JP7568902B2 - Manufacturing method of molded body - Google Patents

Description

The present invention relates to a method for producing a molded body.

Patent Document 1 discloses a technique for manufacturing preforms by compression molding.

JP 2008-173931 A

In Patent Document 1, a preform is formed by compression molding so as not to produce burrs. However, when attempting to perform compression molding so as not to produce burrs, if for some reason the amount of resin put into the female mold becomes slightly less, or if the ambient temperature drops and the fluidity of the molten resin decreases, there is a risk that the resin will not reach the open end of the mouth of the preform, resulting in a manufacturing defect.

The present invention was made in consideration of these circumstances, and aims to provide a method for producing molded bodies that can stably produce molded bodies.

According to the present invention, there is provided a method for manufacturing a molded body, comprising a pouring step, a compression step, and a burr removal step, in which in the pouring step, molten resin is poured into a female mold cavity, in the compression step, a male mold core is inserted into the cavity, the molten resin is sandwiched between the female mold and the male mold, and the molten resin is compressed so that the molten resin overflows from the molding space between the cavity and the core, forming a molded body with burrs, and in the burr removal step, the burrs are removed from the molded body.

In the method of the present invention, compression molding is performed so that the molten resin overflows from the molding space between the female and male dies, forming burrs. In this method, the compression molding conditions are set so that the molten resin overflows, so even if the amount of molten resin input is slightly reduced or the environmental temperature drops and the fluidity of the molten resin decreases, the molding space is filled with molten resin, preventing production defects and allowing for stable production of molded bodies. Burrs are formed on the molded body, but these burrs can be removed in a burr removal process.

Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other.
Preferably, in the method described above, the molten resin is a multi-layer resin sheet in a molten state.
Preferably, in the above-described method, the multilayer resin sheet comprises a lower layer, an intermediate layer, and an upper layer in this order.
Preferably, in the above-described method, the multilayer resin sheet is disposed so that the intermediate layer is parallel to a bottom surface of the cavity.
Preferably, in the method described above, the molded body has a mouth portion provided with an engaging portion to which a discharge member can be attached, and a body portion continuing from the mouth portion, and the inner surface of the cavity is provided with a portion that determines the outer shape of the mouth portion and a portion that determines the outer shape of the body portion.
Preferably, in the method described above, the male mold has a flange portion that protrudes radially beyond the core, and the flange portion is pressed against the female mold to form a thin-walled portion between the burr and the molded body, the thin-walled portion being thinner than the burr.
Preferably, in the above-described method, the female mold is provided with an inclined surface continuing to the opening edge of the cavity, and the edge of the flange portion is pressed against the inclined surface.

1 is a cross-sectional view of a state after molten resin 2 is poured into a cavity 1a of a female mold 1. FIG. 2 is a cross-sectional view showing a state after a core 5a of a male die 5 is pressed against a molten resin 2 from the state shown in FIG. 1. FIG. 3 is a cross-sectional view of a state after the core 5a is further pressed against the molten resin 2 from the state of FIG. 2 to form a folded portion 3b2 in the intermediate layer 3b. 4 is a cross-sectional view showing a state after the core 5a is further pressed against the molten resin 2 from the state shown in FIG. 3, and the molten resin 2 has reached the opening edge 1d of the cavity 1a of the female mold 1. FIG. This is a cross-sectional view of the state after the core 5a is further pressed against the molten resin 2 from the state shown in Figure 4, and the flange portion 5c is pressed against the inclined surface 1e to form a thin-walled portion 10 between the flash 7 and the molded body 8. 1 is a cross-sectional view of a state after a female die 1 and a male die 5 have been removed from a molded body 8 with a burr 7. FIG. 4 is a cross-sectional view of a molded body 8 having burrs 7 after the burrs 7 have been removed. FIG. 1 is a cross-sectional view of a state after the burr 7 has been removed from the molded body 8 with the burr 7 without removing the female die 1 and the male die 5 from the molded body 8 with the burr 7. FIG.

The following describes the embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. In addition, each feature can be an invention independently.

