JP3280750B2 - Insert two-color 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 a two-color insert molding method, and more particularly, to a method for forming a part having low rigidity on an insert part, and applying a low rigidity part to the pressure of the second color resin during insert molding with a second color resin. The present invention relates to a two-color insert molding method in which a portion to be exposed as a product is deformed in close contact with a mold to prevent a second color resin from adhering to a 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 from a first color resin using a first mold, and the insert part is placed in a second mold. To form a cavity, and a second-color resin is injected into the cavity to form a final molded product.

[0003] By the way, for example, in order to improve the gripping condition of the gripping member, the feel thereof, etc., when forming an insert molding member combining a usual resin and an elastomer, when performing the molding by two-color molding, the insert molding member 10 is used. ,
For example, as shown in FIG.
A case will be described in which the projections 3 are protruded and the elastomer 91 having rubber elasticity is embedded in a part of the front and back sides.

[0004] That is, the following method has been attempted for the insert molding of the insert molded member 10 as described above. That is, first, a rod-shaped member 10a having a cross-sectional shape as shown in FIG. 6 is formed by injection molding of a thermoplastic resin (first color resin) such as polypropylene using a first mold. The bar-shaped member 10a has concave portions 11 and 12 on the front and back sides, and is formed so that a relief 13 protrudes from the bottom surface of the concave portion 11 on the front side. Next, as shown in FIG. 7, the rod-shaped member 10a is fixed between the upper and lower molds 21 and 22 to define a cavity C between the second molds 21 and 22, and an olefin-based elastomer is formed in the cavity C. (Second color resin) was injected to obtain an insert molded member 10 as a molded product.

[0005]

However, in the above-mentioned molding method, the rod-shaped member 10a, especially the rod-shaped member 10a molded with a thermoplastic resin, cannot avoid thermal contraction after molding. It is extremely difficult to maintain the dimensions of all the formed rod-shaped members 10a under the influence of the injection pressure, the injection speed, the resin temperature and the like of the resin. For this reason, when the rod-shaped member 10a is fixed in the dies 21 and 22, a gap may be formed between the surface of the rod-shaped member 10a to be brought into close contact with the inner surfaces of the dies 21 and 22, for example, the surface of the relief 13. There is a problem that when the elastomer is injected, the elastomer penetrates into the gap and covers the relief 13, thereby impairing the appearance as a product (producing a product defect).

On the other hand, as a countermeasure against the above-mentioned problem, the bar-shaped member 10a is formed into a size slightly larger than the size of the stationary portion of the dies 21, 22.
When the mold 22 is closed, the rod-shaped member 10a is partially
The molds 21 and 22 are deformed by contacting the molds 21 and 22.
And a method of preventing resin intrusion.

However, in the above method, the rigidity of the rod-shaped member 10a is large, and the rod-shaped member 10a having a large rigidity must be deformed. A new problem arises in that the shape of the insert molded member 10 as a product is also damaged, and the product is likely to be defective. Further, in the above method, since the force acting on the dies 21 and 22 is also excessive, a deformation occurs in the dies 21 and 22 when the molding is repeated, so that it is impossible to effectively prevent the intrusion of the elastomer. Was also found to occur. The latter problem is that the molds 21 and
2 can be solved by adopting a structure that is detachable and replaceable as a nest.
And the problem that product value is diminished.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is directed to a product in which a second color resin permeates between an insert member and a mold without requiring strict accuracy in the molding dimensions of the insert member. Can prevent the occurrence of defects,
It is an object of the present invention to provide a two-color insert molding method capable of obtaining great durability in a mold and not reducing the value as a product.

[0009]

In order to achieve the above-mentioned object, the present invention provides an insert part having a first mold and a first mold.
After molding with a color resin, the insert part is placed in a second mold, and then the second color resin is injected to form an integrated molded article in a state where a part of the insert part is exposed. In the method, the center part in the width direction center and a pair of side piece parts on both sides in the width direction are connected by a low rigidity part, and the surface in the width direction center of the center part is higher than the surface of the both side piece parts. And the rear surface at the center in the width direction of the central portion is formed so as to be recessed inward from the rear surfaces of the both side pieces, and the insert part is formed in the second part.
When the second color resin was injected into the mold, the mold was deformed by the pressure and the entire outer peripheral surface of the insert part was brought into close contact with the second mold.

