Resin molded product and resin molding method

Abstract

To provide a resin molded product and a resin molding method in which a decrease in strength is suppressed and a yield is improved.SOLUTION: A resin molded product includes: a main member made of a first resin; a sub-member formed of a second resin having a higher melting point than the first resin; and a fusion part that connects the main member and the sub-member by being interposed between the main member and the sub-member. A density of an outer part of the main member in contact with the fusion part is higher than the density of an inside of the main member.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006] ,

[0001] The present disclosure relates to a resin molded product and a resin molding method.

Background Art

[0002] Conventionally, injection molding using a mold has been widely used as a method for obtaining a molded product from resin. In this method, molten resin is injected into a cavity formed in a mold at high pressure, and the molded product is taken out of the mold when the resin is cured.

[0003] By the way, when injection molding is used, if the thickness of the molded product exceeds a certain level, the resin may not spread smoothly in the cavity. As a result, sink marks or voids may occur in the molded product. As a technique for avoiding such defects, for example, the one described in Patent Document 1 below is known. Patent Document 1 below describes a technique of foaming a part of the resin by reducing the pressure of the resin flowing into the cavity. Thereby, formation of sink marks and voids due to the resin not reaching is avoided, and good coloring is also said to be obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using the above - mentioned foam molding, the strength of the molded product decreases due to the presence of bubbles. Also, it is difficult to cause uniform foaming throughout the molded product, and there is a problem that the yield of the molded product decreases.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide a resin molded product and a resin molding method that suppress the reduction in strength and improve yield. [Means for solving the problem]

[0007] To solve the above problems, the resin molded product according to this disclosure comprises a main member formed of a first resin, a secondary member formed of a second resin having a higher melting point than the first resin, and a fusion portion interposed between the main member and the secondary member to join the main member and the secondary member, wherein the density of the outer portion of the main member in contact with the fusion portion is higher than the density of the interior of the main member.

[0008] The resin molding method according to this disclosure is a resin molding method for manufacturing the above-mentioned resin molded product, and includes the steps of: forming the main member by laminating the first resin by three-dimensional additive manufacturing; placing the main member inside a mold; and performing injection molding of the sub-member by filling the mold with the second resin, which has been molten so as to be in contact with the main member. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a resin molded product and a resin molding method in which the reduction in strength is suppressed and the yield is improved. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing an example of a resin molded product according to the present disclosure. [Figure 2] This is an enlarged cross-sectional view of a key part of a resin molded product according to an embodiment of the present disclosure. [Figure 3] This is a process diagram showing each step of the resin molding method according to the present disclosure. [Figure 4] This is a cross-sectional view showing a first modified example of the main member according to the embodiment of this disclosure. [Figure 5] This is a cross-sectional view showing a second modified example of the main member according to the embodiment of this disclosure. [Figure 6] This is a plan view showing a modified example of a resin molded product according to the embodiment of this disclosure. [Modes for carrying out the invention]

[0011] (Composition of resin molded product) Hereinafter, a resin molded product 1 and a resin molding method according to the embodiments of this disclosure will be described with reference to Figures 1 to 3. The resin molded product 1 is used as a component of various industrial products. In this embodiment, the application of the resin molded product 1 is not particularly limited.

[0012] As shown in Figures 1 and 2, the resin molded product 1 comprises a main member 10, a sub-member 11, and a fusion joint 12. The main member 10 is, for example, in the form of a thick plate. The main member 10 is formed of a first resin 21. The first resin 21 is made of, for example, nylon 6, and its melting point is 200°C. The main member 10 is integrally formed by three-dimensional additive manufacturing. The main member 10 is configured such that the density of the outer casing 31, which is the part in contact with the sub-member 11 (described later), is higher than the density of the part inside the outer casing 31. More specifically, the outer casing 31 has a high-density structure such as a solid plate. On the other hand, the interior of the main member 10 has a low-density structure such as a truss structure or a porous structure. These outer casing 31 and the interior structure are integrally formed by the first resin 21.

