Preparation method of low-torque integrated ball valve

Abstract

The application discloses a preparation method of a low-torque integrated ball valve, and relates to the field of ball valve components. The method comprises the following steps: PVC valve body granule preparation, PP ball core granule preparation, ball core forming, rubber ring forming, integrated ball valve forming and post-processing. The PVC valve body granule adopts an acrylate flow modifier, an external lubricant and an internal lubricant compound system to significantly improve the melt flowability. A double-lubrication system is formed by spraying silicon oil on the surface of the ball core and the silicone additive in the rubber ring, and the knob is ground and matched with the post-processing and secondary brushing of the silicon oil, so that the operation torque is effectively reduced, the sealing performance is improved, the integrated ball valve with a smooth surface, no defects, no offset of the insert, an operation torque of less than or equal to 15 N.m, no water leakage under a pressure of 2.0 MPa and a service life of more than 8 years is obtained, the balance among injection molding tightness, low torque and high sealing effect is achieved, and the integrated ball valve is suitable for various scenes such as water supply and drainage, chemical transportation and home decoration pipeline.

Description

Technical Field

[0001] This application relates to the field of ball valve components, and in particular to a method for manufacturing a low-torque integrated ball valve. Background Technology

[0002] Ball valves, as important shut-off and regulating devices, are widely used in water supply, chemical, and water treatment industries. PVC (polyvinyl chloride) ball valves, due to their advantages such as light weight, corrosion resistance, and low cost, have been widely used in piping systems. Currently, PVC ball valves mainly exist in two forms: split-type and integrated-type.

[0003] Split-type PVC ball valves are made by injection molding each component, such as the valve body, ball core, and rubber ring, separately, and then assembling them by means of threads, flanges, etc. This makes it easy to replace and repair the parts independently. However, the split structure has more parts, the assembly process is more complicated, and the production cost is higher.

[0004] An integrated ball valve uses injection-molded ball cores, rubber rings, and other components as inserts, placed into a mold, and then the valve body material is injection molded around the inserts, achieving integral molding of the valve body and internal inserts. Integrated ball valves reduce the number of connection interfaces between components, offering advantages such as compact structure, fewer leakage points, and high production efficiency. However, they also have the following technical challenges: during injection molding, issues such as insert movement or insufficient mold filling can easily occur, making it difficult to achieve a balance between tight injection molding, low torque, and high sealing performance in integrated ball valves. Summary of the Invention

[0005] To address the challenge of achieving a balance between tight injection molding, low torque, and high sealing performance in one-piece ball valves, this application provides a method for manufacturing a low-torque one-piece ball valve, aiming to obtain a ball valve with tight injection molding, low operating torque, and excellent sealing performance.

[0006] A method for manufacturing a low-torque integrated ball valve includes the following steps: Preparation of PVC valve body granules: By weight, 100 parts of PVC resin, 4-6 parts of heat stabilizer, 3-5 parts of processing aid ACR-401, 0.5-1.0 parts of external lubricant, 0.5-1.0 parts of internal lubricant, 0.3-0.6 parts of primary antioxidant, and 1.5-2.5 parts of acrylate flow modifier are mixed, kneaded, extruded and granulated to obtain PVC valve body granules; Preparation of PP core granules: 100 parts by weight of PP resin, 25-35 parts by weight of talc, 0.3-0.5 parts by weight of secondary antioxidant, 0.8-1.2 parts by weight of ethylene bis-stearamide, and 0.5-1.0 parts by weight of polyolefin wax are mixed, kneaded, extruded and granulated to obtain PP core granules. Core forming: The PP core granules are injected into the core mold to form a core. After demolding, the core is shaped with a stopper and cooled to obtain a core. Then, silicone oil is sprayed onto the surface of the core to obtain a core coated with silicone oil. Rubber ring molding: Mix 100 parts by weight of thermoplastic elastomer, 0.1-0.5 parts by weight of silicone additives, 0.2-0.4 parts by weight of third antioxidant, and 0.3-0.6 parts by weight of lubricant, and then injection mold to obtain rubber rings; One-piece ball valve molding: Using the PVC valve body granules as the valve body raw material, the ball core and rubber ring coated with silicone oil are used as inserts. The PVC valve body granules are injected into the ball valve mold for injection molding, demolded, and a one-piece ball valve rough product is obtained. Post-processing: After the knob is run-in on the rough integrated ball valve, a second silicone oil is applied to the surface of the ball core. Then the ball valve is closed and allowed to cool naturally. Finally, the ball valve is opened and allowed to cool naturally to obtain a low-torque integrated ball valve.

