A one-piece, non-drilling, dual-color, dual-hardness rotational molding peak ball and its manufacturing method

Abstract

This invention discloses a one-piece, non-drilling, dual-color, dual-hardness rotomolded pick ball and its manufacturing method, relating to the field of sporting goods manufacturing technology. The invention involves pre-setting perforated columns within the mold cavity of a rotomolding mold. Through a two-stage rotomolding process, an outer layer of soft, damping polyethylene and an inner layer of hard, supporting polyethylene are added sequentially. The two polyethylene layers are different colors, both being the body color. After the outer polyethylene layer is heated to a semi-molten, viscous state, the inner polyethylene layer is added. A second heating process fuses the two layers together, simultaneously forming through-holes at the perforated column locations, eliminating the need for subsequent drilling. The resulting pick ball has a dual-layer structure with a soft outer layer and a hard inner layer. The through-hole walls are smooth and burr-free, allowing direct observation of the inner layer color. This invention solves the problems of existing pick balls, such as single color, the need for subsequent drilling, difficulty in coloring polyethylene, and the inability to balance ball control and rigidity. It achieves the technical effects of a dual-color body, one-piece molding, no drilling required, and a balance of rigidity and flexibility.

Description

Technical Field

[0001] This invention relates to the field of sporting goods manufacturing technology, and in particular to a one-piece molded, non-drilling, two-color, dual-hardness rotational molding peak ball and its manufacturing method. Background Technology

[0002] A picket ball is a hollow sphere used in picket ball sports. Its surface has multiple through-holes that regulate air resistance during flight, allowing for a stable trajectory. Currently, pickets are primarily manufactured using a process of rotational molding of single-color polyethylene powder followed by drilling. The specific steps are: pouring single-color polyethylene powder into a rotational molding mold, heating and molding it once in a rotational molding machine, cooling and demolding, and then drilling through-holes into the sphere.

[0003] However, this process still has some drawbacks:

[0004] Firstly, this process can only achieve single-color molding, and cannot produce two-color or multi-color designs for peak balls, resulting in a monotonous product appearance, low recognizability in competitive matches, and limited aesthetic appeal. Subsequent attempts to add color through spraying or printing processes have failed because polyethylene material has low surface energy, resulting in weak adhesion between the sprayed or printed layer and the base material. This leads to problems such as fading and peeling during use, making it impossible to maintain the color effect for a long time.

[0005] Secondly, this process requires a dedicated drilling step after rotational molding to process the through holes on the surface of the Peak ball. During drilling, the cutting action between the drill bit and the ball material can easily generate burrs at the hole opening and wall. These burrs affect the surface finish of the ball, and drilling positioning deviations can cause the through hole position to deviate from the design position. Accumulated hole position deviations can alter the mass distribution of the ball, thus affecting flight stability. Furthermore, the feed force of the drill bit during drilling may induce micro-cracks at the hole edge. These cracks gradually expand after repeated impacts on the ball, ultimately leading to premature ball damage and shortened service life.

[0006] Furthermore, this process uses a single type of polyethylene material to mold the entire ball, resulting in a uniform hardness across all parts of the ball. This makes it impossible to achieve differentiated design for different parts. If a lower-hardness polyethylene is used, the ball is too soft overall, lacking elastic recovery and resulting in slow deformation recovery after impact, leading to insufficient rebound speed and flight distance for competitive play. Conversely, if a higher-hardness polyethylene is used, the ball is too hard overall, with a lower surface friction coefficient, resulting in shorter contact time, poor ball control, and difficulty in achieving precise landing point control. Neither of these extreme cases can meet the performance requirements of competitive peak balls, which need to be both soft on the outside and hard on the inside, combining both rigidity and flexibility.

