of high transparency, good gloss, and high shrinkage and having the performance of rain proof, fire resistance, anti-static, and formability, is widely used in the building materials industry and packaging industry.
To be used in the protection of precision instruments such as circuits, and wires, a polytetrafluoroethylene stretched film has appeared on the market. The polytetrafluoroethylene stretched film, also called as Teflon film, is made of suspended polytetrafluoroethylene resin by molding, sintering, cooling into a work blank, and then by turning, calendering. The polytetrafluoroethylene stretched film has the advantages of the most significant anti-voltage strength and breakdown voltage, and is used as capacitor medium, wire insulation, electrical instrument insulation, sealing gasket and so on.
The polytetrafluoroethylene film is prepared in a bi-directional stretching method. The scanning electron microscope can observe that the film is made of criss-crossed fibers interconnected. Gaps between fiber filaments form micropores of the film. Many micropores are provided on the surface of the film, with about 9 billion micropores per square inch. The diameter of each micropore is mainly about 0.8˜1 μm. However, due to the high crystallinity of polytetrafluoroethylene, the size and shape of the pores generated during the stretching are uneven, and large-sized pores will appear. Moreover, due to the limitation of stretching strength, a larger stretching ratio cannot be used, and the final stretched pores are less, affecting the gas permeability and waterproof performance of the polytetrafluoroethylene stretched film. Therefore, the polytetrafluoroethylene stretched film cannot be used in the protection of precision instruments such as electronic products.
In view of the shortcomings in the prior art, the object of the present disclosure is to provide a polytetrafluoroethylene stretched film having high gas permeability and waterproofness and a preparation method thereof, enhancing the safety of the polytetrafluoroethylene stretched film so that the polytetrafluoroethylene stretched film can be applied to the protection of electronic products.
A gas permeable polytetrafluoroethylene stretched film is prepared by mixing power of a modified polytetrafluoroethylene resin and power of a modified fluoropolymer resin and stretching the resulting mixed product.
The modified polytetrafluoroethylene resin is copolymerised by a mixture of a tetrafluoroethylene monomer and a modified monomer.
The structure of the modified monomer is a compound shown in formula I:
where m: n=(1-2): 20, x denotes 4, 6, 8, 10.
The crystallinity in the system is greatly reduced through the multi-branched structure of the modified polytetrafluoroethylene polymer.
Further, the power of the modified fluoropolymer resin is a copolymer of propylene and tetrafluoroethylene.
The power of the modified fluoropolymer resin may be Asahi Glass AFLAS100 and Asahi Glass AFLAS150.
The addition of modified fluoropolymer powder increases the stretching strength of the polytetrafluoroethylene stretched film to a relatively large extent, and thus the final stretching film is stretched by a greater number of times.
Further, the preparation method of the modified monomer includes:
The reaction equation for the preparation of modified monomers is:
Further, the initiator in the step (1) is azobisisobutyronitrile or benzoyl peroxide.
Further, a preparation method of the power of the modified polytetrafluoroethylene resin comprises:
adding a dispersant, an emulsifier and deionized water into a high-pressure emulsification reactor, and evenly emulsifying at a stirring speed of 1000 to 2000 r/min;
Further, based on a total amount of feedstocks of the prepared power of the modified polytetrafluoroethylene resin as 100%, a mass percentage of each feedstock is as follows:
Further, in the step (1), the dispersant is ammonium perfluorooctanoate, and the emulsifier is perfluoropolyether.
Further, in the step (3), the initiator is selected from one of perfluorbutyryl peroxide or perfluorcaproyl peroxide.
A preparation method of the gas permeable polytetrafluoroethylene stretched film includes the following steps:
Further, a mass ratio of the power of the modified fluoropolymer resin and the power of the modified polytetrafluoroethylene resin is 1: (3-10).
The modified polytetrafluoroethylene polymer provided by the present disclosure has a multi-branched structure, greatly reducing the crystallinity in the system. Therefore, very uniform pores are formed when stretched, thereby having better gas permeability. Meanwhile, due to the uniform pores, no occasional large-sized pore exists, improving the waterproofing effect.
