JP2002018917A - Method for molding solid material-containing resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding a solid material-containing resin molding capable of molding the molding so that a solid material is uniformly exposed on the overall surface of the molding. SOLUTION: The method for molding the solid material-containing resin molding comprises the steps of locating an interval δ (δ>0) between a movable side parting surface 11c of a mold and a fixed side parting surface 12c of the mold, setting to a state in which a volume of the cavity 15 becomes larger than a volume of the molding, and then injecting a mixed material 21 obtained by mixing a conductive filler (solid material) within a resin matrix of a molten resin in the cavity 15. The method also comprises the step of then reducing the volume of the cavity 15 to that of the molding to pressure and compress the material 21 in the cavity 15. The method further comprises the steps of cooling and solidifying the material 21 in a pressurized and compressed state, then separating the movable side 11 of the mold from the fixed side 12 of the mold, and taking out the solidified material 21 as the solid material-containing resin molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a resin material containing a solid material containing a solid material such as a conductive filler.

[0002]

2. Description of the Related Art Conventionally, a solid material containing a conductive fibrous filler (solid material) has been used as a shielding material for electromagnetic noise generated from an operating electronic device or as a grounding member for an electronic device. A resin molded product is used.

[0003] These solid material-containing resin molded products are generally molded by an injection molding method. In other words, when these solid material-containing resin molded products are manufactured by the conventional injection molding method, the resin base material, which is a molten resin, is mixed with the resin base material in a cavity in a completely closed mold. After the mixed material comprising the fibrous filler is filled at a high pressure and the pressure is maintained, the mixed material is cooled and solidified, and then the mold is opened to form a molded product (a solid material-containing resin molded product composed of the mixed material).
Take out.

[0004]

By the way, in order for such a solid material-containing resin molded article to effectively function as a shielding material or a grounding member as described above, it is necessary to increase the conductivity (for example, It is necessary to mold the molded article so that the volume resistivity of the molded article is 300 Ω · cm or less.

In order to increase the conductivity of the solid material-containing resin molded product, it is preferable to mold the molded product such that the fibrous filler is uniformly exposed on the entire surface of the molded product. . This is because, if molded in such a manner, the fibrous filler (conductor) is buried inside the solid material-containing resin molded product, and the surface of the molded product is covered with the resin (nonconductor). This is because the conductivity of the molded article can be surely increased as compared to

However, when a conventional injection molding method is used as described above when molding a solid material-containing resin molded product,
It has been extremely difficult to uniformly expose the solid material to the entire surface of the molded article. That is, first, when the mixed material is injected into the cavity in the mold under high pressure conditions, a portion of the injected mixed material having a relatively high flow rate at the time of injection (for example, near the tip of the mixed material flowing in the cavity). part,
That is, the fibrous filler having a higher specific gravity than the resin base material is unevenly distributed in the portion far from the gate where the mixed material is injected, and the conductivity (volume resistivity) of the solid material-containing resin molded product (mixed material) is increased. However, depending on the density distribution of the fibrous filler in the molded article, there was a case where it was not uniform for each part of the molded article.

When the mixture is injected under high pressure conditions, when the mixture flows in the mold (cavity), the fiber direction (longitudinal direction) of the fibrous filler in the resin base material is changed. And the fibrous fillers in the mixed material are arranged at a distance from each other via the resin base material (non-conductor). In some cases (the volume resistivity increases).

Furthermore, in the process of molding the solid material-containing resin molded article, since the fluidity of the mixture is low due to the inclusion of the fibrous filler, short shots (insufficiently filled) may occur. As a method to prevent short shots, the temperature of the mixed material at the time of injection is set higher than the temperature at the time of injection of the resin base material, etc., which is set when molding a molded article using only the resin base material. Then, it is conceivable to increase the fluidity of the mixed material. However, if such a method is employed, a resin film (skin layer) made of a resin base material is formed on the surface of the molded product, and the fibrous material is formed on the surface The filler is not exposed.

In this case, the conductivity of the molded product is lowered (the volume resistivity value is increased) by the extent that the surface of the molded product (mixed material) is covered with the resin film (nonconductor). It becomes. As a method for preventing short shots, it is conceivable that the injection pressure of the mixed material is set higher than the injection pressure or the like when a molded product is obtained by injecting only the resin base material. In this case, the fibrous filler is damaged, and the conductivity is rather lowered.

