JPH06312433A - Insert two-color molding method - Google Patents

Abstract

PURPOSE:To provide a method for two-color molding an insert in which adherence of second color resin to a surface of an insert component exposed as a product and generation of a product failure such as a deformation of the component can be prevented and durability of molds, etc., can be improved. CONSTITUTION:An insert component 10a having low rigidity parts 52, 53 is molded with first color resin, the component 10a is disposed in molds 21, 22, and second color resin is injected. The low rigidity parts 52, 53 of the component 10a are deformed by a pressure of the second color resin at the time of injecting the second color resin or a pressing force due to contact with the molds 21, 22 to bring surfaces exposed as the product into close contact with the molds 21, 22 and to prevent invasion of the second color resin between the exposed surface of the member 10a and the molds 21, 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insert two-color molding method, and more particularly, to forming a part having a low rigidity in an insert part and applying a pressure of the second color resin to a part having a low rigidity during insert molding with a second color resin. The present invention relates to an insert two-color molding method in which a portion to be exposed as a product is brought into close contact with a mold by preventing the second color resin from adhering to the portion to be exposed as a product.

[0002]

2. Description of the Related Art In insert-type two-color molding (hereinafter referred to as insert two-color molding), generally, an insert part is molded with a first color resin by a first mold, and the insert part is molded in a second mold. To form a cavity, and the second color resin is injected into the cavity to mold the final molded product.

By the way, for example, when molding an insert-molded member in which a normal resin and an elastomer are combined in order to improve the grip condition of the grip member, the feel thereof, etc., when the molding is performed by two-color molding, the insert-molded member 10 is ,
For example, as shown in FIG.
A case will be described in which 3 is projected, and an elastomer 91 having rubber elasticity is embedded in a part of the front and back sides.

That is, for the insert molding of the insert molding member 10 as described above, the following method has been tried. That is, first, a rod-shaped member 10a having a cross-sectional shape as shown in FIG. 6 is molded by a first mold by injection molding of a thermoplastic resin (first color resin) such as polypropylene. The rod-shaped member 10a has concave portions 11 and 12 on the front and back sides, and is provided with a relief 13 protruding from the bottom surface of the concave portion 11 on the front side. Then, as shown in FIG. 7, the rod-shaped member 10a is placed between the upper and lower molds 21 and 22 to define a cavity C between the second molds 21 and 22, and the olefin elastomer is placed in the cavity C. The (second color resin) was injected to obtain the insert-molded member 10 as a molded product.

[0005]

However, in the above-described molding method, the rod-shaped member 10a, especially the rod-shaped member 10a formed of a thermoplastic resin, cannot avoid thermal contraction after the molding, and this thermal contraction cannot be avoided. It is extremely difficult to maintain the dimensions of all the molded rod-shaped members 10a constant, which are greatly affected by the resin injection pressure, the injection speed, the resin temperature, and the like. Therefore, when the rod-shaped member 10a is placed in the molds 21 and 22, a gap may be formed between the surface of the rod-shaped member 10a to be adhered and the inner surfaces of the molds 21 and 22, for example, the surface of the relief 13. However, there is a problem that when the elastomer is injected, the elastomer penetrates into the gap to cover the relief 13 and impair the appearance as a product (cause a product defect).

On the other hand, as a measure against the above-mentioned problem, the rod-shaped member 10a is molded into a size slightly larger than the size of the stationary portion of the molds 21 and 22, and the rod-shaped member 10a is stationary and the mold 21,
When the mold 22 is closed, the rod-shaped member 10a is partially
Molds 21 and 22 by abutting and deforming
The method has been adopted to prevent the resin from invading by closely contacting with.

However, in the above method, the rod-shaped member 10a has a large rigidity, and the rod-shaped member 10a having a large rigidity has to be deformed, so that plastic deformation may occur and the deformation may remain. A new problem arises in that the shape of the insert-molded member 10, which is a product, is impaired and product defects are likely to occur. Further, in the above method, since the force acting on the molds 21 and 22 becomes excessive, the molds 21 and 22 are also deformed when molding is repeated, which makes it impossible to effectively prevent the intrusion of the elastomer. It turned out that also occurs. The latter problem is the mold 21,
The problem can be solved by adopting a structure in which a part of 2 is a detachable and replaceable structure, but the seam of the insert is the insert molding member 10.
It causes the problem that the product value is diminished.

