Manufacturing method

Abstract

To provide a method for producing a resin molded product that does not require a heating step after molding.SOLUTION: A production method includes: a coating step of coating a resin containing a UV curable resin and a thermosetting resin on a thermoplastic resin sheet to form a resin layer; a heating step of heating the resin layer so that the thermosetting resin becomes a cured state; a first irradiation step of irradiating the resin layer with UV so that the UV curable resin becomes a semi-cured state; a molding step of molding the thermoplastic resin sheet on which the resin layer is formed; and a second irradiation step of irradiating the resin layer with UV so that the UV curable resin becomes a cured state, after the molding step. The first irradiation step and the heating step are performed until molding at the molding step is completed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a manufacturing method. [Background technology]

[0002] Conventionally, for products in which a base material is painted, there is a manufacturing method in which a plate-shaped base material is painted and then the base material is molded. In this manufacturing method, pressure is applied to the painted surface during the post-painting process, which may leave marks on the painted surface. Therefore, there are technologies to suppress the marks that are formed when pressure is applied. For example, Patent Document 1 discloses a pre-coated steel sheet in which a clear coating for absorbing pressure is provided on the non-coated surface of the steel sheet, which is the base material. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-185030 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in manufacturing methods where the substrate is painted before molding, there is another challenge: the painted surface is already formed on the substrate, making it difficult to mold during the molding process. These challenges apply not only when the substrate is a steel plate, but also when the substrate is a resin sheet. [Means for solving the problem]

[0005] This disclosure can be implemented in the following forms:

[0006] (1) According to one embodiment of the present disclosure, a method for manufacturing a resin molded product is provided. This manufacturing method comprises: a coating step of applying a resin containing a UV-curing resin and a thermosetting resin to a thermoplastic resin sheet to form a resin layer; a heating step of heating the resin layer so that the thermosetting resin becomes cured; a first irradiation step of irradiating the resin layer with UV light so that the UV-curing resin becomes semi-cured; a molding step of molding the thermoplastic resin sheet on which the resin layer has been formed; and a second irradiation step after the molding step of irradiating the resin layer with UV light so that the UV-curing resin becomes cured, wherein the first irradiation step and the heating step are performed until the molding in the molding step is completed. According to this embodiment, the resin layer contains a UV-curing resin and a thermosetting resin, and by performing the heating step and the first irradiation step, the resin layer can be given stretchability and a desired hardness. Therefore, in the molding step, the thermoplastic resin sheet on which the resin layer has been formed can be properly molded, and even if pressure is applied to the resin layer in steps after the molding step, it is less likely to leave marks. (2) In the above embodiment of the manufacturing method, the integrated amount of UV light in the first irradiation step may be smaller than the integrated amount of UV light in the second irradiation step. According to this embodiment, the UV-curable resin can be brought to a semi-cured state in the first irradiation step, and the UV-curable resin can be brought to a cured state in the second irradiation step. (3) A manufacturing method of the above embodiment, wherein the integrated amount of UV light in the first irradiation step is A1[m J / cm 2 ], the integrated amount of UV light in the second irradiation step is A2[m J / cm 2 If ] is the case, then equation (1) may also be satisfied. A2 / 100 ≤ A1 ≤ A2 / 10 ... (1) In this configuration, the UV-curable resin can be brought to a semi-cured state in the first irradiation step, and the UV-curable resin can be brought to a cured state in the second irradiation step. (4) A manufacturing method according to the above embodiment, wherein the illuminance of the UV in the first irradiation step is the same as the illuminance of the UV in the second irradiation step, and the irradiation time of the UV in the first irradiation step is shorter than the irradiation time of the UV in the second irradiation step. According to this embodiment, by setting the illuminance of the UV to be the same in the first irradiation step and the second irradiation step, but setting the irradiation times to be different from each other, the integrated amount of UV light in the first irradiation step can be made smaller than the integrated amount of UV light in the second irradiation step. (5) In the above embodiment of the manufacturing method, the heating step and the first irradiation step may be performed before the molding step. With this embodiment, the resin layer can be made to a state with low fluidity before the molding step, so that the thermoplastic resin sheet with the resin layer formed on it can be easily handled in the molding step. (6) In the above embodiment of the manufacturing method, the first irradiation step may be performed after the heating step. According to this embodiment, the cured thermosetting resin can inhibit the UV in the first irradiation step, thereby bringing the UV-curing resin to a semi-cured state. (7) In the manufacturing method of the above embodiment, the reaction force when scratching the resin layer after the first irradiation step is measured using an Erichsen hardness tester may be 0.3 N or more and 1.0 N or less. This makes it possible to impart stretchability and desired hardness to the resin layer. [Brief explanation of the drawing]

