A rubber handle sheath forming device and its forming process

Abstract

The present invention discloses a rubber handle sheath forming device and its forming process, including the following steps: mixing polyurethane, polyacrylonitrile, a foaming agent, etc. to obtain an inner layer material and injecting it into the inner layer injection barrel; injecting the outer layer material into the outer layer injection barrel; injecting the outer layer material into the mold to form a wear-resistant layer, and then injecting the inner layer material to fill the mold; the inner layer material foams, and polyacrylonitrile precipitates to form a reticular fiber structure; cooling and demolding to obtain the rubber handle sheath. The present invention uses co-injection foaming technology to simultaneously or continuously inject an inner layer foaming material mainly composed of polyurethane and a relatively hard outer layer rubber material into the handle sheath mold, and prepares an integrated handle sheath with a hard wear-resistant outer layer and a soft foaming inner layer. Among them, the wear-resistant layer significantly improves the wear resistance of the handle sheath, and the foaming inner layer provides a soft grip and good elastic recovery, increasing the comfort of use.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molding, specifically to the foaming molding of plastic state materials, and particularly to a rubber handgrip sheath molding device and its molding process. Background Art

[0002] Rubber handgrip sheaths are widely used in multiple industries. In the field of sports goods, they are commonly found in fitness equipment such as treadmills, cross-trainers, and multi-station gyms, providing users with a comfortable handle grip and effectively reducing hand fatigue. In the vehicle parts industry, whether it is bicycles, motorcycles, or cars, rubber handgrip sheaths can provide a high-quality grip experience and anti-slip performance, thereby enhancing driving comfort and safety.

[0003] A rubber handgrip sheath is a tubular protective structure made of rubber material, usually applied to the handle parts of various equipment and tools, aiming to bring a more comfortable grip experience to users and enhance anti-slip performance. Among them, some handgrip sheaths adopt a multi-layer design, including a buffer layer and a wear-resistant layer, thereby further improving durability and protection effect. In addition, there is also a design of an integrated molding structure, making the sheath more stable and durable.

[0004] However, the current molding process of rubber handgrip sheaths mainly relies on single injection molding or foaming technology, and these technologies have certain limitations in terms of production efficiency, product quality, and functionality. Especially in the manufacturing process of multi-layer structures, a method of preparing layers separately and then bonding is mostly adopted, but the bonding strength between the sheath layers prepared by this method is insufficient, and delamination and cracking are likely to occur.

[0005] Therefore, it is necessary to provide a rubber handgrip sheath molding device and its molding process to solve the above technical problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a rubber handgrip sheath molding device and its molding process.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A molding process for a rubber handgrip sheath, comprising the following steps:

[0008] S1. Uniformly blend 80 parts of polyurethane, 0 - 20 parts of polyacrylonitrile, 0 - 5 parts of foaming agent, 0 - 1 part of stabilizer, 0 - 2 parts of lubricant, and 0 - 1 part of antioxidant by weight to obtain an inner layer material, and add the inner layer material into the inner layer injection barrel;

[0009] S2. Blend 100 parts of the outer rubber material, 0 - 2 parts of vulcanizing agent, 0 - 2 parts of accelerator, 0 - 3 parts of activator, 0 - 5 parts of reinforcing injection agent, 0 - 2 parts of plasticizer, and 0 - 1 part of antioxidant by weight to obtain the outer material, and add the outer material to the outer injection barrel;

[0010] S3. Inject the outer material into the handle sheath mold, and the outer material adheres to the cavity wall of the handle sheath mold to form a wear-resistant layer. The injection degree is set at 30 - 40%;

[0011] S4. Inject the inner material into the central part of the handle sheath mold along with the outer material until the handle sheath mold is 100% filled. After the inner material enters the handle sheath mold, it decompresses and foams, and polyacrylonitrile precipitates from the inner material along with the foaming gas and migrates to the contact boundary between the inner material and the outer material, forming a network fiber structure spanning the inner material and the outer material;

[0012] S5. Lower the temperature of the handle sheath mold to room temperature, do not perform pressure holding, and keep it for 5 - 20 minutes to cool and demold the handle sheath, obtaining a rubber handle sheath.

[0013] In a preferred embodiment of the present invention, in the S1, for the blending of the inner material and the inner injection barrel, the temperature is 280 - 350 °C and the pressure is 8 - 20 MPa.

[0014] In a preferred embodiment of the present invention, the outer rubber material is one of vulcanized rubber, styrene-butadiene rubber, or chloroprene rubber.

[0015] In a preferred embodiment of the present invention, in the S4, the stepwise foaming technology is used to control the foaming process of the inner material, including the following steps:

[0016] S41. Control the initial temperature of the handle sheath mold at 80 - 100 °C and the pressure at 10 - 20 MPa;

[0017] S42. Preliminary foaming stage: After the injection of the inner material starts, the temperature rises by 5 °C every 5 s and the pressure drops by 1 MPa every 5 s;

[0018] S43. Generation and stabilization stage of the foaming gas:

[0019] When the temperature in the handle sheath mold is 110 - 120 °C, maintain the temperature and pressure for 30 - 60 s;

[0020] When the temperature in the handle sheath mold is 130 - 140 °C, maintain the temperature and pressure for 30 - 60 s;

[0021] When the temperature in the handle sheath mold is 150 - 160 °C, maintain the temperature and pressure for 30 - 60 s;

[0022] S44. Inner layer material foam curing:

[0023] Lower the temperature of the handle sheath mold to 80 - 100 °C, lower the pressure to 0.5 - 1.5 MPa, and maintain for 2 - 5 min.