[0007] In the integrated ball valve of this application, the valve body material is a PVC valve body granule with a specific composition. Unlike traditional PVC valve body materials, the PVC valve body granule of this application adopts a compound lubrication system of acrylic flow modifier, external lubricant, and internal lubricant, which significantly reduces the viscosity of PVC melt and improves the fluidity of PVC melt. This allows the ball valve to be molded without excessively high injection pressure, which can prevent the problem of insufficient filling of traditional PVC melt and improve the problem of easy movement of inserts such as ball core and rubber ring during injection molding. This ensures that the PVC melt can quickly and uniformly fill the mold during the integrated molding of the ball valve, wrapping the ball core and rubber ring, laying the foundation for improving the structural stability and low-torque operation of the integrated ball valve. At the same time, the processing aid ACR-401 and heat stabilizer are added. The processing aid ACR-401 improves the melt strength and uniformity, and the heat stabilizer inhibits the decomposition of PVC resin during high-temperature processing. Combined with the uniform filling of PVC melt, the strength of the valve body structure is guaranteed, which is conducive to improving the service life of the integrated ball valve.

[0008] In the integrated ball valve of this application, the ball core material is PP ball core granules with a specific composition. An appropriate amount of talc powder is added to the PP ball core granules as a filler. The talc powder is used to inhibit the crystallization shrinkage of PP resin. At the same time, by reasonably controlling the cooling rate of the ball core, deformation caused by uneven cooling of the ball core is prevented, thus ensuring the rigidity and dimensional stability of the ball core and laying the foundation for low torque operation.

[0009] In the integrated ball valve of this application, the rubber ring is based on thermoplastic elastomer with added silicone additives, and silicone oil is sprayed onto the surface of the ball core during the ball core molding process. These two components form a "dual lubrication" system, significantly reducing the frictional resistance between the ball core, the rubber ring, and the valve body, and laying the foundation for low-torque operation. Furthermore, after the ball valve is integrally molded, the knob is broken in, and a second application of silicone oil further optimizes the lubrication effect of the integrated ball valve, ensuring low-torque operation.

[0010] This application effectively solves the problem of achieving a balance between tight injection molding, low torque, and high sealing effect in integrated ball valves by selecting suitable valve body materials, ball core materials, and rubber ring materials, under suitable injection molding process conditions, and combined with post-processing processes. This results in an integrated ball valve with a smooth and defect-free surface, no insert misalignment, operating torque ≤15N·m, no leakage under 2.0MPa pressure, and a service life ≥8 years.

[0011] In some specific implementations, the extrusion temperature in the PVC valve body granule preparation step is 165-175℃, and the screw speed is 23-26 r / min.

[0012] In this application, the extrusion temperature of the PVC valve body granules is controlled within the range of 165-175℃, which ensures both sufficient plasticization of the PVC valve body granules and prevents the decomposition of PVC resin due to excessively high temperatures. In some specific embodiments, the PVC resin is preferably SG-7 type PVC resin; the heat stabilizer is a calcium-zinc composite stabilizer; the processing aid ACR-401 has an intrinsic viscosity of 10-15 at 25℃; the external lubricant is a polyolefin wax, such as PE wax, PP wax, etc.; the internal lubricant can be any internal lubricant commonly used in the PVC processing field, and the internal lubricant is further preferably stearic acid; the first antioxidant can be any antioxidant commonly used in the PVC processing field or a compound antioxidant, such as antioxidant 1010, antioxidant 1076 and its compound with antioxidant 168, etc.; the acrylate flow modifier is the product of Zibo Huaxing Additives Co., Ltd., model ACR-ZB-101 or model ACR-ZB-175, with an intrinsic viscosity of 0.5-1.5 at 25℃.

[0013] In some specific embodiments, in the PP ball core material preparation step, the talc powder has a particle size range of 1000-1200 mesh. The talc powder particles are small and have a large specific surface area, which makes them more uniformly dispersed in the PP matrix. This is beneficial for obtaining a ball core with better sphericity. At the same time, talc powder can improve the stiffness and dimensional stability of the ball core, and it is not easy to deform or wear even after long-term use, which is conducive to maintaining the stability of the operating torque of the integrated ball valve.

