Bottom heat-resistant reinforced polytetrafluoroethylene container and preparation method thereof

Abstract

The invention relates to the technical field of containers for chemical analysis, in particular to a bottom heat-resistant reinforced polytetrafluoroethylene container and a preparation method thereof. The invention provides a bottom heat-resistant reinforced polytetrafluoroethylene container. The container comprises a cup body and a reinforced heat-resistant layer arranged at the bottom of the cup body, the container is made of a mixture A of a polytetrafluoroethylene granulation material with an average particle size of 401-600 [mu] m and polytetrafluoroethylene suspension resin with an average particle size of 15-30 [mu] m; and the reinforced heat-resistant layer is made of a mixture B of colloidal graphite powder with the average particle size of 40-60 microns and polytetrafluoroethylene suspension resin with the average particle size of 15-30 microns. The container has the characteristics of high corrosion resistance, high temperature resistance, firmness, difficulty in breaking, good anti-sticking effect, convenience in cleaning and the like.

Description

Technical Field

[0001] The invention relates to the technical field of containers for chemical analysis, and in particular to a bottom heat-resistant enhanced polytetrafluoroethylene container and a preparation method thereof. Background Art

[0002] Glass containers or ordinary plastic containers are commonly used test vessels in modern laboratories. However, in the fields of semiconductor manufacturing, high-precision analysis, scientific research, etc., which have extremely high purity requirements, when glass containers or ordinary plastic containers are used for ultrapure chemical analysis, when they encounter corrosive liquids such as strong acids and strong alkalis, there is no guarantee that other materials will precipitate out of them or react with strong acids and strong alkalis. These phenomena will affect the accuracy of the analysis. Glass containers have the disadvantages of not being resistant to high temperatures, being easy to burst when heated, and being fragile. There are safety hazards during heating analysis. Ordinary plastic containers are also not resistant to high temperatures and are easy to adhere to test samples. In order to overcome these defects of traditional test and analysis containers, a container made of a material with excellent chemical corrosion resistance, excellent thermal stability, excellent high and low temperature resistance, and excellent non-stickiness is needed to replace traditional containers in the field of ultrapure analysis.

[0003] Polytetrafluoroethylene (PTFE) is a polymer obtained by polymerization of tetrafluoroethylene as a monomer. Its chemical formula is (C2F4)n. This material has excellent high temperature and low temperature resistance. It is resistant to acid, alkali, and various organic solvents, and is almost insoluble in all solvents. At the same time, polytetrafluoroethylene products also have excellent non-stickiness. Therefore, analytical containers made of polytetrafluoroethylene can replace traditional containers in the field of ultrapure analysis. However, analytical containers made of polytetrafluoroethylene also have some limitations. Polytetrafluoroethylene containers have good high temperature resistance, but when heated above its maximum tolerance temperature (260°C) or when the operating temperature is kept in the high temperature range (≥150°C) for a long time, brown marks will form on its bottom, affecting its mechanical properties. In addition, due to the poor thermal conductivity of polytetrafluoroethylene containers, when the temperature rises or drops sharply, the container is easily brittle or deformed due to rapid temperature changes, affecting the test and posing safety hazards. Therefore, further technological innovation is needed to improve the high temperature resistance of the container to cope with the increasingly higher experimental environment and test requirements. Summary of the invention

[0004] The present invention provides a bottom heat-resistant enhanced polytetrafluoroethylene container and a preparation method thereof. The bottom heat-resistant enhanced polytetrafluoroethylene container provided by the present invention has excellent chemical corrosion resistance, excellent thermal stability, excellent high and low temperature resistance, and excellent non-stickiness. The heat resistance of the container is improved by adding a bottom heat-resistant enhanced layer. It meets the current stringent requirements for analytical laboratory vessels, can be used for a long time at high temperatures, and has a stable structure that is not easily deformed or brittle.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The invention provides a bottom heat-resistant enhanced polytetrafluoroethylene container, the container comprising a cup body and an enhanced heat-resistant layer arranged at the bottom of the cup body; the material of the container is a mixture A of polytetrafluoroethylene granules with an average particle size of 401 to 600 μm and a polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm; the material of the enhanced heat-resistant layer is a mixture B of colloidal graphite powder with an average particle size of 40 to 60 μm and a polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm.

