Method for manufacturing in-mold coated component, and mold

Abstract

When a coating material is injected in the present invention, a flow resistance-increasing part (25) provided to a coating material injection flow path (24) increases the flow resistance of the coating material, and mixes the coating material.

Description

Manufacturing method for in-mold painted parts and mold

[0001] The present invention relates to a method for manufacturing an in-mold painted part and a mold.

[0002] In-mold coating methods have been proposed for resin molded products used in automobiles, home appliances, building materials, and other applications, to impart functionality such as decorative or hard coatings, or to eliminate the need for painting processes or reduce energy consumption during paint drying processes in order to improve environmental resistance. These methods involve injecting a coating material between the surface of a resin molded product and the mold cavity, then curing the coating material inside the mold to produce a molded product with a tightly integrated coating film on the surface of the resin molded product. Recently, in Europe and elsewhere, this method has begun to be adopted for automotive interior and exterior parts, due in part to its environmental resistance. Furthermore, the paint used in in-mold coating has shifted from the traditional one-component heat-curing type to two-component reactive coatings, such as polyol and isocyanate, as described in Patent Document 1. Due to their longer pot life compared to single-component coatings and advances in mixing technology for injection equipment, these coatings have become the mainstream in in-mold coating methods. Figures 7 to 8C show examples of conventional in-mold coating molds, as described in Patent Document 2.

[0003] 7 to 8C , the in-mold coating mold 101 is composed of two molds, a first mold 102 and a second mold 103. The first mold 102 and the second mold 103 are movable relative to each other in the opening and closing direction by an opening / closing device (not shown). The first mold 102 and the second mold 103 are fitted together at an edge 111, and a cavity 112 for molding resin is formed therein. The first mold 102 also has a coating surface 121 on which a coating is applied to the surface of the resin molded in the cavity 112. Furthermore, a recess 131 is formed in the edge 111 of the second mold 103 to provide an auxiliary cavity 113 that communicates with the cavity 112 and extends in the opening and closing direction of the mold 101 around the entire periphery of the cavity 112. This results in the main body 191 and auxiliary molded body 193 of the resin molded product 109 being molded integrally.

[0004] Resin supply means 106 for supplying resin into the cavity 112 is provided on the side of the second mold 103. Furthermore, paint supply means 107 for supplying paint to the cavity 112 is provided on the side of the first mold 102.

[0005] 8A , after the mold 101 is closed, resin is supplied into the cavity 112 by the resin supply means 106. The supplied resin fills the cavity 112, the auxiliary cavity 113, and the undercut portion 192. In this state, the resin is cured to form the resin molded body 109.

[0006] 8B, first mold 102 and second mold 103 are moved relative to each other in the opening and closing direction by the opening and closing means, and a gap for supplying paint is formed between the surface of resin molded body 109 (surface to be coated 196) and the surface of first mold 102. Thereafter, paint is supplied to the gap by paint supply means 107, and a paint film 110 is applied to surface to be coated 196 of resin molded body 109.

[0007] After the painting process is completed and the paint has hardened, the first mold 102 and the second mold 103 are moved relative to each other in the opening and closing direction by the opening and closing means, as shown in Fig. 8C. In this way, a painted part having a paint film 110 on the surface of the resin molded body 109 is obtained.

[0008] However, these conventional methods have had the following issues. When using two or more component reactive paints for color coating, poor mixing in the paint supply machine can result in poor appearance, such as uneven color. To prevent this, measures such as increasing the thickness of the paint film to improve the dispersibility of the color pigment are used. This poses a major challenge when the amount of paint mixed in the paint injector is reduced, such as when working on small parts or when thinning the paint film in an in-mold coating method aimed at reducing paint waste. Even when mixing two-component reactive paints for transparent functional layers such as hard coats, uneven mixing can lead to uncured areas in small volumes. Thus, to ensure superior environmental resistance compared to conventional paints, technology to improve mixing performance in small-volume applications is needed.

[0009] Patent No. 6871157 Patent No. 4512005

[0010] In the conventional configuration, when two or more reactive paints are used, poor mixing in the injector can result in poor appearance quality, such as uneven color or uneven mixing on the painted surface. Furthermore, for small parts or parts where a thin coating thickness is desired, an increase in the amount of paint used is unavoidable. There is a demand for improvements to in-mold coating molds that can suppress uneven color and uneven mixing even when using small amounts of paint.

[0011] The present invention solves the above-mentioned conventional problems, and aims to provide a method for manufacturing in-mold painted parts and a mold that suppresses color unevenness and mixing unevenness even when using a small volume of paint (e.g., 1 cc to 30 cc).

[0012] In order to achieve the above object, one aspect of the present invention relates to a method for manufacturing an in-mold painted part, which comprises injecting two or more liquid reactive paints through a paint injection flow path into a paint film cavity formed between the surface of the mold and the surface of a resin molded body within the mold for the in-mold painted part, and then hardening the paints within the mold to form a paint film on the surface of the resin molded body, and the method manufactures an in-mold painted part having an in-mold painted part, wherein when the paint is injected, the flow resistance is increased by a flow resistance increasing section provided in the paint injection flow path, and the paint is mixed.

[0013] Another aspect of the present invention is an in-mold painted part mold for producing an in-mold painted part in which two or more liquid reactive paints are injected through a paint injection flow path into a paint film cavity adjacent to the surface of a resin molded body, and then the paints are hardened to form a paint film on the surface of the resin molded body, wherein the paint injection flow path is provided with a flow resistance increasing portion that comes into contact with the paint in a direction intersecting the paint injection direction when the paint is injected, thereby increasing the flow resistance of the paint and causing it to mix.

