JP6071804B2 - Injection mold - Google Patents

Description

  The present invention relates to an injection mold used for two-color molding of resin molded products, in-mold coating, and the like.

  Conventionally, resin molded products obtained by injection molding of a thermoplastic resin have been used in various fields. The resin molded product is cooled by injecting and filling molten resin into a cavity formed between the fixed mold and the movable mold in a state where the injection mold including the fixed mold and the movable mold is completely clamped. It is formed into a predetermined shape by solidifying.

  Here, in the resin molded product, the material may be partially different depending on the function, application, and the like. In this case, there is a method in which molded products made of different resins are molded separately and then joined by adhesion, welding, or the like. However, if moldings of different materials are separately molded and then joined, it is not efficient due to an increase in production processes and production facilities, and the interface strength of the joining surface is also difficult. Therefore, in order to improve productivity, adhesiveness, etc., so-called two-color molding, in which different types of materials are injected in stages in the same injection mold, thereby integrally molding resin molded products with partially different materials. Technology is being developed.

  In addition, resin molded products are often coated with a coating or a coating on the surface in order to impart or improve various physical properties such as weather resistance and surface hardness, or to improve design properties. In this case, generally, after a resin molded product is injection-molded, a coating film or a coating film is formed by spraying or roll coating. However, if a coating film or the like is formed after injection molding of a resin molded product, it is also inferior in productivity. In view of this, an in-mold coating molding method (in-mold coating) has been developed in which injection molding and coating or coating of a resin molded product are continuously performed in an injection molding die as in the above two-color molding.

As a specific method of these two-color molding or in-mold coating, as shown in FIG. 3A, a cavity (in a state where the injection mold 100 including the fixed mold 101 and the movable mold 102 is completely clamped ( After the resin W ₀ in a molten state is injected and filled into the primary cavity 110, as shown in FIG. 3B, a resin molded product is injection molded, and then the movable mold 102 is slightly placed as shown in FIG. As shown in FIG. 3D, a different material (different thermoplastic resin, coating material, or paint) W ₁ is injected into the newly formed space (secondary cavity) 111 and cooled and solidified. in, it can be coated or laminated integrally with different materials W ₁ to the resin molded article. 3, reference numeral 103 is a nozzle for injecting molten resin, reference numeral 104 is a runner that connects the nozzle 103 and the cavity 110, and reference numeral 105 is a nozzle for supplying different materials.

However, the conventional two-color molding and in-mold coating have the following problems. That is, when the movable mold 102 is slightly opened after the resin molded product is injection-molded and the different material W ₁ is injected, if the sealing performance between the fixed mold 101 and the movable mold 102 is low, as shown in FIG. In addition, the dissimilar material W ₁ may leak out of the injection mold 100 from the gap between the mold-matching surfaces of the fixed mold 101 and the movable mold 102. This reduces the productivity and quality of the resin molded product. Moreover, when the resin molded product is injection molded, the resin W ₀ is solidified and contracted, so that a slight gap is easily formed in the cavity 110. Also in this respect, the dissimilar material W ₁ is formed between the fixed mold 101 and the movable mold 102. The problem of leaking out of the mold matching surface to the outside of the injection mold 100 increases.

  In order to solve this problem, it is conceivable to design the mold-mating surfaces of the fixed mold and the movable mold with high accuracy and to precisely control the mold temperature. However, there is a limit to the accuracy of the mold-matching surfaces of the fixed mold and the movable mold. In addition, there is a limit to precise control of the mold temperature, and this alone does not prevent leakage reliably.

  Then, the following patent document 1 and the patent document 2 are proposed as a metal mold | die for in-mold coating which solves such a problem. In Patent Literature 1, auxiliary cavities (peripheral cavities) extending in the sliding direction of the movable mold are continuously formed from around the cavity formed in a state where the mold is completely clamped. In this way, an auxiliary cavity is provided around the cavity, and the resin that is solidified in the auxiliary cavity enhances the sealing performance of the mold-matching surface between the fixed mold and the movable mold, thereby preventing paint leakage. . The resin filled in the auxiliary cavity is also solidified and shrunk. However, since the thickness (width) of the auxiliary cavity is as small as 0.1 to 2 mm, even if a gap is generated in the auxiliary cavity due to the solidified shrinkage, the thickness thereof is reduced. It is said that there is no paint leakage because it is very small. In addition, since the thickness of the auxiliary cavity is small as described above, a heater is provided in the vicinity of the auxiliary cavity so that the molten resin is accurately filled in the auxiliary cavity, and the fluidity of the molten resin is further increased, and the filling pressure (injection) Pressure) is higher than general injection molding.

