JP3095335B2 - Injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method,
In particular, the present invention relates to an injection molding method for obtaining a layered product composed of a front layer and a back layer.

[0002]

2. Description of the Related Art Conventionally, as a molding method for obtaining a layered molded product composed of different thermoplastic resins and in which a front surface layer and a back surface layer are clearly distinguished, a method disclosed in Japanese Patent Application Laid-Open No. 5-192951 is known. is there. The molding machine used in this method has a split mold composed of a fixed mold and a movable mold, and is connected to a cavity inside the mold by abutting at a different position from the mold, and has two injection cylinders a and b and two hoppers a and b, and two injection units a and b. Furthermore, the connection between the injection cylinders a and b and the cavity inside the mold is made via sprues a and b and runners a and b, respectively.

In this molding method, different thermoplastic resins a and b are supplied to hoppers a and b, respectively, and plasticized by injection cylinders a and b, respectively, and then the plasticized thermoplastic resin is placed in a mold. At the cavities in the sprues a and b and runner a, respectively.
And b), the plasticized different thermoplastic resins a and b join immediately before the gate of the mold to form a two-layer state, and fill and mold the cavity while maintaining this state. This is a molding method for obtaining a layered molded product.

However, in this method, since the plasticized thermoplastic resin flows in a non-uniform and complicated manner when flowing in the cavity, the obtained layered product is not a completely two-layered state, and furthermore, the layered product is Cannot be made equal in thickness.

[0005]

An object of the present invention is to provide an injection molding method capable of easily obtaining a layered product having two layers having the same thickness in a complete two-layer state. is there.

[0006]

An injection molding method according to the present invention uses a split mold composed of a fixed mold and a movable mold, and differs from two injection cylinders connected to a cavity in the mold. By injecting a thermoplastic resin into the cavity, the different thermoplastic resins are merged immediately before the gate of the split mold, and filled into the cavity and molded, a layered structure composed of a front layer and a back layer is formed. In the injection molding method for obtaining a molded product, the different thermoplastic resins have the same viscosity at the time of injection, and
000 Pa · s.

[0007] The injection speed of injecting the different thermoplastic resin into the cavity is the same, and 10-30 cm ³
/ Sec is preferable. Hereinafter, the present invention will be described in detail. The split mold used in the injection molding method of the present invention is not particularly limited as long as it is composed of a fixed mold and a movable mold. Also, the two injection cylinders are connected to a cavity inside the split mold. It is preferable that the two injection cylinders abut at different positions from the split mold and that the two injection cylinders are installed at an angle, because the molding machine and the mold can be reduced in size.

It is preferable to provide hoppers for storing the thermoplastic resin at the upper portions of the two injection cylinders, because the thermoplastic resin can be easily supplied. Further, it is preferable that the respective injection cylinders and the cavities are connected via the sprue and the runner because the plasticized thermoplastic resin can be smoothly injected into the cavities.

In the injection molding method of the present invention, for example, after different thermoplastic resins accumulated in respective hoppers are plasticized by an injection cylinder, the plasticized thermoplastic resin is injected into a cavity inside a mold. Fire towards each and pass through each sprue and runner,
This is a method in which the plasticized thermoplastic resin joins immediately before the gate of the split mold to form a two-layer state, and fills and molds the cavity while maintaining this state.

In the injection molding method of the present invention, “before the gate” means that the distance to reach the gate is 0 to 15 cm. When the plasticized thermoplastic resin joins at a position far away from the gate of the split mold, immediately after joining, 2
Even if a two-layer state is formed, it becomes difficult to maintain the two-layer state when the plasticized thermoplastic resin moves a long distance to the gate.

The shape of the cavity in the mold is not particularly limited as long as the space is sheet-like, and the cavity may have a shape such as a rib or a boss on any surface. And a backside layer) having the same thickness can be easily obtained. If the gate is located on the center line (on the parting line) in the thickness direction of the cavity cross section, the obtained layered product will be in a complete two-layer state, and the two layers will have the same thickness. Preferred for. It is more preferable that the two different thermoplastic resins that have joined each other across the parting line form a two-layer state because the thickness of the two layers becomes more equal in a more complete two-layer state.

