High-efficiency low-resistance high-uniformity PTFE (Polytetrafluoroethylene) film as well as preparation method and application thereof

Abstract

The invention discloses a high-efficiency, low-resistance and good-uniformity PTFE (Polytetrafluoroethylene) membrane as well as a preparation method and application thereof, and belongs to the field of PTFE membranes. The preparation method of the high-efficiency low-resistance high-uniformity PTFE film comprises the following steps: uniformly mixing PTFE resin and an extrusion aid, and standing in a drying room; then pre-pressing the mixture into a rod-shaped blank, and calendering to obtain a PTFE blank film; degreasing and longitudinally stretching the PTFE blank film to obtain a blank film sample material; in the longitudinal stretching process, the seven rollers are distributed in a staggered mode that four rollers are arranged on the upper portion and three rollers are arranged on the lower portion, and the temperatures and the rotating speeds of the four rollers on the upper portion are different from those of the three rollers on the lower portion; placing the blank film sample material in a drying room for standing, and then transversely stretching to obtain the PTFE film. Wherein the PTFE blank film is stretched at different multiplying powers by adopting an arc-shaped roller surface structure and an asymmetric temperature heating mode, so that the PTFE film with different surface micropore apertures can be obtained.

Description

Technical Field

[0001] The invention belongs to the field of PTFE membranes, and in particular relates to a PTFE membrane with high efficiency, low resistance and good uniformity, and a preparation method and application thereof. Background Art

[0002] The coated filter material in the bag dust removal system has an excellent capture effect on fine dust and is an effective means of controlling industrial flue gas pollution. At the same time, compared with ordinary filter materials, it has the advantages of higher filtration efficiency, easier cleaning, and longer cleaning cycle, and is favored by the majority of users.

[0003] The filtration method of the coated filter media is mainly surface filtration. Through the microporous screening effect of the PTFE film attached to the surface, it is difficult for dust to enter the interior of the filter media, avoiding the dust remaining inside the filter media due to the deep filtration method of traditional filter media, which is not completely removed and causes the overall operation resistance of the filter media to be relatively large.

[0004] The membrane filter material has many advantages, but because the PTFE film is thin and easy to be damaged, the filter material fails and the membrane surface cracks, so the mechanical properties of the membrane need to be improved. At the same time, the filtration resistance of the PTFE film itself will also affect the operation resistance of the entire filter bag and dust removal system, thereby increasing the user's operating costs.

[0005] Although some researchers have tried to solve the resistance of the filter material during operation by adjusting the structure and weight of the filter material, the filtration accuracy has not been improved and cannot meet the actual use requirements. Based on this, the present invention provides a PTFE film with high filtration efficiency and low resistance. Summary of the invention

[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a PTFE membrane with high efficiency, low resistance and good uniformity and a preparation method and application thereof, thereby solving the problems in the prior art.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for preparing a PTFE membrane comprises the following steps:

[0009] The PTFE resin and the extrusion aid are uniformly mixed and placed in a drying room for static standing; the mixed material is then pre-pressed into a rod-shaped blank, and then calendered to obtain a PTFE blank film;

[0010] The PTFE blank film is degreased and longitudinally stretched to obtain a blank film sample; during the longitudinal stretching process, seven rollers are staggered in a manner of four rollers on the top and three rollers on the bottom, and the temperatures and rotation speeds of the four rollers on the top and the three rollers on the bottom are different;

[0011] The green film sample is placed in a drying room to stand, and then stretched transversely to obtain a PTFE film.

[0012] Furthermore, the mass ratio of PTFE resin to extrusion aid is 100:28.

[0013] Furthermore, the temperature of the drying room where the mixed material is placed is 55-60° C., and the standing time is more than 24 hours.

[0014] Furthermore, the ratio of the rotation speeds of the upper four rollers to the lower three rollers is 1:(2-3); the temperature of the upper four rollers is 270-290°C, and the temperature of the lower three rollers is 190-210°C.

[0015] Furthermore, the degreasing temperature is 190°C.