  On the other hand, in Patent Document 2, in order to increase the degree of freedom of the shape of the resin molded product, it is orthogonal to the sliding direction of the movable mold from the periphery of a specially shaped cavity formed in a state where the mold is completely clamped. Auxiliary cavities are continuously formed in the direction.

JP 2001-138334 A JP 2006-264066 A

  In Patent Document 1, providing an auxiliary cavity (peripheral cavity) continuous in the movable sliding direction is effective to some extent for paint leakage. However, it is unavoidable that a gap due to the solidification shrinkage of the resin occurs in the auxiliary cavity. In order to solve this problem, in Patent Document 1, the thickness of the auxiliary cavity is minimized. However, if a heater is purposely provided or the injection pressure is made higher than usual, the equipment cost and running cost are high. In addition, since the gap itself is unavoidable in the auxiliary cavity, the paint leakage cannot be reliably prevented when the paint having a low viscosity is used.

  On the other hand, in Patent Document 2, an auxiliary cavity is provided in order to increase the degree of freedom of the shape of the resin molded product, and the auxiliary cavity extends in a direction orthogonal to the sliding direction of the movable mold. Leakage depends on the mold-matching surface of the fixed mold and the movable mold as in the conventional mold. Therefore, Patent Document 2 does not pay special attention to the sealing properties of the mold-matching surfaces of the fixed mold and the movable mold, and the problem of paint leakage from the mold-matching surfaces of the fixed mold and the movable mold is not solved. .

  Therefore, the present invention solves such problems, and its purpose is to provide an injection mold that can reliably prevent leakage of different materials while reducing costs when performing two-color molding or in-mold coating. It is to provide.

  As a means for this, the present invention includes a fixed mold and a movable mold that can slide relative to the fixed mold, and the fixed mold and the movable mold in a state where the fixed mold and the movable mold are completely clamped. After the resin molded product is injection molded in the cavity formed between the two, the movable mold is slightly opened, and different materials are injected into the newly formed space to integrate with the resin molded product. In the injection mold, a peripheral cavity portion that continues from the periphery of the cavity in the sliding direction of the movable die and a flange cavity that continues outward from the tip of the peripheral cavity portion And a folding cavity portion that is continuous from the tip of the flange cavity portion in the direction opposite to the extending direction of the peripheral cavity portion.

  In the present invention, by providing the peripheral cavity portion continuous in the movable sliding direction around the cavity, it is possible to prevent leakage of different materials to some extent in the first stage. However, since a gap due to the solidification shrinkage of the resin is not avoided in the peripheral surface cavity portion, the effect of preventing the leakage of different materials in the peripheral surface cavity portion is only auxiliary.

  Therefore, in the present invention, the flange cavity portion and the folded cavity portion are further provided continuously from the peripheral cavity portion. According to this, since it becomes a concave shape (upward U shape) in which a recess is formed between the peripheral cavity portion and the folded cavity portion, even if a different material leaks through the clearance of the peripheral cavity portion. Since the dissimilar material stays on the resin solidified at the flange cavity portion while being blocked by the resin solidified at the folded cavity portion, leakage of the dissimilar material can be reliably prevented in the second stage.

  Furthermore, although the detailed principle will be described later, by making the sealing cavity into such a concave shape, the shrinkage force acts in the direction in which the solidified resin comes into close contact with the mold in the folded cavity portion as the resin solidifies and contracts. . As a result, the sealing performance at the mold-matching surface of the fixed mold and the movable mold is greatly increased, and even if a large amount of dissimilar material is leaked, the leakage of the dissimilar material is more reliably prevented in the third stage. Can do.