In the injection molding method of the present invention, two layers having the same thickness means that the ratio of the thickness of the front layer to the back layer (surface layer / back layer) is 0.95 to 1.05. Is in the range. More equally, it is in the range of 0.99 to 1.01. The thermoplastic resin is not particularly limited, and for example, at least one selected from an ABS resin (acrylonitrile-butadiene-styrene resin), a PC resin (polycarbonate), an acrylic resin, a vinyl chloride resin, and the like is used. The thermoplastic resins used in the injection molding method of the present invention are different thermoplastic resins. The different thermoplastic resin means that at least one of the components constituting the thermoplastic resin is different. For example, the types of the resin components constituting the thermoplastic resin and / or the amounts thereof may be different. The types and / or the amounts of additives such as colorants contained in the resin may be different.

Preferably, the different thermoplastics are injected simultaneously into the cavity. In the injection molding method of the present invention, simultaneous injection means that the time difference between the first injection and the subsequent injection of the two injection cylinders is 0 to 0.
It means 0.5 seconds. If they are not injected at the same time, a layered product in which two layers have the same thickness in a complete two-layer state may not be obtained.

The different thermoplastic resins have the same viscosity at the time of injection, and are in the range of 150 to 1000 Pa · s.
The viscosity of different thermoplastic resins at the time of injection is 300-500P
It is preferable to be within the range of a · s. If the viscosities are not equal, or even if the viscosities are equal, if the viscosity is less than 150 Pa.s or more than 1000 Pa.s, the plasticized different thermoplastic resin flows in the cavity in a non-uniform and complicated manner. The layered product obtained is not a complete two-layer state, and a layered product having poor appearance in which the resin of the other layer partially appears on the surface of one layer or the thickness of the two layers is not equal Sometimes.

In the injection molding method of the present invention, the viscosities of different thermoplastic resins at the time of injection are defined as the thermoplastic resin measured at the tip of the injection cylinder (the part where the injection cylinder and the mold are in contact). Is the viscosity. The term “equal in viscosity” means that the value obtained by dividing the viscosity of one thermoplastic resin by the viscosity of the other thermoplastic resin is in the range of 0.9 to 1.1.

It is preferable that the injection speeds at which different thermoplastic resins are injected into the cavity from the two injection cylinders are equal to each other. If the injection speed is within the range of 10 to 30 cm ³ / sec, the plasticized thermoplastic resin will be more uniform in the cavity. In order to flow smoothly, the obtained layered product is more preferably in a more complete two-layer state, and the two layers are more equal in thickness. The injection speeds are the same,
Most preferably, it is in the range of 15 to 30 cm ³ / sec. 10cm ³ / sec even if the injection speed is the same
If it is less than c and more than 30 cm ³ / sec, a layered molded article having poor appearance in which the resin of the other layer partially appears on the surface of one layer.

In the injection molding method of the present invention, the injection speed of different thermoplastic resins means the volume of the thermoplastic resin measured at the tip of the injection cylinder (the part where the injection cylinder and the mold are in contact). Speed. The term “equal” means that the value obtained by dividing the injection speed of one thermoplastic resin by the injection speed of the other thermoplastic resin is in the range of 0.9 to 1.1.

[0018]

According to the injection molding method of the present invention, different thermoplastic resins have the same viscosity at the time of injection,
The characteristic of being within the range of s allows the plasticized thermoplastic resin to flow uniformly when flowing in the cavity, so that the obtained layered product is in a complete two-layer state, A layered article having the same thickness of the two layers is obtained.

The injection speeds at which different thermoplastic resins are injected from two injection cylinders into the cavity are equal,
When it is within the range of 10 to 30 cm ³ / sec, the plasticized thermoplastic resin flows more evenly in the cavity, so that the obtained layered product is in a more complete two-layer state, and thus has two layers. Can be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the injection molding method of the present invention will be described below with reference to the drawings. The following examples do not limit the injection molding method of the present invention. In one example of the injection molding method of the present invention, injection molding is performed using a [molding machine] equipped with the following [die], and [layered molded article]
Is obtained. [Molding Machine] As shown in FIG.
An injection unit A14 and an injection unit B15 are provided.

The mold 13 has a fixed mold 1 and a movable mold 2. In the mold-clamped state, the fixed mold 1 and the movable mold 2 are in close contact with each other with only a slight clearance at the side surface. The upper and lower opposing surfaces of the fixed mold 1 and the movable mold 2 are spaced from each other, and the gap is a cavity 3 serving as a molding space, and has a shape of a layered product.

