Manufacturing methods for resin products

Abstract

To enable the proper production of resin products with decorative elements using the minimum number of steps. [Solution] The method includes: a first step of positioning a decorative body F of a certain length between a movable mold 2 and a fixed mold 3; a second step of heating the decorative body F to a certain temperature; a third step of applying negative pressure to a negative pressure working part while heating or after heating to cause the decorative body F to adhere to the movable mold 2; a fourth step of injecting most of the resin R that constitutes one of the products M with the mold 1 in a semi-closed state with a gap equivalent to the thickness of the decorative body F; and a fifth step after the fourth step of closing the mold 1 completely, cutting the decorative body F into a predetermined shape by the cooperation of a blade 2f formed on the movable mold 2 and a blade 3d formed on the fixed mold 3, guiding the edge of the decorative body F in the resulting shape towards the product molding space 4, and injecting the remaining amount of the resin R that constitutes the product M from the gate 3b.

Description

Technical Field

[0001] This invention relates to an improvement in a method for manufacturing a resin product having a designed surface covered with a decorative body in the form of a film or a sheet.

Background Art

[0002] As a method for manufacturing a resin product having a designed surface covered with a decorative body in the form of a film or a sheet, insert molding using a pre-trimmed decorative body as an insert is known (see Patent Document 1).

[0003] On the other hand, there is also known a method of manufacturing a resin product as described above by injecting molten resin into the product molding space of a mold while trimming a decorative body using the mold as a press so to speak when the mold is in a fully closed state (mold clamping state). (See Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The main problem to be solved by this invention is to obtain this type of resin product more appropriately with a minimum number of steps by injecting molten resin into the product molding space of a mold while trimming the decorative body using the mold as a press so to speak when the mold is in a fully closed state (mold clamping state).

Means for Solving the Problems

[0006] To achieve the above objective, the present invention provides a method for manufacturing a resin product, wherein a decorative body in the form of a film or sheet made of resin that softens upon heating is in close contact with the inner surface of a movable mold facing the product molding space, and molten resin is injected into the product molding space through a gate provided in a fixed mold to produce a resin product equipped with the decorative body, The first step involves opening the mold and positioning the decorative body for a certain length between the movable mold and the fixed mold, Following the first step, a second step is to heat the decorative body positioned between the movable mold and the fixed mold to a certain temperature, A third step involves applying negative pressure to a negative pressure area formed outside the product molding space area in the movable mold while or after the heating is performed, thereby causing the decorative body to adhere tightly to the movable mold. Following the third step, the mold is placed in a semi-closed state with a gap between the movable mold and the fixed mold equal to the thickness of the decorative body, and the fourth step involves injecting the majority of the resin constituting one of the products into the product molding space from the gate. The fourth step is followed by a fifth step in which the mold is fully closed, the decorative body is cut into a predetermined shape by the cooperation of the blade formed in the movable mold and the blade formed in the fixed mold, the edges of the decorative body in that shape are guided toward the product molding space, and the remaining amount of the resin constituting the product is injected into the product molding space from the gate.

[0007] In the fourth step described above, one embodiment of this invention is to further apply negative pressure to the negative pressure application part. [Effects of the Invention]

[0008] According to this invention, the resin product can be appropriately obtained with the minimum number of steps by using the mold as a press to trim the decorative body while injecting molten resin into the product molding space of the mold. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view showing the product produced by the manufacturing method according to the embodiment and the remaining part of the decorative body with the punched-out portion becoming part of the product. [Figure 2] Figure 2 is a perspective view showing an example of a mold used in the manufacturing method described above. [Figure 3] Figure 3 is a perspective view of the movable mold that constitutes the mold. [Figure 4] Figure 4 is a perspective view of the fixed mold that constitutes the aforementioned mold. [Figure 5] Figure 5 is a perspective view of the clamp body, and Figure 5(b) shows the clamp body as viewed from the side where the decorative object is clamped between it and the movable mold. [Figure 6] Figure 6 is a schematic diagram illustrating the first step of the manufacturing method described above. [Figure 7] Figure 7 is a schematic diagram illustrating the second step of the manufacturing method described above. [Figure 8] Figure 8 is a schematic diagram illustrating the third step of the manufacturing method. [Figure 9] Figure 9 is a schematic diagram illustrating the fourth step of the manufacturing method. [Figure 10] Figure 10 is a schematic diagram illustrating the fifth step of the manufacturing method. [Figure 11] Figure 11 is a schematic diagram illustrating the process after the fifth step of the manufacturing method. [Figure 12] Figure 12 is a schematic explanatory diagram showing the process after the step shown in Figure 11 of the manufacturing method. [Figure 13] Figure 13 is an enlarged cross-sectional view showing the main parts of the mold in the third step. [Figure 14] Figure 14 is an enlarged cross-sectional view showing the main parts of the mold in the fourth step. [Figure 15] Figure 15 is an enlarged cross-sectional view showing the main parts of the mold in the fifth step. [Figure 16] FIG. 16 is a cross-sectional configuration diagram showing an enlarged main part of the mold of the study example, where (a) shows the main part of the study example in the mold open state and (b) shows the main part of the study example in the mold closed state.