The present invention has been made in view of the above problems, and is a product obtained by infiltration of the second color resin between the insert member and the mold without requiring strict precision in the molding size of the insert member. It is possible to prevent the occurrence of defects and
It is an object of the present invention to provide an insert two-color molding method in which a die has a high durability and the value of the product is not diminished.

[0009]

In order to achieve the above-mentioned object, the present invention provides an insert part with a first mold by a first mold.
After molding with a colored resin, this insert part is placed in a second mold and then the second colored resin is injected to form an integrated molded product with a part of the insert part exposed. In the method, the insert part, the central portion of the width direction center and the pair of side piece portions on both sides in the width direction are continuous by the low-rigidity portion, and the surface of the center portion in the width direction is more than the surface of the both side piece portions. And the back surface at the center in the width direction of the central portion is recessed inward from the back surfaces of the both side piece portions to be molded.
It was placed in a mold and deformed by the pressure when the second color resin was injected so that the entire outer peripheral surface of the insert part was brought into close contact with the second mold.

The insert two-color molding method is as follows.
The low-rigidity portion is formed by forming a recess on the front and back sides of the insert part and forming a groove on the back side recess, and by forming a recess on the front and back sides of the insert part and the pair of side pieces. The outer peripheral surfaces of the front and back sides of the portion can be chamfered to form an R.

Further, this insert two-color molding method can be configured such that the first color resin is polypropylene and the second color resin is an olefin elastomer, and further, the thickness t _{1 of the} low-rigidity portion in the front and back directions. And the widthwise thickness dimension w ₁ of the side piece portion may be set to one third or less of the front and back direction thickness dimension t ₂ of the side piece portion, respectively.

[0012]

According to the insert two-color molding method of the present invention,
The surface of the central part of the insert part is brought into contact with the mold by the mold closing of the second mold to be pressed to deform the low-rigidity portion and adhere to the mold, and the second part injected into the second mold The low-rigidity portion is deformed by the pressure of the colored resin, and the surface to be exposed as a product of the insert part, that is, the exposed surface, comes into close contact with the mold. Therefore, the second color resin does not enter between the exposed surface and the mold, and it is possible to prevent the occurrence of product defects. The low-rigidity portion is easily deformed, and the exposed surface is only brought into close contact with the pressure of the second color resin, so that the close contact force does not become excessive and deformation of the insert member and the mold is prevented. The mold durability is improved.

In the insert two-color molding method of the present invention, the low-rigidity portion is formed by the groove or chamfer, so that the structure can be simplified and the cost can be reduced.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an embodiment of an insert two-color molding method according to the present invention, FIG. 1 is an overall perspective view seen from the front side of the insert part, and FIG. 2 is an overall perspective seen from the back side of the insert part. FIG. 3 is a cross-sectional view of the insert part. The same parts as those of the above-mentioned prior art are designated by the same reference numerals, and a part of them is shown, and
Omit detailed explanation.

In this embodiment, first, the illustrated rod-shaped member 10a is molded by injection molding of a first color resin of a first mold (not shown), for example, injection molding of polypropylene which is a thermoplastic resin. The rod-shaped member 10a has concave portions 11 and 12 on both front and back surfaces, a relief (corresponding to a convex portion) 13 is formed on the bottom surface of the front concave portion 11, and groove portions 12a are formed on both bottom surfaces of the rear concave portion 12, respectively. Are formed. The relief 13 has a concave portion 1 at its tip (surface).
A predetermined dimension (for example, 2 mm as will be described later) is projected from the height of the upper surface of the side wall 1 of FIG.

That is, the rod-shaped member 10a has a central portion 51 having a rectangular cross section at the center in the width direction (left-right direction in FIG. 1).
Thin portions (low-rigidity portions) 52, 52 are formed by the groove portions 12a on both sides in the width direction, respectively, and the central portion 51 has side piece portions (low-rigidity portions) 53, 52 via the thin-walled portions 52, 52.
It is formed in a cross-sectional shape continuous with 53.