[0024] In a preferred embodiment of the present invention, in S42 and S43, vibrate the handle sheath mold: the vibration frequency is 15 - 30 Hz, the vibration amplitude is 60 - 100 um, and vibrate in multiple directions in sequence and cycle for 2 - 5 s.

[0025] In a preferred embodiment of the present invention, in S4, the injection rate of the inner layer material is 2 - 3 times that of the outer layer material.

[0026] A rubber handle sheath forming device, based on the rubber handle sheath forming process described in any one of the above, includes: an injection system, a handle sheath mold, and a control system for controlling the operation of the injection system and the handle sheath mold;

[0027] The injection system includes: a plurality of injection barrels, a discharge pipe provided on one side of the injection barrels, and a nozzle provided at the other end of the discharge pipe;

[0028] The discharge pipe is a multi - outlet end structure and is respectively connected to a plurality of nozzles;

[0029] The nozzle includes: a discharge port, an inner layer material flow channel and an outer layer material flow channel connected to the discharge pipe;

[0030] The discharge port is docked with the handle sheath mold to inject materials into it;

[0031] The inner layer material flow channel is arranged at the central part of the outer layer material flow channel;

[0032] The handle sheath mold includes: an upper mold and a lower mold combined into a tubular structure cavity for forming a rubber handle sheath;

[0033] The control system includes: a temperature control module, a pressure control module, an injection barrel control module, and an automation control module;

[0034] The temperature control module includes: a plurality of temperature monitoring units and temperature adjustment units; a plurality of the temperature monitoring units are respectively used to monitor the temperatures of the injection barrels and the handle sheath mold, and a plurality of the temperature adjustment units are respectively used to adjust the temperatures of the injection barrels and the handle sheath mold;

[0035] The pressure control module includes: a number of pressure monitoring units and pressure regulating units; the number of pressure monitoring units are respectively used to monitor the pressures of the injection barrel and the handle sheath mold, and the number of pressure regulating units are respectively used to regulate the pressures of the injection barrel and the handle sheath mold;

[0036] The injection barrel control module is used to control the injection rate of a number of injection barrels;

[0037] The automatic control module is used to integrate and control the operations of the injection system, the handle sheath mold and the control system, and precisely execute according to the forming process steps of the rubber handle sheath.

[0038] In a preferred embodiment of the present invention, the number of injection barrels includes: an independent inner layer injection barrel and an outer layer injection barrel.

[0039] In a preferred embodiment of the present invention, the automatic control module is provided with a staged foaming mechanism, including:

[0040] The initial temperature of the handle sheath mold is controlled at 80 - 100 °C, and the pressure is controlled at 10 - 20 MPa;

[0041] In the initial foaming stage after the injection of the inner layer material: the temperature rises by 5 °C every 5 s, and the pressure drops by 1 MPa every 5 s;

[0042] The generation and stabilization stage of the foaming gas:

[0043] When the temperature in the handle sheath mold is 110 - 120 °C, the temperature and pressure are maintained for 30 - 60 s;

[0044] When the temperature in the handle sheath mold is 130 - 140 °C, the temperature and pressure are maintained for 30 - 60 s;

[0045] When the temperature in the handle sheath mold is 150 - 160 °C, the temperature and pressure are maintained for 30 - 60 s;

[0046] Curing of the inner layer material foam:

[0047] The temperature of the handle sheath mold is reduced to 80 - 100 °C, and the pressure is reduced to 0.5 - 1.5 MPa, lasting for 2 - 5 min.

[0048] In a preferred embodiment of the present invention, the control system further includes a vibration module, and the vibration module includes: a number of vibration units; the number of vibration units are evenly distributed on the outer surface of the handle sheath mold.

[0049] The present invention solves the defects in the background art, and the present invention has the following beneficial effects:

[0050] The present invention provides a molding process for a rubber handlebar cover. By using the co-injection foaming technology, an inner foaming material with polyurethane as the main component and an outer rubber material with a harder texture are simultaneously or continuously injected into a handlebar cover mold to prepare an integrated handlebar cover having a hard wear-resistant outer layer and a soft foamed inner layer. The wear-resistant layer significantly improves the wear resistance of the handlebar cover, and the foamed inner layer provides a soft grip and good elastic recovery, thereby increasing the comfort of use. Compared with the prior art, the present invention prepares the rubber handlebar cover by integral molding, which not only significantly improves the production efficiency, but also effectively solves the problems of poor interface connection, delamination and cracking that may occur during the layered preparation and bonding process.

[0051] The present invention adds polyacrylonitrile to the foaming inner layer material. The melting point of polyacrylonitrile is much higher than the foaming temperature of polyurethane. When the inner layer material enters the handlebar cover mold, the pressure decreases, the polyurethane starts to foam, and as the temperature increases, the viscosity of the polyurethane matrix decreases. Due to the thermal stability of polyacrylonitrile, an independent phase is formed in the polyurethane matrix. The polyacrylonitrile will precipitate from the polyurethane with the movement of the foaming gas. Moreover, because the temperature of the polyacrylonitrile is higher than the melting point before injection, the temperature decreases after entering the handlebar cover mold. The precipitation process cooperates with the curing process after the temperature decreases. The polyacrylonitrile achieves the goal of spanning the two interfaces of the inner layer material and the outer layer material, and forms a network-like fiber morphology between the two interfaces, thereby increasing the connection between the inner and outer layers and further reducing the problems of stratification and cracking.

