Dip-molded flange gasket and preparation method thereof

Abstract

The invention belongs to the technical field of gaskets, and particularly relates to a dip-formed flange gasket and a preparation method thereof.The preparation method comprises the following steps that firstly, a flexible graphite plate is taken, cut according to a flange gasket template, cleaned and dried; 2, putting the flexible graphite plate treated in the step 1 into a high-pressure impregnation kettle, heating, vacuumizing to negative pressure, adding impregnation liquid, and reacting until the vacuum degree in the high-pressure impregnation kettle is stable; 3, the vacuum state in the high-pressure impregnation kettle is removed, the pressure in the high-pressure impregnation kettle is increased to 0.85-1.25 MPa, and then heating reaction is conducted; and 4, repeating the step 2 and the step 3 for dipping after the reaction is finished, taking out the sample after dipping, and cleaning and drying to obtain the flange gasket. According to the method, more polytetrafluoroethylene can be immersed into the flexible graphite plate, so that the mechanical property and the leakage-proof property of the material are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of gaskets, and in particular relates to a dip-molded flange gasket and a preparation method thereof. Background Art

[0002] Flexible graphite is a special non-metallic material with low density, low heat capacity, high thermal conductivity, corrosion resistance and good processing performance. It is a rational material for preparing flange gaskets.

[0003] At present, the common methods for preparing flange gaskets of flexible graphite include solution impregnation, surface coating and matrix modification. Among them, the solution impregnation method is the first choice for industrial production because of its simple technical solution and low production cost. The flexible graphite is modified by solution impregnation to improve the comprehensive performance of flexible graphite materials. Common impregnation materials include magnesium borate / phosphoric acid / sodium silicate and organic resin materials. Polytetrafluoroethylene, commonly known as the "king of plastics", has excellent chemical stability, high and low temperature resistance, corrosion resistance, sealing, good anti-aging resistance and hydrophobicity, etc., which makes it widely used in the automotive industry, aerospace, machinery, petrochemical and other fields. In view of the superiority of polytetrafluoroethylene, polytetrafluoroethylene dispersion is used as an impregnating agent to impregnate graphite to make impregnated impermeable graphite, which is used for equipment manufacturing heat exchangers, and can improve the corrosion resistance and high temperature resistance of graphite heat exchangers. However, the current use of polytetrafluoroethylene impregnated graphite materials has the problems of poor impregnation effect and long preparation cycle, which seriously limits industrial utilization. Summary of the invention

[0004] In view of the problems existing in the existing solution impregnation method for preparing composite graphite gaskets mentioned in the background technology, the present invention provides an impregnation-molded flange gasket and a preparation method thereof, which can impregnate more polytetrafluoroethylene into the flexible graphite sheet, thereby greatly improving the mechanical properties and leakage-proof performance of the material.

[0005] The specific precautions of the present invention are as follows:

[0006] A method for preparing a dip-molded flange gasket comprises the following steps:

[0007] Step 1: Take the flexible graphite sheet, cut it according to the flange gasket template, clean it and dry it;

[0008] Step 2: After the treatment in step 1, the flexible graphite sheet is placed in a high-pressure impregnation kettle and heated, and then evacuated to negative pressure, and an impregnation liquid is added thereto, and the reaction is continued until the vacuum degree in the high-pressure impregnation kettle is stable;

[0009] Step 3: Remove the vacuum state in the high-pressure impregnation kettle, pressurize the high-pressure impregnation kettle to 0.85-1.25 MPa, and then heat it for reaction;

[0010] Step 4: After the reaction is completed, repeat the dipping steps 2 and 3. After the dipping is completed, take out the sample, clean and dry it to obtain the flange gasket.

[0011] Furthermore, in the step 1, the compression rate of the flexible graphite sheet is 41% to 42%, the rebound rate is 16% to 17%, and the tensile strength is 8 to 10 MPa.

[0012] Furthermore, the cleaning step in step one is: soaking the cut flexible graphite sheet in distilled water for 20 to 30 minutes, soaking the flexible graphite sheet in anhydrous ethanol for 30 to 60 minutes after ultrasonic treatment, and drying the flexible graphite sheet in an oven at 100 to 110° C. after soaking.

[0013] Furthermore, in the step 2, the vacuum degree is -0.07 to 0.09 MPa, the impregnation liquid is a polytetrafluoroethylene dispersion with a volume concentration of 60%, and the reaction temperature is 40 to 45°C.

[0014] Furthermore, in step three, the reaction temperature is 40-45° C., and the reaction time is 10-25 min.

[0015] Furthermore, the step 4 is repeated 1 to 2 times.