[0007] Finally, some existing technologies attempt to add color or patterns to the surface of a molded monochrome pickle through spray painting or screen printing. However, due to the low surface energy of polyethylene, the adhesion between the coating and the substrate is insufficient. During use, the coating peels off due to repeated impacts between the ball and the racket and the ground, affecting not only the appearance but also potentially leaving foreign objects on the court. Even with flame treatment or corona treatment to increase surface energy, the improvement in adhesion is limited, and the treatment effect diminishes over time, failing to guarantee the integrity of the color for long-term use.

[0008] In summary, existing peak ball manufacturing processes have significant shortcomings in three aspects: color realization, through-hole processing accuracy, and material property distribution. Therefore, this invention proposes a one-piece, non-drilling, two-color, dual-hardness rotational molding peak ball and its manufacturing method to solve the problems existing in the prior art. Summary of the Invention

[0009] To address the aforementioned problems, the present invention aims to provide a one-time molding, non-drilling, two-color, dual-hardness rotational molding peak ball and its manufacturing method. The present invention can solve the problems of single color, need for post-drilling, difficulty in coloring polyethylene, and limited performance in the prior art.

[0010] To achieve the objectives of this invention, the following technical solution is provided: a one-piece molded, non-drilling, dual-color, dual-hardness rotational molded peak ball, comprising a peak ball body, characterized in that: the peak ball body is composed of an outer layer and an inner layer, the outer layer is a soft damping type PE, the inner layer is a rigid support type PE, the outer PE material has a first color, the inner PE material has a second color, and the second color is different from the first color, the peak ball body is provided with through holes, and several groups of through holes are provided, so that the second color of the inner layer can be observed through any of the through holes without damaging the ball.

[0011] Further improvements are made in that: the outer PE material has a Shore hardness D of 40~55 and a melt flow index MI of 2~5 g / 10min, and the inner PE material has a Shore hardness D of 60~75 and a melt flow index MI of 1~3 g / 10min.

[0012] A further improvement is that the surface of the hole wall has a taper of 0.5° to 2°.

[0013] A further improvement is that the surface of the hole wall is also provided with a polytetrafluoroethylene non-stick coating residue layer.

[0014] A method for preparing a one-piece, non-drilling, dual-color, dual-hardness rotational molded pick ball includes the following steps:

[0015] Step 1: Prepare a rotational molding mold, the mold cavity of which is fixed with a perforated column for forming the through hole of the pick ball;

[0016] Step 2: Add the outer PE material to the rotational molding mold, wherein the outer PE material is a soft damping type PE with a Shore hardness D of 40~55, a melt index MI of 2~5 g / 10min, and the outer PE material has a first color;

[0017] Step 3: The rotational molding mold with the added outer PE material is heated and rotated in a rotational molding oven at a temperature of 250~350°C for 6~12 minutes, so that the outer PE material melts and adheres to the inner wall of the mold cavity and the surface of the orifice to form an outer layer, and the inner surface of the outer layer is in a semi-molten viscous state.

[0018] Step 4: Open the rotational molding mold and add the inner layer PE material into the rotational molding mold that has formed the outer layer. The inner layer PE material is rigid support type PE with a Shore hardness D of 60~75 and a melt index MI of 1~3 g / 10min. The inner layer PE material has a second color, which is different from the first color.

[0019] Step 5: Re-lock the mold and push the rotational molding mold with the inner PE material into the rotational molding furnace again for heating and rotation. The heating temperature is 250~350°C and the heating time is 7~15 minutes, so that the inner PE material melts and adheres inside the already formed outer layer to form the inner layer. The outer layer and the inner layer are thermally fused together at the interface, and at the same time, through holes are directly formed at the location of the pore column.

[0020] Step 6: Remove the rotational molding mold and allow it to cool, allowing the sphere to solidify. Then, open the mold and remove the product to obtain a two-color, two-hardness rotational molded peak ball.

[0021] The further improvement is that: in step two, the added mass of the outer PE material is 40% to 70% of the total mass of the outer PE material and the inner PE material, and in step four, the added mass of the inner PE material is 30% to 60% of the total mass of the outer PE material and the inner PE material.