In the present disclosure, the power of the modified polytetrafluoroethylene resin and the power of the modified fluoropolymer resin are mixed so that the stretching strength of the gas permeable polytetrafluoroethylene stretched film can be greatly improved, thereby allowing the final stretched film to be stretched more times, and a higher number of pores per unit mass to be generated, improving the gas permeability.
The present disclosure will be described below in connection with specific embodiments. It is to be noted that the embodiments are examples of the present disclosure, are merely used for illustrating the present disclosure, and are not intended to limit the present disclosure. Other combinations and variations may be made without departing from the spirit or scope of the subject matter of the present disclosure.
The perfluoroalkylethyl acrylate in the present disclosure is purchased from Jinan Guochen Taifu Chemical Co. Ltd. The power of the modified fluoropolymer resin is Asahi Glass AFLAS100 and Asahi Glass AFLAS150 from Asahi Glass Co. Ltd. The polytetrafluoroethylene film and the F46 film are purchased through Taizhou Tongjida New Material Co. Ltd. The rest of reagents and equipment are conventional reagents and equipment in the art.
In parts by weight, 30 parts of perfluoroheptane is added to the reactor as a solvent, the perfluoroheptane was heated to 65° C., then 60 parts of mixture of hydroxyethyl acrylate and 5 parts of perfluoroalkylethyl acrylate were evenly mixed with 0.5 part of azobisisobutyronitrile, the hydroxyethyl acrylate, the perfluoroalkylethyl acrylate and the azobisisobutyronitrile were added dropwise into the reactor at a constant speed, and after the dropwise addition was completed, the reactor was kept warm for 3 hours.
5 parts of isocyanate ethylacrylate was added to the reactor, the temperature was heated to 70° C., the solvent was continuously stirred until content of system-NCO groups content is less than 0.05%.
The reaction system was cooled down and the solvent of perfluoroheptane was removed to obtain the modified monomer-1.
The preparation of modified monomer-2 is basically the same as the preparation of modified monomer-1. The difference of the preparation of modified monomer-2 from the preparation of modified monomer-1 is that the perfluoroalkylethyl acrylate is changed to perfluorohexylethyl acrylate.
The preparation of modified monomer-3 is basically the same as the preparation of modified monomer-1. The difference of the preparation of modified monomer-3 from the preparation of modified monomer-1 is that the perfluoroalkylethyl acrylate is changed to perfluorooctylethyl acrylate.
The preparation of modified monomer-4 is basically the same as the preparation of modified monomer-1. The difference of the preparation of modified monomer-4 from the preparation of modified monomer-1 is that the perfluoroalkylethyl acrylate is changed to perfluorodecylethyl acrylate.
Ammonium perfluorooctanoate, perfluoropolyether and deionized water were added into a high-pressure emulsification reactor, and the ammonium perfluorooctanoate, the perfluoropolyether and the deionized water were evenly emulsified at a stirring speed of 1500 r/min.
The stirring speed was decreased to 300 r/min, and then the temperature in the reactor was increased to 50° C. and the pressure in the reactor was increased to 3.5 MPa.
The tetrafluoroethylene monomer and the mixture of the modified monomer-1 and the perfluorbutyryl peroxide were poured into the high-pressure emulsification reactor through a 2-way high-pressure pump, the tetrafluoroethylene monomer went through one way, and the modified monomer-1 and the initiator went through one way. After all feedstocks poured, the reactor was warmed up to 70° C., cured for 3 hours to prepare the power of modified polytetrafluoroethylene resin.
Based on the total amount of feedstocks as 100%, the mass percentage of each feedstock is as follows:
The preparation of power of modified polytetrafluoroethylene resin-2 is basically the same as the preparation of power of modified polytetrafluoroethylene resin-1. The difference of the preparation of power of modified polytetrafluoroethylene resin-2 from the preparation of power of modified polytetrafluoroethylene resin-1 is that the modified monomer-1 is changed to modified monomer-2.
The preparation of power of modified polytetrafluoroethylene resin-3 is basically the same as the preparation of power of modified polytetrafluoroethylene resin-1. The difference of the preparation of power of modified polytetrafluoroethylene resin-3 from the preparation of power of modified polytetrafluoroethylene resin-1 is that the modified monomer-1 is changed to modified monomer-3.