[0013] The sub-member 11 has, for example, a covering portion 41 that covers the main member 10 from the outside, and a protruding portion 42 that protrudes from the covering portion 41. The thickness of the covering portion 41 is set to be equal to or slightly less than the thickness of the main member 10. The main member 10 does not exist inside the protruding portion 42; it is formed only by the sub-member 11. The thickness of the protruding portion 42 is equal to or slightly less than the thickness of the main member 10. In other words, the thickness of the protruding portion 42 is less than the sum of the thickness of the covering portion 41 of the sub-member 11 and the thickness of the main member 10. The thickness of this protruding portion 42 is set to be less than the maximum wall thickness that can be molded by injection molding. The sub-member 11 is formed of a second resin 22. The second resin 22 is a resin with a higher melting point than the first resin 21. For example, the second resin 22 is nylon 9T, and its melting point is 300°C. It is desirable that the melting point of the second resin 22 be 50°C or more higher than the melting point of the first resin 21. Insofar as this relationship is satisfied, any resin material can be appropriately selected as the first resin 21 and the second resin 22.

[0014] A fusion joint 12 is interposed between the main member 10 and the sub-member 11. The fusion joint 12 is a layered region formed by the melting and hardening of the first resin 21 of the main member 10 and the second resin 22 of the sub-member 11. In other words, the main member 10 and the sub-member 11 are fused together by this fusion joint 12. The method for fusion bonding the main member 10 and the sub-member 11 will be described later.

[0015] (Resin molding method) Next, with reference to Figure 3, a method for molding the resin molded product 1 described above (resin molding method) will be explained. As shown in the figure, this method includes a step S1 for designing the external shape of the main member 10, a step S2 for designing the internal structure of the main member 10, a step S3 for molding the main member 10, a step S4 for placing the main member 10 inside a mold, and a step S5 for injection molding the sub-member 11 using the mold.

[0016] In step S1, based on the shape, dimensions, required strength, weight, etc. of the final resin molded product 1, the external shape of the main member 10 (the shape of the outer contour portion 31 described above) is determined. As an example, in injection molding, when the resin molded product 1 as the final product requires a wall thickness such that a good molded product cannot be obtained, the external shape of the main member 10 including the wall thickness is determined so as to ensure the maximum wall thickness of the sub-member 11 that can be injection molded.

[0017] In step S2, the internal structure of the main member 10 is determined. The internal structure referred to here refers to, for example, a shape when weight reduction and high strength are achieved by forming voids inside the main member 10. More specifically, examples include making the inside of the main member 10 not solid but having a truss structure or a porous structure.

[0018] In step S3, based on the external shape and internal structure determined in step S1 and step S2 above, the main member 10 is formed by three-dimensional laminated manufacturing (AM manufacturing method: Additive Manufacturing) in which the first resin 21 is sequentially laminated.

[0019] In step S4, the main member 10 obtained in step S3 is placed inside the mold. Here, the mold refers to a mold in which a cavity is formed according to the outer shape of the resin molded product 1 which is the final product. With the main member 10 placed inside this mold, step S5 is executed. In step S5, the second resin 22 is press-fitted into the cavity in a molten state so as to contact the main member 10 or surround the main member 10, and the sub-member 11 is injection molded. At this time, due to the heat of the second resin 22, the surface of the first resin 21 forming the main member 10 melts and joins (fuses) with the second resin 22. Then, the first resin 21 and the second resin 22 are cooled and cured, thereby forming the above-mentioned welded portion. Then, the resin molded product 1 is taken out of the mold. Thus, the manufacturing of the resin molded product 1 is completed.

[0020] (Function and Effect) Conventionally, injection molding using a mold has been widely used as a method for obtaining molded products from resin. In this method, molten resin is injected into a cavity formed in a mold at high pressure, and the molded product is taken out of the mold when the resin hardens.

[0021] By the way, when using injection molding, if the thickness of the molded product exceeds a certain level, the resin may not spread smoothly in the cavity. As a result, sink marks or voids may occur in the molded product. As a technique for avoiding such defects, for example, what is called foam molding is known. In foam molding, a part of the resin is foamed by reducing the pressure of the resin flowing into the cavity.