[0022] A further improvement is that the outer surface of the perforated column is provided with a draft angle of 0.5°~2°.

[0023] A further improvement is that the outer surface of the perforated column is coated with a polytetrafluoroethylene non-stick coating.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention utilizes a pre-formed perforated column within the mold and a secondary feeding rotational molding process to directly create through-holes in the peak ball during molding, completely eliminating the need for subsequent drilling. This also results in precise and smooth hole walls, avoiding hole position deviations and burr cracks. Furthermore, the outer layer of soft, damping polyethylene and the inner layer of rigid, supporting polyethylene are thermally fused together during a secondary heating process, forming a double-layer structure that is soft on the outside and hard on the inside. This ensures excellent ball control and friction performance while providing the ball with sufficient rigidity and elastic recovery. In addition, the inner and outer layers use different colored polyethylene materials, and the inner layer color can be directly observed through the through-holes, allowing verification of the dual-color structure without damaging the ball, thus enhancing the product's overall recognizability and performance. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation method of the present invention. Detailed Implementation

[0027] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0028] Example 1

[0029] according to Figure 1 As shown, this embodiment provides a one-piece, non-drilling, two-color, dual-hardness rotational molded pickle, including a pickle body composed of an outer layer and an inner layer. The outer layer is made of soft damping polyethylene with a Shore hardness D of 40, a melt index MI of 2 g / 10min, and a yellow color. The inner layer is made of rigid support polyethylene with a Shore hardness D of 60, a melt index MI of 1 g / 10min, and a blue color. The pickle has multiple through-holes, arranged in several groups. The surface of the through-hole wall has a 0.5° taper, naturally formed by the draft angle of the mold column. This allows the blue color of the inner layer to be directly observed through the through-holes, indicating that the outer and inner layers are different colors and that the inner layer completely covers the inner surface of the pickle.

[0030] Its preparation method includes the following steps:

[0031] Step 1: Prepare the rotational molding mold. In this embodiment, a fixed-hole column mold is used (the mold cavity is fixed with a column for forming the through hole of the pick ball), and the outer surface of the column is provided with a draft angle of 0.5°.

[0032] Step 2: Add the outer layer polyethylene material to the rotational molding mold. The mass of the outer layer polyethylene material added is 40% of the total mass of the outer and inner layer polyethylene materials.

[0033] Step 3: The rotational molding mold with the outer polyethylene material is heated and rotated in a rotational molding oven at 250°C for 6 minutes. During this process, the outer polyethylene material melts and adheres evenly to the inner wall of the mold cavity and the outer surface of each column under the combined action of centrifugal force and gravity, gradually forming a complete shell. At the end of heating, the outer layer has been plasticized and formed, but the inner surface of the outer layer has not been completely solidified and remains in a semi-molten viscous state. A noticeable stickiness can be felt when the inside of the mold is lightly touched with a finger.

[0034] Step 4: Pull the rotational molding mold out of the rotary kiln, open the mold, and add the inner layer polyethylene material into the rotational molding mold that has formed the outer layer. The mass of the inner layer polyethylene material added is 60% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material.

[0035] Step 5: Re-lock the mold and push the rotational molding mold with the inner layer of polyethylene material back into the rotational molding rotary furnace. Continue heating and rotating at 250°C for 7 minutes. During the second heating process, the inner layer of polyethylene material melts and adheres to the inner surface of the already formed outer layer. At the interface, molecular chains diffuse and entangle with the semi-molten inner surface of the outer layer, and the two layers of polyethylene material are thermally fused together into a whole. At the same time, the polyethylene material attached to the surface of the perforated column cannot fuse due to the obstruction of the perforated column, directly forming through holes at the location of the perforated column.

[0036] Step Six: After heating is complete, pull the rotational molding mold out of the rotary oven and allow it to cool naturally in room temperature air to allow the sphere to completely solidify. Once the mold has cooled to room temperature, open the mold and remove the molded product.