[0007] This application utilizes the excellent high temperature resistance and thermal conductivity of graphite materials to improve the high temperature resistance and thermal stability of the bottom of the polytetrafluoroethylene container. Through a special molding process, the enhanced heat-resistant layer of the bottom plate is combined with the cup body to form a whole, thereby improving the heat resistance and thermal stability of the bottom of the polytetrafluoroethylene container and reducing deformation and brittle cracking of the container when used at high temperatures.

[0008] The polytetrafluoroethylene container needs to maintain stable dimensions and not be easily deformed after frequent heating and cooling, which requires the container wall to have a certain wall thickness. The use of polytetrafluoroethylene granules can solve this problem. However, due to the large particle size of polytetrafluoroethylene granules, there are large gaps between the particles, which is easy to cause uneven feeding during the production process, and it is easy to form plaques and uneven structures on the container wall, which increases the surface roughness value of the container and affects the non-stickiness of the container. This phenomenon is also not conducive to the uniform heat transfer of the container. The applicant selects a mixture of small-particle polytetrafluoroethylene suspension resin and large-particle polytetrafluoroethylene granules, and uses small-particle polytetrafluoroethylene suspension resin to fill the gaps generated after the large particles of polytetrafluoroethylene granules, so that the preformed product structure is more uniform. Then, during sintering, it can be uniformly melted into a whole, avoiding the formation of plaques and uneven structures on the container wall, ensuring that the container has excellent non-stickiness, and can also evenly conduct heat to ensure that the entire container is heated evenly, helping to reduce experimental errors.

[0009] Based on the above, the applicant uses a mixture of small-particle polytetrafluoroethylene suspension resin and large-particle polytetrafluoroethylene granulated material as the main material of the container, and composites a reinforced heat-resistant layer containing graphite material at the bottom of the container to improve the overall heat resistance and thermal conductivity of the container. The finally obtained bottom heat-resistant enhanced polytetrafluoroethylene container can be used for a long time at high temperature, is not prone to deformation and brittle cracking, and has a more stable structure, so it is more suitable for use as a high-temperature ultrapure analytical instrument.

[0010] Preferably, in the mixed material A, the mass ratio of the polytetrafluoroethylene granules to the polytetrafluoroethylene suspension resin is (2-3):1.

[0011] Further preferably, in the mixed material A, the mass ratio of the polytetrafluoroethylene granules to the polytetrafluoroethylene suspension resin is (2-2.5):1.

[0012] Further preferably, in the mixed material A, the mass ratio of the polytetrafluoroethylene granules to the polytetrafluoroethylene suspension resin is (2.2-2.4):1.

[0013] Further preferably, in the mixed material A, the mass ratio of the polytetrafluoroethylene granules to the polytetrafluoroethylene suspension resin is 7:3.

[0014] Preferably, in the mixture B, the mass ratio of colloidal graphite powder to polytetrafluoroethylene suspension resin is 2:(7-9).

[0015] Further preferably, in the mixture B, the mass ratio of the colloidal graphite powder to the polytetrafluoroethylene suspension resin is 1:(3.6-4.2).

[0016] Further preferably, in the mixture B, the mass ratio of the colloidal graphite powder to the polytetrafluoroethylene suspension resin is 1:4.

[0017] The present invention also provides a method for preparing the bottom heat-resistant enhanced polytetrafluoroethylene container, comprising:

[0018] S1. The polytetrafluoroethylene granules having an average particle size of 401 to 600 μm and the polytetrafluoroethylene suspension resin having an average particle size of 15 to 30 μm are uniformly mixed to obtain a mixture A, and the colloidal graphite powder having an average particle size of 40 to 60 μm and the polytetrafluoroethylene suspension resin having an average particle size of 15 to 30 μm are uniformly mixed to obtain a mixture B;

[0019] S2. Pressing the mixture B in S1 to obtain a reinforced heat-resistant layer;

[0020] S3. The mixture A in S1 is added to the mold for compaction, followed by the addition of the heat-resistant layer of S2, and then isostatic molding to obtain a preform;

[0021] S4. Sintering the preform in S3 to obtain a bottom heat-resistant enhanced polytetrafluoroethylene container.

