JP3449681B2 - Insert molded body and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an insert molded body and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an insert molding method has been widely used in various fields in which the surface of an insert member is integrally molded so as to be covered with a molding resin. For example, an electric circuit board is used as an insert member, which is covered with a mold resin to be waterproofed. Specifically, the molded body 100 shown in FIG. 8 can be exemplified.
The electric circuit board 102 is covered with the mold resin 103, and the pin-shaped member 105 is provided on the plate surface.

As shown in FIG. 10, the pin-shaped member 105 cooperates with a holding pin 34 provided in the cavity 31 of the mold 30 to prevent the electric circuit board 102 from moving during injection molding. It serves to position the electric circuit board 102 with respect to the molding resin. That is, a metal holding pin 34 is provided from the inner surface of the mold 30 so as to face the pin-shaped member 105, and the molding resin passes through the runner 32 formed in the mold 30 and passes through the electric circuit board. It is injected into the cavity 31 from the plate surface side opposite to the side where the pin-shaped member 105 of 102 is formed. The electric circuit board 102 tries to move by the injection pressure of the injection molding resin, but the pin-shaped member 105 presses the pressing pin 34.
The movement of the resin is regulated by abutting against, and it is integrated with the molding resin in a positioned state. Here, in the conventional molding method, the pin-shaped member 105 is made of a resin having a considerably high softening temperature so that the pin-shaped member 105 does not soften and buckle itself when integrally molded with the molding resin.

[0004]

However, when the pin-shaped member 105 hardly softens during injection molding, no adhesion occurs between the pin-shaped member 105 and the molding resin,
A gap may occur between the pin-shaped member 105 and the mold resin due to the shrinkage of the resin during cooling. Here, a hole 108 (FIG. 8) is formed in the mold resin portion of the obtained molded body after the pressing pin 34 is removed, and when water or the like collects in the hole 108, the hole 108 (FIG. 8) passes through the gap to the electric circuit board 102. There is a drawback that it leaks and loses the waterproof function. For example, as shown in FIG. 9, in the insert molded body 100, the molded resin 103 in the softened state does not get around the electronic component 106 of the electric circuit board 102 well at the time of molding, and bubbles K remain in the molded body portion. There are cases. When such a molded body 100 is attached, for example, in the vicinity of an internal combustion engine or the like, the heat of the molded body 100 warms the air in the bubbles K. Then, when the molded body 100 is cooled by, for example, rain or a car wash, the air in the expanded state is contracted, a pressure difference with the outside is generated, and water is drawn from the gap to cause water leakage. .

Therefore, in order to solve this, it is considered that the pin-shaped member 105 is made of a resin having a low softening temperature, and this is softened during insert molding to cause welding with the mold resin. This time, there is a problem that the pin-shaped member 105 buckles at the time of molding due to the injection pressure of the molding resin and the positioning function is not fulfilled.

An object of the present invention is that when an insert member such as an electric circuit board is covered with a mold resin, a gap or the like may occur between a desired portion of the insert member such as a convex portion for positioning and the mold resin. An object of the present invention is to provide an insert molded body that is effectively prevented and has improved waterproofness, and a method for manufacturing the same.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an insert-molded body in which at least a part of the surface of an insert member is integrally molded so as to be covered with the mold resin. In order to solve the above problem, the first structure is that the insert member has a base resin having a softening temperature difference of 10 ° C. or less with the mold resin, and a filler having a higher softening temperature than any of the base resin and the mold resin. And a composite material forming portion that is arranged so as to be in contact with the mold resin.

In the above structure, a composite material comprising a mixture of a base resin having a softening temperature difference of 10 ° C. or less with the mold resin and a filler having a softening temperature higher than that of either the base resin or the mold resin. The forming portion is provided on the insert member and is arranged so as to contact the mold resin. Then, in the composite material forming portion, the base resin is softened by the contact with the mold resin and is integrated with the mold resin, so that a gap is unlikely to be formed at the contact interface, and, for example, the waterproof property can be improved. Further, in the composite material forming part, since the filler having a higher softening temperature than the mold resin and the base resin is mixed as a kind of skeleton material, even if the base resin is softened during the injection molding, the composite material is mixed by the filler. The shape maintaining force of the material forming portion is enhanced, and for example, buckling during molding can be prevented.