[0037] The pickles prepared using the method described in this embodiment have smooth, burr-free through-holes with hole position deviations controlled within ±0.08 mm. The surface roughness Ra of the hole wall is 0.4 μm, and a uniform yellow polyethylene residue layer is visible on the inner wall of the through-hole. The rebound rate of the spheres was tested to be 72%, indicating that the inner rigid supporting polyethylene layer provides sufficient elastic recovery force. The interfacial peel strength between the outer and inner layers is 4.2 kN / m, and no delamination was observed during the peel test, proving that the two layers are firmly bonded together. The blue inner layer is visible through the through-holes, forming a striking two-tone contrast with the yellow outer layer. This two-tone effect is directly achieved from the polyethylene body material, without the need for spraying or printing.

[0038] Example 2

[0039] This embodiment provides a one-piece, non-drilling, two-color, dual-hardness rotationally molded pickball, including a pickball body composed of an outer layer and an inner layer. The outer layer is made of soft, damping polyethylene with a Shore hardness (D) of 48, a melt index (MI) of 3.5 g / 10min, and a yellow color. The inner layer is made of rigid, supportive polyethylene with a Shore hardness (D) of 68, a melt index (MI) of 2 g / 10min, and a blue color. The pickball has multiple through-holes, which are directly formed by rotational molding. The surface of the through-hole wall has a 1.25° taper. The blue color of the inner layer can be directly observed through any of the through-holes.

[0040] Its preparation method includes the following steps:

[0041] Step 1: Prepare the rotational molding mold. In this embodiment, a fixed-hole column mold is used (the mold cavity is fixed with a column for forming the through hole of the pick ball), and the outer surface of the column is provided with a draft angle of 1.25°.

[0042] Step 2: Add the outer layer polyethylene material to the rotational molding mold. The mass of the outer layer polyethylene material added is 55% of the total mass of the outer and inner layer polyethylene materials.

[0043] Step 3: After locking the rotational molding mold with the outer polyethylene material, push it into the rotational molding rotary oven and heat it at 300°C for 9 minutes. During this process, the outer polyethylene material melts and adheres evenly to the inner wall of the mold cavity and the outer surface of each column under the combined action of centrifugal force and gravity, gradually forming a complete shell. At the end of heating, the outer layer has been plasticized and formed, but the inner surface of the outer layer has not been completely solidified and remains in a semi-molten viscous state. A noticeable stickiness can be felt when lightly touching the inside of the mold with a finger.

[0044] Step 4: Pull the rotational molding mold out of the rotary kiln, open the mold, and add the inner layer polyethylene material into the rotational molding mold that has formed the outer layer. The added mass of the inner layer polyethylene material is 45% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material.

[0045] Step 5: Re-lock the mold, and then push the rotational molding mold with the inner layer polyethylene material into the rotational molding furnace again for heating and rotation. Continue heating and rotation at a heating temperature of 300°C for 11 minutes, so that the inner layer polyethylene material melts and adheres to the inside of the already formed outer layer to form the inner layer. Then the outer layer and the inner layer are thermally fused together at the interface, and at the same time, through holes are directly formed at the location of the pore column.

[0046] Step Six: After heating is complete, pull the rotational molding mold out of the rotary oven and allow it to cool naturally in room temperature air to allow the sphere to completely solidify. Once the mold has cooled to room temperature, open the mold and remove the molded product.

[0047] The pickle produced using the method described in this embodiment has a hole position deviation of ±0.05mm, smooth hole walls with a roughness Ra of 0.3μm, and no drilling burrs or cracks on the inner wall of the hole. The ball's rebound rate was tested at 76%, indicating that the inner rigid supporting polyethylene layer provides good elastic recovery force, while the outer soft damping polyethylene layer undergoes moderate deformation upon impact, increasing the contact time and friction between the ball and the racket. The interfacial peel strength between the outer and inner layers is 4.8 kN / m, indicating a strong bond between the two layers without delamination. The inner blue layer is visible through the through-holes; the two-tone effect is directly presented by the body color of the polyethylene and will not fade or peel off with long-term use.

