Flexible leather injection molding method, mold and injection molding part

Abstract

The invention relates to the technical field of material forming, in particular to a flexible leather injection molding method, a mold and an injection molding part. The flexible leather injection molding method comprises the steps that flexible leather is put into an injection mold, and the mold is closed; the flexible leather is attached and fixed to a front mold body of the injection mold through negative pressure; injection molding raw materials are injected into a cavity of the injection mold, so that the injection molding raw materials are combined with the flexible leather; and opening the film after the plastic is cooled and cured. According to the method, the fitting process and the injection molding process of the flexible leather are combined, the flexible leather is placed in the injection mold in advance, the flexible leather is precisely attached to the surface of the mold through the negative pressure technology, then the injection molding raw material in the hot melting state is directly injected, and integrated forming of the flexible leather and the injection molding raw material is achieved; the manufacturing requirements of products with complex designs such as grooves, craters and button positions can be better met, the attaching technology after injection molding of a traditional technology is completed is omitted, and the design cost and the overall product cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of material molding, and in particular to a flexible leather material injection molding method, a mold and an injection molded part. Background Art

[0002] In the electronics industry, such as mobile phone cases and tablet cases, the surface treatment process of PU leather and similar flexible materials is mainly divided into two different methods to meet different product design and functional requirements.

[0003] First, if Figure 1 and Figure 2 As shown, the first process method focuses on designing and making the bonding substrate 1, such as an injection molded part. This step can realize a 2D plane or 3D curved surface, or even a more complex special-shaped structure, according to the specific structural requirements of the product. After completing the design of the bonding substrate 1, the flexible leather material 5, hot melt adhesive 4 and the bonding substrate 1 are placed in the hot press table, and then the upper mold 2 and the lower mold 3 of the hot press table are closed, and the flexible leather material 5 is bonded to the bonding substrate 1 using the hot melt adhesive 4. This process requires precise control to ensure that the flexible leather material 5 and the bonding substrate 1 are firmly bonded. Finally, through CNC processing technology, the final product shape is cut according to the product design drawings.

[0004] like Figure 3 and Figure 4 As shown, the second process method directly puts the semi-cured bonding substrate 1 and the flexible leather material 5 into the hot press. Then, the upper mold 2 and the lower mold 3 of the hot press are combined. Under the action of high temperature and pressure, the bonding substrate 1 and the flexible leather material 5 are pressed together to form. In this process, the flexible leather material 5 is cured and bonded to the bonding substrate 1, and there is no need to use hot melt adhesive for secondary bonding. This method simplifies the process flow and improves production efficiency.

[0005] Although both processes can effectively achieve the lamination effect of flexible leather materials, they have certain limitations in practical application. At present, these processes are more suitable for processing 2D flat surfaces or 3D smooth curved surfaces, and the curvature height of the product should not exceed 3 mm. In addition, these processes are more suitable for products with smooth backs or relatively simple features.

[0006] For products with complex structures, such as those with grooves, craters, buckles, etc., the above two process methods are incapable of meeting the requirements. These complex structures cannot be directly realized through existing processes, so the design team needs to perform additional design work, such as adding structural materials to the handpiece or additional structural parts to meet the functional and aesthetic requirements of the product. Such processing not only increases the difficulty of process implementation, but also increases production costs. Summary of the invention

[0007] The object of the present invention is to provide a flexible leather material injection molding method, a mold and an injection molded part, so as to reduce the production cost and be applicable to complex structure design.

[0008] In order to solve the above technical problems, the present invention provides a flexible leather material injection molding method, a mold and an injection molded part.

[0009] The flexible leather material injection molding method of the present invention comprises:

[0010] Put the flexible leather material into the injection mold and close the mold;

[0011] Make the flexible leather material fit and fix on the front mold of the injection mold under negative pressure;

[0012] Injecting the injection molding material into the cavity of the injection mold to combine the injection molding material with the flexible leather material;

[0013] After the plastic cools and solidifies, open the film.

[0014] Furthermore, the flexible leather material is negatively pressed against the groove of the injection mold by means of air extraction.