[0014] As described above, according to the manufacturing method and mold for an in-mold painted part of the above aspect of the present invention, when an in-mold painted part is manufactured by injecting two or more liquid reactive paints into a paint film cavity formed between the surface of the mold and the surface of a resin molded body within the in-mold painted part mold through a paint injection flow path, and then hardening the paints within the mold to form a paint film on the surface of the resin molded body, it is possible to provide an in-mold painted part in which color unevenness and mixing unevenness are suppressed even when a small amount of paint is used.

[0015]

[0016] (First Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] 1A to 1D show an example of a method for manufacturing an in-mold painted part according to the first embodiment, and a mold 1 for the in-mold painted part used therefor. This in-mold painted part 23 is, by way of example, a molded part modeled after a housing cover for a home appliance. 1A and 1C are plan views of a resin molded body 9 for an in-mold painted part or an in-mold painted part 23 and the mold, and 1B and 1D are cross-sectional views of the resin molded body 9 or the in-mold painted part 23 and the mold.

[0018] The mold 1 for this in-mold painted part is composed of a first mold 2, a second mold 3, and a third mold 4, and the first mold 2 and the second mold 3 and the third mold 4 are freely interchangeable and freely movable relative to each other in the opening and closing direction by opening / closing means and moving means (not shown). This enables the first mold 2 and the second mold 3 to mold a resin molded body 9, and the third mold 4 and the second mold 3 to further form a paint film 10 on the surface of the resin molded body 9, thereby molding an in-mold painted part 23. Note that when the in-mold painted part 23 refers only to the product portion, it may also include portions molded in addition to the product portion, such as a paint injection channel 24.

[0019] The first mold 2 has, on its mating surfaces, a cavity 12, which is a recess 12a for a resin molded body, which is a product portion, and a recess 12b for forming a paint injection flow path, which communicates with the recess 12a for the resin molded body.

[0020] The second mold 3 has a cavity 12 that includes a protruding portion 12 c facing a recessed portion 12 a for a resin molded body, which is a product portion, and a resin injection flow path 27 that communicates with the cavity 12 .

[0021] When the first mold 2 and the second mold 3 are combined together, a cavity 12 for a resin molded body, which is configured with a recess 12a and a protrusion 12c, is formed inside the molded bodies for molding the resin molded body 9.

[0022] In addition, the second mold 3 is provided with a resin supply means 6, and when combined with the first mold 2, resin is injected into the cavity 12 via a resin injection flow path 27 from an injection molding machine or the like (not shown), thereby obtaining a resin molded product 9.

[0023] The third mold 4 is provided with a coating film cavity 22 for forming a coating film 10 on the surface of the resin molded body 9 molded in the cavity 12, and a coating film injection channel 24 that communicates with the cavity 22 along the coating film injection channel forming recess 12b. The coating film cavity 22 is formed between the surface of the third mold 4 and the surface of the resin molded body 9, and is provided adjacent to the surface of the resin molded body 9. The third mold 4 is also provided with a coating film supply means 7 (represented by a dashed line at a corresponding location in FIG. 1C ). When combined with the second mold 3, two or more reactive coating materials 7A are mixed and injected into the cavity 22 via the coating film injection channel 24 from a coating film supply means 7, such as a coating film injection machine (not shown), to form the coating film 10 on the surface of the resin molded body 9 facing the coating surface. Note that the cavity 22 is not limited to being provided in advance in the third mold 4 as described above; a space corresponding to the cavity 22 may be formed by moving the first mold 2 slightly away from the second mold 3 after resin molding.

[0024] In addition, in the third mold 4 , a flow resistance increasing portion 25 is provided in the paint injection flow path 24 between the paint supply means 7 and the paint film 10 of the resin molded body 9 .

[0025] The flow resistance increasing section 25 contacts the paint 7A in a direction intersecting the injection direction 26 of the paint 7A, thereby increasing the flow resistance and promoting mixing, for example, by generating turbulence in the paint 7A. Specifically, the flow resistance increasing section 25 is configured by connecting a plurality of (e.g., three) trapezoidal or tapered mixing channels 41 that extend horizontally in a planar manner and taper from a wide upstream side to a narrow downstream side in the injection direction 26 of the paint 7A. With this configuration, when the paint 7A flows from the upstream side to the downstream side in the trapezoidal mixing channels 41, for example, the flow channel area at the upstream end of the second mixing channel 41 following the most upstream mixing channel 41 suddenly becomes larger than the flow channel area at the downstream end of the most upstream mixing channel 41. As a result, the pressure is reduced at the upstream end of the second mixing channel 41, generating turbulence and increasing the flow resistance, thereby forcibly promoting mixing of the paint 7A.

[0026] Therefore, since multiple mixing channels 41 are provided in the paint injection channel 24, when the paint 7A flowing into the paint injection channel 24 from the paint supply means 7 passes through the mixing channels 41 in the paint injection channel 24, the channel shape or flow resistance promotes the mixing effect of the paint 7A, allowing the paint 7A to reach the cavity 12 of the product part. Even if the mixing ability of the injection machine is poor, the mixing channels 41 promote the mixing of two or more reactive paints 7A within the mold 1, making it possible to provide an in-mold painted part 23 having a paint film 10 that is free of color and mixing unevenness or has reduced color and mixing unevenness, even when using a small amount of paint. It is desirable that the hardened molding portion of the mixing channels 41 be removed by cutting or other means when the in-mold painted part 23 is finished, or that it be located in a location that does not become part of the product's exterior surface.

[0027] Next, the operations in each step of the method for manufacturing the in-mold painted part 23 according to the first embodiment of the present invention will be described with reference to FIGS. 2A to 2G.