Mode for Carrying Out the Invention

[0010] Hereinafter, based on FIGS. 1 to 16, typical embodiments of this invention will be described.

[0011] The molding method of the resin product M according to this embodiment is to use the mold 1 as a press when the mold 1 is in a fully closed state (mold clamping state), and inject the molten resin R into the product molding space 4 of the mold 1 while trimming the decorative body F, so as to obtain it appropriately with a minimum number of steps. That is, the molding method according to this embodiment does not require a step of trimming the decorative body F in advance, and also does not require a step of setting the thus-trimmed decorative body F as an insert into the mold 1, which is different from insert molding.

[0012] The product M has a design surface Ma formed by the inner surface 2a of the movable mold 2 and a non-design surface Mb formed by the surface 3a of the fixed mold 3 facing the inner surface 2a of the movable mold 2. Such a molding method is to inject the molten resin R into the product molding space 4 from the gate provided in the fixed mold in a state where a resin film-shaped or sheet-shaped decorative body F having a property of softening by heating is adhered to the inner surface 2a of the movable mold 2 facing the product molding space 4 formed between the movable mold 2 and the fixed mold in the fully closed state, and generate a resin product M having a design surface Ma covered by the decorative body F.

[0013] In the illustrated example, the product M has a rectangular plate shape (see Figure 1). One surface is a decorative surface Ma, and the other surface is a non-decorative surface Mb. The decorative element F is provided so as to cover the entire decorative surface Ma and the end surface Mc on the thickness side that extends between the decorative surface Ma and the non-decorative surface Mb. The parts of the product M other than the decorative element F provided in this way are made of the resin R.

[0014] The decorative body F can have a structure in which a printed layer Fc is provided between a base layer Fb made of thermoplastic resin R and a protective layer Fd. By making the protective layer Fd transparent or translucent, the pattern of the printed layer Fc is made visible on the design surface Ma. The base layer Fb is made of a material that has good adhesion to the resin R that constitutes the parts of the product M other than the decorative body F. The printed layer Fc is provided by printing on either the base layer Fb side or the protective layer Fd side. Typically, decorative elements F are used that are in the range of 0.1 mm to 1 mm.

[0015] Figures 2 to 5 show an example of a mold 1 (molding die) that constitutes the manufacturing apparatus. The manufacturing apparatus is composed of such a mold 1, an apparatus base (not shown), and an injection molding machine (not shown). The mold 1 comprises a movable mold 2 and a fixed mold 3. The movable mold 2 has a recess 2b, and the fixed mold 3 has a protrusion 3c that fits into the recess 2b in the semi-closed and fully closed states described later. The space formed between the recess 2b and the protrusion 3c in the semi-closed and fully closed states becomes the product molding space 4 of the product M. A gate 3b is formed in the center of the protrusion 3c of the fixed mold 3, and the injection molding machine is connected to the fixed mold 3 through this gate 3b to inject molten resin R into the product molding space 4. In the illustrated example, the movable type 2 is supported by a device base (not shown) so that it moves horizontally and repeatedly approaches and moves away from the fixed type 3. The device base is equipped with a drive mechanism for the movable type 2. The direction of movement of the movable type 2 may be changed as needed. For example, the movable type 2 may move vertically, repeatedly approaching and moving away from the fixed type 3. In molding a single product M, the drive mechanism controls the movable mold 2 to move from a reference position (mold 1 is in the open state / see Figure 6) that is not in contact with the fixed mold 3 to a first position (mold 1 is in the semi-closed state / see Figure 9) that has a gap between it and the fixed mold 3 equal to the thickness of the decorative body F, and then stops temporarily. After a predetermined time, it moves to a second position (mold 1 is in the fully closed state / see Figure 10) that is in contact with the fixed mold 3, and after a predetermined time, it returns to the reference position (see Figure 11). The injection molding machine is controlled to inject most of the resin R constituting one of the products M from the injection molding machine while it is stopped at the first position, and to inject the remaining amount of resin R from the injection molding machine while it is stopped at the second position.

