JP6933806B2 - Manufacturing method of resin molded product - Google Patents

Description

The present invention relates to a resin molded body (eg, a resin panel) that can be used as a bath lid, a floor board installed in a luggage compartment of a vehicle, or the like.

Patent Document 1 discloses a method of forming a resin molded body formed by sandwiching a core material made of a foam material between two resin sheets and laminating them.

Japanese Unexamined Patent Publication No. 2013-022734

In Patent Document 1, the first and second resin sheets are simultaneously injected, the core material is welded to the first resin sheet, and then the core material is welded to the second resin sheet. Since the core material is welded using the heat of the resin sheet, it is difficult for the core material to be welded to the resin sheet unless the temperature of the resin sheet is sufficiently high. Therefore, the core material is difficult to be welded to the second resin sheet to be welded after the first resin sheet.

In such a situation, the present inventor adopts a new method of starting the injection of the first resin sheet and then starting the injection of the second resin sheet, whereby the core material is welded to the second resin sheet. I tried to solve the problem of difficulty.

Although the problem that the core material is difficult to be welded to the second resin sheet has been solved by the above-mentioned new method, it has been found that a new problem that a step is formed in the vicinity of the parting line of the obtained resin molded body occurs. rice field.

The present invention has been made in view of such circumstances, and it is possible to suppress the occurrence of a step near the parting line of the resin molded product when the timing of injecting the two resin sheets is staggered. It provides a method for producing a resin molded product.

According to the present invention, an injection step, a molding step, and a mold clamping step are provided. In the injection step, the first and second resin sheets are injected between the first and second molds, and the first and second resin sheets are injected. Each of the second molds has a cavity, and in the molding step, the first and second resin sheets are shaped along the inner surfaces of the cavities of the first and second molds, respectively, and in the molding step, the molding is performed. , The first and second molds are molded, and in the injection step, the injection of the first resin sheet is started, and then the injection of the second resin sheet is started, and the edge of the cavity of the first mold is set to the first. 2. Provided is a method for manufacturing a resin molded product, which is configured to be outside the edge of the cavity of the mold.

The present inventor investigated the cause of the step generation near the parting line of the resin molded product, and found that if the timing of ejecting the two resin sheets was shifted, the mold was first molded. It was found that this is because the portion composed of the resin sheet at which the injection was started has a larger degree of shrinkage than the portion composed of the resin sheet at which the injection was started later.

Then, based on such findings, the edge of the cavity of the mold that shapes the resin sheet that started injection first is outside the edge of the cavity that shapes the resin sheet that started injection later. As a result, it was found that the step difference of the resin molded product could be reduced, and the present invention was completed.

Hereinafter, various embodiments of the present invention will be illustrated. The embodiments shown below can be combined with each other.
Preferably, the distance between the edge of the cavity of the first mold and the edge of the cavity of the second mold when the first and second molds are in contact with each other is 0. It is 05 to 1 times.
Preferably, the insert step is provided, in which the insert member is attached to the first resin sheet after the first resin sheet is shaped along the inner surface of the cavity of the first mold.

According to another aspect of the present invention, an injection step, a molding step, an insert step, and a mold clamping step are provided, and in the injection step, the first and second resin sheets are placed between the first and second molds. The first and second molds are respectively provided with cavities, and in the shaping step, the first and second resin sheets are shaped along the inner surfaces of the cavities of the first and second molds, respectively. Then, in the mold clamping step, the first and second molds are molded, and in the injection step, the injection of the first resin sheet is started, and then the injection of the second resin sheet is started, and in the insertion step, the injection of the second resin sheet is started. Provided is a method for producing a resin molded product, wherein an insert member is attached to the first resin sheet after shaping the first resin sheet along the inner surface of the cavity of the first mold.

Preferably, the first and second resin sheets are shaped by vacuum suction by the first and second molds, respectively.
Preferably, the injection of the second resin sheet is started after the first resin sheet is shaped along the inner surface of the cavity of the first mold.
Preferably, the first and second resin sheets are shaped so as to be in direct contact with the first and second molds, respectively, without the intervention of separate members.
Preferably, the injection of the second resin sheet is started after the insert member is attached to the first resin sheet.