[0028] First, in the cross-sectional view of Figure 2A, the first mold 2 and the second mold 3 are combined and clamped, and then, as shown in Figure 2B, the resin supply means 6 of the second mold 3 supplies resin 6A into the interior of the cavity 12 for the resin molded body through the resin injection flow path 27.

[0029] Next, the resin 6A supplied to the cavity 12 for the resin molded body in Figure 2C hardens to form a resin molded body 9, and then the first mold 2 and the second mold 3 are opened, leaving the resin molded body 9 in the second mold 3.

[0030] Next, using a moving means not shown in Figure 2D, the second mold 3 and the third mold 4 are combined and clamped, and then the paint 7A is injected into the coating film cavity 22 via the mixing flow path 41 of the paint injection flow path 24 of the third mold 4 from an injection machine that mixes two or more reactive paints 7A of the paint supply means 7 of Figure 2E.

[0031] At this time, when the paint 7A flows from upstream to downstream within the three trapezoidal mixing channels 41, for example, the flow path area at the upstream end of the second mixing channel 41 following the most upstream mixing channel 41 suddenly becomes larger than the flow path area at the downstream end of the most upstream mixing channel 41. As a result, the pressure is reduced at the upstream end of the second mixing channel 41, causing turbulence, for example, increasing flow resistance and forcibly promoting mixing of the paint 7A. Next, the flow path area at the upstream end of the third mixing channel 41 following the second mixing channel 41 suddenly becomes larger than the flow path area at the downstream end of the second mixing channel 41. As a result, the pressure is reduced at the upstream end of the third mixing channel 41, causing turbulence, for example, increasing flow resistance and forcibly promoting mixing of the paint 7A. In this way, two or more reactive paints 7A can be thoroughly mixed in the paint injection channel 24 and injected into the coating cavity 22.

[0032] Next, after the paint 7A has hardened in FIG. 2F, the second mold 3 and the third mold 4 are opened, and an in-mold painted part 23 in which the paint film 10 is applied to the resin molded body 9 is obtained.

[0033] 2G, the areas other than the product portion are removed by cutting or other processes to obtain an in-mold painted part 23 consisting only of the product portion. A paint film 10 is formed on the surface of the resin molded body 9 in close contact with and integrated with the surface.

[0034] The material for the resin 6A to be molded may be a general-purpose injection molding resin such as PC resin, PC / ABS resin, or ABS resin, or it is also possible to insert an extrusion molded product into the mold and apply a coating film without injection molding.

[0035] The paint 7A used may be a reactive paint of two or more liquids such as polyol and isocyanate, or a three or more liquid system in which a color paint is mixed with the reactive paint.

[0036] As described above, according to the manufacturing method of an in-mold painted part and a mold therefor of the first embodiment, the paint injection channel 24 is provided with a plurality of mixing channels 41 as an example of the flow resistance increasing section 25, so that when the paint 7A that flows into the paint injection channel 24 from the paint supply means 7 passes through the plurality of mixing channels 41 in the paint injection channel 24, the flow channel shape or flow resistance promotes the mixing effect of the paint 7A, and the paint 7A can reach the paint film cavity 22. These mixing channels 41 promote the mixing of two or more liquid reactive paints 7A in the mold 1 even when the paint does not mix well in the injection machine, making it possible to provide an in-mold painted part 23 having a paint film 10 that is free of color and mixing unevenness or has reduced color and mixing unevenness even when a small amount of paint is used.

[0037] 3A to 3D are plan views and cross-sectional views illustrating an example of a mold used in a method for manufacturing an in-mold painted part according to a second embodiment of the present invention. In Figs. 3A to 3D, the same reference numerals are used for the same components as in Figs. 1A to 2G, and their description will be omitted.

[0038] 3A to 3D are examples of molds illustrating the steps of the method for manufacturing an in-mold painted part according to Embodiment 2. The molds and method for manufacturing an in-mold painted part show a molded part, such as a home appliance housing cover, as an example of an in-mold painted part. 3A and 3C are plan views of the mold illustrating the steps of the method for manufacturing an in-mold painted part, and 3B and 3D are cross-sectional views of the mold illustrating the steps of the method for manufacturing an in-mold painted part.

[0039] The second embodiment differs from the first embodiment in that, instead of forming a mixing flow path 41 as an example of a flow resistance increasing section 25 in the third mold 4, a mixing flow path section 42 made of resin 6A is molded by the first mold 2 as another example of a flow resistance increasing section 25, and then, when the paint 7A is injected, the mixing flow path section 42 is made to function as the mixing flow path 41. That is, the first mold 2 has a cavity 12d for molding the mixing flow path section 42 made of resin 6A, and the third mold 4 has a cavity 12e into which the molded mixing flow path section 42 made of resin 6A fits to form the paint injection flow path 24.

[0040] With this configuration, when the paint 7A flowing in from the paint supply means 7 passes through the paint injection flow path 24, the mixing effect is promoted by the flow path shape or flow resistance formed by the mixing flow path section 42, just like the mixing flow path 41, and the paint 7A can reach the cavity 22 of the paint film 10. This mixing flow path section 42 promotes the mixing of two or more liquid reactive paints 7A inside the mold 1, even if the mixability in the injection machine is poor, making it possible to provide an in-mold painted part 23 having a paint film 10 that is free of color and mixing unevenness or has reduced color and mixing unevenness.

[0041] (Examples of the flow resistance increasing section 25) Here, various configurations of the flow resistance increasing section 25 in the first and second embodiments will be illustrated. These examples are also applicable to the third and fourth embodiments described below.

[0042] The flow resistance increasing section 25 is a section that increases flow resistance and promotes mixing by contacting the paint 7A in a direction intersecting the injection direction 26 of the paint 7A when the paint is injected in the paint injection flow path 24 and generating turbulence in the paint 7A.