In the rod-shaped member 10a, the thickness t ₁ of the thin portion 52 in the front / back direction is 1/3 or less of the total dimension t ₂ of the side piece 53 in the front / back direction, and the width w of the side piece 53 in the width direction w.
₁ is formed to be ⅓ or less of the total dimension t ₂ of the side piece portion 53 in the front-back direction. Specifically, the rod-shaped member 10a has, for example, a widthwise total dimension w ₀ of 14 mm and a front-back direction total dimension t _2.
Is 8 mm, the thickness t of the thin portion 52 in the front-back direction is t
₁ and the widthwise dimension w ₁ of the side piece portion 53 are set to 2 mm, and the dimension t ₄ from the back surface to the relief 13 front surface is set to 12 mm.

Next, after the rod-shaped member 10a described above is placed between the second molds 21 and 22 as an insert part, the
The molds 21 and 22 are closed to define the cavity C (see FIG. 7).
reference). Then, this cavity C, that is, the concave portion 11,
A second color resin, for example, an olefinic elastomer is injected into the inside 12. At this time, the olefin elastomer is injected from the recess 12 side. At this time, it is preferable to provide a hot water passage in the thin portion 52. The thickness of the filled elastomer is 3 mm or less for the insert-molded member 10 having the above-described dimensions.

The side piece portion 53 has a widthwise thickness dimension w.
₁ is small and has low rigidity in the width direction, and similarly, thin portion 5
2 also has a small thickness dimension t ₁ in the front-back direction and low rigidity in the front-back direction. Therefore, when the elastomer is injected, each side piece 53
Is deformed outward by the pressure of the elastomer flowing into the groove portion 12a and adheres to the wall surfaces of the second molds 21 and 22, and the side piece portion 53
It is possible to prevent the elastomer from entering between the outer surface of the mold and the wall surfaces of the second molds 21 and 22.

Similarly, in the thin portion 52, the relief 1 of the central portion 51 is also caused by the pressure of the elastomer flowing into the recess 12.
3 is deformed so as to be displaced to the front side and comes into close contact with the wall surface of the second mold 21. That is, in the rod-shaped member 10 a, the pressure of the elastomer flowing into the recess 12 acts upward with the entire bottom surface of the recess 12 as the pressure receiving area, but the pressure of the resin flowing into the recess 11 is the pressure of the recess 11 excluding the relief 13. Only the bottom surface acts as the pressure receiving area downward, and the central portion 51 is displaced upward due to the force due to the difference in the pressure receiving area and is brought into close contact with the mold 21. Therefore, the elastomer injected later into the concave portion 11 is prevented from invading between the relief 13 and the mold 21, and the appearance defect as a product is generated, that is, the outer surface such as the surface of the relief 13 to be exposed. It is possible to prevent the occurrence of inconveniences such as the formation of an elastomer film.

The relief 13 only comes into close contact with the wall surfaces of the second molds 21 and 22 due to the pressure of the elastomer, and the adhesive force does not become excessive, and the side piece portion 53 also comes into close contact with the pressure of the elastomer. Since the proper adhesion can be maintained without passing, the rod-shaped member 10a and the molds 21 and 22 do not deform. Therefore, the deformation of the product can be prevented, the durability of the molds 21 and 22 can be improved, and the inconvenience that the seam is transferred to the product can be prevented without requiring the measures such as the nesting.

In particular, in this embodiment, when the mold is closed, the surface of the central portion 51, that is, the relief 13 is pressed against the die 21, and the central portion 51 elastically deforms the thin portion 52 having low rigidity. Displaces to the back side. Therefore, the relief 13 comes into close contact with the mold 21 without exerting an excessive force on the mold 21, and also from this point, the elastomer, which is the second-color resin, can enter between the relief 13 and the mold 21. Can be prevented more effectively.

FIG. 4 is a sectional view of an insert member of an insert two-color molding method according to another embodiment of the present invention. In this embodiment, the same parts as those in the above-mentioned embodiment are designated by the same reference numerals and the description and illustration thereof are omitted.