The injection unit A14 has an injection cylinder A
16 and a hopper A18. The injection unit B15 includes an injection cylinder B17 and a hopper B19. The injection cylinder A16 and the injection cylinder B17 are connected to the cavity 3. The injection cylinder A16 and the injection cylinder B17 are installed at a certain angle. It is in contact with 13. The contact 2
0 does not coincide with the contact 21. [Mold] As shown in FIG. 1, a mold 13 includes a fixed mold 1 and a movable mold 2, and has a cavity 3 serving as a molding space therein.

The fixed die 1 has a fixed mounting plate 8,
The movable die 2 includes a movable mounting plate 9 and an ejector plate 1.
0 and a spacer block 11. The ejector plate 10 and the spacer block 11
It is used to take out a layered product obtained by injection molding from the fixed mold 1 and the movable mold 2. The injection cylinder A16 is in contact with the mold 13 at the contact point 20, and the injection cylinder B17 is similarly contacted with the contact point 21.
In contact with the mold 13.

The injection cylinder A16 and the cavity 3 are connected via a sprue A4 and a runner A6. Similarly, the injection cylinder B17 and the cavity 3
Are connected via a sprue B5 and a runner B7. The runner A6 and the runner B7 connect the sprue and the gate, and form a single tube near the tip near the cavity 3. This one tube is the thermoplastic resin merging position 22 and is disposed immediately before the gate 23 shown in FIG. The parting line 12
It is a boundary between different thermoplastic resins injected from the injection cylinder A16 and the injection cylinder B17. [Layered Molded Product] FIG. 3 is a view showing the process of filling the cavity 3 with a different thermoplastic resin in more detail. The different thermoplastic resins injected from the injection cylinder A16 and the injection cylinder B17 respectively pass through separate sprues (4, 5) and runners (6, 7) and merge at the thermoplastic resin merging position 22 to form a cavity from the gate 23. 3 is filled. The thermoplastic resin merging position 22 is disposed immediately before the gate 23, and the position of the gate is disposed on the center line in the thickness direction of the cross section of the cavity 3 (on the parting line 12). FIG. 3 shows a state in which the layered product is in the cavity 3 after the molding, and the obtained layered product is composed of the thermoplastic resin A layer 24 and the thermoplastic resin B layer 25.

-Examples 1a to 1c- In FIGS. 1, 2 and 3, the following operations are sequentially performed. The thermoplastic resin A is supplied to a hopper A18, and the thermoplastic resin B is supplied to a hopper B19. After the thermoplastic resin A is plasticized using the injection cylinder A16 and the thermoplastic resin B is plasticized using the injection cylinder B17, each resin is injected toward the cavity 3. At the time of injection, the thermoplastic resin A
And the thermoplastic resin B have the same viscosity,
The operation is performed so as to be 1000 Pa · s.

The injected thermoplastic resin A and thermoplastic resin B were sprue A4 and sprue B5, respectively.
Pass through the runner A6 and the runner B7 and merge at the thermoplastic resin merging position 22. The thermoplastic resin A and the thermoplastic resin B remain in the gate 23 while maintaining the two-layer state.
Further, the cavity 3 is filled and molded to obtain a layered molded product composed of the thermoplastic resin A layer 24 and the thermoplastic resin B layer 25.

In the above, as the injection molding machine shown in FIG. 2, an injection molding machine (TP80 manufactured by Toyo Kikai Metal Co., Ltd.)
G), a white ABS resin (Toyolac 500, manufactured by Toray Co., Ltd.) was used as the thermoplastic resin A, and a black ABS resin (Toyolac 500, manufactured by Toray Co., Ltd.) was used as the thermoplastic resin B. In addition, the shape of the cavity of the injection molding machine is an open plate with a thickness of 3 mm and a size of 50 mm in width.
× length 60 mm, molding was performed while maintaining the mold temperature at 80 ° C. Also, the distance between the thermoplastic resin merging position 22 and the gate 23 is 3 cm, the measuring points of the injection speed of the thermoplastic resin A and the thermoplastic resin B are both at the tip of the cylinder, and both injection speeds are 5.0 cm. ³ / sec
Met. The measurement points of the viscosities of the thermoplastic resin A and the thermoplastic resin B were both at the tip of the cylinder.

The temperatures and viscosities of the thermoplastic resin A and the thermoplastic resin B shown in Table 1 (the thermoplastic resin A
And the temperature and viscosity of the thermoplastic resin B were the same, and the mixture was injected from an injection cylinder and molded. As a result, a layered molded product having the thickness of the thermoplastic resin A and the thickness of the thermoplastic resin B shown in Table 2 was obtained. Each of the obtained layered articles is in a perfect two-layer state, and the thicknesses of the two layers constituting the layered article are equal as shown in Table 2.