[0016] Furthermore, the temperature of the drying room where the blank film sample is placed is 120° C., and the standing time is 2-4 hours.

[0017] Furthermore, the transverse stretching adopts a transverse stretching machine, the temperature of stretching zone 1 is 300-320°C, the temperature of stretching zone 2 is 310-330°C, the temperature of stretching zone 3 is 320-340°C, the temperature of sintering zone is 340-350°C; the stretching ratio is 20.

[0018] A PTFE membrane is prepared using the above preparation method.

[0019] A membrane-coated filter material comprises the above-mentioned PTFE membrane.

[0020] The above-mentioned PTFE membrane is used for preparing coated filter material.

[0021] Beneficial effects of the present invention:

[0022] 1. In the process of preparing the PTFE film, the present invention uses an arc roller surface structure and an asymmetric temperature heating method to stretch the PTFE blank film at different ratios, so that a PTFE membrane with different surface micropore diameters can be obtained, which can better filter dust of different particle sizes in industrial flue gas to achieve ultra-clean emissions.

[0023] 2. Use staggered stretching speeds to improve the overall uniformity of the PTFE blank membrane during the transverse stretching process; the staggered stretching process is arranged in the longitudinal stretching process. Stretching at different speeds during the longitudinal stretching process can obtain fiber nodes of different lengths. During the transverse stretching, the nodes are stretched open to obtain pore sizes of different sizes; and the fiber nodes of different lengths obtained by longitudinal stretching can effectively offset the problem of uneven stretching force during the transverse stretching process, and finally a microporous membrane with better appearance is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a cross-sectional arrangement diagram of the heating rollers in the longitudinal stretching process of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The following examples and comparative examples are used to introduce a method for preparing a PTFE membrane with high efficiency, low resistance and good uniformity. In the examples and comparative examples, the sources of the raw materials are as follows:

[0028] PTFE resin, manufacturer model is Daikin F104;

[0029] The extrusion aid was aviation kerosene, which was purchased from Jinan Xinke Chemical Co., Ltd.

[0030] Example 1

[0031] The preparation method of PTFE membrane comprises the following steps:

[0032] Step 1, preparation of PTFE blank membrane:

[0033] PTFE resin and extrusion aid are mixed evenly in a mixer at a mass ratio of 100:28, and then placed in a drying room at a temperature of 58°C for 24 hours; then the mixture is pre-pressed by a pre-pressing machine to obtain a rod-shaped blank, and then calendered by a calendering machine to obtain a blank film with a thickness of 270μm and a width of 13cm for standby use;

[0034] Step 2, degreasing and longitudinal stretching of PTFE blank film:

[0035] The PTFE blank film obtained in step 1 is degreased and longitudinally stretched in an oven to obtain a blank film sample; the degreasing temperature is 190°C; during the longitudinal stretching process, the seven rollers use different rotation speeds, and the roller surface temperatures are also different, the temperature of the upper four rollers is 270°C, the temperature of the lower three rollers is 190°C, and the rotation speeds of the seven rollers are different, V 上面四个 :V 下面三个 =1:2 (roller arrangement as Figure 1 The blank film feeding speed is 20m / min;

[0036] Step 3, lateral stretching:

[0037] The green film sample obtained in step 2 is placed in a drying room at a temperature of 120°C for 3 hours, and then is transversely stretched by a transverse stretching machine. The temperatures of stretching zones 1 to 3 are 300°C, 310°C, and 320°C, respectively. The temperature of the sintering zone is 340°C. The stretching ratio is 20, and a finished PTFE film is obtained.

[0038] Specific applications:

[0039] The PTFE membrane obtained in step 3 is laminated onto the desired filter material by hot pressing to obtain a membrane-coated filter material with high efficiency and low resistance.