The softening temperature referred to in the present invention is JISK.
Vicat softening point measured by the method specified in 7206.

When manufacturing the above insert molding,
Do the following: That is, an insert member having a composite material forming part made of a mixture of a base resin having a softening temperature difference of 10 ° C. or less with the mold resin and a filler having a softening temperature higher than that of both the base resin and the mold resin. To
It is arranged so that at least the composite material forming portion is located in the cavity of the mold. Then, in that state, a mold resin in a softened state is injected into the cavity, and the insert member is covered with the mold resin, thereby integrating the insert member and the mold resin, and the insert molding having a shape corresponding to the cavity. Get the body. Then, during injection molding, the composite material forming portion is brought into contact with the softened mold resin to soften the base resin and integrate it with the mold resin.
Thereby, the insert molded body can be efficiently manufactured.

When the difference in softening temperature between the mold resin and the base resin exceeds 10 ° C., it becomes difficult to integrate the mold resin and the base resin, and the above-mentioned gaps are easily formed. In this situation, if the injection molding temperature at which both resins are softened is forcedly set, the following problems will occur. First, when the softening temperature of the mold resin is higher, the injection temperature is necessarily considerably higher than the temperature of the base resin, and the base resin is excessively softened and the shape retention force of the composite material forming part is increased. If it is damaged, problems such as buckling are likely to occur. on the other hand,
When the softening temperature of the base resin is high, it is necessary to unnecessarily raise the temperature of the mold resin in order to soften the base resin, which increases energy waste. In addition, as another problem, when the insert member is an electric circuit board having a soldered portion as described later, if the mold resin temperature becomes too high, the soldered portion melts to cause contact failure, semiconductors, etc. There may be a problem such as impairing the characteristics of the electronic component constituted by. Therefore, the difference in softening temperature between the mold resin and the base resin is within 10 ° C. From the viewpoint of integrating the mold resin and the base resin, it is advantageous to minimize the difference in softening temperature between the two. For example, it is possible to use the same resin for the mold resin and the base resin. If possible, the difference in softening temperature is substantially eliminated, and the effect of integration is large.

Next, the insert molded article according to the second structure of the present invention is made of a mixture of a base resin and a filler having a softening temperature higher than any of the base resin and the mold resin. A composite material forming portion disposed so as to contact with the insert member is provided in the insert member, and a mixed resin region in which the base resin and the mold resin are melted is formed at the contact interface portion between the composite material forming portion and the mold resin. It is characterized by

According to the above construction, the mixed resin region in which the base resin and the mold resin are melted is formed near the contact interface between the composite material forming portion and the mold resin.
No gap is formed at the contact interfaces, and the waterproof effect can be enhanced, for example. Further, since the filler having a higher softening temperature than the mold resin and the base resin is mixed in the composite material forming portion, the filler is not easily softened even if the base resin is softened during injection molding. In the same manner as in the configuration of 1, the shape retention force of the composite material forming portion during injection molding is increased,
For example, buckling during molding can be prevented. In addition,
Also in this configuration, it is desirable that the base resin and the mold resin be made of a material having a difference in softening temperature of 10 ° C. or less.

The insert molded body having the second structure can be manufactured in the same manner as the first structure. In this case, the base material resin is softened by bringing the composite material forming portion into contact with the softened mold resin during injection molding, and the base material resin and the mold resin are formed near the contact interface between the composite material forming portion and the mold resin. A mixed resin region which is melted with each other is formed so that the base resin and the mold resin are integrated.

The composite material forming portion can be formed by using resin pellets obtained by kneading a filler and a base resin, and molding the pellets into various shapes by injection molding or extrusion molding.