[0048] Example 3

[0049] This embodiment provides a one-piece, non-drilling, two-color, dual-hardness rotational molded peak ball, including a peak ball body composed of an outer layer and an inner layer. The outer layer is made of soft, damping polyethylene with a Shore hardness (D) of 55, a melt index (MI) of 5 g / 10 min, and a yellow color. The inner layer is made of rigid, supportive polyethylene with a Shore hardness (D) of 75, a melt index (MI) of 3 g / 10 min, and a black color. The peak ball body has several sets of through holes, and the surface of the hole walls has a 2° taper, allowing the black inner layer to be observed through any of the through holes.

[0050] Its preparation method includes the following steps:

[0051] Step 1: Prepare the rotational molding mold. In this embodiment, a fixed-hole column mold is used (the mold cavity is fixed with a column for forming the through hole of the pick ball), and the outer surface of the column has a draft angle of 2°.

[0052] Step 2: Add the outer layer polyethylene material to the rotational molding mold. The mass of the outer layer polyethylene material added is 70% of the total mass of the outer and inner layer polyethylene materials.

[0053] Step 3: The rotational molding mold with the outer polyethylene material is heated and rotated in a rotational molding oven at 350°C for 12 minutes. During this process, the outer polyethylene material melts and adheres evenly to the inner wall of the mold cavity and the outer surface of each orifice under the combined action of centrifugal force and gravity, gradually forming a complete shell. At the end of heating, the outer layer has been plasticized and formed, but the inner surface of the outer layer has not been completely solidified and remains in a semi-molten, viscous state. A noticeable stickiness can be felt when the inside of the mold is lightly touched with a finger.

[0054] Step 4: Pull the rotational molding mold out of the rotary kiln, open the mold, and add the inner layer polyethylene material into the rotational molding mold that has formed the outer layer. The mass of the inner layer polyethylene material added is 30% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material.

[0055] Step 5: Re-lock the mold, and then push the rotational molding mold with the inner layer polyethylene material into the rotational molding furnace again for heating and rotation. Continue heating and rotation at a heating temperature of 350°C for 15 minutes, so that the inner layer polyethylene material melts and adheres to the inside of the already formed outer layer to form the inner layer. Then the outer layer and the inner layer are thermally fused together at the interface, and at the same time, through holes are directly formed at the location of the pore column.

[0056] Step Six: After heating is complete, pull the rotational molding mold out of the rotary oven and allow it to cool naturally in room temperature air to allow the sphere to completely solidify. Once the mold has cooled to room temperature, open the mold and remove the molded product.

[0057] The pickle produced using the method described in this embodiment has a hole position deviation of ±0.06mm, smooth hole walls without burrs, and a low coefficient of friction due to the residual polytetrafluoroethylene layer on the hole wall surface, further reducing wear at the hole edges. Testing showed the ball's rebound rate to be 80%, exhibiting outstanding rigidity, rapid recovery of deformation after impact, and stable flight speed and distance. Furthermore, the outer soft damping polyethylene layer provides moderate surface deformation while maintaining overall rigidity, increasing friction and control during impact. Its interfacial peel strength is 5.1 kN / m, and the two layers are thermally fused together without any delamination or peeling. The black inner layer is visible through the holes, contrasting sharply with the red outer layer, significantly enhancing the ball's recognizability.