[0010] This two-color insert molding method comprises:
The low-rigidity portion is formed with a recess on the front and back sides of the insert part and a groove on the back side recess, so that a recess is formed on the front and back sides of the insert part and the pair of side pieces is formed. The outer peripheral surface of the front and rear end portions of the portion may be rounded.

[0011] The insert two-color molding method of polypropylene the first color resin, a second color resin can be configured to aspects of the olefinic elastomer, further, front and back direction thickness t ₁ of the low-rigidity portion can be configured in the front and back direction thickness mode to 1/3 or less of the dimension t ₂ of each of the side piece portions widthwise thickness w ₁ and the said side piece portions and.

[0012]

According to the insert two-color molding method of the present invention,
The surface of the center portion of the insert part is brought into contact with and pressed by the mold by closing the mold of the second mold, deforming the low-rigidity portion and making close contact with the mold, and the second mold injected into the second mold. The low rigidity portion is deformed by the pressure of the color 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. For this reason, the second color resin does not enter between the exposed surface and the mold, and the occurrence of product defects can be prevented. Then, the low-rigidity portion is easily deformed, and furthermore, the exposed surface only comes into close contact with the pressure of the second color resin, so that the adhering force does not become excessive, and the insert member and the mold are prevented from being deformed. And the mold durability is also improved.

According to the insert two-color molding method of the present invention, by forming the low-rigidity portion with a groove or chamfer, 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 the insert two-color molding method according to the present invention. FIG. 1 is an overall perspective view of the insert component as viewed from the front side, and FIG. 2 is an overall perspective view of the insert component as viewed from the back side. FIG. 3 is a cross-sectional view of the insert part. The same parts as those of the above-described prior art are denoted by the same reference numerals, and some of the parts are illustrated.
Detailed explanation is omitted.

In this embodiment, first, the illustrated rod-shaped member 10a is formed 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 rear surfaces, and a relief (corresponding to a convex portion) 13 is formed on the bottom surface of the concave portion 11 on the front side. Are formed. The tip (surface) of the relief 13 has the concave portion 1.
It protrudes by a predetermined size (for example, 2 mm as will be described later) from the height of the upper surface of the side wall 1.

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, and the central portion 51 has side piece portions (low-rigidity portions) 53, 52 via the thin-walled portions 52, 52.
It is formed into a cross-sectional shape continuous with 53.

The thickness t ₁ of the thin portion 52 in the front-to-back direction of the thin portion 52 is one-third or less of the total size t ₂ of the side portion 53 in the front-to-back direction.
₁ is formed below 1/3 of the front and back direction overall dimensions t ₂ of the side piece portions 53. Specifically, this rod-shaped member 10a has, for example, a total dimension w _{0 in the} width direction of 14 mm and a total dimension t _{2 in the} front-back direction.
Is 8 mm, the thickness t in the front-back direction of the thin portion 52 is
The width dimension w _{1 1} and Gawahen portion 53 is 2 mm, the dimension t ₄ from the back side to the relief 13 surface is set to 12 mm.

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

The side piece 53 has a thickness w in the width direction.
₁ is small and has low rigidity in the width direction.
2 also has a small thickness t ₁ in the front-back direction and low rigidity in the front-back direction, so that when the elastomer is injected, each side piece 53
Are deformed outwardly by the pressure of the elastomer flowing into the groove portion 12a and adhere to the wall surfaces of the second molds 21 and 22, and the side piece 53
It is possible to prevent the intrusion of the elastomer between the outer surface of the first mold and the wall surfaces of the second molds 21 and 22.

Similarly, the thin portion 52 is also pressed by the pressure of the elastomer that has flowed into the recess 12 so that the relief 1 of the central portion 51
3 is deformed so as to be displaced to the front side and closely adheres to the wall surface of the second mold 21. That is, the pressure of the elastomer flowing into the concave portion 12 acts on the rod-shaped member 10a upward with the entire bottom surface of the concave portion 12 as the pressure receiving area, but the pressure of the resin flowing into the concave portion 11 Only the bottom surface acts as a pressure receiving area and acts only downward. The force caused by the difference in the pressure receiving area causes the central portion 51 to be displaced upward and come into close contact with the mold 21. For this reason, the elastomer injected later into the concave portion 11 is prevented from entering between the relief 13 and the mold 21, and the appearance of the product is poor, that is, the outer surface such as the surface of the relief 13 to be exposed. Inconveniences such as formation of an elastomer film on the surface can be prevented.