As the material of the base resin and the mold resin, various thermoplastic resins such as ethylene, propylene,
Homo- or co-addition polymers of vinyl chloride, styrene, vinylidene chloride, methyl methacrylate, fluorinated ethylene, etc., polycondensates of amides, esters, carbonates, phenylene oxides, etc., polyadditions of urethanes, acetals and ethers. A ring-opening polymer such as a system can be adopted. Specific resin names include polystyrene resin, polypropylene resin, acrylonitrile butadiene styrene resin, polycarbonate resin, methacrylic resin, polyamide resin,
Examples thereof include polyacetal resin, polyvinyl chloride resin, acrylic resin, polyurethane resin, nylon resin, polyethylene terephthalate resin, polyphenylene oxide resin, fluororesin, ionomer resin, and polysulfone resin.

A thermosetting resin having the property that the uncrosslinked resin is once softened by heating and then hardened can also be used as the material of the mold resin as long as it can be injection-molded. Typical examples include phenol resins, unsaturated polyester resins, dialerphthalate resins, silicone resins and the like.

On the other hand, as the material of the filler, various inorganic materials such as glass, ceramics (for example, Al ₂ O ₃ etc.) and carbon can be used. Also, plastics (for example, various thermosetting resins) can be used as long as they do not soften at the molding temperature. Incidentally, the filler, from the viewpoint of preventing the occurrence of defects and the like at the time of forming the composite material,
For example, it can be formed into particles or fibers. In this case, the average particle diameter of the particles or the axial cross-sectional diameter of the fiber is 1
It is preferably less than 00 μm. If the average particle diameter and the axial cross-sectional diameter exceed 100 μm, the surface of the composite material forming portion becomes rough and defects such as bubbles are likely to occur at the boundary with the mold resin.

The compounding ratio of the filler to the base resin is preferably adjusted within the range of 10 to 50% by volume. If the blending ratio is less than 10% by volume, the shape retention force of the composite material forming portion when the base resin is softened is insufficient, and problems such as buckling are likely to occur. On the other hand, when the mixing ratio exceeds 50% by volume, the amount of the base resin is insufficient, and defects such as a gap with the mold resin are likely to occur. The blending ratio of the filler is
It is more desirable to adjust in the range of 25 to 35% by volume.

The composite material forming portion can be made, for example, such that the base resin is mainly composed of polypropylene. Since polypropylene is excellent in adhesiveness or mixability with many other resins, it has an advantage that gaps and the like are less likely to occur at the contact interface with the mold resin. On the other hand, the molding resin can also be composed mainly of polypropylene. As a result, for example, when the insert member is composed of an electric circuit board or the like, there is little fear of damaging the soldered part, the electronic component, or the like during injection molding.

When the insert member is configured to include the electric circuit board, the composite material forming portion may be a convex portion protruding from the plate surface of the electric circuit board and provided integrally therewith. For example, this convex portion can be used as a member that cooperates with a holding pin provided in the cavity of the molding die to prevent movement of the electric circuit board during injection molding. Specifically, the insert molding of the present invention can be manufactured by the following method using the insert member as described above. That is, a holding pin is provided on the inner surface of the cavity of the mold at a position corresponding to the convex portion in a state where the electric circuit board is arranged in the cavity so that the tip of the electric circuit board faces the tip of the convex portion. Keep it. Then, the mold resin is injected into the cavity from the side opposite to the side on which the pressing pin of the electric circuit board is formed, and the tip of the pressing pin is brought into contact with the tip of the convex portion, so that the electric The circuit board is prevented from moving to the pressing pin side. In this case, a bottomed hole portion based on the pressing pin is formed in the molded body portion of the obtained insert molded body made of the mold resin,
At the position corresponding to the convex portion on the insert member, the tip end surface of the convex portion serves as the bottom surface and is formed so as to be open to the surface of the molded body portion.