It is a perspective view of the resin molded article 1 of one Embodiment of this invention. It is a block diagram (longitudinal sectional view about the molds 21 and 31 and the member in the vicinity) of the molding machine 10 which can be used for manufacturing the resin molded body 1 of one Embodiment of this invention. It is sectional drawing which shows the state in which the molds 21 and 31 in FIG. 2 are brought close to each other. 4A is an enlarged cross-sectional view of the vicinity of the upper ends of the molds 21 and 31 in FIG. 3, and FIG. 4B is a cross-sectional view showing a state in which the molds 21 and 31 are brought into contact with each other from the state of FIG. 4A. It is sectional drawing which shows the state which the resin sheet 23 was injected between the molds 21 and 31. It is sectional drawing which shows the state after shaping the resin sheet 23 along the cavity inner surface of a mold 21 from the state of FIG. FIG. 6 is a cross-sectional view showing a state after the insert member 7 is attached to the resin sheet 23 and the resin sheet 33 is injected between the dies 21 and 31 from the state of FIG. It is sectional drawing which shows the state after shaping the resin sheet 33 along the cavity inner surface of a mold 31 from the state of FIG. FIG. 5 is an enlarged cross-sectional view corresponding to FIG. 4A showing a state immediately before mold clamping in which the molds 21 and 31 are brought closer to each other from the state of FIG. It is sectional drawing which shows the state after mold compaction | die 21 and 31 from the state of FIG. FIG. 5 is an enlarged cross-sectional view of the vicinity of the upper ends of the molds 21 and 31 in FIG. It is sectional drawing of the state which took out the resin molded body 1 from the state of FIG. It is sectional drawing of the state after excising the burr 41 from the state of FIG. It is sectional drawing corresponding to FIG. 9A in the case of molding using the mold of the reference example. It is sectional drawing which shows the state after mold compaction | die 21 and 31 from the state of FIG. It is sectional drawing of the state which took out the resin molded body 1 from the state of FIG. It is sectional drawing of the state after excising the burr 41 from the state of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The various features shown in the embodiments shown below can be combined with each other. In addition, the invention is independently established for each feature.

1. 1. Structure of Resin Molded Body As shown in FIG. 1, the resin molded body 1 of the embodiment of the present invention includes a front wall 3 and a back wall 4. The front wall 3 and the back wall 4 face each other with a gap. The periphery of the front wall 3 and the back wall 4 is connected by a peripheral wall 6. A parting line PL is provided at substantially the center of the peripheral wall 6 in the thickness direction. There is almost no step between the part 6a on the front wall 3 side and the part 6b on the back wall 4 side of the surrounding wall 6 with respect to the parting line PL, and the part 6a and the part 6b are smoothly connected. Since the skin material is not attached to either the front wall 3 or the back wall 4, it is easily noticeable if there is a step in the parting line PL, but the resin molded body 1 of the present embodiment is manufactured by the manufacturing method described later. Therefore, the occurrence of steps is suppressed.

An insert member 7 (see FIG. 10) is provided between the front wall 3 and the back wall 4. The insert member 7 is a member arranged for the purpose of securing a space between the front wall 3 and the back wall 4 and increasing the strength and heat insulating properties of the resin molded body 1, and is preferably made of a foam. Will be done.

2. Molding machine 10
Next, with reference to FIGS. 2 to 4, a molding machine 10 that can be used to carry out the method for producing a resin molded product according to an embodiment of the present invention will be described. The molding machine 10 includes a pair of resin sheet forming devices 20 and first and second molds 21 and 31. Each resin sheet forming device 20 includes a hopper 12, an extruder 13, an accumulator 17, and a T-die 18. The extruder 13 and the accumulator 17 are connected via a connecting pipe 25. The accumulator 17 and the T-die 18 are connected via a connecting pipe 27.
Hereinafter, each configuration will be described in detail.

<Hopper 12, extruder 13>
The hopper 12 is used to put the raw material resin 11 into the cylinder 13a of the extruder 13. The form of the raw material resin 11 is not particularly limited, but is usually in the form of pellets. The raw material resin is, for example, a thermoplastic resin such as polyolefin, and examples of the polyolefin include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer and a mixture thereof. The raw material resin 11 is charged into the cylinder 13a from the hopper 12 and then melted by being heated in the cylinder 13a to become a molten resin. Further, it is conveyed toward the tip of the cylinder 13a by the rotation of the screw arranged in the cylinder 13a. The screw is arranged in the cylinder 13a, and the molten resin is kneaded and conveyed by its rotation. A gear device is provided at the base end of the screw, and the screw is rotationally driven by the gear device. The number of screws arranged in the cylinder 13a may be one or two or more.