[0058] Example 4

[0059] This embodiment provides a one-piece, non-drilling, two-color, dual-hardness rotationally molded pickball. The pickball consists of an outer layer and an inner layer. The outer layer is made of soft, damping polyethylene with a Shore hardness (D) of 48, a melt index (MI) of 3.5 g / 10min, and a yellow color. The inner layer is a polyethylene blend, composed of 55 parts low-density polyethylene (LDPE) and 45 parts high-density polyethylene (HDPE), with a Shore hardness (D) of 68, a melt index (MI) of 2 g / 10min, and a blue color. The pickball has multiple through-holes, which are directly formed by rotational molding, and the surface of the hole walls has a 1.25° taper. The blue color of the inner layer can be directly observed through any of the through-holes.

[0060] The preparation method is as follows:

[0061] Step 1: Prepare the rotational molding mold. In this embodiment, a fixed-hole column mold is used (the mold cavity is fixed with a column for forming the through hole of the pick ball), and the outer surface of the column is provided with a draft angle of 1.25°.

[0062] Step 2: Add the outer layer polyethylene material to the rotational molding mold. The added mass of the outer layer polyethylene material is 55% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material (in this example, a polyethylene blend).

[0063] Step 3: The rotational molding mold with the outer polyethylene material is heated and rotated in a rotational molding oven at 300°C for 9 minutes. During this process, the outer polyethylene material melts and adheres evenly to the inner wall of the mold cavity and the outer surface of each column under the combined action of centrifugal force and gravity, gradually forming a complete shell. At the end of heating, the outer layer has been plasticized and formed, but the inner surface of the outer layer has not been completely solidified and remains in a semi-molten, viscous state. A noticeable stickiness can be felt when the inside of the mold is lightly touched with a finger.

[0064] Step 4: Pull the rotational molding mold out of the rotary kiln, open the mold, and add the inner layer polyethylene blend into the rotational molding mold that has formed the outer layer. The mass of the inner layer polyethylene blend added is 45% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material.

[0065] Step 5: Re-lock the mold, and then push the rotational molding mold with the inner layer polyethylene material into the rotational molding furnace again for heating and rotation. Continue heating and rotation at a heating temperature of 300°C for 11 minutes, so that the inner layer polyethylene material melts and adheres to the inside of the already formed outer layer to form the inner layer. Then the outer layer and the inner layer are thermally fused together at the interface, and at the same time, through holes are directly formed at the location of the pore column.

[0066] Step Six: After heating is complete, pull the rotational molding mold out of the rotary oven and allow it to cool naturally in room temperature air to allow the sphere to completely solidify. Once the mold has cooled to room temperature, open the mold and remove the molded product.

[0067] The pickballs produced using the method described in this embodiment have a pore position deviation of ±0.05 mm, smooth pore walls with a roughness Ra of 0.3 μm, a sphere resilience of 76%, and an interfacial peel strength of 4.7 kN / m. The inner blue layer is visible through the pores, and the two-tone effect is directly presented by the body color. The inner layer, obtained by blending low-density polyethylene and high-density polyethylene, maintains good toughness while ensuring rigidity and hardness, making the sphere less prone to breakage upon impact.

[0068] Example 5

[0069] This embodiment provides a one-piece, non-drilling, two-color, dual-hardness rotationally molded pickle. The pickle consists of an outer layer and an inner layer. The outer layer is made of soft, damping polyethylene with a Shore hardness (D) of 48, a melt index (MI) of 3.5 g / 10min, and a yellow color. The inner layer is a polyethylene blend composed of 50 parts low-density polyethylene, 42 parts high-density polyethylene, and 8 parts ethylene-acrylic acid copolymer, with a Shore hardness (D) of 72, a melt index (MI) of 2.5 g / 10min, and a blue color. The pickle has multiple through-holes, which are directly formed by rotational molding, and the surface of the hole walls has a 1.25° taper. The blue color of the inner layer can be directly observed through any of the through-holes.

[0070] The preparation method is as follows:

[0071] Step 1: Prepare the rotational molding mold. In this embodiment, a fixed-hole column mold is used (the mold cavity is fixed with a column for forming the through hole of the pick ball), and the outer surface of the column is provided with a draft angle of 1.25°.