As a result, the following effects can be achieved. The position of the electric circuit board does not shift during injection molding, and the insert molded body can be manufactured reliably and easily. Even if the base resin softens when the convex portion is pressed against the pressing pin by the resin injection pressure at the time of molding, the shape retention force of the composite material forming portion is enhanced by the mixing of the filler, so buckling does not occur. To be prevented. Since the softened base resin is integrated with the mold resin and a gap or the like is less likely to be formed between the two, the waterproof property is dramatically improved. For example, even if water or the like enters the bottomed hole portion, it can be reliably cut off, the malfunction of the electric circuit can be prevented, and the reliability can be improved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the examples shown in the drawings. FIG. 1 shows an insert molded body which is an embodiment of the present invention. The insert molded body 1 is integrally molded so that the entire electric circuit board 2 is covered with the molded resin molded portion 3 mainly made of polypropylene. The electric circuit board 2 includes a pin-shaped member (convex portion) 5 as a composite material forming portion, an electronic component 6 that constitutes an electric circuit,
And a connector terminal portion 7 connected to the electric circuit.

As shown in FIG. 2B, the pin-shaped member 5 is integrally provided with the electric circuit board 2 on one end side thereof on both sides in the width direction thereof so as to project from the plate surface thereof. Has been. In addition, at the position corresponding to the pin-shaped member 5, the molded resin molding portion 3 is formed with a bottomed hole portion 8 that opens to the surface of the molding portion 3 with the tip end surface of the pin-shaped member 5 as the bottom surface. . In addition, the connector terminal portion 7 is covered at its base end side with the molded resin molding portion 3, and
The tip side thereof is exposed from the end surface of the molding portion 3. Such an insert molded body 1 is arranged in the vicinity of a diesel engine as a preheating controller for controlling the energization time of preheating elements such as a glow plug and an air heater.

As shown in FIG. 2, the pin-shaped member 5 includes a base resin 20 mainly composed of polypropylene, and the base resin 2
0 or a molding resin, and a mixture with a filler 21 made of glass or ceramic having a higher softening temperature. The filler 21 has an average axial cross-sectional diameter of 100.
The base resin 20 is formed in a fiber shape of less than μm.
To 10 to 50% by volume, preferably 25
It is adjusted in the range of ~ 35% by volume.

The pin-shaped member 5 can be manufactured by injection molding or extrusion molding of pellets obtained by kneading glass fibers and polypropylene resin in a predetermined ratio. Then, as shown in FIG. 3, a mixed resin region 24 in which the base resin 20 and the mold resin are melt-integrated is formed near the contact interface between the pin-shaped member 5 and the mold resin 3. By forming the mixed resin region 24, it is difficult to form a gap at the contact interface between the pin-shaped member 5 and the molded resin molding portion 3, and the waterproof effect is enhanced. Further, in the present embodiment, the filler 21 in the pin-shaped member 5 is not uniformly distributed in the base resin 20, but is unevenly distributed near the central axis thereof. Such a distribution state can be realized, for example, by setting the mold temperature at the time of molding, which is normally room temperature by cooling, to be higher than room temperature by about 30 ° C to 60 ° C.

The method of manufacturing the insert molded body 1 will be described below. FIG. 4 shows an example of a mold used for manufacturing the insert molded body 1. The mold 30 includes a cavity 31, a runner 32, a nest 33, and the like. The insert 33 is fitted between the upper mold 30a and the lower mold 30b on the side of the mold 30 opposite to the runner 32. Further, the nest 33 has a hole portion 33a that opens into the cavity 31, and the connector terminal portion 7 of the electric circuit board 2 is inserted into the hole portion 33a, so that the electric circuit board 2 is kept inside the cavity 31. Play a role in holding. From the inner surface of the upper mold 30a, a metal holding pin 34
However, at a position corresponding to the pin-shaped member 5 of the electric circuit board 2 arranged in the cavity 31, the tip is provided in a protruding form so as to face the tip of the pin-shaped member 5. Further, the runner 32 is formed on the side surface of the mold 30 at a position lower than the electric circuit board 2, and a gate 36 is formed at the tip thereof. Then, with the tip of the pressing pin 34 in contact with the tip of the pin-shaped member 5 of the electric circuit board 2, the softened mold resin 3'is injected from the gate 36.

Here, on the injection molding machine side, the electric circuit board 2
The temperature of the molding resin in the cylinder of the molding machine is 180 to 200 in consideration of the heat resistant temperature of the electronic component 6 provided in the It is set to be in the range of ° C. In this embodiment, polypropylene is used as the mold resin within this temperature range, but other resins may be used as long as they can be injection-molded within this temperature range.