[0010] The present invention has been made to solve the above problems, and an object of the present invention is to provide a solid material-containing resin molded article such that the solid material is uniformly exposed over the entire surface of the solid material-containing resin molded article. An object of the present invention is to provide a method for molding a solid material-containing resin molded article that can be molded.

[0011]

According to the first aspect of the present invention, there is provided a method for molding a solid material-containing resin molded product, which comprises the steps of: An injection step of injecting a mixed material comprising a resin base material as a molten resin and a solid material mixed into the resin base material into the cavity, and after the injection step, By reducing the volume of, the mixture in the cavity is pressed and compressed,
A compression molding step of exposing the solid material to the surface of the mixed material.

According to the method for molding a solid material-containing resin molded product of the present invention, first, in the injection step, the volume of the cavity in the mold is determined by the volume of the molded product (the volume of the molded product molded by the molding method). Since the mixture is injected into the cavity after making it larger, the volume of the cavity becomes larger than when the mixture is injected with the cavity volume equal to the molded product volume. The injection pressure of the mixture required to fill the cavity with the mixture can be reduced by a certain amount.

If the injection pressure of the mixture can be reduced as described above, the difference in the flow rate of each part of the mixture when injected into the cavity (in other words, the quantitative flow rate of each part of the mixture) Since the difference can be reduced, it is possible to prevent the solid material from being unevenly distributed to a specific portion in the mixed material when the injection of the mixed material is completed. And as a result, it can be set as the state where the solid material was uniformly scattered in the mixed material.

In the present invention, since the volume of the cavity is reduced and the mixture in the cavity is pressed and compressed in the compression molding step after the injection step, the solid material is exposed on the surface of the mixture. Will be. That is, for example, when the volume of the cavity is reduced in the compression molding process, and the mixed material spreads to all corners of the cavity (in other words, all the air in the cavity is discharged to the outside via a well-known air vent groove or the like). At that moment, the mixture is impacted from the inner wall of the cavity,
The solid material will be extruded onto the surface of the mixture.

In the present invention, since the solid material can be uniformly dispersed in the mixed material in the injection step, when the compression molding step is completed, the mixed material (solid material-containing resin) The solid material can be uniformly exposed on the entire surface of the molded article).

In the present invention, since the volume of the cavity is increased in the injection step, the temperature of the mixture at the time of injection is increased more than necessary to increase the fluidity of the mixture. Even if no special measures are taken, the occurrence of short shots can be sufficiently prevented.

Therefore, according to the present invention, the temperature of the mixture at the time of injection can be kept relatively low, and as a result,
After the completion of the compression molding step, formation of a resin film (skin layer) on the surface of the mixed material (solid material-containing resin molded product) can be reliably prevented.

When the volume of the cavity is made larger than the volume of the molded product during the injection of the mixture, the injection path (sprue, runner, gate) of the mixture from the outside of the mold to the cavity, an air vent, etc. It is a matter of course that the cavity may be in a state where the cavity has a portion opened outside the mold, except for the groove.

However, in order to prevent the mixture from leaking out of the cavity, when the mixture is injected, the cavity does not have a portion opened to the outside other than the above-described mixture injection path and air vent groove. It is preferable to keep it. On the other hand, as a specific mode of the solid material mixed in the resin base material, the solid material according to claim 2 may be used.

That is, in the molding method of the solid material-containing resin molded product according to the second aspect, in the molding method according to the first aspect, the solid material has a conductive particle shape, a fibrous shape,
Alternatively, it is a flake-like filler.

According to the method of molding a solid material-containing resin molded product according to the second aspect, the solid material is a conductive filler (hereinafter, also simply referred to as “conductive filler”). The solid material-containing resin molded product molded in the above can be suitably used as an electromagnetic noise shielding material, a member for grounding, and the like.

That is, according to the molding method of the second aspect, the conductive filler as a solid material can be uniformly exposed on the entire surface of the solid material-containing resin molded product molded by the molding method. , On the entire surface of the molded article,
Since the density of the conductive filler can be increased, compared to a case where the conductive filler is buried inside the molded article and the surface of the molded article is covered with a resin (defective conductor), or the like. Thus, the molded product has suitable characteristics as an electromagnetic noise shielding material, a member for grounding, and the like.