1. Method for Producing a Molded Article A method for producing a molded article according to one embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 7, the molded body 8 to be manufactured by this method is a cylindrical shape with a bottom. As shown in FIG. 1, the molded body 8 is formed by compression molding using a female mold 1 and a male mold 5. The female mold 1 has a cavity 1a. The cavity 1a has an inner shape that defines the outer shape of the molded body 8 to be manufactured. The male mold 5 has a core 5a. The core 5a is inserted into the cavity 1a of the female mold 1 during molding. The core 5a has an outer shape that defines the inner shape of the molded body 8. When the core 5a is inserted into the cavity 1a, a molding space 6 (shown in FIG. 5) having a shape corresponding to the shape of the molded body 8 is formed between the outer surface of the core 5a and the inner surface of the cavity 1a.

As shown in FIG. 1, the male mold 5 has a core 5a that protrudes from a base 5b, and the base 5b has a flange portion 5c that protrudes radially beyond the core 5a. The female mold 1 has an inclined surface 1e that is continuous with the opening edge 1d of the cavity 1a. The inclined surface 1e is inclined so as to expand radially outward in the direction away from the opening edge 1d of the cavity 1a.

In one example, the molded body 8 is a preform used in blow molding of containers and the like. In this case, as shown in FIG. 7, the molded body 8 has, in one example, a mouth portion 8b provided with an engagement portion 8a to which a discharge member (a member used to discharge the contents, such as a cap or a pump) can be attached, and a body portion 8c continuing from the mouth portion 8b. In this case, the inner surface of the cavity 1a is provided with a portion 1f that determines the outer surface shape of the mouth portion 8b, and a portion 1g that determines the outer surface shape of the body portion 8c.

The method of this embodiment includes a feeding process, a compression process, and a burr removal process. Each process is described below.

1-1. Casting Step In the casting step, molten resin 2 is cast into the cavity 1a of the female die 1 as shown in FIG.

The molten resin 2 is a thermoplastic resin in a molten state. The molten resin 2 may be in the form of a block or a sheet. The molten resin 2 may have a single-layer structure or a multi-layer structure. The molten resin 2 is placed on the bottom surface 1b of the cavity 1a.

In this embodiment, the molten resin 2 is a multilayer resin sheet 3 in a molten state. The multilayer resin sheet 3 includes a lower layer 3a, an intermediate layer 3b, and an upper layer 3c in this order. The lower layer 3a, the intermediate layer 3b, and the upper layer 3c respectively become the outer layer 8f, the intermediate layer 8g, and the inner layer 8h of the molded body 8 to be manufactured (see FIG. 7). The lower layer 3a and the upper layer 3c are composed of, for example, polyolefin (polyethylene, polypropylene, etc.), polyester, etc. The intermediate layer 3b is preferably a barrier layer having better gas barrier properties than the lower layer 3a and the upper layer 3c, and is composed of a resin having excellent gas barrier properties, such as EVOH or aromatic polyamide. The multilayer resin sheet 3 is preferably arranged so that the intermediate layer 3b is parallel to the bottom surface 1b. The number of layers of the multilayer resin sheet 3 may be 2 or 4 or more.

If the width (length in the left-right direction in FIG. 1) of the multilayer resin sheet 3 is W and the thickness (length in the up-down direction in FIG. 1) is T, the value of T/W is, for example, 0.1 to 0.95 (0.56 in FIG. 1), and preferably 0.3 to 0.8. Specific examples of this value are 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 0.95, and may be within a range between any two of the numerical values exemplified here. If the depth (length perpendicular to the paper surface in FIG. 1) of the multilayer resin sheet 3 is D, then D/W is, for example, 0.5 to 1.5, and preferably 0.8 to 1.2. Specifically, this value may be, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, and may be within a range between any two of the values exemplified here.

The molded body 8 produced by the method of this embodiment is, for example, a preform used in blow molding of containers and the like. In order to perform blow molding using a preform, it is necessary to produce a preform with a large wall thickness. By using a multilayer resin sheet 3 with a large T/W value, it becomes possible to produce a multilayer preform with a large wall thickness.

2 to 5, in the compression process, the core 5a of the male die 5 is inserted into the cavity 1a, the molten resin 2 is sandwiched between the female die 1 and the male die 5, and the molten resin 2 is compressed so that the molten resin 2 overflows from the molding space 6 between the cavity 1a and the core 5a, forming a molded body 8 with flash 7. Details of this process are as follows. The explanation will be given by taking the case where the molten resin 2 is a multilayer resin sheet 3 as an example.