[0072] Step 2: Add the outer layer polyethylene material to the rotational molding mold. The added mass of the outer layer polyethylene material is 55% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material (in this example, a polyethylene blend).

[0073] Step 3: The rotational molding mold with the outer polyethylene material is heated and rotated in a rotational molding oven at 300°C for 9 minutes. During this process, the outer polyethylene material melts and adheres evenly to the inner wall of the mold cavity and the outer surface of each column under the combined action of centrifugal force and gravity, gradually forming a complete shell. At the end of heating, the outer layer has been plasticized and formed, but the inner surface of the outer layer has not been completely solidified and remains in a semi-molten, viscous state. A noticeable stickiness can be felt when the inside of the mold is lightly touched with a finger.

[0074] Step 4: Pull the rotational molding mold out of the rotary kiln, open the mold, and add the inner layer polyethylene blend into the rotational molding mold that has formed the outer layer. The mass of the inner layer polyethylene blend added is 45% of the total mass of the outer layer polyethylene material and the inner layer polyethylene material.

[0075] Step 5: Re-lock the mold, and then push the rotational molding mold with the inner layer polyethylene material into the rotational molding furnace again for heating and rotation. Continue heating and rotation at a heating temperature of 300°C for 11 minutes, so that the inner layer polyethylene material melts and adheres to the inside of the already formed outer layer to form the inner layer. Then the outer layer and the inner layer are thermally fused together at the interface, and at the same time, through holes are directly formed at the location of the pore column.

[0076] Step Six: After heating is complete, pull the rotational molding mold out of the rotary oven and allow it to cool naturally in room temperature air to allow the sphere to completely solidify. Once the mold has cooled to room temperature, open the mold and remove the molded product.

[0077] The pickles prepared using the method described in this embodiment have a hole position deviation of ±0.04 mm, smooth hole walls, and a roughness Ra of 0.25 μm. The ball's resilience is 79%, and the interfacial peel strength is 5.2 kN / m. Due to the addition of the ethylene-acrylic acid copolymer, the compatibility between the inner and outer layers is further improved, the interfacial bonding is stronger, and the impact resistance is significantly improved. The ball does not crack after being impacted by a heavy object, and the inner blue layer is visible through the through-holes, resulting in a stable and long-lasting dual-color effect.

[0078] Comparative Example 1

[0079] Pickballs were manufactured using a traditional single-color polyethylene powder rotational molding and drilling process. The specific steps were as follows: Single-color polyethylene powder was poured into a rotational molding mold, locked, and then pushed into a rotational molding furnace for heating and rotation at 280°C for 12 minutes. This molten polyethylene powder adhered to the inner wall of the mold cavity, and after cooling and demolding, a sphere was obtained. A mechanical drilling process was then used to machine through-holes onto the sphere. The polyethylene material used had a Shore hardness of 65 and was a single yellow color. The resulting pickballs exhibited burrs and micro-cracks on the hole walls, with a hole position deviation of ±0.5mm. The inconsistent placement of multiple through-holes resulted in uneven mass distribution and unstable flight trajectories. The overall hardness of the sphere was uniform, lacking both an outer soft control layer and an inner hard support layer, resulting in a hard feel and insufficient control. The sphere surface was a single color, lacking any dual-color effect, leading to low visibility during competition.

[0080] The pickballs prepared in Examples 1 to 3 are compared with the comparative example, and the following advantages are observed: the drilling process is eliminated; the hole position deviation is controlled within ±0.1mm, and the hole wall is smooth and burr-free; the inner and outer colors are directly presented by the polyethylene body material; the outer layer of soft damping polyethylene provides moderate deformation and friction, while the inner layer of hard supporting polyethylene ensures the rigidity and elastic recovery of the ball; the two layers of homologous polyethylene are thermally fused together, and the interfacial peel strength reaches 4.2~5.1 kN / m, with no risk of delamination.