[0022] Preferably, in S2, the pressing pressure is 13-16 MPa.

[0023] More preferably, in S2, the pressing pressure is 14-15 MPa.

[0024] Preferably, in S3, the isostatic molding pressure is 15-20 MPa.

[0025] Further preferably, in S3, the isostatic molding pressure is 17-20 MPa.

[0026] Preferably, in S3, a rubber airbag is provided in the mold; water is filled into the rubber airbag by a high-pressure water pump, and the rubber airbag is expanded to apply a uniform outward pressure to the mixture A and the enhanced heat-resistant layer in the mold.

[0027] Preferably, in S4, the thickness of the enhanced heat-resistant layer accounts for [0.6, 0.7] of the thickness of the bottom plate of the bottom heat-resistant enhanced polytetrafluoroethylene container.

[0028] Preferably, in S4, the sintering temperature is 370-390° C., and the sintering time is 4-6 hours.

[0029] More preferably, when the sintering temperature is below 300° C., the heating rate is 70 to 80° C. / h; when the sintering temperature is above 300° C., the heating rate is 40 to 50° C. / h.

[0030] Further preferably, the cooling rate after sintering is 40-50°C / h, the temperature is cooled to 330°C and kept for 1 hour, then cooled to 300°C and kept for 1 hour, and then cooled to room temperature and taken out.

[0031] Controlling the heating and cooling conditions can ensure that the sintered container reaches the best state in terms of structure and performance. In order to avoid incomplete crystal growth of the material due to excessively rapid heating, which reduces the stability of the container, the applicant controls the heating rate within an appropriate range and sets a change line for the heating rate at 300°C, which can avoid stress inside the material due to excessively rapid temperature changes, thereby avoiding cracks and deformation.

[0032] Furthermore, the melting point of polytetrafluoroethylene is 327°C. When the temperature rises to above 300°C, the polytetrafluoroethylene is completely transformed into an amorphous structure. At this time, the appearance of the container changes from white opaque to a gel-like elastic transparent body. Therefore, the heating rate at this stage needs to be slower to give the polytetrafluoroethylene sufficient time to transform.

[0033] Subsequently, the temperature is kept at 370-390℃ for 4-6 hours to ensure that the phase change process is fully completed and a container with a complete structure is obtained. In the cooling stage, in order to avoid cracking inside or outside the container due to excessive cooling, the cooling rate needs to be controlled to ensure the high quality of the container. It should be noted that the applicant has selected a specific molding process to ensure the quality of the container.

[0034] Therefore, the present invention has the following beneficial effects:

[0035] (1) The present invention utilizes the excellent high temperature resistance and thermal conductivity of graphite materials to improve the high temperature resistance and thermal conductivity of polytetrafluoroethylene containers; and through a special molding process, the enhanced heat-resistant layer and the cup body are composited into an integral bottom heat-resistant enhanced polytetrafluoroethylene container.

[0036] (2) The present invention selects a mixture of a small-particle polytetrafluoroethylene suspension resin and a large-particle polytetrafluoroethylene granulated material as the material of the container; the small-particle powder is used to fill the gaps between the large particles of the granulated material, thereby increasing the wall thickness of the container without reducing the surface roughness of the container, so that the bottom heat-resistant enhanced polytetrafluoroethylene container obtained has high stability, is not easy to deform, and has excellent non-stickiness; and the container material has good uniformity and can evenly conduct heat, and is suitable for long-term use in high temperature environments.