[0014] In some specific embodiments, the second antioxidant can be any antioxidant commonly used in PP processing or a compound antioxidant, such as antioxidant 1010, antioxidant 1076, and their compounding with antioxidant 168, etc. Furthermore, this core system contains a significant amount of talc powder, and uses ethylene bis-stearamide and polyolefin wax as lubricants, which can further improve the surface processing properties of the PP core granules, improve the surface smoothness and sphericity after core molding, and further reduce operating resistance.

[0015] In some specific implementations, the extrusion temperature in the PP ball core material preparation step is 170-180℃, and the screw speed is 25-33 r / min.

[0016] In this application, the extrusion temperature of the PP core material is controlled at 170-180℃. Under the premise of ensuring uniform dispersion of talc powder, excessively high temperature is avoided to prevent PP degradation or talc powder agglomeration, which is conducive to obtaining PP core granules with uniform plasticization and good filler dispersion.

[0017] In some specific implementations, during the core molding step, water at 5-10°C is introduced into the core mold, the core injection temperature is 180-190°C, the injection pressure is 50-100MPa, the holding pressure is 40-50MPa, and the holding time is 35-55s. After the core is shaped using a stopper, it is cooled with flowing water at 15-20°C for 30-45 minutes.

[0018] In the process of forming the ball core, this application controls the appropriate injection temperature, injection pressure and holding time, and introduces water at 5-10℃ into the mold to quickly solidify the ball core inside the mold. After demolding, the ball core is shaped with a stopper and cooled with flowing water at 15-20℃, which effectively controls the cooling rate of the ball core, ensures the stability of the ball core size, and avoids deformation caused by uneven cooling.

[0019] In some specific implementations, the amount of silicone oil sprayed in the core forming step is 0.1-0.2g / piece.

[0020] In this application, spraying an appropriate amount of silicone oil onto the surface of the ball core can reduce the frictional resistance between the ball core and the valve body, and also prevent excessive silicone oil from affecting the bonding strength between the valve body and the insert.

[0021] In some specific implementations, the thermoplastic elastomer used in the ring forming step is a thermoplastic elastomer TPE with a Shore hardness of 70-80A.

[0022] In this application, the rubber ring uses thermoplastic elastomer TPE with a Shore hardness of 70-80A as the main component to balance the wear resistance, resilience and flexibility of the rubber ring, ensuring the sealing effect of the rubber ring while preventing the rubber ring from becoming too hard, which would lead to increased operating torque or brittleness.

[0023] In some specific implementations, during the ring molding process, the injection temperature is 160-170℃, the injection pressure is 60-80MPa, the holding pressure is 30-40MPa, and the holding time is 10-15s.

[0024] In some specific implementations, during the integral molding step of the ball valve, the injection temperature is 170-180℃, the injection pressure is 50-90MPa, the holding pressure is 35-45MPa, the holding time is 15-20s, and the cooling before demolding is 60-90s.

[0025] In the integral molding process of the ball valve in this application, the injection pressure and holding pressure are both below 100MPa. The ball core, rubber ring and other inserts are not easy to move during the valve body injection process. The inserts are tightly connected to the valve body without gaps or offset, which overcomes the problem of increased operating torque caused by ball core offset. At the same time, with the injection temperature of 170-180℃, the PVC melt can be fully flowed to fill the mold, avoiding valve body structural defects caused by insufficient filling, and further ensuring the sealing performance and structural strength of the valve body.

[0026] In some specific implementations, during the post-processing steps, the ball valve knob is rotated clockwise and counterclockwise 5-10 times each during the knob break-in process, the amount of secondary silicone oil applied is 0.05-0.1g / piece, and the ball valve is closed and allowed to cool naturally for 30-60 minutes.

[0027] This application allows the silicone oil to be evenly dispersed on the surface of the ball core through a knob break-in process, promptly exposing and filling areas with insufficient lubrication. A second application of silicone oil further replenishes the lubrication layer. Combined with segmented cooling operations, this ensures that the internal structure of the ball valve is fully stabilized, and the rubber ring fits tightly with the ball core and valve body, improving sealing performance. At the same time, it ensures the overall dimensional stability of the ball valve, with no residual stress, guaranteeing the low torque and stable sealing performance of the integrated ball valve.