  As described above, according to the present invention, it is not always necessary to extremely reduce the thickness of the sealing cavity because it is possible to reliably prevent the leakage of different materials by simply forming the sealing cavity having a predetermined shape. Therefore, it is not necessary to provide a + α device, such as a heater, and it is not necessary to increase the filling pressure of the molten resin more than necessary, so that it is possible to avoid a significant increase in equipment cost and running cost.

It is sectional drawing which shows the shaping | molding process of the injection mold of this invention. It is a principal part expanded sectional view of FIG.1 (b). It is sectional drawing which shows the shaping | molding process of the injection mold of a prior art.

  The injection mold according to the present invention is a two-color molding method in which a resin molded product having a predetermined shape is injection-molded, then the mold is opened slightly, and different thermoplastic resins are injected into a new space and laminated, or a resin molded product. It is suitable for a coating that improves weather resistance, surface hardness, etc., or that imparts new physical properties, or an in-mold coating that is coated with a coating that improves the design by coating the surface. In the present invention, the second-color thermoplastic resin, the film-forming material, the paint for forming the coating film, and the like that are injection-molded on the back floor are collectively referred to as different materials. Based on this, typical embodiments of the present invention will be described with reference to the drawings as appropriate.

As shown in FIG. 1, the injection mold 1 includes a fixed mold 10 and a movable mold 11 that can be slid relative to the fixed mold 10 in a direction in which it is separated from and contacting the fixed mold 10. In addition, on the opposing surfaces of the fixed mold 10 and the movable mold 11, a cavity 20 having a predetermined shape and a continuous sealing cavity 21 are formed in a state where the injection mold 1 is completely clamped. It has become. In the present embodiment, the nozzle 12 for injecting the molten resin W ₀ is provided in the fixed mold 10, and the nozzle 12 and the cavity 20 communicate with each other through the runner 13. On the other hand, the movable mold 11 is provided with a nozzle 14 for injecting or injecting the different material W ₁ into the cavity 20.

The cavity 20 is a space that is inherently necessary for injection molding of a resin molded product. FIG. 1 shows a shape assuming that a plate-shaped resin molded product is molded. Various shapes are designed according to the shape of the molded product. On the other hand, the sealing cavity 21 is a space which is finally unnecessary as a molded product, but is an auxiliary space necessary for preventing the leakage of the different material W ₁ and its shape is important.

  In the present embodiment, the fixed mold 10 has a substantially convex shape, whereas the movable mold 11 has a substantially reverse concave shape. When the injection mold 1 is clamped, the movable mold 11 becomes the fixed mold 10. The mold is matched to cover the protrusion. In addition, the sealing cavity 21 includes a peripheral cavity 21a continuous from the periphery of the cavity 20 toward the fixed mold 10 in the sliding direction of the movable mold 11, and outward (sliding) from the tip of the peripheral cavity 21a. A flange cavity portion 21b continuous in a direction perpendicular to the direction), and a folded cavity portion 21c continuous from the tip of the flange cavity portion 21b toward the movable mold 11 in the direction opposite to the extending direction of the peripheral cavity portion 21a. It is made up of.

The thickness of the peripheral cavity portion 21a is not particularly limited, and in extreme terms, the thickness can be made larger than that of the cavity 20. However, in this case, the material cost is unnecessarily increased, and the resin solidified in the sealing cavity 21 is finally cut out from the resin molded product, so that the labor for the cutting operation increases. Accordingly, the thickness of the peripheral cavity portion 21a is preferably smaller than the thickness of the cavity 20, and more preferably as small as possible. However, if the thickness of the peripheral cavity portion 21a is extremely small, the fluidity of the resin W ₀ is lowered, and a special device or control is required to accurately fill the resin W ₀ . Therefore, the thickness of the peripheral cavity portion 21a is most preferably set to a minimum thickness that allows the resin W ₀ to flow accurately under normal injection molding conditions. Further, the length of the peripheral cavity portion 21a is not particularly limited.