Comparative Examples 1a to 1b In the same manner as in Examples 1a to 1c, the temperatures and viscosities of the thermoplastic resin A and the thermoplastic resin B shown in Table 1 (the thermoplastic resin A in each comparative example) As a result, a layered molded product having the thickness of the thermoplastic resin A and the thickness of the thermoplastic resin B shown in Table 2 was obtained. None of the obtained layered products is partially in a two-layer state, and the thicknesses of the two layers constituting the layered product are not equal as shown in Table 2.

[0030]

[Table 1]

[0031]

[Table 2]

The results in Table 2 are summarized and the thickness ratio of the thickness of the thermoplastic resin A to the thickness of the thermoplastic resin B (the thickness of the thermoplastic resin A / the thickness of the thermoplastic resin B) and the thickness of the thermoplastic resin FIG. 4 shows the relationship between A and the viscosity of the thermoplastic resin B at the time of injection.
The wall thickness ratio becomes 1.0 when the wall thickness is the same. As is clear from FIG. 4, in order to equalize the thicknesses of the two layers constituting the layered molded product, at the time of injection, the viscosities of the thermoplastic resin A and the thermoplastic resin B injected from the injection cylinder are both equal. Thus, it is understood that the pressure needs to be in the range of 150 to 1000 Pa · s. FIG. 4 shows that the viscosity of the thermoplastic resin at the time of injection is preferably 300 to 500 Pa · s.

The viscosity of the thermoplastic resin upon injection is 150 Pa
・ If less than s or more than 1000 Pa · s, 1000
At a viscosity exceeding Pa · s, the thickness ratio becomes approximately 1.0, but the plasticized thermoplastic resin flows in the cavity in an uneven and complicated manner. A layered molded product having poor appearance in which the resin of the layer partially appears is obtained. If the viscosity is less than 150 Pa · s, the thickness ratios will not be equal.

-Examples 2a to 2c- After the operations of Examples 1a to 1c were performed in order, the thermoplastic resin A and the thermoplastic resin B were further injected into an injection cylinder while satisfying the following conditions. The operation is performed so that the injection speeds of the injection from the injection cylinder A16 and the injection cylinder B17 into the cavity 3 are equal to each other, and 10 to 30 cm ³ / sec.

In the above, as the injection molding machine shown in FIG. 2, an injection molding machine (TP80 manufactured by Toyo Kikai Metal Co., Ltd.)
G), a white ABS resin (Toyolac 500, manufactured by Toray Co., Ltd.) was used as the thermoplastic resin A, and a black ABS resin (Toyolac 500, manufactured by Toray Co., Ltd.) was used as the thermoplastic resin B. In addition, the shape of the cavity of the injection molding machine is an open plate with a thickness of 3 mm and a size of 50 mm in width.
× length 60 mm, molding was performed while maintaining the mold temperature at 80 ° C. The distance between the thermoplastic resin merging position 22 and the gate 23 was 3 cm. The measurement points of the injection speeds of the thermoplastic resin A and the thermoplastic resin B are both at the tip of the cylinder, and the measurement points of the viscosity are the same.

In each of the examples, the temperature at the time of injection of the thermoplastic resin A and the thermoplastic resin B was 220 ° C., and the viscosity was 300 Pa · s. The injection speed shown in Table 3 (the injection speed of the thermoplastic resin A and the injection speed of the thermoplastic resin B in each example is the same value), the thermoplastic resin A and the thermoplastic resin B
As a result, a layered molded product having the thickness of the thermoplastic resin A and the thickness of the thermoplastic resin B shown in Table 4 was obtained.
Each of the obtained layered products is in a complete two-layer state,
Moreover, the thicknesses of the two layers constituting the layered product are equal as shown in Table 4, and are equal to or greater than the results shown in Table 2.

Comparative Examples 2a to 2c In the same manner as in Examples 2a to 2c, the injection speeds shown in Table 3 (in each comparative example, the injection speeds of thermoplastic resin A and thermoplastic resin B are the same. As a result of injection and molding of the thermoplastic resin A and the thermoplastic resin B in the above), a layered molded product having the thickness of the thermoplastic resin A and the thickness of the thermoplastic resin B shown in Table 4 was obtained. In each of the obtained layered articles, the thicknesses of the two layers constituting the layered article are not equal as shown in Table 4.