[0028] In summary, this application includes at least the following beneficial technical effects: 1. Low operating torque and easy to use: Through the combination of "silicone oil spraying on the ball core + self-lubrication of the rubber ring + post-treatment break-in", the frictional resistance between the ball core, rubber ring and valve body is significantly reduced. The ball valve operating torque is ≤15N·m, the rotation is smooth and the use is convenient, especially suitable for manual operation scenarios.

[0029] 2. One-piece molding, stable structure: The ball core and rubber ring are molded with the valve body as inserts in one piece using an integrated injection molding process, avoiding the cumbersome process of separate assembly. At the same time, by selecting appropriate valve body raw materials and injection molding parameters, the positioning of the inserts is ensured to be accurate and the fit with the valve body is tight, without gaps or offset. The stability of the one-piece ball valve structure is improved and the service life is extended to more than 8 years.

[0030] 3. Stable dimensions and reliable sealing: The PP ball core is filled with talc powder and combined with a specific cooling and shaping process to obtain a ball core with excellent dimensional stability and no deformation. Secondly, the rubber ring surface is self-lubricating and has good sealing performance, which fits tightly with the ball core and valve body to meet the sealing requirements of various fluid transportation. In addition, the segmented cooling of the integrated ball valve in the post-processing stage makes the internal structure of the ball valve fully stable, and the rubber ring fits tightly with the ball core and valve body to improve the sealing performance. At the same time, it ensures the overall dimensional stability of the ball valve, with no stress residue, and guarantees the low torque and stable sealing performance of the integrated ball valve.

[0031] 4. Controllable process, suitable for industrial mass production: The parameters of each step are clear and controllable. The PVC valve body granules with specific composition have good flowability, smooth injection molding, and no surface defects. The preparation process of ball core and rubber ring is mature, the post-processing process is simple, no new special equipment is required, it is compatible with existing injection molding production lines, and can realize large-scale industrial mass production.

[0032] 5. Low cost and high practicality: Made with conventional raw materials such as PVC and PP, and filled with talc powder to reduce raw material costs, eliminating the need for expensive additives; the product is corrosion-resistant and has good insulation properties, making it suitable for various scenarios such as water supply and drainage, chemical transportation, and home decoration pipes. It offers high cost performance and has broad market application prospects. Detailed Implementation

[0033] The following provides further explanation with reference to specific implementation methods. Example

[0034]

Example 1

[0035] Comparative Example Comparative Example 1 A method for preparing an integrated ball valve differs from [Example 1] in that: in the PVC valve body granule preparation step, an equal mass of PE wax is used instead of an acrylic flow modifier.

[0036] Comparative Example 2 The method for preparing an integrated ball valve differs from that in [Example 1] in that: in the ball core forming step, the ball core mold is not equipped with a chiller, that is, the ball core mold is not circulated with cooling water at a temperature of 8°C. In addition, after the ball core is demolded, it is positioned by a stopper and then cooled naturally in the air, without using flowing water at 18°C ​​for cooling.

[0037] Comparative Example 3 A method for manufacturing an integrated ball valve differs from [Example 1] in that: in the integrated molding step of the ball valve, the injection pressure is 150 MPa and the holding pressure is 100 MPa.

[0038] Comparative Example 4 The method for preparing an integrated ball valve differs from that in [Example 1] in that the step of "closing the ball valve and allowing it to cool naturally for 45 minutes" is omitted in the post-processing steps.

[0039] Performance testing (1) Operating torque: The finished ball valve was opened and closed using a torque tester, and the maximum torque value during the operation was recorded. Each sample was tested 3 times, and 5 samples were randomly selected from each example and comparative example for testing.

[0040] (2) Sealing performance: Install the ball valve into the sealing test device, apply water pressure of 1.0MPa and 2.0MPa respectively with the ball valve closed, and observe whether there is leakage at the connection between the valve body and the ball core within 30s of holding the pressure.

[0041] (3) Injection Molding Appearance: Visually inspect whether the surface of the one-piece ball valve rough product is smooth, whether there are defects such as shrinkage cavities and flash, and check whether the inserts (ball core, rubber ring) have shifted.

[0042] (4) Ball core size deviation: Use a vernier caliper (accuracy ±0.02mm) to measure the outer diameter of the ball core, compare it with the design standard value, and calculate the deviation range.

[0043] Table 1

[0044] Note: The nominal diameter of the integrated ball valve tested above is DN100.