The thickness of the flange cavity portion 21b is preferably the same as the thickness of the peripheral cavity portion 21a. This is because, if the thickness of the flange cavity portion 21b is different from the thickness of the peripheral cavity portion 21a, the fluidity of the resin W ₀ in the flange cavity portion 21b may be extremely reduced or the material cost may be wasted. On the other hand, the length of the flange cavity portion 21 b is not particularly limited, and the upper limit thereof depends on the width of the peripheral edge portion of the fixed mold 10. As will be described later, in order to enhance the storage effect of the different material W ₁ leaking through the peripheral cavity portion 21a, it is desirable to make the length of the flange cavity portion 21b as large as possible. However, in order to prevent leakage of the dissimilar material W ₁ in the present invention, the sealing effect at the folded cavity portion 21c is the main, so that the length of the flange cavity portion 21b is preferably relatively small in order to reduce the material cost. However, in order to ensure the sealing effect in the folded cavity portion 21c, it is preferable that the length of the flange cavity portion 21b is larger than the thickness of the folded cavity portion 21c.

The thickness of the folded cavity portion 21c is also preferably set to the same thickness as the flange cavity portion 21b and the peripheral surface cavity portion 21a for the same reason as the flange cavity portion 21b. On the other hand, the length of the folded cavity portion 21c is not particularly limited, but the length of the folded cavity portion 21c should be made as large as possible in order to enhance the storage effect of the dissimilar material W ₁ leaking through the peripheral cavity portion 21a. desirable. However, since the main effect of preventing leakage of the dissimilar material W ₁ in the present invention is the sealing effect in the folded cavity portion 21c, the length of the folded cavity portion 21c is preferably relatively small in order to reduce the material cost. However, in order to ensure a sealing function, at least the length of the resin W ₀ solidified in the folded cavity portion 21c when the movable mold 11 is slightly opened is in contact with the movable mold 11. That is, the length of the folded cavity portion 21 c> the fine opening amount of the movable mold 11 is set. Moreover, in order to ensure a reliable sealing property, it is preferable to make it longer than the flange cavity part 21b.

In summary, the relationship between the thickness and length of each part in the sealing cavity 21 is preferably as follows.
Thickness: peripheral cavity 21a = flange cavity 21b = folded cavity 21c
Length: peripheral cavity portion 21a> folded cavity portion 21c> flange cavity portion 21b
The length of the flange cavity portion 21b> the thickness of the folded cavity portion 21c However, even if the above relationship is slightly disrupted, the effects of the present invention can be obtained to some extent.

Next, the function of the two-color molding or in-mold coating using the injection mold 1 will be described. First, as shown in FIG. 1A, the injection mold 1 is completely clamped for injection molding of a resin molded product. Thereby, the cavity 20 and the sealing cavity 21 into which the resin W ₀ is injected and filled are defined along the opposing surfaces of the fixed mold 10 and the movable mold 11. In this state, as shown in FIG. 1B, molten resin W ₀ is injected from the nozzle 12 through the runner 13 into the cavity 20. As a result, the resin W ₀ also flows into the sealing cavity 21 communicating with the cavity 20. Then, when sufficiently filled with the resin W ₀ into the cavity 20 and sealing cavity 21, to solidify the resin W ₀ holds it shape. As a result, a resin molded product having a predetermined shape is formed in the cavity 20, and a solidified resin for sealing is formed in the sealing cavity 21.

Next, the movable mold 11 is slightly retracted to slightly open the injection mold 1. Thereby, as shown in FIG. 1C, a new space 22 for injecting the different material W ₁ is formed between the resin W ₀ (resin molded product) solidified in the cavity 20 and the movable mold 11. The In this sense, the cavity 20 can be referred to as a “primary cavity”, and the new space 22 formed by slightly opening the movable mold 11 can be referred to as a “secondary cavity”. Therefore, in the following, the new space 22 is referred to as a “secondary cavity”.

Then, by filling or injecting the different material W ₁ from the nozzle 14 into the secondary cavity 22 and solidifying it, as shown in FIG. 1D, the different material W ₁ is integrally laminated or coated on the resin molded product. can do. At this time, a slight gap may occur in the peripheral cavity portion 21a as the resin W ₀ solidifies and shrinks. However, even if the dissimilar material W ₁ leaks through the gap, the flange 11 is slightly opened as the movable mold 11 is opened. Since a new space is also formed on the cavity portion 21b, the leaked dissimilar material W ₁ is stored in the storage space 23 on the flange cavity portion 21b while being blocked by the resin W ₀ of the folded cavity portion 21c. Thus, leakage from the injection mold 1 is prevented. Moreover, since the resin is solidly sealed by the solidified resin W ₀ in the folded cavity portion 21c, even if a large amount of the different material W ₁ leaks, the leakage of the different material W ₁ is reliably prevented in the folded cavity portion 21c. .