The specific form of the conductive filler may be any of particle, fiber, and flake (flat). And, in the present invention, as described above, in the injection step, the injection pressure of the mixed material can be suppressed to a low level.For example, when the solid material is a fibrous or flake-shaped conductive filler, In addition, it is possible to prevent the longitudinal direction of a large number of conductive fillers from being aligned with the flow direction of the mixture when the mixture flows in the cavity. As a result, a large number of conductive fillers having different longitudinal directions can be arranged so as to overlap on the surface of the mixed material, and the conductivity of the solid material-containing resin molded product can be further improved (in other words, Then, the specific volume resistance can be further reduced).

Next, the molding method of the solid material-containing resin molded article according to the third aspect is the molding method according to the second aspect, wherein the solid material has a volume resistivity of 10 ³ Ω · cm or less. There is a feature. The molding method according to the third aspect shows a specific mode of the characteristics of the conductive filler as a solid material. When the volume resistivity of the conductive filler is set to 10 ³ Ω · cm or less, the solid material-containing resin molded product molded by the molding method can be used as an electromagnetic noise shielding material, a grounding member, or the like. Having more preferable characteristics.

Next, a method for molding a solid material-containing resin molded product according to a fourth aspect of the present invention is the molding method according to any one of the first to third aspects, wherein the compression molding step comprises the steps of: The mixed material is pressurized / compressed such that the volume of the cavity after pressurization / compression is 50% or more and less than 100% of the volume of the cavity before compression.

The molding method according to the fourth aspect shows a specific mode of the degree of change in the volume of the cavity in the compression molding step. Thus, the volume of the cavity after pressurization / compression is 50% or more and 100% or more of the volume of the cavity before pressurization / compression (when the injection step is completed).
If it is configured to have a volume of less than 50%, the stroke length of the movable portion that advances toward the inside of the cavity and reduces the volume of the cavity is shorter than in a case where the volume is configured to be less than 50%. This prevents the mixed material from solidifying before the moving part is completely advanced, and also improves the production efficiency of the solid material-containing resin molded product.

Also, in this case, it is possible to prevent the resin leakage from becoming apparent at the peripheral portion of the movable portion when the movable portion moves forward, as much as the stroke length of the movable portion is short. That is, it is possible to prevent burrs from being generated at a portion of the solid material-containing resin molded product corresponding to the peripheral portion of the movable portion.

The degree of the change in the volume of the cavity in the compression molding step may be further configured as described in claim 5. That is, the method for molding a solid material-containing resin molded product according to claim 5 is the method according to claim 1 to claim 3.
In the molding method according to any one of the above, in the compression molding step, the volume of the cavity after pressurization / compression is 75% or more and less than 100% of the volume of the cavity before pressurization / compression. Pressing and pressing the mixture so that
It is characterized by compression.

In the fifth aspect, the stroke length of the movable portion is further shortened as compared with the fourth aspect. Therefore, the advance of the movable portion is surely completed before the solidification of the mixed material, and the production efficiency of the solid material-containing resin molded product is further improved. In addition, it is possible to more suitably prevent the occurrence of burrs in the solid material-containing resin molded product.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. The solid material-containing resin molded article of this embodiment is obtained by adding a styrene-based thermoplastic elastomer resin as a resin base material to a stainless steel microfiber as a fibrous conductive filler (solid material) (volume resistivity: about 10 ^−5). Ω
(Cm) is mixed with a mixed material (SUSTEC G710PSE; trade name, manufactured by Kawatetsu Techno Research Co., Ltd.).

First, the configuration of a mold and the like for molding the solid material-containing resin molded product will be described. As shown in FIG. 1, in the present embodiment, a mold 10 for molding a solid material-containing resin molded product includes a mold movable side 11 (movable portion) and a mold fixed side 12. In FIG. 1, the projecting portion 11 ′ of the mold movable side 11 on the mold fixed side 12 is in a state of projecting into the opening 12 ′ of the mold fixed side 12.

A cavity 15 as a hollow portion in the mold 10
The boundary is defined by the outer wall 11a of the protrusion 11 'and the inner wall 12a of the opening 12'. The mixture material 21 is configured to be injected into the cavity 15. Specifically, the mixed material 21 is injected from a nozzle of a molding machine (not shown), flows into the cavity 15 from the outside of the mold fixing side 12 through a sprue 16 communicating with the cavity 15 (is injected). It is configured as follows.