<Accumulator 17, T-die 18>
The molten resin is extruded from the resin extrusion port of the cylinder 13a and injected into the accumulator 17 through the connecting pipe 25. The accumulator 17 includes a cylinder 17a and a piston 17b slidable inside the cylinder 17a, so that molten resin can be stored in the cylinder 17a. Then, by moving the piston 17b after a predetermined amount of the molten resin is stored in the cylinder 17a, the molten resin is pushed out from the slit provided in the T die 18 through the connecting pipe 27 and injected to be the first in the molten state. And the second resin sheets 23 and 33 are formed.

<Molds 21, 31>
The resin sheets 23 and 33 are ejected between the molds 21 and 31. As shown in FIGS. 3 to 4, the molds 21 and 31 have cavities 21a and 31a, and pinch-off portions 21b and 31b are provided so as to surround the cavities 21a and 31a. Decompression suction holes (not shown) are provided in the cavities 21a and 31a, and the resin sheets 23 and 33 are decompressed and sucked through the decompression suction holes along the inner surfaces of the cavities 21a and 31a of the molds 21 and 31. It is possible to shape it into a new shape. The decompression suction hole is a very small hole, one end of which is communicated to the inner surface of the cavities 21a and 31a through the inside of the molds 21 and 31, and the other end is connected to the decompression device.

As shown in FIG. 4B, when the molds 21 and 31 are brought close to each other until the pinch-off portions 21b and 31b come into contact with each other, the tip surfaces of the pinch-off portions 21b and 31b come into contact with each other. The contact surface is the parting surface P. Since the edge 21c of the cavity 21a of the mold 21 is configured to be outside the edge 31c of the cavity 31a of the mold 31, the edge 21c is formed on the parting surface P when the molds 21 and 31 are closed. A step 35 is provided between 21c and 31c. When the timing of ejecting the resin sheets 23 and 33 is shifted, a step is likely to occur in the parting line PL of the resin molded body 1, but the resin is formed by not shifting the positions of the edges 21c and 31c as in the present embodiment. The generation of a step on the molded body 1 is suppressed. The principle will be described later.

The distance between the edges 21c and 31c (that is, the step 35) when the molds 21 and 31 are in contact with each other (the state shown in FIG. 4B) is such that the step on the parting line PL of the resin molded body 1 is as small as possible. Is set to, for example, 0.05 to 1 times the thickness of the resin sheet 23, specifically, for example, 0.05, 0.1, 0.15, 0.2, 0.25, 0. 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, It is 0.95 and 1, and may be within the range between any two of the numerical values exemplified here. In other words, this distance is 0.1 to 2 mm, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7. , 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 mm. , It may be within the range between any two of the numerical values exemplified here.

3. 3. Method for Producing Resin Molded Product Here, a method for producing the resin molded product 1 according to the embodiment of the present invention will be described with reference to FIGS. 5 to 10. The method of the present embodiment includes an injection step, a shaping step, an insert step, and a mold clamping step. Hereinafter, a detailed description will be given.

3-1. Injection step In the injection step, as shown in FIGS. 5 to 7, the resin sheets 23 and 33 are injected between the molds 21 and 31. In the present embodiment, the timing of injecting the resin sheets 23 and 33 is deviated. At the stage of FIG. 5, only the resin sheet 23 is injected, and at the stage of FIG. 7, the injection of the resin sheet 33 is started. The timing of injecting the resin sheets 23 and 33 is shifted to reduce the temperature drop of the resin sheet 33 until the insert member 7 is welded to the resin sheet 33 and improve the weldability. Since the insert member 7 is welded to the resin sheet 23 and then welded to the resin sheet 33, in the present embodiment, the resin sheet 23 is injected before the resin sheet 33. The thicknesses of the resin sheets 23 and 33 are the same or different, and are, for example, 0.5 to 5 mm, respectively, specifically, for example, 0.5, 1, 1.5, 2, 2.5, and 3. , 3.5, 4, 4.5, 5 mm, and may be within the range between any two of the numerical values exemplified here. When the thickness of the resin sheet 23 is 1.5 mm or less, the temperature of the resin sheet 23 drops significantly due to the contact of the resin sheet 23 with the mold 23, and the shrinkage of the resin sheet 23 due to the temperature drop is remarkable. Therefore, it is of great significance to apply the present invention.

3-2. Shaped step In the shaping step, as shown in FIGS. 6 to 8, the resin sheets 23 and 33 are brought into contact with the pinch-off portions 21b and 31b, respectively, and vacuum suction is performed by the molds 21 and 31. The resin sheets 23 and 33 are shaped along the inner surfaces of the cavities 21a and 31a. In the present embodiment, since another member such as a skin material is not arranged between the resin sheet 23 and the mold 21 and between the resin sheet 33 and the mold 31, the resin sheets 23 and 33 are respectively. , Is shaped so as to be in direct contact with the molds 21 and 31.