First, as shown in Figure 2, the tip 5a1 of the core 5a is pressed against the multilayer resin sheet 3. Then, the area 3d of the multilayer resin sheet 3 where the tip 5a1 is pressed is recessed, and the molten resin 2 is pushed out of the area 3d. At this time, the multilayer resin sheet 3 expands while maintaining its layered structure, and the end 3e of the multilayer resin sheet 3 comes into contact with the side surface 1c of the cavity 1a, resulting in the state shown in Figure 2.

When the core 5a is pressed further in this state, the molten resin 2 of the multilayer resin sheet 3 is further extruded from the region 3d. The extruded molten resin 2 is then forced into the gap 9 between the side surface 5a2 of the core 5a and the side surface 1c of the cavity 1a, as shown in FIG. 3, and moves toward the opening edge 1d of the cavity 1a. Since the portion of the molten resin 2 that is in contact with the side surface 1c is less likely to move, the intermediate layer 3b is more likely to form a folded portion 3b2 where the intermediate layer 3b is folded back at the crease 3b1, as shown in FIG. 3.

When the core 5a is pressed further in this state, the molten resin 2 in the multilayer resin sheet 3 is further extruded from the region 3d, and the extruded molten resin 2 moves toward the opening edge 1d of the cavity 1a, and the molten resin 2 reaches the opening edge 1d of the cavity 1a, resulting in the state shown in Figure 4. In the conventional technology, the pressing of the core 5a is completed in this state, and a molded body without burrs is removed.

On the other hand, in this embodiment, the core 5a is pressed further in from the state shown in FIG. 4. Then, as shown in FIG. 5, the molten resin 2 overflows from the molding space 6, the overflowing part becomes a flash 7, and a molded body 8 is formed in the molding space 6, so that a molded body 8 with a flash 7 is formed.

In conventional technology, manufacturing defects were likely to occur if the amount of resin injected into the female mold was slightly less for some reason, or if the ambient temperature dropped and the fluidity of the resin decreased. However, in this embodiment, the compression molding conditions are set so that the molten resin 2 overflows, so even if the amount of molten resin 2 injected is slightly less, or if the ambient temperature drops and the fluidity of the molten resin 2 decreases, the molding space 6 will be filled with molten resin 2, thereby suppressing the occurrence of manufacturing defects.

In addition, when the folded portion 3b2 is formed in the intermediate layer 3b, when the pressing of the core 5a is completed in the state shown in FIG. 4, the intermediate layer 3b does not reach the opening edge 1d, and as a result, the intermediate layer 8g may not be formed up to the opening end 8e (shown in FIG. 7) of the molded body 8. In this case, there is a problem that the function (e.g., gas barrier function) of the intermediate layer 8g is not exerted near the opening end 8e. On the other hand, in this embodiment, the core 5a is further pressed in from the state shown in FIG. 4, and at this time the intermediate layer 3b moves toward the opening end 8e of the molded body 8, suppressing the occurrence of the problem that the intermediate layer 8g is not formed up to the opening end 8e of the molded body 8.

As shown in FIG. 5, the core 5a is pressed until the flange portion 5c is pressed against the female die 1, and a thin-walled portion 10 that is thinner than the burr 7 is formed between the burr 7 and the molded body 8 by pressing the flange portion 5c against the female die 1. The burr 7 can be separated from the molded body 8 by tearing the thin-walled portion 10.

Preferably, the edge 5c1 of the flange portion 5c is pressed against the inclined surface 1e. When the edge 5c1 is pressed against the inclined surface 1e, the area of the contact surface is small, so the pressure applied to the molten resin 2 is large, making it easier to reduce the thickness of the thin-walled portion 10.

6 to 8, in the burr removal process, the burr 7 is removed from the molded body 8 having the burr 7. The removed burr 7 can be used for the production of recycled resin, etc.

This step may be performed after removing the female die 1 and male die 5 from the molded body 8 with the burr 7, as shown in Figures 6 and 7, or may be performed without removing the female die 1 and male die 5 from the molded body 8 with the burr 7, as shown in Figure 8.