The movable side 11 of the mold can be moved along arrows A and A 'shown in FIG. 1A by a driving force obtained from a pressurizing cylinder (not shown) to change the volume of the cavity 15. It is configured to be able to. Specifically, first, when the mold movable side 11 is moved in the direction approaching the mold fixed side 12 (the direction of arrow A), the outer edge 11b and the outer edge of the protrusion 11 'along the arrows A and A' are obtained. The engaging inner wall surface 12b of the opening 12 'corresponding to the opening 11b is engaged with the cavity 15 so that the cavity 15 is not opened to the outside except for the sprue 16 (gate) (FIG. 1).
(A)).

On the mold fixed side 12 of the mold movable side 11, a mold movable side parting surface 11c is provided at a portion outside the projection 11 '. On the side of the movable side 11, the mold fixed side parting surface 12 c is provided at a portion corresponding to the mold movable side parting surface 11 c outside the opening 12 ′. After the wall 12b is engaged, the mold movable side 11 is further moved to the mold fixed side 12, and the mold movable side parting surface 11c and the mold fixed side parting surface 12c are moved. Are brought into contact with each other, so that the volume of the cavity 15 becomes the volume of the molded product (the volume of the solid material-containing resin molded product molded in the present embodiment) (see FIG. 1B).

As described above, in this embodiment, the outer edge portion 11b
And the engagement inner wall surface 12b are engaged with each other, and a predetermined interval δ (δ> 0) is placed between the mold movable side parting surface 11c and the mold fixed side parting surface 12c. When the volume of the cavity 15 is made larger than the volume of the molded product, the mold movable side parting surface 11c and the mold fixed side parting surface 12c are brought into contact, and the volume of the cavity 15 is reduced to the volume of the molded product. Since the mold 10 has a so-called cut-out structure (ink cage structure) in which the outer edge portion 11b and the engagement inner wall surface 12b continue to be engaged until the state is reached, for example, as shown in FIG. In the process of changing from the state to the state shown in FIG. 1 (b), the mixture 21 injected into the cavity 15 is formed into the outer edge portion 11b and the engagement inner wall surface 12b as described later.
Is prevented from leaking to the outside through the space.

However, in the present embodiment, the portion from the engagement portion between the outer edge portion 11b and the engagement inner wall surface 12b to the engagement portion between the mold movable parting surface 11c and the mold fixed side parting surface 12c. Next, the state shown in FIG.
A well-known air vent groove (not shown) is also provided to allow the air in the cavity 15 to flow out of the cavity 15 when the state is changed to the above state.

Next, a molding method of the solid material-containing resin molded article of the present embodiment will be sequentially described with reference to FIGS. 1 (a) and 1 (b). First, as shown in FIG.
b is engaged with the engagement inner wall surface 12b so that a space δ (δ> 0) is placed between the mold movable parting surface 11c and the mold fixed side parting surface 12c. Then, the mixed material 21, which has been heated and the resin base material is turned into the molten resin, is injected into the cavity 15 through the sprue 16.

Here, in the present embodiment, the injection of the mixed material 21 is performed in a state where a distance δ (δ> 0) is placed between the mold movable side parting surface 11c and the mold fixed side parting surface 12c. As is clear from the above, the volume of the cavity 15 at the time of the injection is made larger than the volume of the molded product. Specifically, the size of the interval δ is set such that the volume of the molded product is 75% of the volume of the cavity 15 at the time of the injection.

Therefore, in this embodiment, the injection of the mixed material 21 into the cavity 15 is performed in a state where the volume of the cavity 15 at the time of injection is equal to the volume of the molded article (that is, δ = 0). In comparison, the injection pressure of the mixture 21 required for filling the cavity 15 with the mixture 21 can be reduced by the increase in the volume of the cavity 15.

In this embodiment, as a result of reducing the injection pressure of the mixture 21 to such an extent that a suitable injection into the cavity 15 having a large volume as described above is possible, the mixture injected into the cavity 15 is reduced. Difference in flow velocity for each part 21 (in other words, quantitative flow rate difference for each part of the mixture 21)
However, for example, the size is smaller than in the case where the mixture 21 is injected without lowering the injection pressure into the cavity having the volume of the molded product.

