Manufacturing method of traceless fluororubber sealing ring

Abstract

The invention relates to the technical field of sealing elements, and particularly discloses a manufacturing method of a traceless fluororubber sealing ring, which comprises a lap joint step of lapping two ends of a rubber strip into a ring, and specifically comprises the following steps: preparing a lap joint mold, communicating a rubber injection hole in the middle of a strip-shaped mold cavity of the lap joint mold, and forming cooling channels in the edges of two sides of the strip-shaped mold cavity; the two ends of a rubber strip in a raw rubber state are arranged in the strip-shaped mold cavity, and the lap joint surfaces directly face the rubber injection holes; closing the mold, pressurizing, starting heating, opening a cooling circulation system, and injecting raw rubber into the rubber injection hole in the heating process; the lap joint mold is heated to the vulcanization temperature, the temperature of a cooling channel is controlled to be 120 DEG C or below, and heat-preservation and pressure-maintaining vulcanization is conducted. According to the invention, the cooling channels are creatively arranged on the edges of the two sides of the lap joint mold, and the cooling circulation system is externally connected to carry out temperature gradient control on the lap joint mold, so that raw rubber at the positions of the cooling channels is prevented from being in a semi-vulcanization state; therefore, the unexpected effect of inhibiting the generation of uncontrolled deflection elastic stress and deformation at the lap joint after secondary vulcanization is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of sealing parts, and in particular to a method for manufacturing a traceless fluororubber sealing ring. Background Art

[0002] In order to meet the market demand for diversified sizes, fluorinated rubber generally adopts a flat vulcanization production process. This mature process not only has stable production performance, but also ensures tear force performance, smaller product size deviation, and higher product qualification rate. However, under the existing technology, for larger fluorinated rubber sealing rings with an inner diameter greater than 350mm, the use of large molds is a production method with high costs and low feasibility in terms of mold processing and machine size, so the segmented vulcanization process is generally used.

[0003] The segmented vulcanization process is to send a part of the rubber product into the vulcanizer for vulcanization, and then move to the next section after the vulcanization is completed, and then vulcanize the entire rubber product section by section. For example: China's public patent document (CN101209585A) discloses a method for preparing a large fluororubber O-ring, which specifically does not vulcanize the two ends, but first vulcanizes the middle section of the fluororubber strip section by section, and then overlaps the unvulcanized two ends into a ring shape and vulcanizes it again, thus eliminating the process of multiple-section docking and achieving uniform mechanical properties at most positions of the sealing ring. However, the overlapping force formed by the unvulcanized two ends in the disclosed flat mold still cannot meet the requirements of the sealing environment and tearing force of large-sized sealing rings.

[0004] To this end, the Chinese patent document (CN113844038A) discloses the use of uncured raw rubber strips and forming docking cuts at both ends of the raw rubber strips, then placing the docking section in a flat mold with the docking position facing the injection port of the flat mold, injecting raw rubber through the injection port during the mold heating process, and under the action of the injection pressure and the fluidity of the raw rubber, the raw rubber is uniformly infiltrated into the docking cuts and uniformly contacts with the cuts at both ends over a large area, and then the raw rubber and the raw rubber strips are strongly combined during the heat preservation and pressure vulcanization, and there is no obvious interface after trimming. However, the fluororubber sealing ring processed by this process generates uncontrolled biased elastic stress during the second vulcanization, which causes the cylinder at the interface to deform. Summary of the invention