In this embodiment, both side surfaces of the rod-shaped member 10a which is an insert member, that is, the edges of the outer surface of the side piece portion 53 in the front and back direction are notched into curved surfaces, and so-called R chamfering is performed to provide low rigidity and low rigidity. The portion 53a is formed. In this embodiment, the bottom surface of the recess 12 on the back side is flat and the groove 12a is omitted. Even in this example,
When the rod-shaped member 10a is placed in the molds 21 and 22 and the elastomer is injected, the low-rigidity portion 53a of the side piece portion 53 is deformed and comes into close contact with the wall surfaces of the second molds 21 and 22. Therefore, the intrusion of elastomer can be prevented, and the occurrence of product defects can be prevented.

In the above-described embodiments, polypropylene is used as the first color resin and olefin elastomer is used as the second color resin, but various resins can be used without being limited to these resins.

Further, according to the present invention, only the low-rigidity portion which is easily deformed when it comes into contact with the mold is formed on the insert part, and the low-rigidity part is deformed by the injection pressure of the second color resin on the insert part. It goes without saying that only by forming a part, it can be achieved.

[0027]

As described above, according to the present invention, a low-rigidity portion such as a thin-walled portion or a side piece portion having low rigidity is formed in the insert part by the first mold, and the mold of the second mold is closed. The low-rigidity portion is deformed by the pressing force due to the contact with the mold at the time and the pressure of the second-color resin at the time of insert molding with the second-color resin so that the portion to be exposed as a product is brought into close contact with the second mold, In order to prevent the second color resin from entering between the exposed portion and the second mold, the durability of the second mold is not deteriorated, and the insert member is not deformed.
It is possible to obtain an effect that it is possible to prevent a product defect such as coating the exposed portion of the molded product with the second color resin.

[Brief description of drawings]

FIG. 1 is an overall perspective view of an insert part in a two-color insert molding method according to an embodiment of the present invention viewed from the front side.

FIG. 2 is an overall perspective view of the same insert part viewed from the back side.

FIG. 3 is a cross-sectional view of the insert part.

FIG. 4 is a cross-sectional view of an insert part in an insert two-color molding method according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an insert-molded member molded by a prior art two-color molding method.

FIG. 6 is a cross-sectional view of an insert part used for molding the same insert-molded member.

FIG. 7 is a schematic cross-sectional view of a mold used for the insert molding.

[Explanation of symbols]

 10 Insert Molded Member 10a Insert Member (Bar Member) 11, 12 Recess 12a Groove 13 Relief (Convex) 21,22 Second Mold 51 Center Part 52 Thin Part 53 Side Piece 53a Low Rigid Part C Cavity

Claims (5)

[Claims] 1. A part of an insert part is exposed by molding the insert part with a first color resin by a first mold, then placing the insert part in a second mold and then injecting a second color resin. In an insert two-color molding method for molding an integrated molded product in a state where the insert part is formed, the center part of the width direction center and a pair of side piece parts on both sides in the width direction are continuous by a low-rigidity part, and the center part The insert has a front surface at the center in the width direction of the portion projecting from the surface of the both side piece portions, and a back surface at the center in the width direction of the central portion is recessed inward from the back surfaces of the both side piece portions. Is placed in the second mold, and when the second color resin is injected, the resin is deformed by the pressure so that the entire outer peripheral surface of the insert part comes into close contact with the second mold. Insert two-color molding method. 2. The insert two-color molding method according to claim 1, wherein the low-rigidity portion is formed by forming a recess on the front and back surfaces of the insert part and forming a groove on the back surface-side recess. 3. The low-rigidity portion is formed by forming recesses on the front and back surfaces of the insert part and chamfering the outer peripheral surfaces of the front and back surface end portions of the pair of side pieces. The insert two-color molding method described. 4. The thickness dimension t _{1 of the} low-rigidity portion in the front-back direction and the thickness dimension w _{1 of the} side piece in the width direction are set to 1/3 or less of the thickness dimension t ₂ in the front-back direction of the side piece portion. The insert two-color molding method according to claim 1, 2 or 3, characterized in that. 5. The insert two-color molding method according to claim 1, wherein the first color resin is polypropylene which is a thermoplastic resin, and the second color resin is an olefin elastomer.