[0081] The foregoing has shown and described 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 embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its framework and scope of application, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A one-piece molded, non-drilling, two-color, dual-hardness rotational molded peak ball, comprising a peak ball body, characterized in that: The pick ball body is composed of an outer layer and an inner layer. The outer layer is made of soft damping PE, and the inner layer is made of rigid support PE. The outer PE material has a first color, and the inner PE material has a second color, which is different from the first color. The pick ball body is provided with through holes, and there are several groups of through holes. Without damaging the ball, the second color of the inner layer can be observed through any of the through holes.

2. The one-piece molded, non-drilling, dual-color, dual-hardness rotational molded peak ball according to claim 1, characterized in that: The outer PE material has a Shore hardness D of 40-55 and a melt flow index MI of 2-5 g / 10min, while the inner PE material has a Shore hardness D of 60-75 and a melt flow index MI of 1-3 g / 10min.

3. The one-piece molded, non-drilling, dual-color, dual-hardness rotational molded peak ball according to claim 1, characterized in that: The surface of the hole wall has a taper of 0.5° to 2°.

4. The one-piece molded, non-drilling, dual-color, dual-hardness rotational molded peak ball according to claim 1, characterized in that: The surface of the hole wall is also provided with a residual layer of polytetrafluoroethylene non-stick coating.

5. A method for preparing a one-piece, non-drilling, two-color, dual-hardness rotomolded pick ball, applicable to the one-piece, non-drilling, two-color, dual-hardness rotomolded pick ball described in any one of claims 1-5, characterized in that: Includes the following steps: Step 1: Prepare a rotational molding mold, the mold cavity of which is fixed with a perforated column for forming the through hole of the pick ball; Step 2: Add the outer PE material to the rotational molding mold, wherein the outer PE material is a soft damping type PE with a Shore hardness D of 40~55, a melt index MI of 2~5 g / 10min, and the outer PE material has a first color; Step 3: The rotational molding mold with the added outer PE material is heated and rotated in a rotational molding oven at a temperature of 250~350°C for 6~12 minutes, so that the outer PE material melts and adheres to the inner wall of the mold cavity and the surface of the orifice to form an outer layer, and the inner surface of the outer layer is in a semi-molten viscous state. Step 4: Open the rotational molding mold and add the inner layer PE material into the rotational molding mold that has formed the outer layer. The inner layer PE material is rigid support type PE with a Shore hardness D of 60~75 and a melt index MI of 1~3 g / 10min. The inner layer PE material has a second color, which is different from the first color. Step 5: Re-lock the mold and push the rotational molding mold with the inner PE material into the rotational molding furnace again for heating and rotation. The heating temperature is 250~350°C and the heating time is 7~15 minutes, so that the inner PE material melts and adheres inside the already formed outer layer to form the inner layer. The outer layer and the inner layer are thermally fused together at the interface, and at the same time, through holes are directly formed at the location of the pore column. Step 6: Remove the rotational molding mold and allow it to cool, allowing the sphere to solidify. Then, open the mold and remove the product to obtain a two-color, two-hardness rotational molded peak ball.

6. The method for preparing a one-piece molded, non-drilling, dual-color, dual-hardness rotational molding pick ball according to claim 5, characterized in that: In step two, the mass of the outer PE material added is 40% to 70% of the total mass of the outer PE material and the inner PE material. In step four, the mass of the inner PE material added is 30% to 60% of the total mass of the outer PE material and the inner PE material.

7. The method for preparing a one-piece molded, non-drilling, dual-color, dual-hardness rotational molding pick ball according to claim 5, characterized in that: The outer surface of the perforated column is provided with a draft angle of 0.5°~2°.

8. The method for preparing a one-piece molded, non-drilling, dual-color, dual-hardness rotational molding pick ball according to claim 5, characterized in that: The outer surface of the perforated column is coated with a polytetrafluoroethylene non-stick coating.

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