[0043] The cross-sectional shape of the paint injection flow path 24 equipped with the flow resistance increasing section 25, which intersects (e.g., is perpendicular to) the flow start direction f1, in other words, the injection direction 26, can be a quadrangle, rectangle, square, triangle, polygon, triangle or quadrangle or polygon with rounded corners, circle, ellipse, or semicircle, etc.

[0044] 4A shows an example of the flow resistance increasing portion 25 on both side walls of the paint injection channel 24 when the direction of the paint injection channel 24 changes with respect to the flow start direction f1 of the paint injection channel 24, in other words, with respect to the injection direction 26. In this example, the cross-sectional area of ​​the channel does not change.

[0045] In FIG. 4A (a), the paint injection flow path 24 can be configured to turn once in the direction f2 at an angle of 45 degrees relative to the flow starting direction f1, and then turn 90 degrees in the direction f3 relative to the flow starting direction f1, or turn 135 degrees in the direction f4 relative to the flow starting direction f1.

[0046] In FIG. 4A (b), the paint injection flow path 24 can be configured to bend once in the direction f5 at an angle of 90 degrees relative to the flow start direction f1, and then turn again at an angle of 90 degrees in the direction f6, in the same manner as the flow start direction f1.

[0047] In FIG. 4A (c), the paint injection channel 24 can be configured as an inverted Z-shaped channel that turns slightly back in the direction f7 at an angle of 60 degrees relative to the flow start direction f1, and then turns again 90 degrees in the direction f8, in the same direction as the flow start direction f1.

[0048] 4A(d), the paint injection channel 24 may be a W-shaped channel 24d that meanders in a linear zigzag pattern relative to the flow start direction f1. In this case, it is preferable for the channel 24d to meander two or more times.

[0049] 4A(e), the paint injection channel 24 may be a channel 24e that meanders in a curved zigzag pattern relative to the flow start direction f1. In this case, it is preferable for the channel 24e to meander two or more times.

[0050] 4A(f), the paint injection channel 24 may be configured as a channel 24f that meanders in an inverted S-shape, zigzagging along a U-shape relative to the flow start direction f1. In this case, it is preferable for the channel 24f to meander two or more times.

[0051] As a result of this configuration, both side walls of each paint injection flow path 24 function as an example of a flow resistance increasing section 25, and when the paint is injected, the paint 7A comes into contact with both side walls in a direction intersecting the injection direction 26 of the paint 7A, thereby generating turbulence in the paint 7A, thereby increasing the flow resistance and promoting mixing.

[0052] As another example of the flow resistance increasing section 25, Figure 4B shows a case where turbulence is generated due to pressure reduction caused by a sudden large change in the flow path cross-sectional area at the area change section 25a when proceeding in the flow direction of the paint injection flow path 24, or where turbulence is generated due to a collision between the paint 7A and the downstream end wall of the connecting section that undergoes an area change (i.e., the end wall at the downstream end of the upstream flow path), thereby increasing the flow resistance.

[0053] 4B(a), the paint injection channel 24 can be configured as a channel in which one large rectangular channel r1 and one small rectangular channel r2, which are smaller than channel r1, are alternately arranged and connected along the flow direction with their centerlines aligned when viewed from above or the side. In this case, the connecting portion between the large rectangular channel r1 and the small rectangular channel r2 forms an area-changing portion 25a, and paint 7A collides with the downstream end wall of the large rectangular channel r1 at the connecting portion, thereby increasing the flow resistance.

[0054] In Figure 4B (b), the paint injection channel 24 can be configured as a channel in which, when viewed from above or from the side, one large rectangular channel r1 and one small rectangular channel r2, each smaller than the channel r1, are alternately arranged and connected along the flow direction with their centerlines aligned, i.e., a channel configured with multiple combinations of the configuration shown in Figure 4B (a). In this configuration, each connection between the large rectangular channel r1 and the small rectangular channel r2 forms an area-changing section 25a, and paint 7A collides with the downstream end wall of the large rectangular channel r1 at each connection, increasing flow resistance. Furthermore, at the area-changing section 25a, where the small rectangular channel r2 connects to the large rectangular channel r1, when the paint 7A flows from the upstream small rectangular channel r2 into the upstream end of the adjacent downstream large rectangular channel r1, the cross-sectional area of ​​the channel suddenly increases, resulting in a reduced pressure and increasing flow resistance.

[0055] 4B(c), the paint injection channel 24 can be a single triangular channel t that tapers in the flow direction when viewed from above or the side. In this case, both side walls of the triangular channel t become area-changing portions 25a, and the paint 7A collides with both tapered side walls of the triangular channel t, thereby increasing the flow resistance.

[0056] In FIG. 4B (d), the paint injection channel 24 can be configured as a series of connected triangular channels t, each tapered along the flow direction when viewed from above or the side, with their centerlines aligned and their downstream and upstream ends overlapping. In this configuration, both side walls of each triangular channel t and the connecting portion between adjacent triangular channels t each serve as an area-changing portion 25a. That is, paint 7A collides with the area-changing portion 25a, which is the tapered side wall of each triangular channel t, thereby increasing flow resistance. Furthermore, at the area-changing portion 25a, which is the connecting portion connecting two adjacent triangular channels t, when paint 7A flows from the upstream triangular channel t to the upstream end of the adjacent downstream triangular channel t, the cross-sectional area of ​​the channel suddenly increases, resulting in a reduced pressure and increasing flow resistance.