[0037] (3) The method for preparing the bottom heat-resistant enhanced polytetrafluoroethylene container provided by the present invention utilizes a multi-level sintering process to obtain a high-quality container with a complete structure and fully developed internal crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of a bottom heat-resistant enhanced polytetrafluoroethylene container.

[0039] Figure 2 Schematic diagram of the molding process flow. DETAILED DESCRIPTION

[0040] The present invention is further described below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0041] The sources and properties of the raw materials used in the specific implementation of the present invention are as follows: polytetrafluoroethylene suspension resin, JF-4TM, with an average particle size of 15 to 30 μm, purchased from Zhejiang Juhua Co., Ltd.; polytetrafluoroethylene granulation material, JH-4A2, with an average particle size of 401 to 600 μm, purchased from Zhejiang Juhua Co., Ltd.; colloidal graphite is F-special grade 2, with an average particle size of 40 to 60 μm, purchased from Shanghai Colloid Chemical Plant; carbon fiber, with an average particle size of 40 to 60 μm, purchased from Qingdao Yuanhui Composite Materials Co., Ltd.

[0042] [Example]

[0043] Example 1

[0044] according to Figure 2 The process shown completes the implementation of this section, as follows:

[0045] S1. According to the ratio in Table 1, polytetrafluoroethylene granules with an average particle size of 401 to 600 μm and polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm are mixed in a mass ratio of 7:3 to obtain a mixture A, and colloidal graphite powder with an average particle size of 40 to 60 μm and polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm are mixed in a mass ratio of 1:4 to obtain a mixture B.

[0046] S2. The mixed material B in S1 is pressed at 15 MPa to obtain a reinforced heat-resistant layer, wherein the outer diameter of the reinforced heat-resistant layer obtained is 0.2 to 0.3 mm smaller than the upper opening size of the isostatic molding die.

[0047] S3. After the rubber airbag of the isostatic molding mold is filled with water, check whether the rubber airbag and the mold bottom plate are installed vertically, and exhaust the air in the rubber airbag. Place the mold flat on a stable table, and add the mixture A in S1 into the mold; during the feeding process, always keep the rubber airbag in the center of the mold. After the feeding is completed, compact the material on the top of the mold and add the reinforced heat-resistant layer of S2. Cover the mold cover to press the mold tightly, turn on the high-pressure water pump and press at 20Mpa to obtain the preform. In this process, the reinforced heat-resistant layer is perfectly combined with the polytetrafluoroethylene container under pressure to form a whole, and the finished product is obtained after sintering and machining. Figure 1 shown.

[0048] The amount of mixture B and mixture A added is selected according to the size of the mold, wherein the thickness of the enhanced heat-resistant layer is ensured to be 0.6-0.7 of the thickness of the container bottom plate; the required mold size can be calculated based on the customer's size requirements for the product and the shrinkage rate of the raw materials.

[0049] S4. The preform in S3 is sintered at 380°C for 5h to obtain a bottom heat-resistant enhanced polytetrafluoroethylene container; wherein, when the sintering temperature is below 300°C, the heating rate is 75°C / h; when the sintering temperature is above 300°C, the heating rate is 45°C / h; after sintering, the cooling rate is 45°C / h, the temperature is cooled to 330°C and kept for 1h, then cooled to 300°C and kept for 1h, and then cooled to room temperature and taken out.

[0050] Comparative Examples 1 to 4 were prepared in the same manner as in Example 1 according to the formulations in Table 1 to obtain different polytetrafluoroethylene containers; compared with Example 1, Comparative Examples 1 to 4 were identical to Example 1 except for the formulations in Table 1.

[0051] Table 1 Proportions of various embodiments / comparative examples Table 1

[0052]

[0053] Note: PTFE suspension resin A is the raw material used in mixture A, and PTFE suspension resin B is the raw material used in mixture B; the sum of the mass of PTFE granules and PTFE suspension resin A is 100wt%, and the sum of the mass of colloidal graphite powder and PTFE suspension resin B is 100wt%.