[0052] During the injection process, the present invention first injects the outer layer material to adhere to the wall of the mold cavity of the handlebar cover mold to form a wear-resistant layer. After the injection degree reaches 30-40%, the inner layer material and the outer layer material are injected synchronously, and the inner layer material is in the center of the outer layer material, and the injection rate of the inner layer material is 2-3 times that of the outer layer material, ensuring that the inner layer material is always wrapped by the outer layer material during the injection and subsequent foaming process, effectively preventing the inner layer material from being exposed, significantly improving the molding efficiency of the rubber handlebar cover, and effectively improving the product yield.

[0053] The present invention proposes a staged foaming technology. After the inner layer material starts to foam, the duration of the foaming process is effectively extended through a series of temperature, pressure and pressure holding time controls. This provides sufficient precipitation time for polyacrylonitrile in the polyurethane matrix, ensuring that more polyacrylonitrile can be smoothly precipitated to the contact boundary between the inner layer material and the outer layer material. This technical improvement significantly increases the connection anchor points between the inner layer material and the outer layer material, thereby greatly reducing the delamination and cracking problems that may occur during the use of the product, and improving the stability and durability of the overall structure.

[0054] By introducing vibration assistance during the foaming process of the inner layer material and combining it with the co-injection foaming technology, the present invention effectively reduces the viscosity of the injection material melt, thereby significantly improving its fluidity. This innovative method helps to achieve a more uniform melt distribution and better mold filling performance during the co-injection foaming molding process. At the same time, this method can also significantly reduce common defects in the injection molding process, such as weld lines, sinks, and warping, thus greatly improving the finished product quality of the rubber handle sheath.

[0055] During the foaming process of the inner layer material of the present invention, multi-directional sequential cyclic vibration is used in combination with the staged foaming technology. Through the multi-directional vibration effect, the foaming gas molecules can be more uniformly dispersed in the polyurethane matrix, thereby generating finer and more uniformly distributed foam cell structures. This improvement significantly increases the precipitation amount and uniformity of polyacrylonitrile in the inner layer material, thereby promoting the migration of polyacrylonitrile to the contact boundary between the inner layer material and the outer layer material. In addition, the multi-directional vibration helps the precipitated polyacrylonitrile fibers to change direction and achieve cross-linking, thereby constructing a complex network fiber structure that spans the inner and outer layer materials. This network fiber structure not only enhances the structural integrity of the handle sheath but also significantly improves its mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0057] Figure 1 It is a process flow chart of the molding of a rubber handle sheath according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0059] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0060] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the protection scope of the present application.

[0061] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific circumstances.

[0062] As Figure 1 shown, the present invention provides a forming process for a rubber handgrip sheath, including the following steps:

[0063] S1. Uniformly blend 80 parts of polyurethane, 0 - 20 parts of polyacrylonitrile, 0 - 5 parts of foaming agent, 0 - 1 part of stabilizer, 0 - 2 parts of lubricant, and 0 - 1 part of antioxidant, etc. by weight to obtain the inner layer material, and add the inner layer material into the inner layer injection barrel.

[0064] S2. Uniformly blend 100 parts of outer layer rubber material, 0 - 2 parts of vulcanizing agent, 0 - 2 parts of accelerator, 0 - 3 parts of activator, 0 - 5 parts of reinforcing injection agent, 0 - 2 parts of plasticizer, and 0 - 1 part of antioxidant, etc. by weight to obtain the outer layer material, and add the outer layer material into the outer layer injection barrel.

[0065] S3. Inject the outer layer material into the handgrip sheath mold. The outer layer material adheres to the cavity wall of the handgrip sheath mold to form a wear-resistant layer, and the injection degree is set at 30 - 40%.

[0066] S4. Inject the inner layer material into the central part of the handgrip sheath mold along with the outer layer material until the handgrip sheath mold is 100% filled. After the inner layer material enters the handgrip sheath mold, it is depressurized and foamed. The polyacrylonitrile precipitates from the inner layer material along with the foaming gas and migrates to the contact boundary between the inner layer material and the outer layer material, forming a network fiber structure spanning the inner layer material and the outer layer material.

[0067] S5. Reduce the temperature of the handgrip sheath mold to room temperature, do not perform pressure holding, and keep it for 5 - 20 min to cool and demold the handgrip sheath, obtaining the rubber handgrip sheath.

[0068] The present invention provides a molding process for a rubber handle sheath. Using co-injection foaming technology, an inner layer foaming material mainly composed of polyurethane and an outer layer rubber material with a harder texture are simultaneously or continuously injected into a handle sheath mold to prepare an integrated handle sheath with a hard and wear-resistant outer layer and a soft foaming inner layer. Among them, the wear-resistant layer significantly improves the wear resistance of the handle sheath, and the foaming inner layer provides a soft grip and good elastic recovery, increasing the comfort of use. Compared with the prior art, the present invention prepares the rubber handle sheath by integral molding, which not only significantly improves the production efficiency, but also effectively solves problems such as poor interfacial connection, delamination and cracking that may occur during the process of preparing by layering and then bonding.

[0069] In step S1, for the blending of the inner layer material and the inner layer injection barrel, the temperature is 280 - 350 °C and the pressure is 8 - 20 MPa. The melting point of polyurethane in the inner layer material is about 180 °C, and the melting point of polyacrylonitrile is about 300 °C. The setting of the temperature and pressure of the blender and the inner layer injection barrel can ensure that both polyurethane and polyacrylonitrile in it are in a molten state, ensuring their blending effect.