[0057] 4B(e), the paint injection channel 24 can be configured as a channel in which the upstream and downstream sides of the channel in FIG. 4B(d) are arranged in the opposite direction relative to the flow direction. In this case, each connecting portion between adjacent triangular channels t becomes an area-changing portion 25a, and the paint 7A collides with the downstream end wall of the channel t upstream of each connecting portion, thereby increasing the flow resistance.

[0058] In (f) of Figure 4B, when the two mold halves 3 and 4 of the mold 1 are divided into an upper mold and a lower mold when viewed from the side, the paint injection channel 24 can be formed by alternating rectangular channels r3, which have cavities only in the upper mold, with rectangular channels r4, which have cavities in both the upper and lower molds. Here, the connecting portions between the rectangular channels r3 and r4 form area-changing portions 25a, and paint 7A impinges on the downstream end walls of the rectangular channels r3 and r4 upstream of each connecting portion, thereby increasing flow resistance. When forming a paint injection channel in the lower mold (e.g., second mold 3) in this configuration, it is necessary to form a paint injection channel-forming recess for the lower mold of the rectangular channel r4 in advance in a portion facing the paint injection channel-forming recess 12b of the upper mold (e.g., first mold 2) in Figure 1B, for example, to prevent molding resin from flowing into the latter recess.

[0059] In (g) of Figure 4B, by configuring only the upper mold side of the flow path in (f) of Figure 4B, it is possible to create a flow path in which one large rectangular flow path r5 and one small rectangular flow path r6 smaller than flow path r5 are alternately arranged and connected, as in (b) of Figure 4B. In this case, the connecting portion between the large rectangular flow path r5 and the small rectangular flow path r6 becomes the area change portion 25a, and paint 7A collides with the downstream end wall of the large rectangular flow path r5 at each connecting portion, increasing flow resistance. Furthermore, in the area change portion 25a, which is the connecting portion where the small rectangular flow path r6 is connected to the large rectangular flow path r5, when paint 7A flows from the upstream small rectangular flow path r6 to the upstream end of the adjacent downstream large rectangular flow path r5, the flow path cross-sectional area suddenly increases, resulting in a reduced pressure state and increasing flow resistance.

[0060] As a result of this configuration, the area change section 25a when the cross-sectional area of ​​each flow path changes functions as another example of the flow resistance increasing section 25, and when paint is injected, the paint 7A comes into contact with both side walls in a direction intersecting the injection direction 26 of the paint 7A, generating turbulence in the paint 7A, thereby increasing the flow resistance and promoting mixing.

[0061] 4C shows yet another example of flow resistance increasing section 25, in which baffle plate sections protruding from the side wall in a direction intersecting the flow direction of paint injection channel 24, for example in a direction perpendicular to the flow direction, are arranged at intervals along the flow direction, and the paint 7A collides with the baffle plate sections to generate turbulence, thereby increasing the flow resistance. Note that the baffle plate sections may be formed by cutting out from a mold, or may be formed into the mold by welding or inserting.

[0062] 4C(a), when viewed from above or the side, baffle portions j are arranged at intervals along the flow direction, alternately on opposing side walls 24a of the paint injection channel 24, protruding from one side wall 24a to the vicinity of the opposing other side wall 24a in a direction perpendicular to the flow direction of the paint injection channel 24. Here, the baffle portions j function as flow resistance increasing portions 25, and the paint 7A collides with each baffle portion j, thereby increasing the flow resistance.

[0063] In Figure 4C (b), when the two dies 3, 4 of the mold 1 are divided into an upper die and a lower die when viewed from the side, the paint injection passage 24 is formed only on the side wall 24a, which is the upper surface of the upper die, with baffle plates j that protrude downward perpendicular to the flow direction of the paint injection passage 24 to the vicinity of the mold mating surface and are arranged at intervals along the flow direction. Here, the baffle plates j function as flow resistance increasing sections 25, and the paint 7A increases its flow resistance as it collides with each baffle plate j. Note that a linear flow path is secured near the mold mating surface of each baffle plate j, making it easier for the injection pressure of the paint 7A to reach the cavity 12 in the product section.

[0064] In (c) of Figure 4C, when the two molds 3, 4 of the mold 1 are divided into an upper mold and a lower mold when viewed from the side, the paint injection passages 24 are formed on the side wall 24a of the upper mold and the side wall 24a of the lower mold, and baffle plates j that protrude in a vertical direction perpendicular to the flow direction of the paint injection passage 24 to the vicinity of the mold mating surface are arranged at intervals along the flow direction. In this case, the baffle plates j function as flow resistance increasing sections 25, and the paint 7A increases its flow resistance as it collides with each baffle plate j. Note that a linear flow path is secured near the mold mating surface of each baffle plate j, making it easier for the injection pressure of the paint 7A to reach the cavity 12 in the product section. When forming a paint injection flow path in the lower mold (e.g., second mold 3) as in this configuration, for example, as shown in Figure 1B, it is necessary to form in advance a paint injection flow path forming recess for the lower mold side of paint injection flow path 24 in the part opposite to the paint injection flow path forming recess 12b in the upper mold (e.g., first mold 2), so as to prevent molding resin from flowing into the latter recess.

[0065] In (d) of Figure 4C, when viewed from above or the side, square pillar-shaped baffle sections b protruding from each side wall 24a of the paint injection channel 24 to near the center of the channel 24 in a direction perpendicular to the flow direction of the channel 24 are alternately arranged at intervals along the flow direction to form unevenness on the side walls. Here, the baffle sections b function as flow resistance increasing sections 25, and the paint 7A increases its flow resistance as it collides with each baffle section b. Note that a straight flow path is secured near the center of the channel 24 for each baffle section b, making it easier for the injection pressure of the paint 7A to reach the cavity 12 in the product section.