[0054] Comparative Example 5

[0055] S1. According to the ratio in Table 2, polytetrafluoroethylene granules with an average particle size of 401 to 600 μm and polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm are mixed in a mass ratio of 7:3 to obtain a mixture A, and colloidal graphite powder with an average particle size of 40 to 60 μm and polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm are mixed in a mass ratio of 1:4 to obtain a mixture B.

[0056] S2. The mixed material B in S1 is pressed at 30 MPa to obtain a reinforced heat-resistant layer, wherein the outer diameter of the reinforced heat-resistant layer obtained is 0.2 to 0.3 mm smaller than the upper opening size of the isostatic molding die.

[0057] S3. After the rubber bladder of the isostatic molding mold is filled with water, check whether the rubber bladder is installed vertically to the mold bottom plate, and exhaust the air in the rubber bladder. Place the mold flat on a stable table, and add the mixture A in S1 into the mold; during the feeding process, always keep the rubber bladder in the center of the mold. After the feeding is completed, compact the material on the top of the mold and add the enhanced heat-resistant layer of S2, cover the mold cover to press the mold tightly, and turn on the high-pressure water pump to press at 20Mpa to obtain the preform. In this process, the enhanced heat-resistant layer is perfectly combined with the polytetrafluoroethylene container under pressure to form a whole.

[0058] The amount of mixture B and mixture A added is selected according to the size of the mold, wherein the thickness of the enhanced heat-resistant layer is ensured to be 0.6 to 0.7 of the thickness of the container bottom plate; the required mold size can be calculated based on the customer's size requirements for the product and the shrinkage rate of the raw materials.

[0059] S4. The preform in S3 is sintered at 380°C for 5h to obtain a bottom heat-resistant enhanced polytetrafluoroethylene container; wherein, when the sintering temperature is below 300°C, the heating rate is 75°C / h; when the sintering temperature is above 300°C, the heating rate is 45°C / h; after sintering, the cooling rate is 45°C / h, the temperature is cooled to 330°C and kept for 1h, then cooled to 300°C and kept for 1h, and then cooled to room temperature and taken out.

[0060] Comparative Examples 5 to 19 were prepared in the same manner as Comparative Example 5 according to the formulations in Table 2 to obtain different enhanced heat-resistant layers; compared with Comparative Example 5, Comparative Examples 5 to 19 are completely identical to Comparative Example 5 except for the different formulations in Table 2.

[0061] Table 2 Proportions of various embodiments / comparative examples

[0062]

[0063]

[0064] Note: PTFE suspension resin B is the raw material used in mixed material B.

[0065] Comparative Example 20

[0066] This comparative example is basically the same as Example 1, except that the colloidal graphite powder with an average particle size of 40 to 60 μm in the S1 mixture B is replaced by an equal amount of carbon fiber powder with an average particle size of 40 to 60 μm.

[0067] Comparative Example 21

[0068] This comparative example is basically the same as Example 1, except that the composite of the reinforced heat-resistant layer is eliminated and a polytetrafluoroethylene container is obtained according to the process of Example 1.

[0069]

Performance test

[0070] 1. Selection of raw materials

[0071] The bottom heat-resistant enhanced polytetrafluoroethylene containers / polytetrafluoroethylene containers prepared in Example 1 and Comparative Examples 1 to 4 and Comparative Examples 20 to 21 were subjected to appearance tests, including surface roughness, container wall thickness and appearance. The results are shown in Table 3.

[0072] Table 3 Comparison of apparent performance

[0073] Surface roughness Ra / μm Container wall thickness / mm Appearance Example 1 0.89 2.5 Meet the requirements Comparative Example 1 1.80 2.5 Meet the requirements Comparative Example 2 0.80 2.4 There are depressions on the inner wall of the container Comparative Example 3 0.85 2.5 There are depressions on the inner wall of the container Comparative Example 4 0.70 2.0 There are depressions on the inner wall of the container Comparative Example 20 0.89 2.5 Cracks on the bottom Comparative Example 21 0.89 2.5 Meet the requirements

[0074] The standard requirements for polytetrafluoroethylene containers are as follows: surface roughness Ra ≤ 1.00μm; container wall thickness ≤ 2.5mm; appearance requirements, the inner wall of the container is smooth and free of depressions.