[0040] Example 2

[0041] The preparation method of PTFE membrane comprises the following steps:

[0042] Step 1, preparation of PTFE blank membrane:

[0043] PTFE resin and extrusion aid are mixed evenly in a mixer at a mass ratio of 100:28, and then placed in a drying room at a temperature of 58°C for 24 hours; then the mixture is pre-pressed by a pre-pressing machine to obtain a rod-shaped blank, and then calendered by a calendering machine to obtain a blank film with a thickness of 270μm and a width of 13cm for standby use;

[0044] Step 2, degreasing and longitudinal stretching of PTFE blank film:

[0045] The PTFE blank film obtained in step 1 is degreased and longitudinally stretched in an oven to obtain a blank film sample; the degreasing temperature is 190°C; during the longitudinal stretching process, the seven rollers use different rotation speeds, and the roller surface temperatures are also different, the temperature of the upper four rollers is 280°C, the temperature of the lower three rollers is 200°C, and the rotation speeds of the seven rollers are different, V 上面四个 :V 下面三个 =1:2.5 (roller arrangement as Figure 1 The blank film feeding speed is 20m / min;

[0046] Step 3, lateral stretching:

[0047] The green film sample obtained in step 2 is placed in a drying room at a temperature of 120°C for 3 hours, and then is transversely stretched by a transverse stretching machine. The temperatures of stretching zones 1 to 3 are 310°C, 320°C and 330°C respectively, the temperature of the sintering zone is 345°C, and the stretching ratio is 20 to obtain a finished PTFE film.

[0048] Specific applications:

[0049] The PTFE membrane obtained in step 3 is laminated onto the desired filter material by hot pressing to obtain a membrane-coated filter material with high efficiency and low resistance.

[0050] Example 3

[0051] The preparation method of PTFE membrane comprises the following steps:

[0052] Step 1, preparation of PTFE blank membrane:

[0053] PTFE resin and extrusion aid are mixed evenly in a mixer at a mass ratio of 100:28, and then placed in a drying room at a temperature of 58°C for 24 hours; then the mixture is pre-pressed by a pre-pressing machine to obtain a rod-shaped blank, and then calendered by a calendering machine to obtain a blank film with a thickness of 270μm and a width of 13cm for standby use;

[0054] Step 2, degreasing and longitudinal stretching of PTFE blank film:

[0055] The PTFE blank film obtained in step 1 is degreased and longitudinally stretched in an oven to obtain a blank film sample; the degreasing temperature is 190°C; during the longitudinal stretching process, the seven rollers use different rotation speeds, and the roller surface temperatures are also different, the temperature of the upper four rollers is 290°C, the temperature of the lower three rollers is 210°C, and the rotation speeds of the seven rollers are different, V 上面四个 :V 下面三个 =1:3 (roller arrangement as Figure 1 The blank film feeding speed is 20m / min;

[0056] Step 3, lateral stretching:

[0057] The green film sample obtained in step 2 is placed in a drying room at a temperature of 120°C for 3 hours, and then is transversely stretched by a transverse stretching machine. The temperatures of stretching zones 1 to 3 are 320°C, 330°C and 340°C respectively, the temperature of the sintering zone is 350°C, and the stretching ratio is 20 to obtain a finished PTFE film.

[0058] Specific applications:

[0059] The PTFE membrane obtained in step 3 is laminated onto the desired filter material by hot pressing to obtain a membrane-coated filter material with high efficiency and low resistance.

[0060] Comparative Example 1

[0061] The preparation method of PTFE membrane comprises the following steps:

[0062] Step 1, preparation of PTFE blank membrane:

[0063] PTFE resin and extrusion aid (the extrusion aid was purchased from Jinan Xinke Chemical Co., Ltd.) were mixed evenly in a mixer at a mass ratio of 100:28, and then placed in a drying room at a temperature of 58h for 24h; then the mixture was pre-pressed by a pre-pressing machine to obtain a rod-shaped blank, and then calendered by a calendering machine to obtain a blank film with a thickness of 270μm and a width of 13cm for standby use;

[0064] Step 2, degreasing and longitudinal stretching of PTFE blank film:

[0065] The PTFE blank film obtained in step 1 is degreased and longitudinally stretched in an oven to obtain a blank film sample; the degreasing temperature is 190°C; during the longitudinal stretching process, there are also seven rollers, and the arrangement is the same as in Example 1, but the roller surface has no slope, is flat and smooth, and the temperature of the seven roller surfaces is consistent, all at 220°C.