The relief 13 only comes into close contact with the walls of the second molds 21 and 22 by the pressure of the elastomer, and the contact force does not become excessive. Also, the side piece 53 also comes into close contact with the pressure of the elastomer. Since the proper adhesion force can be maintained, the rod-shaped member 10a and the molds 21 and 22 are not deformed. Therefore, deformation as a product can be prevented, the durability of the molds 21 and 22 can be improved, and inconveniences such as transfer of a seam to the product without the above-described measures such as nesting can be prevented.

Particularly, in this embodiment, when the mold is closed, the surface of the central portion 51, that is, the relief 13 abuts against the mold 21 and is pressed, and the central portion 51 elastically deforms the thin portion 52 having low rigidity. Displaced to the back side. Therefore, the relief 13 adheres to the mold 21 without exerting an excessive force on the mold 21, and from this point, the elastomer as the second color resin infiltrates between the relief 13 and the mold 21. Can be more effectively prevented.

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 portions as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, both sides of the rod-shaped member 10a, which is an insert member, that is, the front and back edges of the outer surface of the side piece 53 are cut into curved surfaces, and so-called R chamfering is performed to reduce rigidity and reduce rigidity. A portion 53a is formed. In this embodiment, the bottom surface of the concave portion 12 on the back side is flat and the groove 12a is omitted. Even in this example,
When the rod-shaped member 10a is fixed in the molds 21 and 22 and the elastomer is injected, the low-rigidity portion 53a of the side piece 53 is deformed and adheres to the wall surfaces of the second molds 21 and 22. Therefore, intrusion of the elastomer can be prevented, and occurrence of a product defect can be prevented.

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

Further, the present invention provides a low rigidity part which is easily deformed when the insert part is brought into contact with a mold, and which is deformed by the injection pressure of the second color resin into the insert part. It is needless to say that the achievement is achieved only by forming the part.

[0027]

As described above, according to the present invention, a low-rigidity portion such as a thin-walled portion or a side portion having low rigidity is formed on the insert part by the first die, and the second die is closed. The part to be exposed as a product by deforming the low-rigidity part by the pressing force due to contact with the mold at the time or the pressure of the second color resin at the time of insert molding with the second color resin is brought into close contact with the second mold, To prevent the second color resin from entering between the portion to be exposed and the second mold, without lowering the durability of the second mold and without deforming the insert member.
The effect is obtained that it is possible to prevent product defects, such as coating the portion of the molded product to be exposed with the second color resin.

[Brief description of the drawings]

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

FIG. 2 is an overall perspective view of the insert component as 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 two-color molding method of the prior art.

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Insert molding member 10a Insert member (bar-shaped member) 11, 12 Concave part 12a Groove part 13 Relief (convex part) 21, 22 Second mold 51 Central part 52 Thin part 53 Side piece 53a Low rigidity part C cavity

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-50055 (JP, A) JP-A-3-81127 (JP, A) JP-A-2-289319 (JP, A) JP-A-60-1985 193621 (JP, A) Hikaru 1-123562 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B29C 45/14 B29C 45/16

Claims (5)

(57) [Claims] 1. After molding an insert part with a first color resin using a first mold, placing the insert part in a second mold, injecting a second color resin to expose a part of the insert part. In the insert two-color molding method of molding a molded product integrated in a state in which the insert part is formed, a center portion in the center in the width direction and a pair of side pieces on both sides in the width direction are connected by a low rigidity portion, A center surface in the width direction of the portion protrudes from a surface of the both-side pieces, and a back surface at the center in the width direction of the center portion is recessed inward from a back surface of the both-side pieces; Is fixed in the second mold and deformed by the pressure when the second color resin is injected, so that the entire outer peripheral surface of the insert part is brought 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 concave portion on the front and back surfaces of the insert component and forming a groove in the rear surface side concave portion. 3. The low-rigidity portion according to claim 1, wherein a concave portion is formed on the front and back sides of the insert part, and the outer peripheral surfaces of the front and back sides of the pair of side pieces are chamfered. The two-color insert molding method as described in the above. 4. The thickness t _{1 of the} low rigidity portion in the front and back direction and the thickness w _{1 of the} side piece in the width direction are set to be not more than _１ ／ of the thickness t ₂ in the front and back direction of the side piece. The two-color insert molding method according to claim 1, 2 or 3, wherein: 5. The two-color insert molding method according to claim 1, wherein the first color resin is a thermoplastic resin, polypropylene, and the second color resin is an olefin-based elastomer.