[0015] Furthermore, an exhaust hole connected to the cavity of the front mold is provided on the front mold of the injection mold, and air is exhausted through the exhaust hole.

[0016] Furthermore, there are a plurality of air extraction holes which are evenly distributed on the front mold of the injection mold.

[0017] Furthermore, a positioning column is provided in the injection mold to roughly position the flexible leather material, and a positioning ring groove is provided in the injection mold to precisely position the flexible leather material.

[0018] The present invention also provides a flexible leather material injection molding mold, comprising a front mold and a rear mold;

[0019] The front mold is provided with an air extraction hole connected to the mold cavity of the front mold, and the air extraction hole is used to extract air so as to fix the flexible leather material on the front mold by negative pressure;

[0020] The rear mold is provided with an injection hole for injecting injection molding raw materials to fit the injection molding raw materials with the flexible leather material.

[0021] Furthermore, there are a plurality of air extraction holes which are evenly distributed on the front mold of the injection mold.

[0022] Furthermore, the flexible leather material injection molding mold is provided with a positioning column for roughly positioning the flexible leather material, and is also provided with a positioning ring groove for finely positioning the flexible leather material.

[0023] The present invention also provides an injection molded part, comprising an injection molded substrate and a flexible leather material covering the injection molded substrate, wherein a permeation layer is provided between the injection molded substrate and the flexible leather material, and the permeation layer is formed by mutual penetration of the injection molded substrate and the flexible leather material so that the two are fixedly connected.

[0024] Furthermore, the thickness of the permeable layer is 0.001-0.01 mm.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] This application combines the laminating process of flexible leather with the injection molding process. By pre-placing the flexible leather in the injection mold, using negative pressure technology to make it accurately fit the mold surface, and then directly injecting the hot-melt injection molding material, the flexible leather and the injection molding material are integrally formed. This method overcomes the limitations of traditional processes in processing complex structural products, can better adapt to the manufacturing needs of products with complex designs such as grooves, craters, buckles, etc., and saves the laminating process after the injection molding of the traditional process, reducing the design cost and the overall product cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process of bonding a 2D flat bonding substrate to a flexible leather material using hot melt adhesive in the prior art;

[0028] Figure 2 It is a schematic diagram of the process of bonding a 3D curved surface bonding substrate to a flexible leather material using hot melt adhesive in the prior art;

[0029] Figure 3 It is a schematic diagram of a process of directly placing a semi-cured 2D flat bonding substrate and a flexible leather material into a hot press for bonding in the prior art;

[0030] Figure 4 It is a schematic diagram of a process of directly placing a semi-cured 3D curved surface bonding substrate and a flexible leather material into a hot press for bonding in the prior art;

[0031] Figure 5 It is a flow chart of an embodiment of the flexible leather material injection molding method of the present invention;

[0032] Figure 6 A top view of the front mold of the flexible leather material injection molding mold of the present invention;

[0033] Figure 7 for Figure 6 AA section schematic diagram of the front mold in FIG;

[0034] Figure 8 It is a top view of the rear mold of the flexible leather material injection molding mold of the present invention;

[0035] Fig. 9 for Figure 8 BB section diagram of the rear mold.

[0036] Reference numerals:

[0037] 1. Laminating substrate; 2. Upper mold of hot press; 3. Lower mold of hot press; 4. Hot melt adhesive; 5. Flexible leather;

[0038] 6. Exhaust hole; 7. Positioning column; 8. Annular protrusion; 9. Annular groove. DETAILED DESCRIPTION

[0039] The flexible leather material injection molding method, mold and injection molded part of the present invention will be described below in conjunction with schematic diagrams, wherein preferred embodiments of the present invention are shown, and it should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0040] The serial numbers of the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention 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 understood as a limitation to the present invention.

[0041] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to facilitate and clearly assist in illustrating the purpose of the embodiments of the present invention.