[0022] However, when using the above-mentioned foam molding, since the density of the molded product decreases due to the presence of air bubbles, the strength and rigidity of the molded product decrease. Also, it is difficult to cause uniform foaming throughout the molded product, and there is also a problem that the yield of the molded product decreases. Therefore, in the present embodiment, the above-described respective configurations and methods are adopted.

[0023] According to the above configuration, the melting point of the second resin 22 forming the sub-member 11 is higher than the melting point of the first resin 21 forming the main member 10. Thereby, when melting the second resin 22 to form the sub-member 11, the main member 10 also melts. Therefore, the fusion part 12 is stably formed between the main member 10 and the sub-member 11, and it becomes possible to firmly join these main member 10 and sub-member 11. On the other hand, when the melting point of the first resin 21 is lower than the melting point of the second resin 22, even if the second resin 22 is melted, the first resin 21 does not melt. For this reason, the welding part is not stably formed, and there is a risk that the joining of the main member 10 and the sub-member 11 becomes incomplete. As a result, the yield of the resin molded product 1 decreases. However, according to the above configuration, it is possible to reduce such a risk and improve the yield of the resin molded product 1.

[0024] Furthermore, in the above configuration, the density of the outer casing 31 of the main member 10 is higher than the density of the interior of the main member 10. Therefore, compared to the case where the entire main member 10, including the outer casing 31, is made of a low-density structure such as a truss structure or a porous structure, the heat resistance of the surface (outer casing 31) of the main member 10 is improved. This reduces the possibility that the outer casing 31 may also melt when the second resin 22 is melted. On the other hand, if the outer casing 31 melts easily, it can cause deformation or damage to the main member 10, which poses a risk of reducing the yield of the final product, the resin molded product 1. With the above configuration, it is possible to significantly reduce such risks and further improve the yield of the resin molded product 1.

[0025] Furthermore, in the above method, the main member 10 is first placed inside the mold, and the sub-member 11 is injection-molded so as to be in contact with the main member 10. In other words, insert molding is performed so that the second resin 22 is distributed around the main member 10. As a result, the amount of second resin 22 required for injection molding is reduced, and the wall thickness of the part formed by the second resin 22 is kept small. As a result, compared to forming the entire resin molded product 1 by injection molding alone, it is possible to obtain a large resin molded product 1 while avoiding the occurrence of sink marks and voids caused by insufficient distribution of the resin material (second resin 22). In particular, it is known that the maximum wall thickness that can be molded by injection molding alone is limited to about 5 mm, but with the above method, it is possible to stably obtain a resin molded product 1 with a wall thickness exceeding this value. This improves the yield of the resin molded product 1 and makes it possible to reduce manufacturing costs.

[0026] The embodiments of this disclosure have been described above. It is possible to make various modifications and improvements to the above configuration and method without departing from the gist of this disclosure.

[0027] For example, regarding the internal structure of the main member 10 described in the above embodiment, a more specific example (first modified example) can be considered, as shown in Figure 4. In the example shown in the figure, the main member 10 has void portions 51 and a skeletal portion 52. The void portions 51 are spaces containing air. The skeletal portion 52 surrounds these void portions 51. In Figure 4, as an example, the outer shape of the main member 10 is rectangular, and the skeletal portion 52 is provided along the diagonals inside. That is, each of the void portions 51 is triangular in shape. Furthermore, the skeletal portion 52 has wall portions 61 that form the void portions 51 and the outer casing portion 31, and an internal structure portion 62 formed inside the wall portions 61. The internal structure portion 62 is a structure that bears the strength of the main member 10, and as an example, Figure 4 shows an example in which a truss structure is adopted.

[0028] According to the above configuration, since the main member 10 has a skeletal portion 52 and a void portion 51, the overall weight of the resin molded product 1 can be reduced compared to when the main member 10 has a solid structure. Furthermore, the air contained in the void portion 51 can provide the resin molded product 1 with heat insulation and sound insulation properties. In other words, the resin molded product 1 can be given functionality other than strength. Moreover, according to the above configuration, since the skeletal portion 52 has a wall portion 61 and an internal structure portion 62, it can be made even lighter compared to when the skeletal portion 52 has a solid structure. In addition, compared to when the skeletal portion 52 is simply formed solid, the internal structure portion 62 preferentially bears the strength, so the overall strength of the main member 10 can be further improved.