[0066] As shown in (e) of Figure 4C, each side wall 24a of each paint injection channel 24 is not limited to a flat wall, but may be a curved, uneven surface so that the paint 7A collides with the curved, uneven surface, thereby increasing the flow resistance.

[0067] As shown in FIG. 4C(f), baffle plates j may be arranged in a zigzag pattern in each paint injection passage 24 to achieve the same effect as in FIG. 4A(d).

[0068] As shown in FIG. 4C(g), baffle plates j may be arranged in a V-shape in each paint injection passage 24 to achieve the same effect as in FIG. 4B(d).

[0069] As a result of being configured in this manner, each baffle section j or baffle section b functions as yet another example of the flow resistance increasing section 25, and when the paint is injected, the paint 7A comes into contact with the baffle section j or b in a direction intersecting the injection direction 26 of the paint 7A, thereby generating turbulence in the paint 7A and increasing the flow resistance, thereby promoting mixing.

[0070] However, if the flow resistance of the paint 7A due to the flow resistance increasing section 25 is excessively increased, the flowability of the paint 7A into the cavity 12 of the product section will be impaired, so it may be necessary to adjust the balance between the two. In other words, if the shape has an excessively high flow resistance (in other words, high pressure loss), problems such as unfilled paint in the cavity 12 or residual bubbles due to increased viscosity will occur, and to prevent these problems from occurring, flow design using, for example, flow analysis of reactive paints is required. For example, as a result of using flow analysis, it is possible to design the shape and arrangement of the flow resistance increasing section 25 so that the filling time for commercially available isocyanate paint is kept to a few seconds or about 5 seconds.

[0071] (Embodiment 3) Figures 5A to 5D illustrate an example of a mold used in a manufacturing method for an in-mold painted part according to Embodiment 3 of the present invention. Figures 5A and 5C are plan views of the mold illustrating the resin molding and in-mold painting steps of the manufacturing method for an in-mold painted part, and Figures 5B and 5D are cross-sectional views of the mold illustrating the resin molding and in-mold painting steps of the manufacturing method for an in-mold painted part. In Figures 5A to 5D, the same components as those in Figures 1A to 4C are designated by the same reference numerals, and their descriptions will be omitted. This manufacturing method and mold for an in-mold painted part show a molded part such as a home appliance housing cover as an example of an in-mold painted part 23.

[0072] The difference between the present embodiment 3 and the embodiments 1 and 2 is that the mixing flow path 43 is not a flat flow path that extends horizontally as in the embodiments 1 and 2, but a three-dimensional mixing flow path 43 that extends three-dimensionally in the vertical direction by stacking and offsetting a plurality of elongated rectangular flow paths in a stepped manner. More specifically, the three-dimensional mixing flow path 43 and the three-dimensional mixing flow path section 44 are formed as the paint injection flow path 24 on the way where the paint 7A flows into the coating film cavity 22 of the product section.

[0073] The three-dimensional mixing flow path section 44 is molded from resin 6A using the cavity 12h on the mating surface of the second mold 3 and the cavity 12g on the mating surface of the first mold 2 as the bottom surface or side wall of the paint injection flow path 24, and is made by partially stacking elongated rectangular plate members in a stepped manner along the longitudinal direction.

[0074] The three-dimensional mixing flow path 43 is composed of a three-dimensional mixing flow path portion 44 made of resin and the cavity 12i on the mating surface of the third mold 4, and is formed by connecting thin, rectangular flow paths that are partially overlapped in a stepped manner along the longitudinal direction. The three-dimensional mixing flow path 43, in which flow paths are overlapped in a stepped manner in this way, corresponds to the flow resistance increasing portion 25 in (b) of Figure 4A.

[0075] With this configuration, when the paint 7A flowing from the paint supply means 7 passes through the three-dimensional mixing channel 43, which functions as the flow resistance increasing section 25, the flow channel shape or flow resistance formed by the three-dimensional mixing channel section 44 made of resin 6A enhances the mixing effect, allowing the paint 7A to reach the coating film cavity 22 of the product section. By having the three-dimensional mixing channel 43 and three-dimensional mixing channel section 44 function as the flow resistance increasing section 25, the mixing of two or more reactive paints 7A in the mold 1 is promoted, even when mixing is poor in the injection machine, making it possible to provide an in-mold painted part 23 having a coating film 10 that is free of color and mixing unevenness or has reduced color and mixing unevenness. It is desirable to locate the three-dimensional mixing channel 43 and three-dimensional mixing channel section 44 in a location that will not be removed by cutting or otherwise become part of the product's exterior surface when the finished molded product is produced.

[0076] (Embodiment 4) Figures 6A to 6D illustrate an example of a mold used in a manufacturing method for an in-mold painted part according to Embodiment 4 of the present invention. Figures 6A and 6C are plan views of the mold illustrating the resin molding and in-mold painting steps of the manufacturing method for an in-mold painted part, and Figures 6B and 6D are cross-sectional views of the mold illustrating the molding and in-mold painting steps of the manufacturing method for an in-mold painted part. In Figures 6A to 6D, the same components as those in Figures 1A to 5D are designated by the same reference numerals, and their descriptions will be omitted. This manufacturing method and mold for an in-mold painted part show a molded part that is modeled after a home appliance housing cover, as an example of an in-mold painted part.

[0077] The fourth embodiment differs from the first, second and third embodiments in that the resin molded body 9 is molded in a separate process from the paint injection (in-mold painting) process.

[0078] 6A and 6B, in the resin molding process, a first mold 2 having a cavity 12 for the resin molded body 9 is combined with a second mold 3 having a resin supply means 6 arranged along a paint injection flow path 24 to resin mold the resin molded body 9. Here, resin molding is carried out one after another, regardless of the operation of the next in-mold painting process, and the second mold 3 holding the resin molded body 9 is sent to the in-mold painting process.