[0042] The inventors have found that in the field of electronic product casing manufacturing, the existing PU leather bonding process mainly faces severe technical challenges of material structure complexity and process adaptability. Traditional hot melt adhesive and hot pressing processes have obvious limitations and cannot effectively process product surfaces with complex structural features. Among them, the key technical problems are concentrated in the difficulty of achieving accurate and stable bonding between flexible leather and injection molded parts, especially for products with complex structures such as grooves, craters, and buckles. In the production process of smartphone casings, this technical problem is particularly prominent. Taking the production of smartphone back covers as an example, its design includes multiple structural features of different depths, such as circular grooves around the camera and structural buckles on the side. When traditional processes try to bond PU leather to such complex surfaces, serious quality defects such as uneven bonding, wrinkle accumulation, and partial detachment will occur.

[0043] To overcome these limitations, the present application explored a variety of possible solutions, one of which is to improve the hot pressing process by designing a special pressure distribution device to adapt to complex surfaces. However, this method is still difficult to completely solve the aforementioned problems, and there are still problems of complex process and high cost.

[0044] Another consideration is to use a multi-step lamination process, first laminating the simple area, and then performing a secondary treatment for the complex structure area. However, this method will significantly increase production time and cost, and is prone to visible defects at the seams. After in-depth analysis, the applicant realized that the key lies in how to establish a tighter and more uniform bond between the flexible leather and the injection molded part. This prompted the applicant to explore the possibility of combining the lamination process with the injection molding process.

[0045] In one embodiment, if Figure 5 As shown, the flexible leather material injection molding method of the present application comprises the following steps:

[0046] S100: Put the flexible leather material into the injection mold and close the mold;

[0047] S200: making the flexible leather material fit and fix on the front mold of the injection mold under negative pressure;

[0048] S300: injecting the injection molding material into the cavity of the injection mold to combine the injection molding material with the flexible leather material;

[0049] S400: Open the film after the plastic cools and solidifies.

[0050] Specifically, the present application proposes an innovative idea: directly combining the flexible leather material with the injection molding raw material during the injection molding process. The core of this method is to utilize the hot melt state of the injection molding raw material during the injection molding process so that it can form a tight combination with the flexible leather material pre-placed in the mold. In order to realize this concept, the present application designs a special injection mold structure. An exhaust hole 6 is set on the front mold of the mold, and the negative pressure technology is used to enable the flexible leather material to be accurately attached to the mold surface, including complex structural features. This step solves the problem of fine structure that is difficult to handle in traditional methods.

[0051] Next, after the flexible leather is fixed in place, the hot-melt injection material is injected. The injection material flows under high temperature and pressure, and can fully penetrate the microstructure of the flexible leather to form a strong mechanical bond. This method can not only adapt to complex surface structures, but also achieve stronger adhesion at the molecular level. Finally, by controlling the cooling process, it is ensured that the injection material and the flexible leather form a stable integrated structure. This cooling process can also further optimize the surface quality and reduce possible stress deformation.

[0052] Among them, flexible leather refers to a thin sheet material with softness and elasticity, which can be specifically realized by PU (polyurethane leather), PU-like leather or rubber leather, wherein the PU-like leather can be TPU (thermoplastic polyurethane rubber) or silicone leather. Injection mold refers to a tool used for injection molding, which can be specifically realized by a mold composed of a front mold and a back mold. Negative pressure bonding refers to a technology that makes flexible leather closely adhere to the surface of the mold by exhausting air, which can be specifically realized by setting an exhaust hole 6 on the mold and connecting an air suction valve.

[0053] The core innovation of this application is to combine the laminating process of flexible leather with the injection molding process. By pre-placing the flexible leather in the injection mold and using negative pressure technology to make it accurately fit on the mold surface, and then directly injecting the hot-melt injection molding material, the flexible leather and the injection molding material are integrally formed. This method overcomes the limitations of traditional processes in processing complex structural products, can better adapt to the manufacturing needs of products with complex designs such as grooves, craters, buckles, etc., and saves the laminating process after the injection molding of the traditional process, reducing the design cost and the overall product cost.