[0070] In step S1, it is preferred to use Desmodur® series materials of Bayer for polyurethane; it is preferred to use powdery Zytel® series materials of DuPont for polyacrylonitrile. In this step, polyurethane particles and polyacrylonitrile powder are added to the blender in proportion for melt mixing. After mixing for 2 - 5 min, functional additives such as foaming agents, stabilizers, lubricants and antioxidants are added to the remaining materials in the blender, and then mixing continues for 5 - 10 min to form the inner layer material.

[0071] It should be noted that the foaming agent is added in the final stage of mixing. After adding, mixing continues for 5 - 20 s and then it is immediately transferred to the inner layer injection barrel.

[0072] In this embodiment, the foaming agent used is azobisisobutyronitrile or sodium bicarbonate, which forms a foam structure in the inner layer material, increasing the elasticity and cushioning performance of the inner layer material.

[0073] In this embodiment, the stabilizer used is calcium stearate or zinc stearate, which prevents the inner layer material from degrading during processing or use.

[0074] In this embodiment, the lubricant used is stearic acid or paraffin, which reduces the friction coefficient of the inner layer material and improves the processing performance.

[0075] In this embodiment, the antioxidant used is 2,6 - di - tert - butyl - 4 - methylphenol or butylated hydroxyanisole, which is used to extend the service life of the inner layer material and prevent oxidation and deterioration.

[0076] The outer rubber material in this embodiment is one of vulcanized rubber, styrene-butadiene rubber or chloroprene rubber. Styrene-butadiene rubber is preferably used as the matrix material of the wear-resistant layer, providing good wear resistance and cost-effectiveness.

[0077] In this embodiment, the accelerator used is one of diphenyltetramethylthiuram disulfide and diphenyldimethylthiuram disulfide to accelerate the vulcanization process.

[0078] In this embodiment, the activator used is zinc oxide or stearic acid to improve the activity of the vulcanizing agent.

[0079] In this embodiment, the reinforcing injection agent used is carbon black or silane coupling agent. Carbon black is preferably used to improve the strength and wear resistance of the rubber.

[0080] In this embodiment, the plasticizer used is dibutyl phthalate or diisobutyl phthalate to increase the softness and plasticity of the outer material.

[0081] By adopting two independent injection barrels, the present invention realizes the synchronous preparation of the inner foaming material and the outer wear-resistant material, improves the preparation efficiency, and ensures the independence and stability of the two materials during the preparation process.

[0082] In step S3, according to the volume of the handle sheath mold, the injection speed and time of the outer material are controlled so that the filling degree of the outer material in the handle sheath mold is controlled within 30-40%. First, a stable outer material layer is constructed in the handle sheath mold, which can provide a solid foundation for the subsequent injection of the inner material and help maintain the structural integrity of the handle sheath.

[0083] During the injection process of step S4, the inner material is accurately injected into the central part of the outer material, thereby pushing the outer material to move orderly towards the inner side of the handle sheath mold. At the same time, the synchronous injection operation of the outer material is also carried out steadily. When the outer material moves towards the inner side of the handle sheath mold under the push of the inner material, the newly injected outer material tightly wraps around the surface of the inner material, thus ensuring the structural integrity and sealing of the handle sheath and effectively preventing the leakage problem of the inner material.

[0084] The present invention adds polyacrylonitrile to the foaming inner layer material. The melting point of polyacrylonitrile is much higher than the foaming temperature of polyurethane. When the inner layer material enters the handlebar cover mold, the pressure decreases, the polyurethane starts to foam, and as the temperature increases, the viscosity of the polyurethane matrix decreases. Due to the thermal stability of polyacrylonitrile, an independent phase is formed in the polyurethane matrix. The polyacrylonitrile will precipitate from the polyurethane with the movement of the foaming gas. Moreover, because the temperature of the polyacrylonitrile is higher than the melting point before injection, the temperature decreases after entering the handlebar cover mold. The precipitation process cooperates with the curing process after the temperature decreases. The polyacrylonitrile achieves the goal of spanning the two interfaces of the inner layer material and the outer layer material, and forms a network-like fiber morphology between the two interfaces, thereby increasing the connection between the inner and outer layers and further reducing the problems of stratification and cracking.

[0085] In step S4, the foaming process of the inner layer material is controlled by using a staged foaming technology, including the following steps:

[0086] S41, the initial temperature of the handle cover mold is controlled at 80-100°C, and the pressure is controlled at 10-20MPa;

[0087] S42, initial foaming stage: after the injection of the inner layer material begins, the temperature increases by 5°C every 5 seconds and the pressure decreases by 1MPa every 5 seconds; the combination of increased temperature and reduced pressure helps to start the decomposition of the foaming agent and generate gas, while the reduced pressure helps the gas diffuse in the material to form foam.

[0088] S43, the generation and stabilization stage of foaming gas:

[0089] When the temperature in the handlebar cover mold is 110-120°C, maintain the temperature and pressure for 30-60 seconds;

[0090] When the temperature in the handlebar cover mold is 130-140°C, maintain the temperature and pressure for 30-60 seconds;

[0091] When the temperature in the handlebar cover mold is 150-160°C, maintain the temperature and pressure for 30-60 seconds;

[0092] Slow temperature and pressure adjustment, as well as the pressure holding stage after adjustment, can delay and control the foaming process.

[0093] S44, inner layer material foam curing:

[0094] The temperature of the handlebar cover mold is reduced to 80-100℃, and the pressure is reduced to 0.5-1.5MPa for 2-5min. After this step of process, the inner layer material has been fully foamed, and the outer layer material fits the handlebar cover mold tightly. To ensure that the product meets the use requirements, the inner wall of the handlebar cover mold is accurately set with various patterns or dents according to actual needs.