[0007] [Figure 1] This is a flowchart showing the steps in the manufacturing process of resin molded products. [Figure 2] This is a schematic diagram illustrating each step of the manufacturing process. [Figure 3] This diagram illustrates the relationship between UV irradiation and the curing state of UV-curable resin. [Modes for carrying out the invention]

[0008] A. Embodiments: Figure 1 is a flowchart showing the steps of the manufacturing process for realizing the manufacturing method of resin molded product 1. Figure 2 is a schematic diagram illustrating each step of the manufacturing process.

[0009] As shown in "S20" in Figure 2, the resin molded product 1 manufactured in this manufacturing process mainly comprises a thermoplastic resin sheet 10 and a resin layer 20 disposed on the thermoplastic resin sheet 10. The resin molded product 1 in this embodiment is used for the interior or exterior of a vehicle. Vehicle interiors include, for example, car seats. The resin layer 20 can provide the resin molded product 1 with scratch resistance, chemical resistance, and weather resistance.

[0010] Incidentally, if the resin layer 20 is made of a thermosetting resin and the resin layer 20 is heat-cured after the thermoplastic resin sheet 10 is molded, then it becomes necessary to prepare a heating furnace capable of accommodating a molded product with a large volume. The larger the heating furnace, the greater the energy required for heating. Therefore, in this embodiment, the resin layer 20 is formed on the thermoplastic resin sheet 10 and cured before the thermoplastic resin sheet 10 is molded. This makes the heating furnace for heat-curing the resin layer 20 more compact, reduces energy consumption, and reduces CO2 emissions.

[0011] In a manufacturing method in which a resin layer 20 is formed on a thermoplastic resin sheet 10 and then the thermoplastic resin sheet 10 is molded, the resin layer 20 also needs to be deformable along the mold. In other words, the resin layer 20 is required to be stretchable. In addition, even if pressure is applied to the resin layer 20 in a post-molding process, the resin layer 20 is required to be hard enough so that no marks are left on it.

[0012] The inventors used a resin 30 containing a UV curable resin 31 and a thermosetting resin 32 as the resin material for forming the resin layer 20. Before molding, the resin layer 20 was heated and irradiated with UV (ultraviolet rays) so that the integrated light amount was within a specific range, and it was found that the resin layer 20 could be adjusted to a desired hardness while being given stretchability. And after molding, it was found that by irradiating the resin layer 20 with UV again, appropriate scratch resistance, chemical resistance, and weather resistance could be imparted to the resin layer 20. Details are described below.

[0013] Hereinafter, the steps of the manufacturing process will be described as "S". In S10 as the coating step in FIG. 1, the resin 30 is coated on the thermoplastic resin sheet 10 to form the resin layer 20. In the present embodiment, the thickness of the resin layer 20 is about 5 μm or more and 25 μm or less. As shown in "S10" in FIG. 2, the resin 30 includes a UV curable resin 31 and a thermosetting resin 32. The thermosetting resin 32 is in a particulate state and is dispersed in the UV curable resin 31. In the present embodiment, the resin 30 is transparent, but a colored resin 30 may be used.

[0014] As the material of the thermoplastic resin sheet 10, an AES resin can be used. As the UV curable resin 31, an acrylic resin can be used. As the thermosetting resin 32, an acrylic urethane resin can be used. In the following description, "the thermoplastic resin sheet 10 on which the resin layer 20 is formed" may be described as "the laminated sheet LS". As an apparatus for applying the resin 30 to the thermoplastic resin sheet 10, a roll coater, a slit coater, or the like can be used.

[0015] In S12 as the heating step in FIG. 1, the laminated sheet LS is heated in a heating furnace so that the thermosetting resin 32 contained in the resin layer 20 becomes a cured state. In the present embodiment, the heating temperature is about 90°C or more and 120°C or less. In the present embodiment, the heating time is about 5 minutes or more and 20 minutes or less.