Therefore, when the injection of the mixed material 21 is completed, the conductive filler in the mixed material 21 is prevented from being unevenly distributed to a specific portion in the mixed material 21. As a result, the conductive filler is uniformly distributed in the mixed material 21. It is in a state of being scattered. On the other hand, when the mixture 21 is injected as described above, this time, FIG.
As shown in (b), the mold movable side parting surface 11c
Then, the mixed material 21 in the cavity 15 is pressurized and compressed by bringing the mold and the fixed parting surface 12c into contact with each other to reduce the volume of the cavity 15 to the volume of the molded product.

Then, after that, the mixed material 21 is added to FIG.
In the state of (b), it is cooled and solidified.
1 is moved in the direction of arrow A 'so that the movable mold side 11 and the fixed mold side 12 are completely separated from each other, and then the solidified mixed material 21 (solid material-containing resin molded product) can be taken out. If
The molding of the solid material-containing resin molded article is completed.

Here, in this embodiment, when the mixed material 21 in the cavity 15 is pressurized and compressed, the conductive filler is exposed on the surface of the mixed material 21, so that the molded resin material containing solid material is molded. Can be suitably used as an electromagnetic noise shielding material, a member for grounding, and the like.

That is, first, as the volume of the cavity 15 is reduced, the air in the cavity 15 flows out of the cavity 15 through the above-described air vent groove, and the mixed material 21 spreads to every corner of the cavity 15. In this state, at that moment, the mixed material 21 receives an impact from the inner wall surface (the outer wall 11a and the inner wall surface 12a) of the cavity 15,
The conductive filler is pressed out onto the surface of the mixture 21.

In this embodiment, when the mixture 21 is injected into the cavity 15, the conductive filler is mixed with the mixture 21.
When the pressurization and compression are completed as described above, the conductive filler is uniformly exposed on the entire surface of the solid material-containing resin molded product (mixture 21). Since the density of the conductive filler increases over the entire surface of the molded article, the conductive filler is buried inside the molded article, and the surface of the molded article is covered with resin (non-conductor). As compared with such a case, the conductivity of the molded product is increased (the volume resistivity value is reduced), and the molded product has characteristics suitable as an electromagnetic noise shielding material, a member for grounding, and the like. is there.

In the present embodiment, the conductive filler is constituted as a fibrous filler. In the present embodiment, however, since the injection pressure of the mixed material 21 is suppressed to a low level as described above, The longitudinal direction of the conductive filler is prevented from being aligned with the flow direction of the mixed material 21 when the mixed material 21 flows in the cavity 15.

Therefore, in this embodiment, for example,
The longitudinal directions of a large number of conductive fillers in 1 are aligned so that the individual conductive fillers are arranged at a distance from each other via a resin base material (non-conductor). The conductivity of the solid material-containing resin molded product to be molded is increased (the volume specific resistance value is decreased) by the amount in which a large number of conductive fillers are arranged so as to overlap on the surface of the mixed material 21.

In this embodiment, as described above, the injection pressure of the mixture 21 is kept low, and the volume of the cavity 15 is reduced after the completion of the injection, so that a uniform pressure is applied to the entire mixture 21. Since the molding method is performed by applying the molding method, the residual stress inside the solid material-containing resin molded product is reduced as compared with the case where the molded product is molded by the conventional injection molding method. In addition, deformation such as warpage that can occur in the molded article is also suppressed to a small extent.

In this embodiment, although the fluidity of the mixture 21 when injected into the cavity 15 is low by the amount of the conductive filler, the volume of the cavity 15 is small.
When the injection of the mixed material 21 is performed, measures are taken to increase the fluidity of the mixed material 21 by increasing the temperature of the mixed material 21 more than necessary at the time of injection, because the temperature is increased. Even without this, the occurrence of short shots can be sufficiently prevented.

Therefore, in this embodiment, the temperature of the mixture 21 at the time of injection can be kept relatively low. As a result, after the completion of pressurization and compression after injection, the mixture 2
Forming a resin film (skin layer) on the surface of 1 (solid material-containing resin molded product) can be reliably prevented.

Further, in this embodiment, as described above,
The volume (molded product volume) of the cavity 15 after compression is the same as that of the cavity 15 before pressurization / compression (when the injection of the mixture 21 is completed).
Is configured to change the volume to 75% of the volume. Therefore, in the present embodiment, the stroke length of the mold movable side 11 is shorter than that in the case where the volume is changed to, for example, less than 50%, so that the mold movable side 11 is moved in the arrow A direction. Figure 1
The mixture 21 is prevented from solidifying before reaching the state (b), and the production efficiency of the solid material-containing resin molded product is improved.