[0079] In the in-mold painting process, which is separate from the resin molding process, a second mold 3 holding a resin molded body 9 is combined with a third mold 4 having a cavity 22 for a paint film, and then the molds are clamped using a press machine (not shown), and paint 7A is injected from a paint supply means 7 to form a paint film 10.

[0080] In this way, by separating the resin molding and in-mold painting processes and carrying them out independently, it is possible to improve production flexibility.

[0081] Furthermore, the in-mold painting process can be designed independently from the resin molding process, and a configuration in which paint 7A is injected from the vertical surface of the product (i.e., from a direction perpendicular to the flow direction of the paint injection flow path 24) as paint supply means 8 in place of paint supply means 7, as in the case of paint supply means 8 in the cases of Figures 6C and 6D, becomes possible.

[0082] It should be noted that any of the various embodiments or modifications described above can be appropriately combined to achieve the effects of each. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features from different embodiments or examples are also possible.

[0083] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0084] (Technology 1) In a method for manufacturing an in-mold painted part, two or more liquid reactive paints are injected through a paint injection flow path into a paint film cavity formed between the surface of the mold and the surface of a resin molded body within the mold, and then the paints are cured within the mold to form a paint film on the surface of the resin molded body. In this method, the flow resistance is increased and the paint is mixed when the paint is injected using a flow resistance increasing section provided in the paint injection flow path.

[0085] In addition, two or more liquid reactive paints may be injected into a paint film cavity adjacent to the surface of the resin molded body through a paint injection channel in the mold for an in-mold painted part. Also, the paints may be cured in the mold to form a paint film that is tightly integrated with the surface of the resin molded body, thereby forming an in-mold painted part.

[0086] (Technology 2) In the method for manufacturing an in-mold painted part according to Technology 1, the flow resistance increasing section is configured by connecting a plurality of tapered flow paths so that the flow path cross-sectional area in a direction intersecting the paint injection direction gradually decreases and then increases as the paint proceeds in the paint injection direction, and when the paint is injected, the flow resistance of the paint is increased by the plurality of tapered flow paths to mix it.

[0087] (Technology 3) The method for manufacturing an in-mold painted part according to Technology 1, wherein the flow resistance increasing section is configured with a serpentine flow path that snakes in a direction in which the paint is poured, and when the paint is poured, the paint is made to snake through the serpentine flow path, thereby increasing the flow resistance of the paint and mixing it.

[0088] (Technology 4) The method for manufacturing an in-mold painted part according to Technology 1, wherein the flow resistance increasing section is composed of a plurality of baffle sections extending in a direction intersecting the paint injection direction, and the plurality of baffle sections increase the flow resistance of the paint and mix it when the paint is injected.

[0089] (Technology 5) The method for producing an in-mold painted part according to any one of Technologies 1 to 4, wherein the paint is a reactive mixed type paint of two or more liquids of polyol and isocyanate.

[0090] (Technology 6) The method for manufacturing an in-mold painted part according to any one of Technologies 1 to 5, wherein the paint injection flow path having the increased flow resistance portion is formed during resin molding of the resin molded body before the paint is injected.

[0091] (Technology 7) In an in-mold painted part mold for manufacturing an in-mold painted part in which two or more liquid reactive paints are injected through a paint injection flow path into a paint film cavity adjacent to the surface of a resin molded body, and then the paints are hardened to form a paint film on the surface of the resin molded body, the in-mold painted part mold is provided with a flow resistance increasing part in the paint injection flow path that comes into contact with the paint in a direction intersecting the paint injection direction when the paint is injected, thereby increasing the flow resistance of the paint and causing it to mix.

[0092] Two or more liquid reactive paints may be injected into a cavity for a coating film adjacent to the surface of the resin molded body through a coating film injection channel, and the paints may be cured to form a coating film that is tightly integrated with the surface of the resin molded body, thereby forming an in-mold coated part.

[0093] (Technology 8) An in-mold painted part mold according to Technology 7, wherein the flow resistance increasing section is configured by connecting a plurality of tapered flow paths so that the flow path cross-sectional area in a direction intersecting the paint injection direction gradually decreases and then increases as the paint proceeds in the paint injection direction, and the paint is mixed by increasing the flow resistance of the paint due to the plurality of tapered flow paths when the paint is injected.

[0094] (Technology 9) An in-mold painted part mold according to Technology 7, wherein the flow resistance increasing section is configured with a serpentine flow path that snakes in the direction of injection of the paint, and when the paint is injected, the serpentine flow path causes the paint to snake, increasing the flow resistance of the paint and causing it to mix.

[0095] (Technology 10) An in-mold painted part mold according to Technology 7, wherein the flow resistance increasing section is composed of a plurality of baffle sections extending in a direction intersecting the paint injection direction, and the plurality of baffle sections increase the flow resistance of the paint and mix it when the paint is injected.

[0096] (Technology 11) The mold for in-mold painted parts according to any one of Techniques 7 to 10, wherein the paint is a reactive mixed type paint of two or more liquids of polyol and isocyanate.

[0097] (Technology 12) The mold for an in-mold painted part according to any one of Technologies 7 to 11, which has a cavity that forms the paint injection flow path having the increased flow resistance portion during resin molding of the resin molded body before the paint is injected.

[0098] With this configuration, when manufacturing an in-mold painted part in which two or more liquid reactive paints are injected through a paint injection flow path into a paint film cavity formed between the surface of the mold and the surface of a resin molded body within the mold, and then the paint is hardened within the mold to form a paint film on the surface of the resin molded body, it is possible to provide an in-mold painted part in which color unevenness and mixing unevenness are suppressed even when a small amount of paint is used.