[0005] The purpose of the present invention is to provide a method for manufacturing a traceless fluororubber sealing ring, wherein the manufactured sealing ring can achieve a cylindrical shape without traces and elastic stress.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A method for manufacturing a traceless fluororubber sealing ring includes a step of overlapping two ends of a rubber strip to form a ring, wherein the overlapping step is specifically as follows: S31, preparing a lap joint mold, wherein the lap joint mold has a strip-shaped mold cavity, a glue injection hole is connected in the middle of the strip-shaped mold cavity, and cooling channels are opened at the edges of the lap joint mold on both sides of the strip-shaped mold cavity, and the cooling channels are externally connected to a cooling circulation system; S32, the two ends of the rubber strip in the raw rubber state are placed in the strip-shaped mold cavity with the overlapping surface facing the glue injection hole; S33, closing the mold, applying pressure and starting heating, while opening the cooling circulation system, and injecting raw rubber into the injection hole during the heating process; S34, the overlapping mold is heated to the vulcanization temperature and the temperature at the cooling channel is controlled at 80°C to 120°C, and the vulcanization is carried out by maintaining heat and pressure.

[0007] Furthermore, the lap mold includes an upper mold plate and a lower mold plate, the mating surfaces of the upper mold plate and the lower mold plate are correspondingly provided with strip mold cavities, the injection hole is provided on the upper mold plate, and cooling channels are provided on the edges of the upper mold plate and the lower mold plate.

[0008] Furthermore, the distance between the cooling channel and the edge of the overlapping mold is 35mm-60mm.

[0009] Furthermore, the distance between the cooling channel and the edge of the overlapping mold is 50 mm.

[0010] Furthermore, the cooling medium of the cooling circulation system is cooling liquid or cooling gas.

[0011] Furthermore, both ends of the rubber strip in step S2 are in a raw rubber state.

[0012] Furthermore, the angle between the normal direction of the overlapping surfaces at both ends of the rubber strip in step S2 and the pressure direction of mold closing is 30°-60°, and the normal direction passes through the center point of the overlapping surface and is located on the vertical plane where the center line of the strip mold cavity is located.

[0013] Furthermore, the mold clamping pressure in step S32 is 15 MPa to 20 MPa.

[0014] Furthermore, the raw rubber injection pressure in step S33 is 10 MPa to 15 MPa.

[0015] Furthermore, it also includes a segmented vulcanization step before the overlapping step.

[0016] Furthermore, the segmented vulcanization step uses a vulcanization mold with single-side cooling or double-side cooling.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention innovatively proposes to open cooling channels on both side edges of the overlapping mold and connect an external cooling circulation system to control the temperature gradient of the overlapping mold, control the head and tail raw rubber parts at the cooling channel position to be softened without vulcanization, and avoid the raw rubber at the cooling channel position being in a semi-vulcanized state, thereby achieving the unpredictable effect of suppressing the uncontrolled lateral elastic stress and deformation generated at the overlapping joint after secondary vulcanization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a partial view of the seamless overlap of the sealing ring made by the present invention.

[0019] Figure 2 This is a partial view of the overlapping portion of the sealing ring prepared in Comparative Example 1.

[0020] Figure 3 This is a partial view of the overlapping portion of the sealing ring prepared in Comparative Example 2.

[0021] Figure 4 It is a schematic diagram of the overlapping mold structure of the present invention. DETAILED DESCRIPTION

[0022] In order to make the above features and advantages of the present invention more obvious and easy to understand, embodiments are given below with reference to the accompanying drawings for detailed description as follows. Example 1

[0023] The present embodiment provides a method for manufacturing a seamless fluororubber sealing ring, including a raw rubber preparation step, a segmented vulcanization step, and a overlapping step of overlapping the two ends of the rubber strip into a ring.

[0024] The raw rubber preparation steps are as follows: fluororubber Viton A401C and additives are mixed and thinned, extruded and cut into raw rubber strips according to the length of a sealing ring with an inner diameter of 400 mm, and the mixing temperature is not higher than 75°C.