[0016] The present invention also provides a flange gasket formed by dipping, which comprises the following components in parts by weight: 7 to 8 parts of polytetrafluoroethylene and 92 to 93 parts of flexible graphite.

[0017] Furthermore, the compression rate of the flange gasket is 31% to 32%, the rebound rate is 23% to 24%, the tensile strength is 48 to 50 MPa, and the leakage rate is 1.8×10-2×10 cm 3 / s.

[0018] Beneficial effects of the present invention:

[0019] Compared with pure flexible graphite sheets, the flange gasket prepared by the preparation method provided by the present invention has improved compression performance and resilience performance to a certain extent due to the addition of flexible material polytetrafluoroethylene. In addition, due to the preparation method provided by the present invention, more polytetrafluoroethylene can be immersed in the flexible graphite sheet, which greatly improves the tensile strength and anti-leakage performance of the sheet. DETAILED DESCRIPTION

[0020] Example 1

[0021] This embodiment provides a method for preparing a dip-molded flange gasket, comprising the following steps:

[0022] Step 1: Take the flexible graphite sheet, cut it according to the flange gasket template, clean it and dry it;

[0023] Specifically, a flexible graphite sheet is cut according to the flange gasket template prepared as required, and after cutting, it is soaked in distilled water for 20 minutes for ultrasonic treatment to remove impurities, and after ultrasonic treatment, the flexible graphite sheet is soaked in anhydrous ethanol for 30 minutes to remove oil stains, and after soaking, the flexible graphite sheet is placed in an oven at 105° C. and dried, and then naturally cooled for use. The flexible graphite sheet selected in this embodiment has a compression rate of 41.34%, a rebound rate of 16.43%, and a tensile strength of 8.95 MPa.

[0024] Step 2: After the treatment in step 1, the flexible graphite sheet is placed in a high-pressure impregnation kettle and heated, and then evacuated to negative pressure, and an impregnation liquid is added thereto, and the reaction is continued until the vacuum degree in the high-pressure impregnation kettle is stable;

[0025] Specifically, the flexible graphite sheet treated in step 1 is added to a high-pressure impregnation kettle, first heated to 40°C and then evacuated to a negative pressure of -0.09 MPa, and the impregnant is absorbed in a negative pressure state. In this embodiment, the impregnant is a polytetrafluoroethylene dispersion with a volume concentration of 60%, and the negative pressure is maintained for 10 minutes after the negative pressure is absorbed and does not change.

[0026] Step 3: Remove the vacuum state in the high-pressure impregnation kettle, pressurize the high-pressure impregnation kettle to 0.85-1.25 MPa, and then heat it for reaction;

[0027] Specifically, after the reaction of step 2 is over, the vacuum state in the high-pressure impregnation kettle is removed, and the high-pressure impregnation kettle is pressurized to 0.85 MPa by an air compressor, and then the temperature is raised to 40 degrees to react for 20 minutes to allow the impregnant to penetrate into the flexible graphite.

[0028] Step 4: After the reaction is completed, repeat the dipping steps 2 and 3. After the dipping is completed, take out the sample, clean and dry it to obtain the flange gasket.

[0029] Specifically, after the reaction of step three is complete, steps two and three are repeated once, and after the immersion is completed, the sample is taken out, rinsed in distilled water, and dried at 105° C. to prepare the product.

[0030] This embodiment also provides a dip-molded flange gasket, which includes the following components in parts by weight: 7.69 parts of polytetrafluoroethylene and 92.31 parts of flexible graphite.

[0031] Example 2

[0032] This embodiment provides a method for preparing a dip-molded flange gasket, comprising the following steps:

[0033] Step 1: Take the flexible graphite sheet, cut it according to the flange gasket template, clean it and dry it;

[0034] Specifically, a flexible graphite sheet is cut according to the flange gasket template prepared as required, and after cutting, it is soaked in distilled water for 20 minutes for ultrasonic treatment to remove impurities, and after ultrasonic treatment, the flexible graphite sheet is soaked in anhydrous ethanol for 30 minutes to remove oil stains, and after soaking, the flexible graphite sheet is placed in an oven at 105° C. and dried, and then naturally cooled for use. The flexible graphite sheet selected in this embodiment has a compression rate of 41.34%, a rebound rate of 16.43%, and a tensile strength of 8.95 MPa.

[0035] Step 2: After the treatment in step 1, the flexible graphite sheet is placed in a high-pressure impregnation kettle and heated, and then evacuated to negative pressure, and an impregnation liquid is added thereto, and the reaction is continued until the vacuum degree in the high-pressure impregnation kettle is stable;

[0036] Specifically, the flexible graphite sheet treated in step 1 is added to a high-pressure impregnation kettle, first heated to 40°C and then evacuated to a negative pressure of -0.07MPa, and the impregnant is absorbed in a negative pressure state. In this embodiment, the impregnant is a polytetrafluoroethylene dispersion with a volume concentration of 60%, and the negative pressure is maintained for 20 minutes after the negative pressure is absorbed and does not change.