[0099] Furthermore, when manufacturing an in-mold painted part by injecting two or more liquid reactive paints into a paint film cavity adjacent to the surface of a resin molded body within a mold for the in-mold painted part via a paint injection flow path, and then curing the paint within the mold to tightly and integrally form a paint film on the surface of the resin molded body, it becomes possible to provide an in-mold painted part in which color unevenness and mixing unevenness are suppressed even when a small amount of paint is used.

[0100] The manufacturing method and mold for in-mold painted parts according to the above-mentioned aspects of the present invention use a reactive paint such as a mixed type polyurethane paint of two or more liquids such as polyol and isocyanate, and the paint is injected into the mold to form a paint film in order to coat the surface of a resin molded product inside the mold and impart functionality such as decoration, hard coating, or antibacterial properties. In such a manufacturing method and mold for in-mold painted parts, a zone for mixing the paint is provided in the paint injection path, which makes it possible to compensate for insufficient mixing by the paint injector, and to provide in-mold painted parts with reduced color unevenness and mixing unevenness even in small-volume products.

[0101] DESCRIPTION OF SYMBOLS 1 Mold for in-mold painted part 2 First mold 3 Second mold 4 Third mold 6 Resin supply means 6A Resin 7 Paint supply means 7A Reactive paint 8 Three-dimensional paint supply means 9 Resin molded body 10 Paint film 11 Edge portion 12 Cavity for resin molded body 12a to 12d Cavity 22 Cavity for paint film 23 In-mold painted part 24 Paint injection flow path 24a Side wall 24d, 24e, 24f Serpentine flow path 25 Increased flow resistance portion 25a Area change portion 26 Paint injection direction 27 Resin injection flow path 28 Mold for resin molding 41 Mixing flow path 42 Mixed-shaped molded body 43 Three-dimensional mixing flow path 44 Three-dimensional mixed-shaped molded body 113 Auxiliary cavity 121 Painted surface 131 Recess 191 Main body 192 Undercut portion 193 Auxiliary molded body 196 Surface to be painted b Baffle plate portion f1 Flow start direction f2 to f8 Flow direction j Baffle plate portion r1 to r6 Rectangular flow path t Triangular flow path

Claims

1. A method for manufacturing an in-mold painted part, in which two or more liquid reactive paints are injected through a paint injection passage into a paint film cavity formed between the surface of a mold and the surface of a resin molded body within the mold, and then the paint is hardened within the mold to form a paint film on the surface of the resin molded body, wherein the method increases the flow resistance and mixes the paint when it is injected using a flow resistance increasing section provided in the paint injection passage.

2. A method for manufacturing an in-mold painted part as described in claim 1, wherein the flow resistance increasing section is configured by connecting a plurality of tapered flow paths so that the flow path cross-sectional area in a direction intersecting the paint injection direction gradually decreases and then increases as the paint is injected, and when the paint is injected, the flow resistance of the paint is increased by the plurality of tapered flow paths, thereby mixing the paint.

3. A method for manufacturing an in-mold painted part as described in claim 1, wherein the flow resistance increasing section is composed of a serpentine flow path that meanders in the paint injection direction, and when the paint is injected, the paint is made to meander through the serpentine flow path, thereby increasing the flow resistance of the paint and mixing it.

4. A method for manufacturing an in-mold painted part as described in claim 1, wherein the flow resistance increasing section is composed of a plurality of baffle sections extending in a direction intersecting the paint injection direction, and when the paint is injected, the plurality of baffle sections increase the flow resistance of the paint and mix it.

5. A method for producing an in-mold painted part according to any one of claims 1 to 4, wherein the paint is a reactive mixture type paint of two or more liquids of a polyol and an isocyanate.

6. A method for manufacturing an in-mold painted part as described in any one of claims 1 to 4, wherein the paint injection flow path having the increased flow resistance portion is formed during resin molding of the resin molded body before the paint is injected.

7. An in-mold painted part mold for manufacturing an in-mold painted part in which two or more liquid reactive paints are injected through a paint injection flow path into a paint film cavity adjacent to the surface of a resin molded body, and then the paint is hardened to form a paint film on the surface of the resin molded body, the in-mold painted part mold being provided with a flow resistance increasing section in the paint injection flow path that comes into contact with the paint in a direction intersecting the paint injection direction when the paint is injected, thereby increasing the flow resistance of the paint and mixing it.

8. An in-mold painted part mold as described in claim 7, wherein the flow resistance increasing section is configured by connecting a plurality of tapered flow paths so that the flow path cross-sectional area in a direction intersecting the paint injection direction gradually decreases and then increases as the paint proceeds in the paint injection direction, and when the paint is injected, the flow resistance of the paint is increased by the plurality of tapered flow paths, thereby mixing the paint.

9. An in-mold painted part mold as described in claim 7, wherein the flow resistance increasing section is composed of a serpentine flow path that meanders in the paint injection direction, and when the paint is injected, the paint is made to meander through the serpentine flow path, thereby increasing the flow resistance of the paint and mixing it.

10. An in-mold painted part mold as described in claim 7, wherein the flow resistance increasing section is composed of a plurality of baffle sections extending in a direction intersecting the paint injection direction, and when the paint is injected, the plurality of baffle sections increase the flow resistance of the paint to mix it.

11. The mold for in-mold painted parts according to any one of claims 7 to 10, wherein the paint is a reactive mixture type paint of two or more liquids of polyol and isocyanate.

12. A mold for an in-mold painted part as described in any one of claims 7 to 10, having a cavity that forms the paint injection flow path having the increased flow resistance portion during resin molding of the resin molded body before the paint is injected.

Images