[0016] In S14 as the first irradiation step of FIG. 1, the laminated sheet LS is irradiated with UV so that the UV curable resin 31 contained in the resin layer 20 becomes in a semi-cured state. Thereby, the resin layer 20 can be imparted with stretchability and hardness such that traces are hardly left when pressure is applied. Specifically, in S14 of the present embodiment, UV with an illuminance of 250 mW / cm 2 is irradiated to the laminated sheet LS so that the integrated light quantity becomes 20 mJ / cm 2 . In the present embodiment, the laminated sheet LS being conveyed is irradiated with UV using a UV light.

[0017] In this manufacturing process, there are two steps of irradiating UV for curing the UV curable resin 31, namely S14 and S20 described later. Comparing S14 and S*20*, the integrated light quantity of UV in S14 is smaller than the integrated light quantity of UV in S20. When the integrated light quantity of UV in S14 is A1 [m J / cm 2 and the integrated light quantity of UV in S20 is A2 [m J / cm 2 , A1 and A2 satisfy the following formula (1). A2 / 100 ≦ A1 ≦ A2 / 10 ···(1)

[0018] Here, the semi-cured state is the state before reaching the cured state. When the UV-curable resin 31 contained in the resin layer 20 is continuously irradiated with UV light of a constant intensity, the initial fluid state changes to a cured state as the irradiation time increases. The state of the UV-curable resin 31 can be evaluated by the hardness of the resin layer 20. When the relationship between irradiation time and hardness is investigated, and the state in which the rate of change of hardness, which is the amount of change in hardness with respect to a unit irradiation time of UV, is defined as being below a standard value is defined as the cured state, then the semi-cured state is defined as a state in which the rate of change of hardness is greater than the standard value. In this embodiment, the semi-cured state of the UV-curable resin 31 is evaluated by the hardness of the resin layer 20. In S14, which brings the UV-curable resin 31 to a semi-cured state, the UV irradiation conditions are adjusted so that the hardness of the resin layer 20 falls within a predetermined hardness range. Specifically, the hardness range is the range in which the reaction force measured when the resin layer 20 after S14 is scratched using an Erichsen hardness tester is between 0.3N and 1.0N.

[0019] The state of the UV-curing resin 31 can also be evaluated by the viscosity of the resin layer 20. Similar to the hardness described above, if the relationship between irradiation time and viscosity is examined and the state in which the rate of change of viscosity (the amount of change in viscosity with respect to a unit of UV irradiation time) is less than or equal to a standard value is defined as the cured state, then the semi-cured state is defined as the state in which the rate of change of viscosity is greater than the standard value.

[0020] Figure 3 illustrates the relationship between UV irradiation and the curing state of the UV-curable resin 31 in S14. When UV is irradiated onto resin 30 containing thermosetting resin 32 and UV-curable resin 31, it is thought that the curing of the UV-curable resin 31 is inhibited because the UV is blocked by the thermosetting resin 32. Furthermore, it is thought that the closer the resin layer 20 is to the thermoplastic resin sheet 10, the less UV reaches it, thus inhibiting curing. In this way, by using resin 30 containing not only UV-curable resin 31 but also thermosetting resin 32, the UV-curable resin 31 can be made to a semi-cured state. The content of UV-curable resin 31 and thermosetting resin 32 in resin 30 is determined and adjusted in advance through experiments, etc., so that a semi-cured state is achieved in S12.

[0021] The inventors have confirmed that when a resin layer 20 containing only the UV-curing resin 31 and no thermosetting resin 32 is irradiated with UV light, it is not easy to partially cure the resin layer 20, even by limiting the UV intensity and irradiation time. In other words, this manufacturing method achieves partial curing of the resin 30 by using a resin 30 containing both the thermosetting resin 32 and the UV-curing resin 31, and by adjusting the UV irradiation conditions.

[0022] In step S16 of Figure 1, the laminated sheet LS is formed by vacuum forming. Specifically, as shown in "S16" of Figure 2, the laminated sheet LS, which includes a thermoplastic resin sheet 10 that has been plasticized by heating, is placed on the vacuum forming mold 81, and the inside of the vacuum forming mold 81 is vacuum-suctioned. As a result, the laminated sheet LS is formed along the vacuum forming mold 81.