[0025] The segmented vulcanization step is specifically as follows: taking a segmented vulcanization mold to vulcanize the raw rubber strip segment by segment, the head end 260mm of the rubber strip is exposed outside the right side of the segmented vulcanization mold, the left edge of the segmented vulcanization mold is provided with a cooling hole and an external cooling system, the cooling system is turned on during the process of mold closing, heating and pressurizing, the vulcanization temperature is 160°C, the pressure is 20MPa, and the temperature at the cooling hole is 135°C; after the vulcanization is completed, the mold is opened, the first segment is divided into a vulcanized part and a semi-vulcanized part, the vulcanized part is moved out of the segmented vulcanization mold and the semi-vulcanized part is moved to the right side of the segmented vulcanization mold, and the adjacent unvulcanized part enters the left side of the segmented vulcanization mold, and then the mold is closed, heated and pressurized, and cooling is turned on, so that the vulcanization is completed segment by segment, and at this time, both ends of the rubber strip are in a raw rubber state.

[0026] The head and tail lengths L0 should satisfy the following formula: Where: L is the length of the strip cavity of the overlapping mold, and M is the distance between the cooling channel and the edge of the mold.

[0027] The overlapping steps are specifically as follows: S31, prepare a lap mold, the lap mold includes an upper mold plate and a lower mold plate, the upper mold plate and the lower mold plate have corresponding strip mold cavities on their mating surfaces, the length of the strip mold cavity is 600mm, a glue injection hole 11 is connected in the middle of the strip mold cavity, the glue injection hole 11 is opened on the upper mold plate, and cooling channels 12 are opened at 50mm positions on the edges of the upper mold plate and the lower mold plate, the cooling channels 12 are located on the left and right sides of the strip mold cavity and respectively penetrate the front and rear sides of the upper mold plate and the front and rear sides of the lower mold plate, such as Figure 4 The cooling channel 12 is connected to an external cooling circulation system, and the cooling medium of the cooling circulation system is cooling water (in some other examples, the cooling medium may also be cooling gas).

[0028] S32. The rubber strip is beveled at both ends to form overlapping surfaces, which are placed in the strip mold cavity with the overlapping surfaces facing the injection hole 11. The angle between the normal direction of the overlapping surfaces at both ends of the rubber strip and the pressure direction of the mold is 45°, and the normal direction passes through the center point of the overlapping surface and is on the vertical plane where the center line of the strip mold cavity is located.

[0029] S33, mold clamping, pressurizing to 20MPa and starting heating, while opening the cooling circulation system, injecting raw rubber Viton A401C into the injection hole 11 during the heating process, the injection pressure is 15MPa, under the action of the injection pressure and the fluidity of the raw rubber, the raw rubber evenly penetrates into the butt cut and evenly contacts with the cuts at both ends over a large area.

[0030] S34, the overlapping mold is heated to 160°C and the temperature at the cooling channel is controlled below 120°C, and the vulcanization is carried out by heat preservation and pressure maintenance. Example 2

[0031] The difference between this embodiment and the above-mentioned embodiment 1 is only in the segmented vulcanization step. The mold used in the segmented vulcanization step of this embodiment is the same as the overlapping mold, both of which are 600mm flat molds. There are cooling channels at 50mm positions on the left and right edges. The head end 275mm of the rubber strip is exposed on the right side of the mold. The vulcanization temperature is 160°C, the pressure is 20MPa, and the temperature at the cooling channel is 135°C. After the vulcanization is completed, the mold is opened. The first segment is divided into a vulcanized part and a semi-vulcanized part on both sides. The adjacent unvulcanized part enters the left side of the mold. The right semi-vulcanized section of the previous segment is controlled not to be at the corresponding position of the cooling channel so that the right semi-vulcanized section can be vulcanized at high temperature during the vulcanization process of the next segment. Then the mold is closed, heated and pressurized, and cooling is started. In this way, the vulcanization is completed segment by segment. At this time, both ends of the rubber strip are in a raw rubber state.

[0032] The head and tail lengths L0 should satisfy the following formula: Where: L is the length of the strip cavity of the overlapping mold, and M is the distance between the cooling channel and the edge of the mold.

[0033] Comparative Example 1 The difference between this comparative example and the above-mentioned embodiment 1 is only that the overlapping mold is different. The overlapping mold of this comparative example has a cooling channel and a glue injection hole on only one side, and the head and tail overlapping lengths are the same.