[0095] The present invention proposes a staged foaming technology. After the inner layer material starts to foam, by controlling a series of temperatures, pressures, and holding times, the duration of the foaming process is effectively extended. This provides sufficient precipitation time for polyacrylonitrile in the polyurethane matrix, ensuring that more polyacrylonitrile can smoothly precipitate to the contact boundary between the inner layer material and the outer layer material. This technical improvement significantly increases the connection anchor points between the inner layer material and the outer layer material, thereby greatly reducing the delamination and cracking problems that may occur during the use of the product, and enhancing the overall structural stability and durability.

[0096] In steps S42 and S43, the handle sheath mold is vibrated: the vibration frequency is 15 - 30 Hz, the vibration amplitude is 60 - 100 um, and it vibrates in multiple directions in sequence and cycles for 2 - 5 s.

[0097] In this embodiment, the vibration direction vibrates clockwise in sequence along the vibration points on the cross-section of the handle sheath mold, and the vibration points are evenly distributed on the surface of the handle sheath mold. Through multi-directional cyclic vibration, it can be ensured that all corners and complex geometric features of the mold can be fully filled with the material, reducing dead corners and incomplete filling problems.

[0098] The present invention effectively reduces the viscosity of the injection material melt by introducing vibration assistance means during the foaming process of the inner layer material and combining it with the co-injection foaming technology, thereby significantly improving its fluidity. This innovative method helps to achieve a more uniform melt distribution and better mold filling performance during the co-injection foaming molding process. At the same time, this method can also significantly reduce common defects in the injection molding process, such as weld lines, sinks, and warping, thus greatly improving the finished product quality of the rubber handle sheath.

[0099] During the foaming process of the inner layer material of the present invention, multi-directional sequential cyclic vibration is used in combination with the staged foaming technology. Through the multi-directional vibration effect, the foaming gas molecules can be more evenly dispersed in the polyurethane matrix, thereby generating finer and more uniformly distributed foam cell structures. This improvement significantly increases the precipitation amount and uniformity of polyacrylonitrile in the inner layer material, and further promotes the migration of polyacrylonitrile to the contact boundary between the inner layer material and the outer layer material. In addition, the multi-directional vibration helps the precipitated polyacrylonitrile fibers to change direction and cross-link, thereby constructing a complex network fiber structure that spans the inner and outer layer materials. This network fiber structure not only enhances the structural integrity of the handle sheath, but also significantly improves its mechanical properties.

[0100] In step S4, the injection rate of the inner layer material is 2 - 3 times that of the outer layer material.

[0101] During the injection process of the present invention, the outer layer material is first injected and adheres to the cavity wall of the handle sheath mold to form a wear-resistant layer. After the injection degree reaches 30-40%, the inner layer material and the outer layer material are simultaneously injected. Moreover, the inner layer material is located at the central part of the outer layer material, and the injection rate of the inner layer material is 2-3 times that of the outer layer material, ensuring that the inner layer material is always wrapped by the outer layer material during the injection and subsequent foaming processes, effectively preventing the exposure of the inner layer material, significantly improving the forming efficiency of the rubber handle sheath, and effectively enhancing the product qualification rate.

[0102] The present invention also provides a rubber handle sheath forming device, including: an injection system, a handle sheath mold, and a control system for controlling the operation of the injection system and the handle sheath mold.

[0103] The injection system in this embodiment includes: a plurality of injection barrels, a discharge pipe provided on one side of the injection barrel, and a nozzle provided at the other end of the discharge pipe; the discharge pipe is a multi-outlet end structure and is respectively connected to a plurality of nozzles, that is, the discharge pipe connected to one injection barrel can be connected to a plurality of nozzles, and a plurality of nozzles correspond to processing a plurality of handle sheath molds to achieve synchronous processing of multiple products.

[0104] The nozzle in this embodiment includes: a discharge port, an inner layer material flow channel and an outer layer material flow channel connected to the discharge pipe; the discharge port is docked with the handle sheath mold to inject materials into it; the inner layer material flow channel is arranged at the central part of the outer layer material flow channel. It should be noted that the inner flow channel and the outer flow channel are two concentrically sleeved annular flow channels, and the inner flow channel is arranged in the middle of the outer flow channel.

[0105] The handle sheath mold in this embodiment includes: an upper mold and a lower mold combined into a tubular structure cavity for forming the rubber handle sheath.

[0106] The control system in this embodiment includes: a temperature control module, a pressure control module, an injection barrel control module and an automation control module; the temperature control module includes: a plurality of temperature monitoring units and a temperature adjustment unit; the plurality of temperature monitoring units are respectively used to monitor the temperatures of the injection barrels and the handle sheath mold, and the plurality of temperature adjustment units are respectively used to adjust the temperatures of the injection barrels and the handle sheath mold; the pressure control module includes: a plurality of pressure monitoring units and a pressure adjustment unit; the plurality of pressure monitoring units are respectively used to monitor the pressures of the injection barrels and the handle sheath mold, and the plurality of pressure adjustment units are respectively used to adjust the pressures of the injection barrels and the handle sheath mold; the injection barrel control module is used to control the injection rates of the plurality of injection barrels, which is achieved through valve control.

[0107] The automation control module in this embodiment is used to integrate and control the operations of the injection system, the handle sheath mold and the control system to accurately execute according to the forming process steps of a rubber handle sheath.