[0075] From the data in Table 3, it can be seen that as the amount of polytetrafluoroethylene granules is reduced, the surface roughness value of the container decreases from 1.80μm to 0.89μm, which meets the standard requirements. As the amount of polytetrafluoroethylene suspension resin increases, the raw materials that can be added to the material cavity begin to decrease, which causes the wall thickness of the container blank to become thinner. After turning, the thinner parts of the inner wall of the container will be dented due to insufficient thickness. Therefore, in order to ensure the surface roughness of the polytetrafluoroethylene container and maintain a suitable wall thickness, the surface of the container is not easy to corrode and is strong and durable. The applicant selects small-particle polytetrafluoroethylene suspension resin to fill the gaps between large-particle polytetrafluoroethylene granules to ensure the surface roughness of the container, and by adjusting the ratio of the two, it is ensured that the wall thickness of the container meets the design requirements.

[0076] In addition, by replacing the colloidal graphite powder in mixture B with carbon fiber powder of the same particle size, it was found that its processing performance was poor and cracks appeared in the bottom plate.

[0077] 2. Enhance the composite of heat-resistant layer

[0078] The reinforced heat-resistant layers (referred to as SH layers) prepared in accordance with Example 1 and Comparative Examples 5 to 19 exhibit different phenomena during the pressing process, and the polytetrafluoroethylene containers prepared in accordance with Example 1 and Comparative Examples 5 to 19 exhibit different phenomena during the heat resistance test, and the results are recorded in Table 4.

[0079] Table 4 Phenomenon Record Table

[0080]

[0081] From Table 4, we can see that when the unit pressure of pressing is 30Mpa and 25Mpa, the reinforced heat-resistant layer has cracks and the test fails. When the unit pressure is 8Mpa, the reinforced heat-resistant layer cannot be formed and cannot be used for the next production; therefore, the unit pressure is 15Mpa. The reinforced heat-resistant layer of 30wt% graphite + 70wt% PTFE also cracks under 15Mpa, so it is excluded.

[0082] Subsequently, the polytetrafluoroethylene containers corresponding to the groups with no cracks in the reinforced heat-resistant layer were placed on an asbestos net and heated at 250°C for 1 hour. The state of the polytetrafluoroethylene containers was observed, and it was found that the performance of the container with 20wt% graphite + 80wt% PTFE met the requirements and was the best choice.

[0083] 3. Heat resistance

[0084] The heat resistance performance of the bottom heat-resistant enhanced polytetrafluoroethylene containers prepared in Example 1, Comparative Examples 1 to 4 and Comparative Examples 20 to 21 was tested, and the results are shown in Table 5.

[0085] Method for determining the maximum heat-resistant temperature: Place the polytetrafluoroethylene container on the asbestos net, and start heating it using an electric heater with a settable temperature. Heat it to 150°C and keep it warm for 10 minutes, then observe the state of the container. If there is no change, increase the temperature by 5°C and keep it warm for 10 minutes, and so on.

[0086] Point temperature measurement method: While determining the highest heat-resistant temperature, use multiple thermocouples or temperature sensors placed at different positions of the beaker to monitor the temperature changes at each point. Bottom: Select the center point of the bottom of the beaker as the bottom measurement point. In the middle, select 1 / 4, 1 / 2, 3 / 4, and 4 / 4 of the beaker height as the four middle measurement points; among them, any point on the circumference formed by 1 / 4, 1 / 2, 3 / 4, and 4 / 4 of the beaker height can be used as a measurement point at that height. Top: Select the top center point opposite the bottom center point as the top measurement point.