[0045] As shown in Table 1, the integrated ball valve prepared in Example 1 exhibits excellent overall performance, with an operating torque ≤15 N·m, no leakage under 2.0 MPa pressure, a smooth valve body surface, tight fit with the insert without misalignment, and a ball core size deviation of only ±0.2 mm. In Comparative Example 1, replacing the acrylate flow modifier with an equal mass of PE wax resulted in shrinkage cavities in the valve body, localized gaps between the valve body and the insert, decreased sealing performance of the integrated ball valve, and increased operating torque. Comparative Example 2 used a different ball core cooling method than Example 1, leading to an increased ball core size deviation of ±0.8 mm and a significant increase in operating torque. Comparative Example 3 experienced insert misalignment due to excessive injection pressure, resulting in increased operating torque. Comparative Example 4 omitted the cooling step of closing the ball valve during post-processing, leading to decreased sealing performance and increased operating torque in the integrated ball valve. These comparisons fully demonstrate the advantages of the technical solution presented in achieving a balance between tight injection molding, low torque, and high sealing performance.

[0046] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for manufacturing a low-torque integrated ball valve, characterized in that, Includes the following steps: Preparation of PVC valve body granules: By weight, 100 parts of PVC resin, 4-6 parts of heat stabilizer, 3-5 parts of processing aid ACR-401, 0.5-1.0 parts of external lubricant, 0.5-1.0 parts of internal lubricant, 0.3-0.6 parts of primary antioxidant, and 1.5-2.5 parts of acrylate flow modifier are mixed, kneaded, extruded and granulated to obtain PVC valve body granules; Preparation of PP core granules: 100 parts by weight of PP resin, 25-35 parts by weight of talc, 0.3-0.5 parts by weight of secondary antioxidant, 0.8-1.2 parts by weight of ethylene bis-stearamide, and 0.5-1.0 parts by weight of polyolefin wax are mixed, kneaded, extruded and granulated to obtain PP core granules. Core forming: The PP core granules are injected into the core mold to form a core. After demolding, the core is shaped with a stopper and cooled to obtain a core. Then, silicone oil is sprayed onto the surface of the core to obtain a core coated with silicone oil. Rubber ring molding: Mix 100 parts by weight of thermoplastic elastomer, 0.1-0.5 parts by weight of silicone additives, 0.2-0.4 parts by weight of third antioxidant, and 0.3-0.6 parts by weight of lubricant, and then injection mold to obtain rubber rings; One-piece ball valve molding: Using the PVC valve body granules as the valve body raw material, the ball core and rubber ring coated with silicone oil are used as inserts. The PVC valve body granules are injected into the ball valve mold for injection molding, demolded, and a one-piece ball valve rough product is obtained. Post-processing: After the knob is run-in on the rough integrated ball valve, a second silicone oil is applied to the surface of the ball core. Then the ball valve is closed and allowed to cool naturally. Finally, the ball valve is opened and allowed to cool naturally to obtain a low-torque integrated ball valve.

2. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the PVC valve body granule preparation process, the extrusion temperature is 165-175℃ and the screw speed is 23-26 r / min.

3. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the preparation of PP core material, the particle size of talc powder ranges from 1000 to 1200 mesh.

4. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the PP ball core material preparation process, the extrusion temperature is 170-180℃ and the screw speed is 25-33r / min.

5. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the core molding process, water at 5-10℃ is introduced into the core mold, the core injection temperature is 180-190℃, the injection pressure is 50-100MPa, the holding pressure is 40-50MPa, and the holding time is 35-55s.

6. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the core forming process, after the core is shaped by the plug, it is cooled with flowing water at 15-20℃ for 30-45 minutes.

7. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the core forming process, the amount of silicone oil sprayed is 0.1-0.2g / piece.

8. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the ring molding process, the thermoplastic elastomer is TPE with a Shore hardness of 70-80A, the injection temperature is 160-170℃, the injection pressure is 60-80MPa, the holding pressure is 30-40MPa, and the holding time is 10-15s.

9. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the one-piece molding process of the ball valve, the injection temperature is 170-180℃, the injection pressure is 50-90MPa, the holding pressure is 35-45MPa, the holding time is 15-20s, and the cooling before demolding is 60-90s.

10. The method for manufacturing a low-torque integrated ball valve according to claim 1, characterized in that: In the post-processing steps, during the knob break-in process, rotate the ball valve knob clockwise and counterclockwise 5-10 times each, apply 0.05-0.1g of secondary silicone oil per knob, and allow the ball valve to cool naturally for 30-60 minutes after closing.

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