[0016] The manufacturing method according to this embodiment includes the following first to fifth steps. Figures 6 to 12 schematically illustrate the gist of each step of the manufacturing method to facilitate understanding, and are not intended to match the shape and structure of the mold 1 shown in Figures 2 to 5 and Figures 13 to 15, nor are the thickness of the decorative body F depicted in these figures.

[0017] (First step) The first step is to open the mold 1, feed out a certain length of the decorative body F from the roll-shaped decorative body Fa, and position this certain length of decorative body F between the movable mold 2 and the fixed mold 3. In the illustrated example, the movable mold 2 is equipped with a clamping body 5. The clamping body 5 is frame-shaped when the movable mold 2 is viewed from the front side in the direction of movement, and is provided so as to position the recess 2b of the movable mold 2 in the space 5a within the frame, and is supported by the movable mold 2 in such a state that it is able to move horizontally between a clamping position (Figure 6) in which the decorative object F is sandwiched between the movable mold 2 and the recess 2b, and a non-clamping position (Figure 12) in which the decorative object F is passed between the movable mold 2 and the clamping body 5. The clamp body 5 is supported on the movable type 2 side by a support pin (not shown) that is provided on the movable type 2 so as to be movable in the horizontal direction. In the illustrated example, the upper edge of the clamp body 5 is integrally provided with an upward-extending shielding plate 5b, which is on the supply side of the decorative body F. This prevents the heat applied by the heater body 6 in the second step below from acting on the area of ​​the decorative body F that constitutes the product M to be molded in the next order. With the clamp body 5 in the non-clamping position, a certain length of the decorative material F is fed from the roll-shaped decorative material F between the movable mold 2 and the clamp body 5 to supply a decorative material F that can constitute the design surface Ma of one product M between the movable mold 2 and the fixed mold 3. Then, by moving the clamp body 5 to the clamping position (see Figure 6), the decorative material F is held by the movable mold 2. In the illustrated example, a circumferential rib 5d is formed on the surface 5c of the clamp body 5 facing the movable mold 2, surrounding the frame space 5a. At the clamping position, the clamping force on the decorative body F is concentrated at this circumferential rib 5d, applying a constant tension to the region of the decorative body F located in the frame space 5a. This makes it easier to cut the decorative body F in the fifth step described below. The decorative body F has a width that covers the recess 2b vertically and horizontally.

[0018] Furthermore, when preparing the decorative body F in a roll shape, it is preferable that the side with the protective layer Fd be on the inside of the roll, from the viewpoint of preventing damage to the printed layer Fc and adhesion of foreign matter.

[0019] Furthermore, if the decorative element F is charged, dust may adhere to it, and indentations may occur on the design surface Ma of the product M at the points where dust adheres. To prevent this, it is preferable to first remove static electricity by blowing ions obtained from an ionizer onto the decorative element F as it is fed out (using a blower), and second to maintain positive pressure in the space where the mold 1 is placed in the manufacturing apparatus to prevent dust from entering this space.

[0020] (Second step) The second step is to heat the decorative body F, which is located between the movable mold 2 and the fixed mold 3, to a certain temperature after the first step. In the illustrated example, a heater body 6 having an area that covers at least the space 5a within the frame of the clamp body 5 is moved between the movable type 2, which is in the open state, and the fixed type 3, and the decorative object F held by the clamp body 5 is heated by this heater body 6 for a predetermined time (see Figure 7). Typically, such a heater 6 is controlled to heat the decorative body F to approximately 150 degrees Celsius. Furthermore, the heater body 6 is provided in the manufacturing apparatus so as to be movable between a standby position and a heating position that enables heating. After heating is completed, it is removed from between the movable mold 2 and the fixed mold 3 and transported to a predetermined standby position.