First, as shown in FIG. 5A, the mold 30
In the mold open state, the insert 33 is inserted into the connector terminal portion 7 of the electric circuit board 2 and is placed in the mold 30. Next, as shown in FIG. 3B, the mold 30 is clamped to bring the pressing pin 34 into contact with the tip of the pin-shaped member 5. Then, in this state, as shown in FIG. 6C, the mold resin 3 ′ in the softened state is injected into the cavity 31 via the runner 32 and the gate 36. Here, as shown in FIG. 6, the electric circuit board 2 receives a force that pushes the board 2 upward due to the injection pressure of the molding resin 3 ′, but the pin-shaped member 5 contacts the pressing pin 34. Its movement is restricted because it is in contact with it.

Then, when the mold resin 3 is further injected and comes into contact with the pin-shaped member 5, the base resin 20 begins to soften. However, the filling material 21 of the pin-shaped member 5
Is made of glass having a much higher softening temperature than the base resin 20 and the mold resin 3 made of polypropylene resin, and therefore is hardly softened even when the mold resin 3'is injected. As a result, the pin-shaped member 5 can continue to block the movement of the electric circuit board 2 against the resin injection pressure without buckling.

Then, as shown in FIG. 7, the pin-shaped member 5
However, when it is covered with the softened mold resin 3 ′, the base resin 20 near its surface is softened, and the base resin 20 and the mold resin are mutually separated near the contact interface between the pin-shaped member 5 and the mold resin 3 ′. Mixed resin regions 24 (FIG. 3) that are fused and integrated are formed. Here, in the present embodiment, as described above, the filler 21 is unevenly distributed in the vicinity of the central axis in the pin-shaped member 5, so that the base resin 20 is predominant in the outer portion of the pin-shaped member 5. While the integration with the molding resin proceeds well, at the same time, the filler 21 gathers in the vicinity of the center to enhance its shape maintaining force, and the buckling of the pin-shaped member 5 is effectively suppressed.

When the mold resin 3'is cooled and cured, the mold 30 is opened as shown in FIG. 5 (d), and the electric circuit board 2 and the mold resin molding portion 3 are finally integrated. The insert molded body 1 is collected.

The filler 21 is not limited to glass and ceramics as long as it has a higher softening temperature than the molding resin, and various other materials such as ceramics such as alumina can be used. . Further, the filler 21 may be formed of particles rather than fibers. Further, the base resin 20 and the mold resin 3 ′ can of course be made of resins other than polypropylene, and if the difference in softening temperature is within 10 ° C., they are made of resins of different materials. You may.

[Brief description of drawings]

FIG. 1 is a side sectional view and a plan view showing an example of an insert molded body of the present invention.

FIG. 2 is a schematic view showing a mixed state of the resin in the composite material forming part.

FIG. 3 is a partially enlarged explanatory view of an insert molded body.

FIG. 4 is a side sectional view and a plan sectional view showing an insert molded body and a mold.

FIG. 5 is a process explanatory view showing an example of a method for manufacturing an insert molded body.

FIG. 6 is a partially enlarged view of FIG.

FIG. 7 is a partially enlarged view of FIG.

FIG. 8 is a conceptual diagram of a conventional insert molded body.

FIG. 9 is an explanatory diagram showing the problem.

FIG. 10 is a cross-sectional view of a mold used for manufacturing an insert molded body.

[Explanation of symbols]

1 Insert molding 2 Electric circuit board (insert member) 3 Mold resin molding part 5 Pin-shaped member (convex part, composite material forming part) 8 Bottomed hole 20 Base resin 21 Filling material 24 Molten resin area 30 molds 31 cavity 34 Holding member

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-95014 (JP, A) JP-A-4-263913 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 33/00-33/76 B29C 45/00-45/84

Claims (15)