[0023] As described above, the UV-curing resin 31 is in a semi-cured state. Furthermore, the thermosetting resin 32 of this embodiment has the property of being deformable by external force even after curing. Therefore, in S16, the laminated sheet LS can be deformed along the vacuum molding die 81. Once the deformation of the laminated sheet LS is complete, the laminated sheet LS is cooled until the thermoplastic resin sheet 10 solidifies. After that, the laminated sheet LS is removed from the vacuum molding die 81.

[0024] In S18 of Figure 1, the foam layer 40 is formed. Specifically, the molded laminated sheet LS is fitted into the upper mold 82. Here, the hardness of the resin layer 20 is within a predetermined hardness range. Therefore, even when the laminated sheet LS is fitted into the upper mold 82, mold marks on the resin layer 20 are suppressed.

[0025] After the molded laminated sheet LS is fitted into the upper mold 82, the upper mold 82 with the molded laminated sheet LS fitted is placed on top of the lower mold 83. An internal space 84 is formed between the molded laminated sheet LS and the lower mold 83. Foamed resin material is injected into the internal space 84 through a channel (not shown). As a result, the foamed resin material fills the internal space 84, and a foamed layer 40 is formed beneath the laminated sheet LS. In this embodiment, the material of the foamed layer 40 is foamed polyurethane.

[0026] In step S20, which is the second irradiation step in Figure 1, UV light is irradiated onto the resin layer 20 so that the UV-curable resin 31 becomes cured, and this manufacturing process is completed.

[0027] As described above, the integrated UV light intensity in S20 is greater than the integrated UV light intensity in S14. Specifically, in S20 of this embodiment, the illuminance is 250 mW / cm². 2 The UV light has an integrated luminous intensity of 2000 mJ / cm². 2 The laminated sheet LS is irradiated in this manner. As a result, the UV-curable resin 31 hardens, and the resin molded product 1 is given appropriate scratch resistance, chemical resistance, and weather resistance.

[0028] According to the embodiments described above, the manufacturing process of the resin molded product 1 includes S10, S12, S14, S16, and S20. In S10, a resin 30 containing a UV curable resin 31 and a thermosetting resin 32 is applied to the thermoplastic resin sheet 10 to form a resin layer 20. In S12, the resin layer 20 is heated so that the thermosetting resin 32 becomes a cured state. In S14, the resin layer 20 is irradiated with UV so that the UV curable resin 31 becomes a semi-cured state. S12 and S14 are performed before the molding of the thermoplastic resin sheet 10 in S16 is completed. Note that "the molding in S16 is completed" means "after the thermoplastic resin sheet 10 is molded, the thermoplastic resin sheet 10 becomes a solid state by cooling". By performing S12 and S14, stretchability and a desired hardness can be imparted to the resin layer 20. Therefore, in S16, the laminated sheet LS can be appropriately molded, and even when the molded laminated sheet LS is fitted into the upper mold 82 in S18, it is possible to make it difficult for the resin layer 20 to leave a mold mark.

[0029] Also, the integrated light amount of UV in S14 is smaller than the integrated light amount of UV in S20. Also, when the integrated light amount of UV in S14 is A1 [m J / cm 2 , and the integrated light amount of UV in S20 is A2 [m J / cm 2 , the formula (1) is satisfied. Thereby, in S14, the UV curable resin 31 can be made into a semi-cured state, and in S20, the UV curable resin 31 can be made into a cured state.

[0030] The illuminance of UV in S14 is the same as the illuminance of UV in S20. The irradiation time of UV in S14 is shorter than the irradiation time of UV in S20. Therefore, in S14 and S20, by setting the irradiation time to different times while setting the illuminance of UV to be the same, the integrated light amount of UV in S14 can be made smaller than the integrated light amount of UV in S20.

[0031] Furthermore, steps S12 and S14 are performed before S16. The resin 30 in its initial state is fluid. Therefore, before molding in S16, the UV-curing resin 31 is brought to a semi-cured state and the thermosetting resin 32 is brought to a cured state. This makes it possible to easily handle the laminated sheet LS in S16 during molding. Also, step S14 is performed after S12. This allows the cured thermosetting resin 32 to block the irradiated UV in S14.