[0038]

[Table 3]

[0039]

[Table 4]

The results shown in Table 4 are summarized, and the thickness ratio between the thickness of the thermoplastic resin A and the thickness of the thermoplastic resin B [the thickness of the thermoplastic resin A / the thickness of the thermoplastic resin B] and the thickness of the thermoplastic resin The relationship between the injection speed of A and the thermoplastic resin B is shown in FIG. The wall thickness ratio becomes 1.0 when the wall thickness is the same. As is apparent from FIG. 5, in order to make the thicknesses of the two layers constituting the layered product equal, the viscosities of the thermoplastic resin A and the thermoplastic resin B injected from the injection cylinder are both equal. It can be seen that the injection speed of the thermoplastic resin A and the injection speed of the thermoplastic resin B need to be equal to each other so as to be in the range of 10 to 30 cm ³ / sec. FIG. 5 shows that the injection speed is preferably in the range of 15 to 30 cm ³ / sec.

If the injection speed is less than 10 cm ³ / sec or exceeds 30 cm ³ / sec, the thickness ratio will be out of 1.0.

[0042]

The injection molding method of the present invention uses a split mold composed of a fixed mold and a movable mold, and separates different thermoplastic resins from two injection cylinders connected to a cavity in the mold. Injection molding method for obtaining a layered product composed of a surface layer and a back surface layer by injecting into a cavity, joining different thermoplastic resins immediately before the gate of the split mold, filling the cavity, and molding. In the above, since the viscosities of different thermoplastic resins at the time of injection are both equal and within a range of 150 to 1000 Pa · s, a layered product having two layers having the same thickness in a complete two-layer state can be easily prepared. Can be obtained.

The injection speed for injecting different thermoplastic resins into the cavity is the same, and 10 to 30 cm ³ / sec.
Within this range, it is possible to easily obtain a layered molded product in which the two layers have the same thickness in a more complete two-layer state.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of a molding machine used in an embodiment of the present invention.

FIG. 2 is a schematic view illustrating an example of a mold used in an embodiment of the present invention.

FIG. 3 is a schematic view showing a step of filling a different thermoplastic resin into a cavity in an embodiment of the present invention in more detail, and showing an example of a layered product obtained.

FIG. 4 shows the relationship between the viscosity of the thermoplastic resin A and the thermoplastic resin B at the time of injection and the thickness ratio of the obtained layered molded product in Examples 1a to 1c and Comparative Examples 1a to 1b. FIG.

FIG. 5 shows the relationship between the injection speed of the thermoplastic resin A and the thermoplastic resin B and the thickness ratio of the obtained layered molded product in Examples 2a to 2c and Comparative Examples 2a to 2c. FIG.

[Description of Signs] 1 Fixed type 2 Movable type 3 Cavity 4 Sprue A 5 Sprue B 6 Runner A 7 Runner B 8 Fixed type mounting plate 9 Movable type mounting plate 10 Ejector plate 11 Spacer block 12 Parting line 13 Mold 14 Injection Unit A 15 Injection unit B 16 Injection cylinder A 17 Injection cylinder B 18 Hopper A 19 Hopper B 20 Contact point of injection cylinder A 21 Contact point of injection cylinder B 22 Thermoplastic resin joining position 23 Gate 24 Thermoplastic resin A layer 25 Heat Plastic resin B layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-278070 (JP, A) JP-A-5-192961 (JP, A) JP-A-6-190860 (JP, A) JP-A-63-1988 139719 (JP, A) JP-A-62-71619 (JP, A) JP-A-61-22919 (JP, A) JP-A-2-253910 (JP, A) JP-A-3-207625 (JP, A) JP-A-53-14759 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. A split mold composed of a fixed mold and a movable mold, wherein different thermoplastic resins are injected into said cavity from two injection cylinders connected to the cavity inside said mold, and said different heat is injected into said cavity. In the injection molding method for obtaining a layered product composed of a surface layer and a back surface layer by joining a plastic resin immediately before the gate of the split mold and filling and molding the cavity, the different thermoplastic resin is used. An injection molding method, wherein the viscosities of the resins at the time of injection are both equal and within the range of 150 to 1000 Pa · s. 2. The injection speed of injecting the different thermoplastic resin into the cavity is equal to each other, and is 10 to 30 cm ^3.
The injection molding method according to claim 1, wherein the ratio is within the range of / sec.