In this embodiment, when the movable side of the mold 11 is advanced, the stroke length of the movable side of the mold 11 is shorter.
It is also possible to prevent the resin leakage from appearing at the peripheral portion of the mold movable side 11 (the portion near the outer edge portion 11b). That is, it is possible to prevent burrs from being generated at a portion of the solid material-containing resin molded product corresponding to the peripheral portion of the mold movable side 11.

In the above description, the step of injecting the mixture 21 into the cavity 15 as shown in FIG. 1A corresponds to the injection step of the present invention, and the step of injecting the mixture 21 as shown in FIG. The step of pressing and compressing the mixture 21 in the cavity 15 after the injection of 21 is completed corresponds to the compression molding step of the present invention.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
Various embodiments can be adopted. For example, in the above embodiment, the mixed material 21 is described as being composed of a resin base material that is a styrene-based thermoplastic elastomer resin, and a solid material made of stainless steel (conductive filler as stainless microfiber). The material of the resin base material and the solid material may be any as long as it has physical properties suitable for use of the solid material-containing resin molded product molded from the mixed material 21.

Therefore, as the resin base material, for example, PA
Resin (polyamide resin), PC resin (polycarbonate resin), PP resin (polypropylene resin), POM resin (polyoxymethylene resin), ABS resin (acrylonitrile-butadiene-styrene resin), TPS resin (styrene-based elastomer), TPU resin (Urethane-based elastomer), TPO resin (olefin-based elastomer), and TPEE resin (ester-based elastomer).

As the solid material, for example, iron, SU
It may be made of S, copper, nickel, aluminum, brass, tin, silver, carbon black, carbon fiber, nickel-plated carbon fiber, or the like. In the above-described embodiment, the solid material is described as a fibrous material. However, the present invention is not limited to this. For example, the solid material may be a particulate material or a flake (flat) material depending on the application. Is also good.

Further, the molding method shown in the above embodiment can be widely applied to a case where a solid material-containing resin molded product is desired to be molded such that the solid material is uniformly exposed on the entire surface of the molded product. In that sense, the solid material does not have to be conductive. On the other hand, in the above embodiment,
After injection of the mixture 21 into the cavity 15, the cavity 1
When the volume of the mold 5 was reduced, the mold movable side 11 was moved to the mold fixed side 12, but other positional relationships between the mold movable side 11 and the mold fixed side 12 were not changed. Members (movable parts)
May be advanced into the cavity 15 to reduce the volume of the cavity 15.

Hereinafter, a specific example of the mode in which another member (movable portion) is advanced into the cavity 15 will be described with reference to FIGS. In FIGS. 2 and 3, members having the same functions are denoted by the same reference numerals even if they have different shapes from those shown in FIG. 1, and the description of these members is omitted or simplified. I do.

FIG. 2A is a view showing a state when the mixed material 21 is injected into the cavity 15 (a state before pressurization / compression), and FIG.
FIG. 4 is a diagram showing a state in which the reduction of the volume has been completed (a state after pressurization and compression). In the embodiment shown in FIG. 2, the portion corresponding to the thick portion 21a on the mold movable side 11 (see FIG. 2) is used to prevent the sink from occurring at the thick portion 21a (see FIG. 2B) in the molded product. 2, a compression pin 32 (movable part) is provided at a position corresponding to the lower end of the thick part 21a), and only the compression pin 32 is advanced into the cavity 15 after the injection of the mixture 21.

Specifically, first, the mold movable side parting surface 11c and the mold fixed side parting surface 12c are brought into contact with each other so that the cavity 15 is fixed to the mold movable side parting surface 11c. Except for an air vent groove (not shown) provided between the side parting surface 12c and the sprue 16 (specifically, a gate 16c communicating from the sprue 16 to the cavity 15 via the runner 16b), the mold is opened outside the mold 10. After removing the sprue 1
The mixed material 21 is injected into the cavity 15 through 6. At this time, the compression pin 32 is moved downward (in a direction away from the cavity 15) so that the volume of the portion corresponding to the thick portion 21a in the cavity 15 becomes larger than the volume of the portion when the molding of the solid material-containing resin molded product is completed. ).