[0021] (Third step) The third step is to apply negative pressure to a negative pressure area formed outside the region that becomes the product molding space 4 in the movable mold 2, while or after heating, to bring the decorative body F into close contact with the movable mold 2. In the illustrated example, the movable type 2 is provided with a circumferential groove 2c surrounding the recess 2b at the location between the inner edge of the clamp body 5 facing the internal space 5a of the clamping position and the recess 2b. This circumferential groove 2c is used to create negative pressure between the decorative body F held by the clamp body 5 and the movable type 2, more specifically between the protective layer Fd of the decorative body F and the inner surface 2a of the recess 2b on the movable side 2. In other words, in the illustrated example, the circumferential groove 2c functions as a negative pressure area. In other words, the decorative body F has a width that covers the area where the circumferential groove 2c is formed in the movable mold 2, and is in close contact with the movable mold 2 due to the action of the negative pressure. Typically, the vacuum ejector is connected to the circumferential groove 2c through a flow path 2d provided inside the movable mold 2. In Figure 3, reference numeral 2e indicates the end of the flow path 2d formed at the bottom of the circumferential groove 2c. Since the decorative body F is softened in the second step, the decorative body F can be molded in this third step to generally conform to the inner surface 2a of the movable mold 2 (the inner surface of the recess 2b).

[0022] (Fourth step) The fourth step is to inject most of the resin R that constitutes one of the products M into the product molding space 4 through the gate 3b, with the mold 1 in a semi-closed state (Figures 9 and 14) with a gap S equivalent to the thickness of the decorative body F between the movable mold 2 and the fixed mold 3. In the illustrated example, the movable mold 2 is equipped with a blade body 2f, described later, so as to surround the recess 2b. In a semi-closed state, where the movable mold 2 is moved to a position where the gap S is formed between the blade body 2f of the movable mold 2 and the blade body 3d of the fixed mold 3, described later, in the direction of movement x of the movable mold (Figures 2, 6, and 13), most of the resin R that constitutes one of the products M is injected. Typically, about 90% of the resin R that constitutes one of the products M is injected into the product molding space 4 through the gate 3b of the fixed mold 3. In the third step, the decorative body F is molded to roughly conform to the inner surface 2a of the movable mold 2 (the inner surface of the recess 2b). In this fourth step, the injection pressure of the resin R causes the decorative body F to adhere tightly to the inner surface 2a of the movable mold 2, and in particular, even in the inner corner 2i where the bottom surface 2g and the side surface 2h of the recess 2b meet, the decorative body F adheres tightly to the inner surface 2a of the movable mold 2 without any gaps. In this fourth step, it is also preferable to apply negative pressure to the negative pressure application part. Furthermore, if the inclined inner surface 3h of the circumferential rib 3e, which constitutes the blade body 3d of the fixed mold 3, is formed by an end mill that moves from the top 3f of the circumferential rib 3e toward the base 3g, a fine recess can be formed on the inner surface 3h that extends from the top 3f toward the base 3g. In this way, the negative pressure can be easily applied to the product molding space 4 even in the semi-closed state by using this fine recess as a flow path.

[0023] The decorative body F is stretched to some extent by the action of pressure and heat when molten resin R is injected. In the illustrated example, the resin R flows and spreads radially from the gate 3b formed in the center of the protrusion 3c of the fixed mold 3, and the decorative body F is stretched to some extent by this flow of resin R. However, in this fourth step, since the gap S is formed between the movable mold 2 and the fixed mold 3, the stretched portion can be released outside the product molding space 4, and the decorative body F can be made to adhere tightly to the entire inner surface 2a of the movable mold 2 without creating gaps due to trapped air or wrinkles as described later. If the stretched portion of the decorative element F cannot be released outside the product molding space 4, wrinkles will form on the decorative element F, particularly at the end face Mc of the product M. This manufacturing method effectively suppresses the occurrence of such wrinkles.

[0024] (The fifth step) The fifth step, after the fourth step, involves closing the mold 1 completely (Figures 10 and 15), and using the combined action of the blade 2f formed on the movable mold 2 and the blade 3d formed on the fixed mold 3 to cut the decorative body F into a predetermined shape (this cutting position is shown by a dashed line in Figure 10). The edges of the decorative body F, now in this shape, are then guided towards the product molding space 4, and the remaining amount of the resin R constituting the product M is injected through the gate 3b.