(57) [Claims] 1. An insert-molded article integrally formed by covering at least a part of the surface of an insert member with a mold resin, wherein the insert member has a difference in softening temperature from the mold resin of 10 ° C. or less. There is provided a composite material forming section which is made of a mixture of a certain base resin and a filler having a softening temperature higher than that of any of the base resin and the mold resin and which is arranged so as to be in contact with the mold resin. An insert molded body characterized by. 2. An insert-molded body in which at least a part of the surface of the insert member is integrally molded so as to be covered with the mold resin, wherein the insert member comprises a base resin and any of the base resin and the mold resin. And a composite material forming part which is composed of a mixture with a filler having a high softening temperature and is arranged so as to be in contact with the mold resin, and a contact interface part between the composite material forming part and the mold resin, An insert molded body, wherein a mixed resin region in which the base resin and the mold resin are melted with each other is formed. 3. The base resin and the molding resin are
The insert molded article according to claim 2, wherein a material having a difference in softening temperature thereof within 10 ° C is used. 4. In the composite material forming portion, the base resin is mainly composed of polypropylene, and the filler is made of glass or ceramics.
The insert molding according to any one of 1 to 3. 5. The insert molded body according to claim 1, wherein the mold resin is mainly composed of polypropylene. 6. The insert member includes an electric circuit board, and the composite material forming portion is a convex portion protruding from a plate surface of the electric circuit board and integrally provided with the electric circuit board. The insert molded body according to any one of 1. 7. A molded body portion made of the molding resin is provided at a position corresponding to the convex portion on the insert member, and the tip end surface of the convex portion is opened to the surface of the molded body portion as a bottom surface. The insert molding according to claim 6, wherein a bottom hole portion is formed. 8. The difference in softening temperature from the mold resin is 10 ° C.
An insert member having a composite material forming portion made of a mixture of a base resin which is within the range and a filler having a softening temperature higher than any of the base resin and the mold resin, and at least the composite member for the cavity of the mold. By disposing the material forming portion so as to be located in the cavity, injecting the mold resin in a softened state into the cavity in that state, and covering the insert member with the mold resin, the insert member and the mold are molded. The base resin is softened by integrating it with a resin to obtain an insert-molded body having a shape corresponding to the cavity and contacting the composite material forming portion with the softened mold resin during the injection molding. At the same time, this is integrated with the molding resin, and a method for manufacturing an insert-molded body. 9. An insert member having a composite material forming portion made of a mixture of a base resin and a filler having a softening temperature higher than that of either the base resin or the mold resin is provided at least for the cavity of the mold. Arranging the composite material forming portion so as to be located in the cavity, injecting the softened mold resin into the cavity in that state, and covering at least a part of the surface of the insert member with the mold resin. By integrating the insert member and the mold resin with each other, an insert molded body having a shape corresponding to the cavity is obtained, and the composite material forming portion is brought into contact with the softened mold resin during the injection molding. While softening the base resin, the base resin is formed near the contact interface between the composite material forming portion and the mold resin. To form a mixed resin region and Rudo resin is melted together with each other, the manufacturing method of the insert molded body, characterized in that so as to integrate the said mold resin and the base resin. 10. The method for manufacturing an insert-molded article according to claim 9, wherein the base resin has a difference in softening temperature with respect to the mold resin of 10 ° C. or less. 11. The method for producing an insert-molded article according to claim 8, wherein polypropylene is used as the base resin and glass or ceramic is used as the filler. 12. The method for producing an insert-molded body according to claim 11, wherein the glass or ceramic is formed into a fibrous shape. 13. The method for producing an insert molded article according to claim 8, wherein polypropylene is used as the molding resin. 14. The insert member includes an electric circuit board, and the composite material forming portion is a convex portion protruding from a plate surface of the electric circuit board and integrally provided with the electric circuit board. The method for manufacturing an insert molded body according to any one of 8 to 13. 15. From the inner surface of the cavity of the mold, the tip is opposed to the tip of the convex portion at a position corresponding to the convex portion when the electric circuit board is arranged in the cavity. A pressing pin is provided so as to project into the cavity, and the mold resin is injected into the cavity from a side of the electric circuit board opposite to the side where the pressing pin is formed. 15. The method for manufacturing an insert-molded body according to claim 14, wherein the electric circuit board is prevented from moving toward the pressing pin side by contacting the tip end portion of the convex portion.