[0108] Several injection barrels in this embodiment include: an inner injection barrel and an outer injection barrel that are independent of each other.

[0109] The automatic control module in this embodiment is provided with a phased foaming mechanism, including:

[0110] The initial temperature of the handle sheath mold is controlled at 80 - 100 °C, and the pressure is controlled at 10 - 20 MPa;

[0111] In the initial foaming stage after the injection of the inner layer material: the temperature rises by 5 °C every 5 s, and the pressure drops by 1 MPa every 5 s;

[0112] The generation and stabilization stage of the foaming gas:

[0113] When the temperature in the handle sheath mold is 110 - 120 °C, the temperature and pressure are maintained for 30 - 60 s;

[0114] When the temperature in the handle sheath mold is 130 - 140 °C, the temperature and pressure are maintained for 30 - 60 s;

[0115] When the temperature in the handle sheath mold is 150 - 160 °C, the temperature and pressure are maintained for 30 - 60 s;

[0116] Curing of the inner layer material foam:

[0117] The temperature of the handle sheath mold is reduced to 80 - 100 °C, and the pressure is reduced to 0.5 - 1.5 MPa, lasting for 2 - 5 min.

[0118] The control system in this embodiment further includes a vibration module, and the vibration module includes: several vibration units, and the vibration units preferably use electric vibrators; several vibration units are evenly distributed on the outer surface of the handle sheath mold.

[0119] The present invention provides a rubber handle sheath forming device, which is connected to multiple nozzles through a discharge pipe with multiple outlet ends, thereby realizing synchronous processing of multiple handle sheath molds. This design enables the device to process multiple products simultaneously, significantly improving production efficiency and effectively shortening the production cycle. In addition, the device is also equipped with an automatic control module, which can accurately execute the forming process steps of the rubber handle sheath, ensuring that each sheath is precisely produced according to the preset parameters, thereby improving the stability and consistency of the product.

[0120] Example 1, preparing a rubber handle sheath sample based on the above-mentioned forming process of a rubber handle sheath.

[0121] Step 1: Mix 80 parts by weight of polyurethane particles, 15 parts of polyacrylonitrile powder, 3 parts of azobisisobutyronitrile, 1 part of calcium stearate, 1 part of stearic acid, and 1 part of 2,6 - di - tert - butyl - 4 - methylphenol solvent evenly to obtain the inner layer material. Add the inner layer material to the inner injection barrel. The temperature of the mixer and the inner injection barrel is set at 320 °C, and the pressure is 18 MPa.

[0122] Mix 100 parts by weight of styrene - butadiene rubber particles, 1 part of vulcanizing agent, 1 part of diphenyl disulfide tetramethylthiuram, 2 parts of zinc oxide, 3 parts of carbon black, 1 part of dibutyl phthalate, and 1 part of 2,6 - di - tert - butyl - 4 - methylphenol solvent evenly to obtain the outer layer material. Add the outer layer material to the outer injection barrel. The temperature of the mixer and the outer injection barrel is set at 180 °C, and the pressure is 10 MPa.

[0123] Step 2: Preheat the handgrip sheath mold to 90 °C first, and control the internal pressure at 10 MPa.

[0124] Step 3: Inject the outer layer material into the handgrip sheath mold. When the filling degree of the outer layer material in the handgrip sheath mold reaches 30%, start injecting the inner layer material into the handgrip sheath mold along with the outer layer material. The injection speed of the inner layer material is 2.5 times that of the outer layer material injection rate. The inner layer material is injected earlier than the outer layer material and is completed until the handgrip sheath mold is 100% filled. After the inner layer material enters the handgrip sheath mold, relieve the pressure and foam.

[0125] During the foaming process of the inner layer material, the generation and stabilization stage of the foaming gas:

[0126] When the temperature in the handgrip sheath mold is 110 °C, maintain the temperature and pressure for 45 s;

[0127] When the temperature in the handgrip sheath mold is 130 °C, maintain the temperature and pressure for 45 s;

[0128] When the temperature in the handgrip sheath mold is 150 °C, maintain the temperature and pressure for 45 s;

[0129] In this step, vibrate the handgrip sheath mold: the vibration frequency is 20 Hz, the vibration amplitude is 80 μm, vibrate in multiple directions in sequence and cycle, and change the direction every 5 s.

[0130] Step 4: After the inner layer material foaming is completed, lower the temperature of the handgrip sheath mold to 80 °C, the pressure to 1 MPa, and maintain for 3 min to cure the foam of the inner layer material.

[0131] Step 5: Lower the temperature of the handgrip sheath mold to room temperature, do not keep the pressure, and maintain for 15 min. Finally, cool and demold the handgrip sheath to obtain the rubber handgrip sheath.

[0132] Example 2. Based on Example 1, a rubber handgrip sheath is prepared, with the difference that 5 parts of polyacrylonitrile powder are added to the inner layer material.

[0133] Example 3. Based on Example 1, a rubber handgrip sheath is prepared, with the difference that no polyacrylonitrile powder is added to the inner layer material.

[0134] Example 4. Based on Example 1, a rubber handgrip sheath is prepared, with the difference in the foaming process control of the inner layer material: the temperature of the handgrip sheath mold is 150 °C, the pressure is 3 MPa. After the injection of the inner layer material starts, the pressure in the handgrip sheath mold is reduced to 1 MPa after 10 s, and the temperature and pressure are kept unchanged until the inner layer foam material is cured.

[0135] Example 5. Based on Example 1, a rubber handgrip sheath is prepared, with the difference that the temperature and pressure of the handgrip sheath mold are always controlled at 80 °C and 1 MPa.