[0029] Furthermore, as shown in Figure 5 as a second modified example, the main member 10 can also have a configuration having the outer casing 31 and the honeycomb portion 70. The honeycomb portion 70 forms a plurality of polygonal small chambers 71. For example, the small chambers 71 are hexagonal in shape. A plurality of such small chambers 71 are connected adjacent to each other. The outer casing 31 covers these small chambers 71 from the thickness direction.

[0030] According to the above configuration, the structural strength of the main member 10 can be further improved by forming a honeycomb section 70 having polygonal chambers 71. At the same time, the main member 10 can be further reduced in weight by forming the chambers 71.

[0031] Furthermore, although not shown in the diagram, it is also possible to mix a fibrous material into the first resin 21 of the main component 10 described above. In other words, the main component 10 functions as a fiber-reinforced resin. In this case, the tensile strength of the fibrous material further improves the strength and rigidity of the main component 10. As a result, the structural strength of the resin molded product 1 as the final product can be further increased.

[0032] In the embodiments and modifications described above, examples were mainly described in which the wall thickness of the resin molded product 1 is adjusted and supplemented by the main members 10. However, as shown in Figure 6, it is also possible to supplement the dimensions in the planar direction with the main members 10. Specifically, in the example shown in the figure, the grid-like main members 10 are arranged with gaps between them, and the sub-members 11 are interposed to fill the gaps. In other words, when the distance between the opening 80 of one main member 10 and the opening 80 of the other main member 10 is large (when the planar dimension is large), the sub-members 11 are interposed to supplement the distance. With this configuration as well, it is possible to avoid the occurrence of sink marks and voids and to stably obtain a good resin molded product 1, similar to the above.

[0033] <Note> The resin molded product 1 and the resin molding method described in each embodiment can be understood, for example, as follows.

[0034] (1) The resin molded product 1 according to the first embodiment comprises a main member 10 formed of a first resin 21, a sub-member 11 formed of a second resin 22 having a higher melting point than the first resin 21, and a fusion portion 12 interposed between the main member 10 and the sub-member 11 to join the main member 10 and the sub-member 11, wherein the density of the outer casing 31 of the main member 10 in contact with the fusion portion 12 is higher than the density of the inside of the main member 10.

[0035] According to the above configuration, the melting point of the second resin 22 forming the sub-member 11 is higher than the melting point of the first resin 21 forming the main member 10. As a result, when the second resin 22 is melted to form the sub-member 11, the main member 10 also melts together with it. Therefore, a fused portion 12 is stably formed between the main member 10 and the sub-member 11, making it possible to firmly join the main member 10 and the sub-member 11. Furthermore, since the density of the outer portion 31 of the main member 10 is higher than the density of the interior of the main member 10, the heat resistance of the outer portion 31 is improved. This reduces the possibility that the outer portion 31 may also melt when the second resin 22 is melted.

[0036] (2) The resin molded product 1 according to the second embodiment is the resin molded product 1 of (1), wherein the main member 10 has a void portion 51 that contains air and a skeletal portion 52 that surrounds the void portion 51.

[0037] According to the above configuration, the resin molded product 1 can be made lighter because the main member 10 has a skeletal portion 52 and a void portion 51 formed within it. Furthermore, the air contained within the void portion 51 can provide the resin molded product 1 with heat insulation and sound insulation properties.

[0038] (3) The resin molded product 1 according to the third embodiment is the resin molded product 1 of (2), wherein the skeletal portion 52 has a wall portion 61 that forms the void portion 51 and an internal structural portion 62 formed inside the wall portion 61 that bears strength.

[0039] With the above configuration, since the skeletal part 52 has a wall surface part 61 and an internal structure part 62, the skeletal part 52 can be made even lighter. In addition, compared to the case where the skeletal part 52 is simply formed solid, the internal structure part 62 bears the load of strength, so the strength of the main member 10 can be further improved.