[0037] Step 3: Remove the vacuum state in the high-pressure impregnation kettle, pressurize the high-pressure impregnation kettle to 0.85-1.25 MPa, and then heat it for reaction;

[0038] Specifically, after the reaction of step 2 is over, the vacuum state in the high-pressure impregnation kettle is removed, and the high-pressure impregnation kettle is pressurized to 0.95 MPa by an air compressor, and then the temperature is raised to 40 degrees to react for 20 minutes to allow the impregnant to penetrate into the flexible graphite.

[0039] Step 4: After the reaction is completed, repeat the dipping steps 2 and 3. After the dipping is completed, take out the sample, clean and dry it to obtain the flange gasket.

[0040] Specifically, after the reaction of step three is complete, steps two and three are repeated once, and after the immersion is completed, the sample is taken out, rinsed in distilled water, and dried at 105° C. to prepare the product.

[0041] This embodiment also provides a dip-molded flange gasket, which includes the following components in parts by weight: 7.21 parts of polytetrafluoroethylene and 92.79 parts of flexible graphite.

[0042] Example 3

[0043] This embodiment provides a method for preparing a dip-molded flange gasket, comprising the following steps:

[0044] Step 1: Take the flexible graphite sheet, cut it according to the flange gasket template, clean it and dry it;

[0045] Specifically, a flexible graphite sheet is cut according to the flange gasket template prepared as required, and after cutting, it is soaked in distilled water for 20 minutes for ultrasonic treatment to remove impurities, and after ultrasonic treatment, the flexible graphite sheet is soaked in anhydrous ethanol for 30 minutes to remove oil stains, and after soaking, the flexible graphite sheet is placed in an oven at 105° C. and dried, and then naturally cooled for use. The flexible graphite sheet selected in this embodiment has a compression rate of 41.34%, a rebound rate of 16.43%, and a tensile strength of 8.95 MPa.

[0046] Step 2: After the treatment in step 1, the flexible graphite sheet is placed in a high-pressure impregnation kettle and heated, and then evacuated to negative pressure, and an impregnation liquid is added thereto, and the reaction is continued until the vacuum degree in the high-pressure impregnation kettle is stable;

[0047] Specifically, the flexible graphite sheet treated in step 1 is added to a high-pressure impregnation kettle, first heated to 40°C and then evacuated to a negative pressure of -0.08MPa, and the impregnant is absorbed in a negative pressure state. In this embodiment, the impregnant is a polytetrafluoroethylene dispersion with a volume concentration of 60%, and the negative pressure is maintained for 20 minutes after the negative pressure is absorbed and does not change.

[0048] Step 3: Remove the vacuum state in the high-pressure impregnation kettle, pressurize the high-pressure impregnation kettle to 0.85-1.25 MPa, and then heat it for reaction;

[0049] Specifically, after the reaction of step 2 is over, the vacuum state in the high-pressure impregnation kettle is removed, and the high-pressure impregnation kettle is pressurized to 0.85 MPa by an air compressor, and then the temperature is raised to 40 degrees to react for 15 minutes to allow the impregnant to penetrate into the flexible graphite.

[0050] Step 4: After the reaction is completed, repeat the dipping steps 2 and 3. After the dipping is completed, take out the sample, clean and dry it to obtain the flange gasket.

[0051] Specifically, after the reaction of step three is complete, steps two and three are repeated twice. After the immersion is completed, the sample is taken out, rinsed in distilled water, and dried at 105° C. to prepare the product.

[0052] This embodiment also provides a dip-molded flange gasket, which includes the following components in parts by weight: 7.87 parts of polytetrafluoroethylene and 92.13 parts of flexible graphite.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that the parameters in the preparation method are different. Specifically, the pressurization pressure in step 3 of this comparative example is 0.5 MPa, and the other experimental parameters and steps are consistent with Example 1. The flange gasket prepared in this comparative example includes 5.11 parts of polytetrafluoroethylene and 94.89 parts of flexible graphite.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that the parameters in the preparation method are different. Specifically, Step 2 and Step 3 are not repeated in Step 4 of this comparative example, and other experimental parameters and steps are consistent with Example 1. The flange gasket prepared in this comparative example includes 3.37 parts of polytetrafluoroethylene and 96.63 parts of flexible graphite.