[0066] Step 3, lateral stretching:

[0067] The green film sample obtained in step 2 is placed in a drying room at a temperature of 120°C for 3 hours, and then is transversely stretched by a transverse stretching machine. The temperatures of stretching zones 1 to 3 are 310°C, 320°C and 330°C respectively, the temperature of the sintering zone is 345°C, and the stretching ratio is 20 to obtain a finished PTFE film.

[0068] Specific applications:

[0069] The PTFE membrane obtained in step 3 is laminated onto the desired filter material by hot pressing to obtain a membrane-coated filter material with high efficiency and low resistance.

[0070] Experimental testing

[0071] 1) The properties of the finished PTFE membranes prepared in Examples 1-3 and Comparative Example 1 were tested, and the test results are shown in Table 1 below:

[0072] Table 1 Finished PTFE membrane performance test results

[0073]

[0074] It can be seen from Table 1 that the air permeability / resistance and filtration efficiency of the PTFE membrane obtained by staggered stretching are better than those of the conventional preparation process, and the performance of the PTFE membrane obtained in Example 2 is the best.

[0075] 2) The finished PTFE membranes prepared in Examples 1-3 and Comparative Example 1 were used to prepare membrane filter materials, and the performance of the membrane filter materials was tested. The test results are shown in Table 2:

[0076] Table 2 Test results of membrane filter material performance

[0077]

[0078] It can be seen from Table 2 that after the PTFE membrane obtained by offset stretching is coated, the air permeability, resistance and filtration efficiency of the filter material are better than those of the PTFE membrane coated filter material obtained by conventional process.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0080] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a PTFE membrane, characterized in that: The following steps are involved: The PTFE resin and the extrusion aid are uniformly mixed and placed in a drying room for static standing; the mixed material is then pre-pressed into a rod-shaped blank, and then calendered to obtain a PTFE blank film; The PTFE blank film is degreased and longitudinally stretched to obtain a blank film sample; during the longitudinal stretching process, seven rollers are staggered in a manner of four rollers on the top and three rollers on the bottom, and the temperatures and rotation speeds of the four rollers on the top and the three rollers on the bottom are different; The green film sample is placed in a drying room to stand, and then stretched transversely to obtain a PTFE film.

2. The method for preparing a PTFE membrane according to claim 1, wherein: The mass ratio of PTFE resin to extrusion aid is 100:

28.

3. The method for preparing a PTFE membrane according to claim 1, characterized in that: The temperature of the drying room where the mixed material is placed is 55-60° C., and the standing time is more than 24 hours.

4. The method for preparing a PTFE membrane according to claim 1, characterized in that: The rotation speed ratio of the upper four rollers and the lower three rollers is 1:(2-3); the temperature of the upper four rollers is 270-290°C, and the temperature of the lower three rollers is 190-210°C.

5. The method for preparing a PTFE membrane according to claim 1, characterized in that: The degreasing temperature is 190°C.

6. The method for preparing a PTFE membrane according to claim 1, characterized in that: The temperature of the drying room where the blank film sample is placed is 120° C., and the standing time is 2-4 hours.

7. The method for preparing a PTFE membrane according to claim 1, characterized in that: The transverse stretching adopts a transverse stretching machine, the temperature of stretching zone 1 is 300-320°C, the temperature of stretching zone 2 is 310-330°C, the temperature of stretching zone 3 is 320-340°C, the temperature of sintering zone is 340-350°C; the stretching ratio is 20.

8. A PTFE membrane, characterized in that It is prepared using the preparation method described in any one of claims 1 to 7.

9. A membrane filter material, characterized in that: Comprising a PTFE membrane as claimed in claim 8.

10. Use of the PTFE membrane according to claim 8 in preparing membrane filter material.

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