[0040] (4) The resin molded product 1 according to the fourth embodiment is a resin molded product 1 according to any one embodiment of (1) to (3), wherein the main member 10 further comprises a fibrous material mixed with the first resin 21.

[0041] According to the above configuration, since a fibrous material is mixed into the first resin 21 of the main member 10, the tensile strength is supplemented by the fibrous material. This makes it possible to further improve the strength of the main member 10.

[0042] (5) The resin molded product 1 according to the fifth embodiment is a resin molded product 1 according to any one embodiment of (1) to (4), wherein the main member 10 has a honeycomb portion 70 that forms a plurality of small chambers 71 formed in a polygonal shape, and an outer casing portion 31 that covers the honeycomb portion 70 from the thickness direction.

[0043] According to the above configuration, the honeycomb section 70 having polygonal chambers 71 can be formed, thereby further improving the strength of the main member 10. At the same time, the main member 10 can be made even lighter.

[0044] (6) A resin molding method according to the sixth embodiment is a resin molding method for manufacturing a resin molded product 1 according to any one embodiment of (1) to (5), comprising the steps of: forming the main member 10 by laminating the first resin 21 by three-dimensional additive manufacturing; placing the main member 10 inside a mold; and filling the mold with the second resin 22, which has been molten so as to be in contact with the main member 10, to perform injection molding of the sub-member 11.

[0045] In the above method, the main component 10 is first placed inside the mold, and the sub-component 11 is injection-molded so as to be in contact with the main component 10. This reduces the proportion of the second resin 22 required for injection molding. As a result, compared to forming the entire resin molded product 1 solely by injection molding, it is possible to obtain a large resin molded product 1 while avoiding sink marks and voids caused by incomplete distribution of the resin material. [Explanation of symbols]

[0046] 1…Resin molded product 10…Main component 11... Sub-member 12...Fusion part 21…First resin 31…Outer shell 41... Covering part 42...Protruding part 22... Second resin 51...Void part 52...Skeletal part 61...Wall section 62...Internal structure 70... Honeycomb section 71... Komuro 80…Opening

Claims

1. A main component formed from a first resin, A sub-member formed of a second resin having a higher melting point than the first resin, A fusion portion interposed between the main member and the sub-member to join the main member and the sub-member, Equipped with, The density of the outer casing in contact with the fused portion of the main member is higher than the density of the interior of the main member. The outer casing of the main member is plate-shaped, The interior of the main component is a resin molded product having a truss structure or a porous structure.

2. A main component formed from a first resin, A sub-member formed of a second resin having a higher melting point than the first resin, A fusion portion interposed between the main member and the sub-member to join the main member and the sub-member, Equipped with, The density of the outer casing in contact with the fused portion of the main member is higher than the density of the interior of the main member. The main member is, A void containing air, A skeletal structure surrounding the void, It has, The aforementioned skeletal part is, The wall portion that forms the aforementioned void, An internal structural part formed on the inside of the wall surface and bearing the load, A resin molded product having the following properties.

3. The resin molded article according to claim 1 or 2, wherein the main member further comprises a fibrous material mixed with the first resin.

4. A main component formed from a first resin, A sub-member formed of a second resin having a higher melting point than the first resin, A fusion portion interposed between the main member and the sub-member to join the main member and the sub-member, Equipped with, The density of the outer casing in contact with the fused portion of the main member is higher than the density of the interior of the main member. The main member is, A honeycomb section that forms multiple small chambers in a polygonal shape, The outer casing covers the honeycomb portion from the thickness direction, A resin molded product having the following properties.

5. A main member formed of a first resin, A sub-member formed of a second resin having a higher melting point than the first resin, A fusion portion interposed between the main member and the sub-member to join the main member and the sub-member, Equipped with, A resin molding method for producing a resin molded product in which the density of the outer casing in contact with the fused portion of the main member is higher than the density of the interior of the main member, The steps include: forming the main component by laminating the first resin using three-dimensional additive manufacturing; The steps include: placing the main member inside the mold; The steps include: filling the mold with the second resin, which has been molten so as to be in contact with the main member, to perform injection molding of the sub-member; A resin molding method including the following.

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