[0087] Table 5 Heat resistance performance comparison table

[0088] Maximum heat resistance temperature / ℃ Example 1 260 Comparative Example 1 260 Comparative Example 2 260 Comparative Example 3 260 Comparative Example 4 260 Comparative Example 20 255 Comparative Example 21 250

[0089] Table 6 Heat transfer capacity comparison table

[0090] Bottom / ℃ Central 1 / 4 / ℃ Central 1 / 2 / ℃ Central 3 / 4 / ℃ Central 4 / 4 / ℃ Top / ℃ Example 1 260 259 257 254 251 252 Comparative Example 1 260 257 255 251 248 248 Comparative Example 2 260 259 256 253 249 249 Comparative Example 3 260 259 256 252 249 250 Comparative Example 4 260 258 255 250 246 247 Comparative Example 20 255 254 251 247 244 244 Comparative Example 21 250 249 247 244 238 240

[0091] It can be seen from Tables 5 to 6 that the bottom heat-resistant enhanced polytetrafluoroethylene container provided by the present invention has good heat resistance and heat transfer uniformity.

Claims

1. A bottom heat-resistant enhanced polytetrafluoroethylene container, characterized in that: The container comprises a cup body and a reinforced heat-resistant layer arranged at the bottom of the cup body; the material of the container is a mixture A of polytetrafluoroethylene granules with an average particle size of 401 to 600 μm and polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm; the material of the reinforced heat-resistant layer is a mixture B of colloidal graphite powder with an average particle size of 40 to 60 μm and polytetrafluoroethylene suspension resin with an average particle size of 15 to 30 μm.

2. The bottom heat-resistant enhanced polytetrafluoroethylene container according to claim 1, characterized in that: In the mixed material A, the mass ratio of the polytetrafluoroethylene granulated material to the polytetrafluoroethylene suspension resin is (2-3):

1.

3. The bottom heat-resistant enhanced polytetrafluoroethylene container according to claim 1 or 2, characterized in that: In the mixed material B, the mass ratio of colloidal graphite powder to polytetrafluoroethylene suspension resin is 2:(7-9).

4. The method for preparing a bottom heat-resistant enhanced polytetrafluoroethylene container according to any one of claims 1 to 3, characterized in that: include: S1. The polytetrafluoroethylene granules having an average particle size of 401 to 600 μm and the polytetrafluoroethylene suspension resin having an average particle size of 15 to 30 μm are uniformly mixed to obtain a mixture A, and the colloidal graphite powder having an average particle size of 40 to 60 μm and the polytetrafluoroethylene suspension resin having an average particle size of 15 to 30 μm are uniformly mixed to obtain a mixture B; S2. Pressing the mixture B in S1 to obtain a reinforced heat-resistant layer; S3. The mixture A in S1 is added to the mold for compaction, followed by the addition of the heat-resistant layer of S2, and then isostatic molding to obtain a preform; S4. Sintering the preform in S3 to obtain a bottom heat-resistant enhanced polytetrafluoroethylene container.

5. The preparation method according to claim 4, characterized in that: In S2, the pressing pressure is 13-16 MPa; in S3, the isostatic molding pressure is 15-20 MPa.

6. The preparation method according to claim 4, characterized in that: In S3, a rubber airbag is provided in the mold; water is filled into the rubber airbag by a high-pressure water pump, and the rubber airbag is expanded to apply a uniform outward pressure to the mixture A and the enhanced heat-resistant layer in the mold.

7. The preparation method according to claim 4, characterized in that: In S4, the thickness of the enhanced heat-resistant layer accounts for [0.6, 0.7] of the thickness of the bottom plate of the bottom heat-resistant enhanced polytetrafluoroethylene container.

8. The preparation method according to claim 4, characterized in that: In the step S4, the sintering temperature is 370-390° C., and the sintering time is 4-6 hours.

9. The preparation method according to claim 8, characterized in that: When the sintering temperature is below 300°C, the heating rate is 70-80°C / h; when the sintering temperature is above 300°C, the heating rate is 40-50°C / h.

10. The preparation method according to claim 8 or 9, characterized in that: After sintering, the cooling rate is 40-50°C / h, the temperature is cooled to 330°C and kept for 1 hour, then cooled to 300°C and kept for 1 hour, and then cooled to room temperature and taken out.

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