Furthermore, the removal of the burrs 7 may be performed before or after a post-process is performed on the molded body 8. For example, when the molded body 8 is a preform used for blow molding, an example of a post-process is blow molding. This blow molding may be performed without reheating the molded body 8, or may be performed by reheating the molded body 8.

In one example, the female die 1 is removed from the molded body 8, and the molded body 8 is placed in the cavity of a split mold for a container with the molded body 8 attached to the male die 5. In this state, air is blown into the molded body 8 through an air flow path built into the male die 5 to perform blow molding. This method allows for efficient production of blow molded bodies. In this case, burrs may be removed before or after removing the female die 1.

If the engaging portion 8a is caught on the female mold 1 and the female mold 1 cannot be removed when the molded body 8 is attached to the male mold 5, the female mold 1 may be configured so that the portion including the portion 1f that defines the outer shape of the mouth portion 8b and the portion including the portion 1g that defines the outer shape of the body portion 8c are separable from each other, and blow molding may be performed with the portion 1g removed from the molded body 8 and the portion 1f attached to the molded body 8. The portion 1f may be an integral structure or a split mold. If the portion 1f is an integral structure, the male mold 5 can be removed from the molded body 8 after blow molding, and then the portion 1f can be removed from the molded body 8. If the portion 1f is a split mold, the portion 1f can be removed from the molded body 8 before the male mold 5 is removed from the molded body 8 after blow molding.

The above steps make it possible to obtain a molded body 8 from which burrs 7 have been removed. The volume V1 of the resin constituting the molded body 8 is smaller than the volume V2 of the molten resin 2 poured into the female mold 1 by the amount of the burrs 7. Therefore, V2/V1>1. Also, since too much burr 7 leads to increased manufacturing costs, it is preferable that V2/V1<2. V2/V1 is preferably 1.05 to 1.5, and specifically, for example, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 1.95, and may be within a range between any two of the numerical values exemplified here.

2. Other embodiments: The above method can be used to manufacture containers that can be formed only by compression molding, such as coffee portions. It can also be used to manufacture bottomed cylindrical objects other than containers, such as caps.

1: Female mold 1a: Cavity 1b: Bottom surface 1c: Side surface 1d: Opening edge 1e: Inclined surface 1f: Part 1g: Part 2: Molten resin 3: Multilayer resin sheet 3a: Lower layer 3b: Middle layer 3b1: Fold 3b2: Folded portion 3c: Upper layer 3d: Region 3e: End 5: Male mold 5a: Core 5a1: Tip 5a2: Side surface 5b: Base 5c: Flange portion 5c1: Edge 6: Molding space 7: Flash 8: Molded body 8a: Engagement portion 8b: Mouth portion 8c: Body portion 8d: Bottom portion 8e: Opening edge 8f: Lower layer 8g: Middle layer 8h: Upper layer 9: Gap 10: Thin portion

Claims (6)

A method for producing a molded body, comprising the steps of:
The method includes a feeding step, a compression step, and a burr removal step,
In the injection step, molten resin is injected into a cavity of a female mold,
In the compression step, a male core is inserted into the cavity, the molten resin is sandwiched between the female and male dies, and the molten resin is compressed so that the molten resin overflows from a molding space between the cavity and the core, thereby forming a molded body with flash;
The male die includes a flange portion that protrudes radially beyond the core,
The flange portion is pressed against the female die to form a thin-walled portion between the flash and the molded body that is thinner than the flash,
In the burr removing step, the burrs are removed from the compact. 2. The method of claim 1 ,
The method, wherein the molten resin is a multilayer resin sheet in a molten state. 3. The method of claim 2,
The multilayer resin sheet comprises a lower layer, an intermediate layer, and an upper layer in this order. 4. The method of claim 3,
The multilayer resin sheet is positioned such that the intermediate layer is parallel to a bottom surface of the cavity. The method according to any one of claims 1 to 4,
The molded body includes a mouth portion provided with an engagement portion to which a discharge member can be attached, and a body portion connected to the mouth portion,
The method, wherein an inner surface of the cavity has a portion that defines the outer surface shape of the mouth portion and a portion that defines the outer surface shape of the body portion. The method according to any one of claims 1 to 5 ,
The female mold is provided with an inclined surface that is continuous with an opening edge of the cavity,
An edge of the flange portion is pressed against the inclined surface.