The preparation of power of modified polytetrafluoroethylene resin-4 is basically the same as the preparation of power of modified polytetrafluoroethylene resin-1, the difference of the preparation of power of modified polytetrafluoroethylene resin-4 from the preparation of power of modified polytetrafluoroethylene resin-1 is that the modified monomer-1 is changed to modified monomer-4.
10 parts of Asahi Glass AFLAS100 and 100 parts of the power of modified polytetrafluoroethylene resin-1 were evenly mixed, the mixed power was pressed into round strips at 50° C., then the round strips were calendered at 60° C. to form a base film, where the thickness of the base film is 90 mm.
The base film in the step (1) was degreased at 250° C., after the degreasion, the base film was stretched longitudinally by a factor of 7, and then the base film was stretched horizontally by a factor of 4.
(3) The stretched film in the step (2) was sintered at 350° C. for 1 minute to obtain the gas permeable polytetrafluoroethylene stretched film.
Embodiment two is basically the same as the embodiment two. The difference of the embodiment two from the embodiment one is that 10 parts of Asahi Glass AFLAS100 are changed to 20 parts of Asahi Glass AFLAS100 in the step (1), and the powder of modified polytetrafluoroethylene resin-1 is changed to the power of modified polytetrafluoroethylene resin-2.
Embodiment three is basically the same as the embodiment one. The difference of the embodiment three from the embodiment one is that 10 parts of Asahi Glass AFLAS100 are changed to 30 parts of Asahi Glass AFLAS100 in the step (1), and the powder of modified polytetrafluoroethylene resin-1 is changed to the power of modified polytetrafluoroethylene resin-3.
Embodiment four is basically the same as the embodiment one. The difference of the embodiment four from the embodiment one is that Asahi Glass AFLAS100 are changed to AFLAS150 in the step (1), and the powder of modified polytetrafluoroethylene resin-1 is changed to the power of modified polytetrafluoroethylene resin-4.
The comparative example one is basically the same as the embodiment one. The difference of the comparative example one from the embodiment one is that the power of modified fluoropolymer resin is changed in an equal amount of the power of modified polytetrafluoroethylene resin-1.
The base film was broken during the stretching process in the step (2).
Commercially available polytetrafluoroethylene film
Commercially available F46 film
Gas permeability and waterproofness tests were conducted after testing the size of the pores of the products in the embodiment 1 to 4 and comparative examples 2 and 3 in the following methods. The test results are shown in Table 1.
Gas permeability: the test method is GBT36138-2018 polytetrafluoroethylene flat microfiltration film for sterilization.
Waterproofness: the test method is GB/T 4745-2012 textile waterproofness performance testing and evaluation of spray method.
Pore diameter: the test method is based on HYT 039-1995 microporous filter film pore performance testing method.
It can be seen from the comparison of Embodiments one to four with Comparative Examples two and three, the gas permeable polytetrafluoroethylene stretched film provided by the present disclosure has smaller and more even pore space, better gas permeability and better waterproofness.
In Comparative Example one, the film was broken during the stretching so that the power of the modified fluoropolymer resin added in the present disclosure is able to improve the stretching strength to a relatively large extent, thereby allowing the final stretched film to be stretched more times.
The preceding embodiments aim to only illustrate the technical concepts and features of the present disclosure, and allow those skilled in the art to understand the contents of the present disclosure and to implement the present disclosure, and are not intend to limit the scope of the present disclosure. Any equivalent changes or modifications made in accordance with the spirit of the present disclosure shall be within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211247190.8 | Oct 2022 | CN | national |
This application is a continuation of International Patent Application No. PCT/CN2023/122387 with a filing date of Sep. 28, 2023, designating the United States, now pending, and further claims priority to Chinese Patent Application No. 202211247190.8 with a filing date of Oct. 12, 2022. The content of the aforementioned applications, including any intervening amendments thereto, is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2023/122387 | Sep 2023 | WO |
| Child | 18827030 | US |