[0025] In the illustrated example, the blade body 2f of the movable type 2 is composed of an edge-shaped protruding corner portion 2k that comes into contact with the entrance side surface 2h of the recess 2b in the movable type 2, which is aligned with the direction of movement of the movable type 2, and the recess surrounding surface 2j located outside the recess 2b. In other words, the blade body 2f of the movable type 2 is circumferential, bordering the entrance of the recess 2b of the movable type 2. On the other hand, the blade body 3d of the fixed mold 3 is composed of the top portion 3f of the circumferential rib 3e that protrudes toward the movable mold 2, fringing the edge of the top surface 3j of the protrusion 3c of the fixed mold 3, which is oriented perpendicular to the direction of movement of the movable mold 2. The outer surface 3i of the circumferential rib 3e, located on the side surface 3k of the protrusion 3c, slides against the side surface 2h of the movable mold 2 on the entrance side during the movement of the movable mold 2. The inner surface 3h of the circumferential rib 3e (the surface in the product molding space 4) facing the outer surface 3i is inclined in a direction that gradually increases the distance between it and the outer surface 3i as it approaches the base 3g of the circumferential rib 3e. During the process in which the movable mold 2 moves from the semi-closed state to the fully closed state, the decorative body F located between the movable mold 2 and the fixed mold 3 is divided into a punched portion Fe (see Figure 1) that covers the entire design surface Ma formed by the movable mold 2 in the product M, and the remaining portion Ff (see Figure 1). In the fully closed state, the protrusion 3c of the fixed mold 3 fits into the recess 2b of the movable mold 2, and a contact portion (not shown) formed on the movable mold 2 side and a contacted portion (not shown) formed on the fixed mold 3 side come into contact outside the product molding space 4, forming a product molding space 4 between the movable mold 2 and the fixed mold 4 that matches the outer shape of the product M. The fourth step prevents wrinkles from forming at the edges of the punched-out portion Fe, and after cutting, the edges of the punched-out portion Fe are guided in a curled shape by the inclination of the inner surface 3h of the circumferential rib 3e, so that the cut end Fg (see Figure 15) faces the central side of the convex portion 3c of the fixed die 3, that is, the product molding space 4 side (the inner side of the product molding space 4 with respect to the cutting position). Specifically, the edges of the punched-out portion Fe are bent or curved at any position around the center of the punched-out portion Fe so that the cut end Fg faces the product molding space 4 side. As shown in Figure 16, if the shape of the mold 1 near the cutting edge is such that the edge of the punched portion Fe cannot be guided as described above, wrinkles W (see Figure 16(b)) will form on this edge. However, by doing as described above, such wrinkles W can be suppressed. Then, by injecting the remaining amount of resin R, the resin R spreads to the side surface 2h of the recess 2b of the movable mold 2 on the entrance side. As described above, the resin R also enters and spreads into the inner side y (see Figure 15) of the edge of the bent or curved punched portion Fe from the central side of the product molding space 4. As a result, a product M is obtained in which the entire design surface Ma is appropriately covered with the decorative body F.

[0026] After the fifth step, mold 1 is opened (see Figure 11), product M is separated from movable mold 2 (see Figure 11), and product M remains in fixed mold 3 equipped with gate 3b. Product M is separated from fixed mold 3 by ejector pins 7 provided on fixed mold 3 (see Figure 12), and the molding of one product M is completed. The decorative body F, from which the punched portion Fe remaining between the movable mold 2 and the fixed mold 3 has been removed, is moved downwards from the mold 1 in the first step of molding the next product M (see Figure 12).

[0027] Naturally, the present invention is not limited to the embodiments described above, but includes all embodiments that can achieve the objectives of the present invention. [Explanation of Symbols]

[0028] 1. Mold 2 Movable type 2f blade body 3 Fixed type 3d blade body F Decorative material

Claims

1. A method for producing a resin product comprising: injecting molten resin into the product molding space through a gate provided in a fixed mold, while a decorative body in the form of a film or sheet made of resin that softens upon heating is in close contact with the inner surface of a movable mold facing the product molding space, the decorative body is injected into the product molding space, thereby producing a resin product equipped with the decorative body. The first step involves opening the mold and positioning the decorative body for a certain length between the movable mold and the fixed mold, Following the first step, a second step is to heat the decorative body positioned between the movable mold and the fixed mold to a certain temperature, A third step involves applying negative pressure to a negative pressure area formed outside the product molding space area in the movable mold while or after the heating is performed, thereby causing the decorative body to adhere tightly to the movable mold. Following the third step, the mold is placed in a semi-closed state with a gap between the movable mold and the fixed mold equal to the thickness of the decorative body, and the fourth step involves injecting the majority of the resin constituting one of the products into the product molding space from the gate. A method for manufacturing a resin product, comprising the fourth step, after which the mold is fully closed, the decorative body is cut into a predetermined shape by the cooperative action of a blade formed in the movable mold and a blade formed in the fixed mold, the edges of the decorative body having been shaped are guided toward the product molding space, and the remaining amount of the resin constituting the product is injected into the product molding space from the gate.

2. The method for manufacturing a resin product according to claim 1, wherein in the fourth step, a negative pressure is further applied to the negative pressure application part.

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