[0057] The performance of the flange gaskets prepared by the above embodiments and comparative examples was tested, wherein the leakage rate was tested according to the test method B in the GB / T12385-1990 standard, using water or nitrogen as the medium to test the leakage rate of the plate. The tensile strength was tested according to the following experimental method: the sample was cut into a 100mm×20mm specification shape, the middle distance of the clamp was 50mm, and the thickness of the three points in the middle of the strip flexible graphite plate and at both ends of the clamp was measured. The average value of the three points was taken as its average thickness h. The tensile strength of the strip graphite plate was calculated according to the formula f=F / (hb), where F is the tensile force when the strip graphite plate breaks, and b is the width of the strip graphite plate. The average value of the three graphite plates was taken as the tensile strength of the graphite plate. The compression rate and rebound rate detection method is as follows: take several samples, stack them together, ensure that the stacking thickness is between 1.5 and 2mm, and use a compression rebound tester to determine its compression rate and rebound rate. Measure 3 different points and take their arithmetic mean as the compression rate and rebound rate of the sample. The experimental results are shown in Table 1 below:

[0058] serial number Compression rate (%) Rebound rate (%) Tensile strength(MPa) <![CDATA[Leakage rate (cm 3 / s)]]> Example 1 31.5 23.4 49.2 <![CDATA[1.9×10 -4 ]]> Example 2 31.3 23.3 48.6 <![CDATA[1.9×10 -4 ]]> Example 3 31.8 23.7 49.1 <![CDATA[1.9×10 -4 ]]> Comparative Example 1 36.5 20.2 25.4 <![CDATA[9.4×10 -4 ]]> Comparative Example 2 38.4 21.6 24.7 <![CDATA[1.1×10 -3 ]]>

[0059] Analysis of experimental results: From the above experimental results, it can be seen that the flange gasket prepared by the preparation method provided by the present invention has improved compression performance and resilience performance compared with pure flexible graphite sheet due to the addition of flexible material polytetrafluoroethylene, and due to the preparation method provided by the present invention, more polytetrafluoroethylene can be immersed in the flexible graphite sheet, which greatly improves the tensile strength and anti-leakage performance of the sheet.

[0060] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view. In addition, it should be understood that although this specification is described in accordance with the embodiments, it does not contain only one technical solution. This narrative of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a dip-molded flange gasket, characterized in that: The following steps are involved: Step 1: Take the flexible graphite sheet, cut it according to the flange gasket template, clean it and dry it; Step 2: After the treatment in step 1, the flexible graphite sheet is placed in a high-pressure impregnation kettle and heated, and then evacuated to negative pressure, and an impregnation liquid is added thereto, and the reaction is continued until the vacuum degree in the high-pressure impregnation kettle is stable; Step 3: Remove the vacuum state in the high-pressure impregnation kettle, pressurize the high-pressure impregnation kettle to 0.85-1.25 MPa, and then heat it for reaction; Step 4: After the reaction is completed, repeat the dipping steps 2 and 3. After the dipping is completed, take out the sample, clean and dry it to obtain the flange gasket.

2. The method for preparing a dip-molded flange gasket according to claim 1, characterized in that: In the step 1, the compression rate of the flexible graphite sheet is 41% to 42%, the rebound rate is 16% to 17%, and the tensile strength is 8 to 10 MPa.

3. The method for preparing a dip-molded flange gasket according to claim 2, characterized in that: The cleaning step in step 1 is as follows: soaking the cut flexible graphite sheet in distilled water for 20 to 30 minutes with ultrasound, soaking the flexible graphite sheet in anhydrous ethanol for 30 to 60 minutes after ultrasound, and drying the flexible graphite sheet in an oven at 100 to 110° C. after soaking.

4. The method for preparing a dip-molded flange gasket according to claim 3, characterized in that: In the step 2, the vacuum degree is -0.07 to 0.09 MPa, the impregnation liquid is a polytetrafluoroethylene dispersion with a volume concentration of 60%, and the reaction temperature is 40 to 45°C.

5. The method for preparing a dip-molded flange gasket according to claim 4, characterized in that: In the step 3, the reaction temperature is 40-45° C. and the reaction time is 10-25 min.

6. The method for preparing a dip-molded flange gasket according to claim 5, characterized in that: The step 4 is repeated 1 to 2 times.

7. A dip-molded flange gasket, characterized in that: The flange gasket is prepared by the preparation method described in any one of claims 1 to 5, and comprises the following components in parts by weight: 7 to 8 parts of polytetrafluoroethylene and 92 to 93 parts of flexible graphite.

8. The dip-molded flange gasket according to claim 7, characterized in that: The flange gasket has a compression rate of 31% to 32%, a rebound rate of 23% to 24%, a tensile strength of 48 to 50 MPa, and a leakage rate of 1.8×10 -4 ~2×10 -4 cm 3 / s.