The principle of improving the sealing performance due to the presence of the folded cavity portion 21c will be described in detail. First, immediately after injecting a sufficient amount of molten resin W ₀ into the cavity 20 and the sealing cavity 21, the resin W ₀ is filled to every corner in the sealing cavity 21 as shown in FIG. There are no gaps. However, the molten resin W ₀ has a property of shrinking when solidified. This solidification shrinkage acts in all directions up, down, left and right. Therefore, as shown in FIG. 2B, in the cavity 20, a slight gap may be formed above and around the resin W _{0 due} to solidification shrinkage. Although the resin W ₀ contracts also in the peripheral cavity portion 21a, the movable mold 11 is contracted by contracting in the cavity 20 side and inward (fixed mold 10 side) due to the influence of the resin W ₀ in the cavity 20. A slight gap may be formed on the side and the lower side of the glue. Similarly, in the flange cavity portion 21b, the resin W ₀ contracts while being pulled toward the cavity 20 side and inside (the fixed mold 10 side) in conjunction with the peripheral surface cavity portion 21a, so that a slight gap is generated below. obtain.

Further, in the folded cavity portion 21c, the resin W ₀ contracts while being pushed up to the cavity 20 side due to the influence of the flange cavity portion 21b, so that a slight gap can be formed not only below but also above. The most important point in the present invention, the flange cavity portion 21b that extends in a direction perpendicular to the sliding direction of the movable die 11, when the resin W ₀ of the flange cavity 21b is solidified shrinkage, As indicated by the arrow in FIG. 2B, the resin W ₀ in the folded cavity portion 21 c is solidified while being pulled in a direction in which the resin W ₀ is brought into close contact with the movable mold 11. This improves the sealability at the folded cavity 21c, the leakage of different materials W ₁ can be reliably prevented.

As mentioned above, although typical embodiment of this invention was described, it is not restricted to this, A various deformation | transformation is possible in the range which does not deviate from the summary of this invention. For example, the nozzle 12 and the runner 13 for the resin W ₀ can be provided not only in the fixed mold 10 but also in the movable mold 11. Further, the different material W ₁ can also be supplied from the nozzle 14 to the secondary cavity 22 via the runner.

  Further, the fixed mold 10 and the movable mold 11 are not limited to the relative positional relationship shown in FIG. 1, but may be turned upside down or installed so as to rotate 90 ° and slide left and right. In this case, each direction described in the above embodiment naturally varies depending on the relative positional relationship between the fixed mold 10 and the movable mold 11. Alternatively, the fixed mold 10 can be concave and the movable mold 11 can be convex.

DESCRIPTION OF SYMBOLS 1 Injection mold 10 Fixed mold 11 Movable mold 12.14 Nozzle 13 Runner 20 (Primary) cavity 21 Sealing cavity 21a Peripheral cavity part 21b Flange cavity part 21c Folding cavity part 22 Secondary cavity 100 Injection mold 101 Fixed Mold 102 Movable mold 110 Cavity W ₀ Resin W ₁ Dissimilar material

Claims (1)

A fixed mold and a movable mold that is slidable relative to the fixed mold, and the cavity is formed between the fixed mold and the movable mold in a state where the fixed mold and the movable mold are completely clamped. After injection molding the resin molded product, the movable mold is slightly opened, an injection mold for injecting a different material into the newly formed space and integrating with the resin molded product,
In the injection mold, a peripheral cavity portion that continues from the periphery of the cavity in the sliding direction of the movable die, a flange cavity portion that continues outward from the tip of the peripheral cavity portion, and the flange cavity have a seal cavity consisting of a folded cavity portion from the tip parts contiguous to the extending direction opposite of the circumferential surface cavity,
The injection mold, wherein the cavity and the sealing cavity communicate with each other in a state where the fixed mold and the movable mold are completely clamped.

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