[0054] The working principle of the present application can be described in detail as follows: First, in step S100, a flexible leather material is placed in an injection mold. The injection mold is composed of a front mold and a back mold, such as Figure 6 and Figure 7As shown, the front mold is provided with an exhaust hole 6 connected to the mold cavity. The flexible leather material is placed on the mold cavity surface of the front mold, and its shape and size match the mold cavity. Then, in step S200, the flexible leather material is fixed to the front mold of the injection mold by vacuuming. The exhaust hole 6 is connected to the suction valve, and the suction valve is started to evacuate air, so that the flexible leather material is tightly attached to the mold surface under the action of negative pressure, including the complex structural feature area. This step ensures that the flexible leather material maintains a stable position during the subsequent injection molding process to avoid wrinkles or deformation.

[0055] Then, in step S300, the injection molding material is injected into the mold cavity of the injection mold. The injection molding material is in a hot-melt state under high temperature and high pressure, and is injected into the mold cavity through the injection hole. The hot-melt injection molding material can fully flow and penetrate into the microstructure of the flexible leather material to form a permeation layer, thereby forming a strong mechanical bond.

[0056] Finally, in step S400, the mold is opened after the plastic is cooled and solidified. After the mold is opened, the final product shape can be cut through CNC processing technology. In this process, the injection molding material gradually cools down and forms a stable integrated structure with the flexible leather material. The control of the cooling process is crucial to ensure product quality. The surface quality can be optimized and possible stress deformation can be reduced by adjusting the cooling time and temperature.

[0057] The injection molded part obtained after cooling includes an injection molding substrate and a flexible leather material covering the injection molding substrate, wherein the injection molding substrate is formed after the injection molding raw material is solidified, and the permeation layer is formed by the mutual penetration of the injection molding substrate and the flexible leather material so that the two are fixedly connected. Preferably, the thickness of the permeation layer is 0.001-0.01 mm. The thickness of the permeation layer formed by different material combinations is different, for example, it can be 0.003 mm, 0.005 mm or 0.008 mm.

[0058] The key to this method is to use the hot melt state of the injection molding material during the injection molding process to achieve a close combination with the flexible leather. The choice of negative pressure bonding technology is to solve the problem of deep grooves and fine structures that are difficult to handle in traditional methods, ensuring that the flexible leather can be accurately bonded to the mold surface, including complex structural features. This combination of technologies significantly improves the bonding quality and applicability of flexible leather and injection molded parts, especially for products with complex structures. Through this method, complex structure injection molded parts with surfaces covered with flexible leather can be manufactured, especially injection molded parts with complex three-dimensional curved surfaces or concave-convex structures, such as the back cover of a smartphone with multiple grooves of different depths. This technology not only improves the aesthetics and touch of the product, but also overcomes the limitations of traditional processes in handling complex structures, significantly improving production efficiency and product quality.

[0059] In one of the embodiments, the flexible leather material is negatively pressed against the groove of the injection mold by means of vacuum.

[0060] The air extraction method of the present application can be implemented by various methods. For example, an air extraction hole 6 connected to the cavity of the front mold can be provided on the front mold of the injection mold, and air is extracted through the air extraction holes 6. The air extraction hole 6 can be one or more, and the more the number of air extraction holes 6, the better the uniformity of the flexible leather material is.

[0061] As a preferred embodiment, the air extraction holes 6 can be circular, oval or other suitable shapes, and the diameter can be between 0.5 mm and 2 mm, for example, 1 mm or 1.5 mm. The number and distribution density of the air extraction holes 6 can be adjusted according to the size and complexity of the mold. For example, for a mold surface of 200 mm×300 mm, 50 to 100 air extraction holes 6 can be evenly distributed.

[0062] The air extraction holes 6 can be evenly distributed on the front mold to ensure that the flexible leather material can be evenly attached to the mold surface. In other embodiments, the air extraction holes 6 can also be unevenly arranged. In addition, an air suction valve can be connected to the air extraction holes 6 for air extraction. The air suction valve can accurately adjust the intensity and duration of the air extraction to adapt to flexible leather materials of different types and thicknesses, so that the air extraction process can be more accurately controlled.