In the present embodiment, the timing of shaping the resin sheets 23 and 33 is shifted, and only the resin sheet 23 is shaped at the stage of FIG. 6, and the resin sheet 33 is shaped at the stage of FIG.

3-3. Insert step In the insert step, as shown in FIGS. 6 to 7, the insert member 7 is welded to the resin sheet 23. When the insert member 7 is made of a foam, one surface 7a of the insert member 7 is welded to the resin sheet 23 by melting the foam by the heat of the resin sheet 23. The other surface 7b of the insert member 7 is welded to the resin sheet 33 at the time of mold clamping shown in FIG. In the present embodiment, since the resin sheet 33 is ejected later than the resin sheet 23, the temperature of the resin sheet 33 at the time of molding is increased by that amount, and the weldability of the insert member 7 is improved. Further, when the insert member 7 is welded to the resin sheets 23 and 33, the corners 7c of the insert member 7 are melted and rounded along the inner surface shapes of the cavities 21a and 31a.

3-4. Mold-clamping step In the mold-clamping process, the molds 21 and 31 are mold-clamped as shown in FIG. As a result, the resin sheets 23 and 33 are welded to each other along the pinch-off portions 21b and 31b, and a resin molded body 1 having a shape along the inner surface of the cavity formed by the pair of molds 21 and 31 is obtained. The outside of the pinch-off portions 21b and 31b is the burr 41. After that, the resin molded body 1 shown in FIG. 1 is obtained by opening the molds 21 and 31 to take out the resin molded body 1 and removing the burrs 41. In the present embodiment, since the resin sheet 33 is ejected later than the resin sheet 23, the temperature of the resin sheet 33 at the time of molding is increased by that amount, and the weldability between the resin sheets 23 and 33 is improved. As a result, the strength of the parting line PL is increased.

By the way, in the state immediately after the resin sheet 23 is shaped by being sucked into the mold 21 under reduced pressure (the state shown in FIG. 6), the resin sheet 23 is in close contact with the inner surface of the cavity 21a on the entire inner surface of the cavity 21a. However, after that, while the insert of the insert member 7 and the injection and shaping of the resin sheet 33 are performed, the heat of the resin sheet 23 is taken away by the mold 21 and the resin sheet 23 is rapidly cooled. This cooling causes shrinkage stress in the resin sheet 23. The mold 21 continues decompression suction even after the resin sheet 23 is shaped, but since a decompression suction hole is not usually provided in the vicinity of the parting surface P, the resin by the mold 21 is provided at this portion. The adsorption of the sheet 23 is weak. Therefore, when a shrinkage stress is generated in the resin sheet 23, as shown in FIG. 9, the resin sheet 23 shrinks in the vicinity of the parting surface P and peels off from the inner surface 21d of the cavity 21a, immediately before the mold clamping step is performed. At this point, the state is as shown in FIG. On the other hand, since the resin sheet 33 is shaped at the stage of FIG. 8, since the time until the time when the mold clamping step is performed is short, the resin sheet 33 is in close contact with the inner surface of the cavity 31a on the entire inner surface of the cavity 31a. .. That is, only the resin sheet 23 is peeled off from the inner surface 21d of the cavity 21a in the vicinity of the parting surface P.

In the molds 21 and 31 of the present embodiment, the edge 21c of the cavity 21a of the mold 21 is configured to be outside the edge 31c of the cavity 31a of the mold 31. Therefore, the shrinkage of the resin sheet 23 is offset by the distance between the edges 21c and the edges 31c, and the positions of the bent portions 23a and 33a of the resin sheets 23 and 33 in the vicinity of the pinch-off portions 21b and 31b coincide with each other. There is.

When the mold is fastened from the state of FIG. 9, the resin sheets 23 and 33 are welded and integrated as shown in FIGS. 10 to 11. At this time, of the resin sheets 23 and 33, the portions sandwiched by the pinch-off portions 21b and 31b are pushed out to the cavity side, and the protrusions 36 are formed in the vicinity of the welding surface of the resin sheets 23 and 33.

FIG. 12 shows a state in which the resin molded body 1 is taken out from the molds 21 and 31 from the state of FIG. When the burr 41 is removed from the state of FIG. 12 at the end 41a of the burr 41, the state shown in FIG. 13 is obtained. The trace of removing the end portion 41a becomes the parting line PL. There is almost no step between the part 6a on the front wall 3 side and the part 6b on the back wall 4 side of the surrounding wall 6 with respect to the parting line PL, and the part 6a and the part 6b are smoothly connected.