[0136] Example 6. Based on Example 1, a rubber handgrip sheath is prepared, with the difference in the foaming stage of the inner layer material: after the injection of the inner layer material starts, the temperature rises by 5 °C every 5 s, and the pressure drops by 1 MPa every 5 s; there is no temperature and pressure holding stage in the middle until the temperature rises to 150 °C, and the increase in temperature and the decrease in pressure are stopped.

[0137] Example 7. Based on Example 1, a rubber handgrip sheath is prepared, with the difference that during the foaming process of the inner layer material, no vibration is applied to the handgrip sheath mold.

[0138] Example 8. Based on Example 1, a rubber handgrip sheath is prepared, with the difference that vibration is applied to the handgrip sheath mold: the vibration frequency is 45 Hz, the vibration amplitude is 120 μm, and the multi-directional vibration is cycled in turn, and the direction is changed every 10 s.

[0139] Example 9. Based on Example 1, a rubber handgrip sheath is prepared, with the difference that vibration is applied to the handgrip sheath mold: the vibration frequency is 20 Hz, the vibration amplitude is 80 μm, and an intermittent vibration of 5 s / time is carried out using one vibration unit, and the vibration is carried out along the vertical injection direction.

[0140] The rubber handgrip sheaths prepared in the above examples are subjected to peel tests and tensile tests. Among them, the peel test is carried out according to the standard of GB / T 2791-1995, and the tensile test is carried out according to the standard of GB / T 528-1992. The test results are shown in Table 1.

[0141] Table 1. Test results of the performance of the rubber handgrip sheath

[0142]

[0143] Based on the content of Table 1, it can be concluded that the rubber handle sheaths prepared in Example 1 and Example 2 performed well in both the peel test and the tensile test. In Example 2, the performance in peel strength was cross because less polyacrylonitrile powder was added in the inner layer material, resulting in fewer connections between the two interfaces of the inner layer material and the outer layer material of the handle sheath, and the formed network-like fibers were sparser. In Example 3, since no polyacrylonitrile powder was added, the connection between the inner layer material and the outer layer material relied on the inherent viscosity and the connection caused by curing, and the prepared rubber handle sheath was prone to delamination and cracking.

[0144] In Example 4, the initial pressure was low and decreased to 1 MPa within 10 s, resulting in too fast a foaming process of the inner layer material. Polyacrylonitrile did not have sufficient time to precipitate and transfer to the contact boundary between the inner layer material and the outer layer material, and sufficient connections could not be formed. In Example 5, the temperature and pressure remained constant during the injection of the inner layer material. The constant preparation conditions were not conducive to the decomposition of the foaming agent and the diffusion of gas, resulting in insufficient foaming and insufficient strength. In Example 6, stagewise pressure holding was not carried out during the generation and stabilization stages of the foaming gas. After the temperature increased by 5 °C every 5 s and the pressure decreased by 1 MPa every 5 s, the stage of maintaining the temperature and pressure was not carried out until the temperature increased to 150 °C and the increase in temperature and the decrease in pressure were stopped. The rapid temperature and pressure changes might lead to an unstable foaming process, insufficient precipitation and migration of polyacrylonitrile, and affect the bonding between the inner and outer layer materials.

[0145] In Example 7, there was no auxiliary vibration during the foaming process. The amount and uniformity of polyacrylonitrile precipitation in the inner layer material were insufficient, and the cross-linking of the precipitated polyacrylonitrile fibers was not much, resulting in an insufficiently complex network-like fiber structure spanning the inner and outer layer materials, and thus the peel strength performance was slightly poor. In Example 8, although vibration assistance was used during the foaming process, the vibration frequency of 45 Hz and the vibration amplitude of 120 µm were too high, resulting in uneven material filling and excessive dispersion, affecting the internal structure and performance of the material. In addition, the vibration changing direction every 10 s led to a non-uniform fiber direction distribution and an insufficiently complex network-like fiber structure, thus affecting the peel strength and tensile properties. In Example 9, an intermittent vibration of 5 s / time was carried out using a single vibration unit, and the vibration was only along the direction perpendicular to the injection direction. This vibration method led to a single fiber precipitation direction and could not form a network structure, and the bonding strength between the inner and outer layer materials was poor.

[0146] Based on the inspiration of the ideal embodiments of the present invention, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A forming process for a rubber handle sheath, characterized in that, It includes the following steps: S1. Uniformly blend 80 parts by weight of polyurethane, 0 - 20 parts by weight of polyacrylonitrile, 0 - 5 parts by weight of foaming agent, 0 - 1 part by weight of stabilizer, 0 - 2 parts by weight of lubricant, and 0 - 1 part by weight of antioxidant to obtain the inner layer material, and add the inner layer material into the inner layer injection barrel; S2. Uniformly blend 100 parts by weight of outer layer rubber material, 0 - 2 parts by weight of vulcanizing agent, 0 - 2 parts by weight of accelerator, 0 - 3 parts by weight of activator, 0 - 5 parts by weight of reinforcing injection agent, 0 - 2 parts by weight of plasticizer, and 0 - 1 part by weight of antioxidant to obtain the outer layer material, and add the outer layer material into the outer layer injection barrel; S3. Inject the outer layer material into the handle sheath mold. The outer layer material adheres to the cavity wall of the handle sheath mold to form a wear-resistant layer, and the filling degree is set at 30 - 40%; S4. Inject the inner layer material into the central part of the handle sheath mold along with the outer layer material until the handle sheath mold is 100% filled. After the inner layer material enters the handle sheath mold, depressurize and foam it. The polyacrylonitrile precipitates from the inner layer material along with the foaming gas and migrates to the contact boundary between the inner layer material and the outer layer material to form a network fiber structure spanning the inner layer material and the outer layer material; S5. Lower the temperature of the handle sheath mold to room temperature, without pressure holding, and keep it for 5 - 20 min to cool and demold the handle sheath to obtain a rubber handle sheath.