Next, the compression pin 32 is moved upward (cavity 1).
5), and the volume of the portion corresponding to the thick portion 21a in the cavity 15 is reduced so that the volume of the portion corresponding to the thick portion 21a becomes a desired volume. Therefore, in this embodiment, even if there is a void that may become sink in a portion corresponding to the thick portion 21 a in the cavity 15 when the mixed material 21 is injected into the cavity 15, the portion is formed by the compression pin 32. By pressing, the above-mentioned gap is eliminated, and generation of sink can be prevented.

If the volume of the portion corresponding to the thick portion 21a in the cavity 15 is reduced by moving the compression pin 32 upward, the entire volume of the cavity 15 is reduced. Since the entire mixture 21 is pressurized and compressed, the same effect as in the above embodiment can be obtained in this mode.

That is, first, the mixed material 21 is placed in the cavity 1
5, the compression pin 32 is located at the lower side, and the mixture 21
Can be suppressed to a relatively low level. When the injection pressure is suppressed in this manner, the conductive filler (solid material)
1 is uniformly scattered.

When the mixed material 21 in this state is pressurized and compressed by moving the compression pin 32, the conductive filler is mixed with the mixed material 21 (solid material-containing resin molded product) in the same manner as in the above embodiment. ) Is uniformly exposed on the entire surface. On the other hand, the embodiment shown in FIG. 3 differs from the embodiment shown in FIG. 2 only in the position of the compression pin 32 before and after the pressurization and compression of the mixture 21. In FIG. 3, FIG.
FIG. 3B is a diagram showing a state when the mixed material 21 is injected into the cavity 15, and FIG. 3B is a diagram showing a state where the volume of the cavity 15 has been reduced.

The embodiment shown in FIG. 3 is similar to the embodiment shown in FIG.
(Refer to (b)), the compression pin 32 located at the position corresponding to the thin portion 21b is preferably
Before the injection of the mixture 21, the lower portion (in a direction away from the cavity 15) so that the volume of the portion corresponding to the thin portion 21 b in the cavity 15 is larger than the volume of the portion when the molding of the solid material-containing resin molded product is completed. In the state where it has been moved.

Therefore, when injecting the mixed material 21 into the cavity 15, the volume of the portion corresponding to the thin portion 21b in the cavity 15 is increased (therefore, the volume of the cavity 15 is increased). The mixed material 2 in the portion corresponding to the thin portion 21b.
1 is improved, and the injection pressure of the mixture 21 can be reduced accordingly.

Then, as shown in FIG. 3B, the compression pin 32 is moved upward (toward the cavity 15), and the volume of the cavity 15 corresponding to the thin portion 21b becomes the desired volume. By doing so, the entire mixture 21 in the cavity 15 is pressurized and compressed, so that the same operation and effect as in the embodiment shown in FIG. 2 can be obtained.

In the embodiment shown in FIGS. 2 and 3, the pressurizing and compressing of the mixture 21 in the cavity 15 may be performed by the protruding pin 31 instead of the compression pin 32. That is, the protruding pin 31 normally separates the mold movable side 11 and the mold fixed side 12 after the pressurization and compression of the mixture 21 shown in FIG. 2B and FIG. 3B. At this time, the solid material-containing resin molded product (mixing material 21) is protruded and functions as a device for separating the molded product from the mold 10. However, the pressing and pressing shown in FIG. 2 (b) and FIG. If the same operation as the compression pin 32 is performed at the time of compression, the volume of the cavity 15 can be reduced and the mixture 21 can be pressurized and compressed by the movement of the protrusion pin 31.

Next, experimental examples supporting the effects obtained by employing the molding method of the above-described embodiment will be described with reference to FIGS. [Experimental Example] In this experiment, the solid material-containing resin molded product molded by the molding method of the above-described example was compared with the solid material-containing resin molded product molded by the conventional injection molding method in terms of the electromagnetic noise shielding material and the like. It was verified whether or not it has suitable characteristics as a member for grounding.

First, the method of this experiment will be described with reference to FIG. In this experiment, first, a 150 mm × 70 mm × 1.7 mm sheet member (hereinafter referred to as “spec sheet 1”) was obtained from the mixture material 21 having the same material as the mixture material 21 of the above embodiment by the molding method of the above embodiment. 3), and three sheet-shaped members having the same dimensions as the sheet-shaped member of specification 1 (hereinafter, also referred to as “sheet-shaped member of specification 2”) formed by three conventional injection molding methods. One sheet was molded.