Here, problems when molding is performed using the molds 21 and 31 of the reference example in which the positions of the edges 21c and 31c of the cavities of the molds 21 and 31 are the same using FIGS. 14 to 17. Will be described.

When such a mold is used, as shown in FIG. 14, when only the resin sheet 23 contracts in the vicinity of the pinch-off portion 21b and peels off from the inner surface of the cavity 21a, the resin sheet in the vicinity of the pinch-off portions 21b and 31b. The positions of the bent portions 23a and 33a of 23 and 33 are displaced.

When the mold is fastened from the state of FIG. 14, the ends of the resin sheets 23 and 33 are welded and integrated as shown in FIG. At this time, of the resin sheets 23 and 33, the portions sandwiched by the pinch-off portions 21b and 31b are pushed out to the cavity side, and the protrusions 36 are formed in the vicinity of the welding surface of the resin sheets 23 and 33. Further, at this time, the resin sheet 23 is pushed inward by the resin extruded to the cavity side, so that the step between the resin sheets 23 and 33 is promoted.

FIG. 16 shows a state in which the resin molded body 1 is taken out from the molds 21 and 31 from the state of FIG. When the burr 41 is removed from the state of FIG. 16 at the end 41a of the burr 41, the state shown in FIG. 17 is obtained. The trace of removing the end portion 41a becomes the parting line PL. A groove 37 is formed at a position adjacent to the parting line PL due to a step between the resin sheets 23 and 33. Therefore, a step is formed between the portion 6a on the front wall 3 side and the portion 6b on the back wall 4 side of the peripheral wall 6 with respect to the parting line PL.

4. Other Embodiments-The injection of the resin sheet 33 can be started at an arbitrary timing after the injection of the resin sheet 23 is started. The injection of the resin sheet 33 may be started before the shaping of the resin sheet 23, after the shaping of the resin sheet 23, before the sticking of the insert member 7, or after the sticking of the insert member 7. From the viewpoint of reducing the temperature drop of the resin sheet 33, the injection of the resin sheet 33 is preferably started after the molding of the resin sheet 23, and more preferably after the insert member 7 is attached.
-The insert member 7 can be omitted.

1: Resin molded body 3: Front wall 4: Back wall 6: Peripheral wall 6a: Part 6b: Part 7: Insert member 7a: Surface 7b: Surface 10: Molding machine 11: Raw material resin 12: Hopper 13: Extruder 13a: Cylinder 17: Accumulator 17a: Cylinder 17b: Piston 18: T-die 20: Resin sheet forming device 21: First mold 21a: Cavity 21b: Pinch-off portion 21c: Edge 21d: Inner surface 23: First resin sheet 23a: Bending portion 25 : Connecting pipe 27: Connecting pipe 31: Second mold 31a: Cavity 31b: Pinch-off part 31c: Edge 33: Second resin sheet 33a: Bending part 35: Step 36: Protrusion 37: Groove 41: Burr P: Parting surface PL: Parting line

Claims (7)

It has an injection process, a shaping process, and a mold clamping process.
In the injection step, the first and second resin sheets are injected between the first and second molds.
The first and second molds each have a cavity and
In the shaping step, the first and second resin sheets are shaped along the inner surfaces of the cavities of the first and second molds, respectively.
In the mold clamping step, the first and second molds are molded and molded.
In the injection step, after the injection of the first resin sheet is started, the injection of the second resin sheet is started, and the injection is started.
A method for manufacturing a resin molded product, wherein the edge of the cavity of the first mold is configured to be outside the edge of the cavity of the second mold. The distance between the edge of the cavity of the first mold and the edge of the cavity of the second mold when the first and second molds are in contact with each other is 0.05 to 1 of the thickness of the first resin sheet. The method according to claim 1, which is double. Equipped with an insert process
The method according to claim 1 or 2, wherein in the insert step, the insert member is attached to the first resin sheet after shaping the first resin sheet along the inner surface of the cavity of the first mold. The method according to any one of claims 1 to 3 , wherein the first and second resin sheets are formed by being sucked under reduced pressure by the first and second molds, respectively. The method according to any one of claims 1 to 4 , wherein injection of the second resin sheet is started after shaping the first resin sheet along the inner surface of the cavity of the first mold. The first and second resin sheets are formed so as to be in direct contact with the first and second molds without using separate members, respectively, according to any one of claims 1 to 5. The method of description. The method according to claim 3, wherein injection of the second resin sheet is started after the insert member is attached to the first resin sheet.

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