2. The forming process of a rubber handgrip sheath according to claim 1, characterized in that: In the said S1, for the blending of the inner layer material and the inner layer injection barrel, the temperature is 280 - 350 °C and the pressure is 8 - 20 MPa.

3. The forming process of a rubber handgrip sheath according to claim 1, characterized in that: The said outer layer rubber material is one of vulcanized rubber, styrene-butadiene rubber, or chloroprene rubber.

4. The forming process of a rubber handle sheath according to claim 1, characterized in that: In the said S4, use the staged foaming technology to control the foaming process of the inner layer material, including the following steps: S41. Control the initial temperature of the handle sheath mold at 80 - 100 °C and the pressure at 10 - 20 MPa; S42. Preliminary foaming stage: After the injection of the inner layer material starts, the temperature rises by 5 °C every 5 s and the pressure drops by 1 MPa every 5 s; S43. Generation and stabilization stage of the foaming gas: When the temperature in the handle sheath mold is 110 - 120 °C, keep the temperature and pressure for 30 - 60 s; When the temperature in the handle sheath mold is 130 - 140 °C, keep the temperature and pressure for 30 - 60 s; When the temperature in the handle sheath mold is 150 - 160 °C, keep the temperature and pressure for 30 - 60 s; S44. Foam curing of the inner layer material: Lower the temperature of the handle sheath mold to 80 - 100 °C and the pressure to 0.5 - 1.5 MPa, and keep it for 2 - 5 min.

5. The forming process of a rubber handgrip sheath according to claim 4, characterized in that: In the said S42 and S43, apply vibration to the handle sheath mold: the vibration frequency is 15 - 30 Hz, the vibration amplitude is 60 - 100 μm, and vibrate in multiple directions in sequence and cycle for 2 - 5 s.

6. The forming process of a rubber handgrip sheath according to claim 1, characterized in that: In the said S4, the injection rate of the inner layer material is 2 - 3 times that of the outer layer material.

7. A rubber handle sheath forming device, based on the rubber handle sheath forming process described in any one of claims 1-6, characterized in that, It includes: An injection system, a handle sheath mold, and a control system for controlling the operation of the injection system and the handle sheath mold; The said injection system includes: several injection barrels, a discharge pipe arranged on one side of the injection barrels, and a nozzle arranged at the other end of the discharge pipe; The said discharge pipe is a multi-outlet end structure and is respectively connected to several nozzles; The nozzle includes: a discharge port, an inner material flow channel and an outer material flow channel connected to the discharge pipe; The discharge port is docked with the handle sheath mold to inject materials into it; The inner material flow channel is arranged at the central part of the outer material flow channel; The handle sheath mold includes: an upper mold and a lower mold combined into a tubular cavity for the molding of the rubber handle sheath; The control system includes: a temperature control module, a pressure control module, an injection barrel control module and an automation control module; The temperature control module includes: a number of temperature monitoring units and temperature adjustment units; a number of the temperature monitoring units are respectively used for monitoring the temperatures of the injection barrel and the handle sheath mold, and a number of the temperature adjustment units are respectively used for adjusting the temperatures of the injection barrel and the handle sheath mold; The pressure control module includes: a number of pressure monitoring units and pressure adjustment units; a number of the pressure monitoring units are respectively used for monitoring the pressures of the injection barrel and the handle sheath mold, and a number of the pressure adjustment units are respectively used for adjusting the pressures of the injection barrel and the handle sheath mold; The injection barrel control module is used for controlling the injection rate of a number of injection barrels; The automation control module is used for integrating and controlling the operations of the injection system, the handle sheath mold and the control system to accurately execute according to the forming process steps of the rubber handle sheath.

8. A rubber handle sheath forming device according to claim 7, characterized in that: A number of the injection barrels include: an independent inner layer injection barrel and an outer layer injection barrel.

9. A rubber handgrip sheath forming device according to claim 7, characterized in that: The automation control module is provided with a staged foaming mechanism, including: The initial temperature of the handle sheath mold is controlled at 80 - 100 °C, and the pressure is controlled at 10 - 20 MPa; In the initial foaming stage after the injection of the inner layer material: the temperature rises by 5 °C every 5 s, and the pressure drops by 1 MPa every 5 s; The generation and stabilization stage of the foaming gas: When the temperature in the handle sheath mold is 110 - 120 °C, the temperature and pressure are maintained for 30 - 60 s; When the temperature in the handle sheath mold is 130 - 140 °C, the temperature and pressure are maintained for 30 - 60 s; When the temperature in the handle sheath mold is 150 - 160 °C, the temperature and pressure are maintained for 30 - 60 s; The curing of the inner layer material foam: The temperature of the handle sheath mold is reduced to 80 - 100 °C, and the pressure is reduced to 0.5 - 1.5 MPa, lasting for 2 - 5 min.

10. A rubber handle sheath forming device according to claim 7, characterized in that: The control system further includes a vibration module, and the vibration module includes: a number of vibration units; a number of the vibration units are evenly distributed on the outer surface of the handle sheath mold.

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