[0063] The connection position of the suction valve can be adjusted according to the specific structure of the mold to ensure the effectiveness of the vacuum process. For example, the suction valve can be set at different positions of the front mold to better control the negative pressure distribution in each area.

[0064] In a specific embodiment, the injection mold for producing the back cover of a smart phone has a front mold size of 150 mm×75 mm. 80 circular air extraction holes 6 are evenly distributed on the surface of the front mold, each of which has a diameter of 1 mm. The air extraction holes 6 are distributed in a grid shape, with a horizontal spacing of 10 mm and a vertical spacing of 8 mm.

[0065] When in use, first put the cut PU leather into the mold, then close the mold. Start the vacuum system, gradually increase the negative pressure to -0.08MPa within 5 seconds, and maintain this negative pressure for 10 seconds to ensure that the PU leather is completely attached to the mold surface. Then, inject ABS injection molding material preheated to 220℃ through the injection hole, the injection pressure is 60MPa, and the pressure holding time is 15 seconds. Finally, after cooling for 60 seconds, open the mold and take out the finished product.

[0066] Through this method, a PU leather-covered mobile phone back cover with a smooth surface, no bubbles and no wrinkles can be produced. It can maintain a good fit even on the corners and curved parts, greatly reducing the waste caused by poor leather bonding.

[0067] In one of the embodiments, in order to achieve precise positioning, a positioning column 7 is provided in the injection mold to roughly position the flexible leather material, and a positioning ring groove is provided in the injection mold to finely position the flexible leather material.

[0068] The present application provides a positioning column 7 in the mold for rough positioning, which can ensure that the flexible leather material is roughly in the correct position during the injection molding process. The positioning ring groove is used to accurately adjust the position of the flexible leather material to ensure that it does not deviate during the molding process. The technical features of rough positioning and fine positioning can effectively solve the problem of accurate positioning of flexible leather materials in complex injection molding processes by cooperating with each other.

[0069] Specifically, the positioning posts 7 can be arranged in a variety of ways. For example, a plurality of positioning posts 7 can be arranged on the front mold and / or the back mold of the injection mold, and positioning holes can be opened at corresponding positions on the flexible leather material. When the flexible leather material is placed, the positioning posts 7 pass through the positioning holes on the flexible leather material to achieve preliminary rough positioning. The number and distribution of the positioning posts 7 can be reasonably designed according to the size and shape of the flexible leather material. Generally, 3-6 positioning posts 7 can be arranged, evenly distributed on the edge of the mold.

[0070] There are also many variations in the design of the locating ring groove. Figure 7 and Figure 8 As shown, a circle of annular protrusions 8 can be provided on the front mold of the injection mold along the edge of the flexible leather material, and correspondingly, a matching annular groove 9 can be provided on the back mold.

[0071] For example, the annular protrusion 8 has a width of 5 mm, a height of 4 mm, and a sidewall draft angle of 5°, and correspondingly, the annular groove 9 also has a width of 5 mm, a depth of 4 mm, and a sidewall draft angle of 5°. Of course, the annular protrusion 8 and the annular groove 9 can also be set to other sizes.

[0072] When the mold is closed, the edge of the flexible leather material is clamped between the annular structure and the annular groove 9 to achieve precise positioning. In other embodiments, the annular groove 9 can also be arranged on the front mold, and the annular protrusion 8 is arranged on the back mold.

[0073] This combination of coarse and fine positioning has significant advantages in solving the problem of flexible leather positioning. Coarse positioning ensures the approximate position of the flexible leather, while fine positioning further limits the edge movement of the flexible leather. The two work together to effectively prevent the deformation and displacement of the leather caused by high temperature and high pressure during the injection molding process. This design is particularly suitable for products with complex shapes, such as electronic product housings with grooves, craters or buckles.