[0032] B. Other embodiments: (B1) In the above embodiment, S12, which heats the laminated sheet LS, is performed before S14, which irradiates the laminated sheet LS with UV light. The order of S12 and S14 is not limited to this. For example, S14 may be performed before S12, or S12 and S14 may be performed in parallel. The thermosetting resin 32 inhibits the irradiated UV light even in its initial state before it reaches a cured state. Therefore, by using resin 30, the UV-curing resin 31 can be made to a semi-cured state. In addition, the heat used to plasticize the thermoplastic resin sheet 10 in S16 may be used as the heat to cure the thermosetting resin 32. In other words, S12 and S16 may be performed in parallel. By curing the thermosetting resin 32 before the molding of the laminated sheet LS is completed, the use of a large heating furnace to heat the molded product of the laminated sheet LS is avoided, and thus CO2 emissions can be reduced.

[0033] (B2) In the above embodiment, the integrated UV light quantity in S14 and the integrated UV light quantity in S20 satisfy equation (1). The integrated UV light quantities of S14 and S20 are not limited to this. The integrated UV light quantities of S14 and S20 should be set appropriately according to the properties of the resin 30.

[0034] (B3) In the above embodiment, the UV irradiance in S14 is the same as the UV irradiance in S20, and the UV irradiation time in S14 is shorter than the UV irradiation time in S20. The UV irradiation conditions in S14 and S20 are not limited to this. For example, the UV irradiation time in S14 and the UV irradiation time in S20 may be set to be the same, and the UV irradiance in S14 may be set to be less than the UV irradiance in S20. Alternatively, both the UV irradiance and the irradiation time may be set to be different in S14 and S20. By setting the integrated UV light amount in S14 to be less than the integrated UV light amount in S20, the UV-curing resin 31 can be easily adjusted to a semi-cured state in S14.

[0035] (B4) In the above embodiment, the resin molded product 1 includes a foamed layer 40, but this manufacturing method can also be applied to a resin molded product 1 that does not include a foamed layer 40. In the process after S16, the laminated sheet LS is grasped and transported by, for example, a robot. When grasped, pressure is applied to the laminated sheet LS. Here, the resin layer 20 is given the desired hardness by S12 and S14. Therefore, even when pressure is applied by grasping, it is possible to make it less likely for the resin layer 20 to be left with a grasp mark.

[0036] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0037] 1…Resin molded product, 10…Thermoplastic resin sheet, 20…Resin layer, 30…Resin, 31…UV curing resin, 32…Thermosetting resin, 40…Foam layer, 81…Vacuum forming mold, 82…Upper mold, 83…Lower mold, 84…Internal space, LS…Laminated sheet

Claims

1. A method for manufacturing resin molded products, A coating step in which a resin containing a UV-curing resin and a thermosetting resin is applied to a thermoplastic resin sheet to form a resin layer, A heating step involves heating the resin layer so that the thermosetting resin becomes cured, A first irradiation step involves irradiating the resin layer with UV light so that the UV-curable resin becomes semi-cured, A molding step of forming the thermoplastic resin sheet on which the resin layer is formed, The process includes a second irradiation step in which UV light is irradiated onto the resin layer after the molding step so that the UV-curable resin becomes cured, A manufacturing method comprising performing the first irradiation step and the heating step until the molding in the molding step is completed.

2. A manufacturing method according to claim 1, A manufacturing method wherein the integrated amount of UV light in the first irradiation step is smaller than the integrated amount of UV light in the second irradiation step.

3. A manufacturing method according to claim 2, A1 [mJ / cm²] is the total amount of UV light in the first irradiation step. ２ ], the integrated amount of UV light in the second irradiation step is A2 [mJ / cm²]. ２ A manufacturing method that satisfies formula (1) when ]. A2 / 100≦A1≦A2 / 10...(1)

4. A manufacturing method according to claim 2, The illuminance of the UV in the first irradiation step is the same as the illuminance of the UV in the second irradiation step. A manufacturing method wherein the irradiation time of the UV in the first irradiation step is shorter than the irradiation time of the UV in the second irradiation step.

5. A manufacturing method according to claim 1, A manufacturing method comprising performing the heating step and the first irradiation step before the molding step.

6. A manufacturing method according to claim 5, A manufacturing method comprising performing the first irradiation step after the heating step.

7. A manufacturing method according to claim 6, A manufacturing method wherein, after the first irradiation step, the reaction force when scratching the resin layer is measured using an Erichsen hardness tester is 0.3 N or more and 1.0 N or less.

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