[0034] Comparative Example 2 The difference between this comparative example and the above-mentioned embodiment 1 is only that the overlapping mold is different. The overlapping mold of this comparative example does not have a cooling channel and has a glue injection hole, and the head and tail overlapping lengths are the same.

[0035] The sealing rings prepared in the above-mentioned embodiments 1-2 and comparative examples 1-2 were subjected to secondary vulcanization under the same process conditions. According to the ASTM D412 test standard, the tearing force was measured to be 6 MPa to 7 MPa. However, both embodiments 1 and 2 can obtain cylinders without marks and elastic stress, and the overlapped parts have no marks. Figure 1 As shown, in the comparative examples 1-2, uncontrolled lateral elastic stress appears at the overlap, as shown in FIG. Figure 2-3 shown.

[0036] 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. The above embodiments and descriptions are only for illustrating 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, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention shall be defined by the attached claims and their equivalents.

Claims

1. A method for manufacturing a traceless fluororubber sealing ring, characterized in that: The method comprises overlapping the two ends of the rubber strip to form a ring, wherein the overlapping step is specifically as follows: S31, preparing a lap joint mold, wherein the lap joint mold has a strip-shaped mold cavity, a glue injection hole is connected in the middle of the strip-shaped mold cavity, and cooling channels are opened at the edges of the lap joint mold on both sides of the strip-shaped mold cavity, and the cooling channels are externally connected to a cooling circulation system; S32, the two ends of the rubber strip in the raw rubber state are placed in the strip-shaped mold cavity with the overlapping surface facing the glue injection hole; S33, closing the mold, applying pressure and starting heating, while opening the cooling circulation system, and injecting raw rubber into the injection hole during the heating process; S34, the overlapping mold is heated to the vulcanization temperature and the temperature at the cooling channel is controlled at 80°C to 120°C, and the vulcanization is carried out by maintaining heat and pressure.

2. The method for making a seamless fluororubber sealing ring according to claim 1, characterized in that: The overlapping mold comprises an upper mold plate and a lower mold plate, and strip-shaped mold cavities are correspondingly opened on the mold surfaces of the upper mold plate and the lower mold plate. The injection hole is opened on the upper mold plate, and cooling channels are opened on the edges of the upper mold plate and the lower mold plate.

3. The method for manufacturing a traceless fluororubber sealing ring according to claim 1, characterized in that: The distance between the cooling channel and the edge of the overlapping mold is 35mm-60mm.

4. The method for manufacturing a traceless fluororubber sealing ring according to claim 3, characterized in that: The distance between the cooling channel and the edge of the overlapping mold is 50 mm.

5. The method for manufacturing a seamless fluororubber sealing ring according to claim 1, characterized in that: The cooling medium of the cooling circulation system is cooling liquid or cooling gas.

6. The method for manufacturing a seamless fluororubber sealing ring according to claim 1, characterized in that: The angle between the normal direction of the overlapping surfaces at both ends of the rubber strip in step S2 and the pressure direction of the mold closing is 30°-60°, and the normal direction passes through the center point of the overlapping surface and is located on the vertical plane where the center line of the strip mold cavity is located.

7. The method for manufacturing a seamless fluororubber sealing ring according to claim 1, characterized in that: The mold clamping pressure in step S32 is 15 MPa to 20 MPa.

8. The method for manufacturing a seamless fluororubber sealing ring according to claim 1, characterized in that: The raw rubber injection pressure in step S33 is 10MPa to 15MPa.

9. The method for manufacturing a seamless fluororubber sealing ring according to any one of claims 1 to 8, characterized in that: It also includes a segmented vulcanization step before the overlapping step.

10. The method for manufacturing a traceless fluororubber sealing ring according to claim 9, characterized in that: The segmented vulcanization step is a vulcanization mold with single-side cooling or double-side cooling.

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