[0074] As a preferred embodiment, four positioning posts 7 can be set on the front mold of the injection mold, respectively located at the four corners of the mold, and each positioning post 7 has a diameter of 3 mm and a height of 5 mm. Accordingly, four positioning holes with a diameter of 3.1 mm are pre-opened on the flexible leather. The positioning ring groove can be designed as a continuous annular structure with a width of 2 mm and a depth of 1 mm, distributed along the entire edge of the flexible leather. During the injection molding process, the flexible leather is first placed in the mold so that the positioning post 7 passes through the positioning hole. Then the mold is closed, and the positioning ring groove will accurately fix the edge of the flexible leather. Then negative pressure adsorption and injection molding are carried out, and the flexible leather can be kept in a predetermined position throughout the process.

[0075] Therefore, the technical solution of the present application can effectively solve the positioning problem of flexible leather during the injection molding process, ensuring the accuracy and quality of the molded parts. Through precise positioning, the deformation and defects of the product can be significantly reduced, and the yield rate can be improved.

[0076] The present application also provides a flexible leather injection molding mold, whose structure is the same as the structure of the injection mold in the flexible leather injection molding method in the above technical solution, and can be used to implement the flexible leather injection molding method in the above technical solution, which will not be repeated here.

[0077] The present application also provides an injection molded part, which is made by the flexible leather injection molding method described in any one of the above technical solutions, and the injection molded part includes an injection molding substrate and a flexible leather covering the injection molding substrate, and the injection molding substrate is formed after the injection molding raw material is solidified, and the permeation layer is formed by the mutual penetration of the injection molding substrate and the flexible leather so that the two are fixedly connected. Preferably, the thickness of the permeation layer is 0.001-0.01 mm. The thickness of the permeation layer formed by different material combinations is different, for example, it can be 0.003 mm, 0.005 mm or 0.008 mm.

[0078] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for injection molding of flexible leather, characterized in that: include: Put the flexible leather material into the injection mold and close the mold; Make the flexible leather material fit and fix on the front mold of the injection mold under negative pressure; Injecting the injection molding material into the cavity of the injection mold to combine the injection molding material with the flexible leather material; After the plastic cools and solidifies, open the film.

2. The flexible leather material injection molding method according to claim 1, characterized in that: The flexible leather material is pressed against the groove of the injection mold under negative pressure by means of air extraction.

3. The flexible leather material injection molding method according to claim 2, characterized in that: An air extraction hole connected with the cavity of the front mold is arranged on the front mold of the injection mold, and air is extracted through the air extraction hole.

4. The flexible leather material injection molding method according to claim 3, characterized in that: There are a plurality of air extraction holes which are evenly distributed on the front mold of the injection mold.

5. The flexible leather material injection molding method according to claim 1, characterized in that: A positioning column is arranged in the injection mold to roughly position the flexible leather material, and a positioning ring groove is arranged in the injection mold to finely position the flexible leather material.

6. A flexible leather injection molding mold, characterized in that: Including front mold and back mold; The front mold is provided with an air extraction hole connected to the mold cavity of the front mold, and the air extraction hole is used to extract air so as to fix the flexible leather material on the front mold by negative pressure; The rear mold is provided with an injection hole for injecting injection molding raw materials to fit the injection molding raw materials with the flexible leather material.

7. The flexible leather material injection molding mold according to claim 6, characterized in that: There are a plurality of air extraction holes which are evenly distributed on the front mold of the injection mold.

8. The flexible leather material injection molding mold according to claim 6, characterized in that: The flexible leather material injection molding mold is provided with a positioning column for roughly positioning the flexible leather material, and is also provided with a positioning ring groove for precisely positioning the flexible leather material.

9. An injection molded part, characterized in that: The flexible leather material is made by the injection molding method of any one of claims 1 to 5, comprising an injection molding substrate and a flexible leather material covered on the injection molding substrate, wherein a permeation layer is provided between the injection molding substrate and the flexible leather material, and the permeation layer is formed by mutual penetration of the injection molding substrate and the flexible leather material so that the two are fixedly connected.

10. The injection molded part according to claim 9, characterized in that: The thickness of the permeable layer is 0.001-0.01 mm.

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