Next, as shown in FIG. 4, a columnar member 51 having a diameter of φ8 mm and a plate thickness of 1.7 mm is punched from a plurality of positions of each sheet-like member, and the DC resistance value of the columnar member 51 in the plate thickness direction is punched out. R was measured. Specifically, the columnar member 51 is sandwiched between the two electrodes 61 and 62 connected to the digital multimeter 60, and the resistance value R output to the display 60a of the digital multimeter 60 is read to obtain a columnar shape. The DC resistance R of the member 51 was measured.

Then, the resistance value R measured as described above is obtained.
Into the following equation (1), the volume specific resistance value ρ (Ω · Ω) of the columnar member 51 having the resistance value R is obtained.
cm) was calculated, and an average value ρave (Ω · cm) was calculated from the volume specific resistance value obtained from the columnar member 51 punched from the same portion of another sheet member having the same specification.

Ρ = R × π × (0.4) ² ÷ 0.17 (1) FIG. 5 shows the volume resistivity ρave (Ω · cm) of the sheet-like member of the specification 1 calculated as described above. ). In FIG. 5, when the mixture 21 is disposed in the cavity 15, the point indicating the volume specific resistance value of a portion of the mixture 21 closest to the sprue 16 (gate) is indicated by P. Indicates a point.

In FIG. 5, the distribution of the volume resistivity in the downward direction with reference to the point P indicates the distribution of the volume resistivity along the inflow direction of the mixture 21 from the sprue 16. The distribution of the volume specific resistance in the left-right direction indicates the distribution of the volume specific resistance along the direction perpendicular to the direction in which the mixture 21 flows from the sprue 16.

As can be seen from FIG. 5, in the sheet-like member of specification 1 to which the present invention was applied, it was confirmed that the portion having a volume resistivity of 300 Ω · cm or less exceeded 60% of the entire portion. . On the other hand, although not shown in the drawings, in the drawing made from the sheet-shaped member of the specification 2 to which the conventional injection molding method is applied in the same manner as in FIG. Was confirmed.

This is because the conductive filler is uniformly exposed on the surface of the sheet-shaped member of the specification 1 in a wider area than the surface of the sheet-shaped member of the specification 2 (that is, in a wide area which can be said to be substantially the entire surface), This shows that the sheet-shaped member of specification 1 has characteristics more suitable as an electromagnetic noise shielding material, a member for grounding, and the like than the sheet-shaped member of specification 2.

The fact that the conductive filler is exposed in a wider area of the surface of the sheet-like member of the specification 1 can be confirmed by actually observing the surface of the sheet-like member of both specifications. It was confirmed from what I saw. Here, the results of surface observation of a portion (for example, a portion corresponding to the point Q in FIG. 5) where the flow rate of the mixture 21 at the time of injection is considered to be relatively high in the sheet-like members of both specifications are shown. 6 is shown.

FIG. 6 is a schematic diagram showing how the conductive filler was distributed on the surface of the sheet member of both specifications. As shown in FIG. 6B, in the sheet-shaped member of the specification 2, the fiber direction (longitudinal direction) of the conductive filler 25 in the resin base material 23 is in the flow direction of the mixture 21 (the left-right direction in FIG. 6). ), It was confirmed that a large number of conductive fillers 25 in the mixed material 21 were arranged at a distance from each other via the resin base material 23.

On the other hand, in the sheet member of specification 1,
The injection pressure at the time of injecting the mixture 21 into the cavity 15 when molding the sheet member is smaller than the injection pressure at the time of injecting the mixture 21 into the cavity 15 when molding the sheet member of specification 2. As shown in FIG. 6 (a), a large number of conductive fillers 2 can be reduced by the amount that can be kept low.
5 is prevented from being aligned with the flow direction of the mixed material 21 in the mixed material 21, and a large number of conductive fillers 25 having different fiber directions are arranged overlapping on the surface of the mixed material 21. Was confirmed.

Therefore, in the sheet-shaped member of the specification 1, a large number of the conductive fillers 2 are arranged by the large number of the conductive fillers 25 overlapping on the surface of the mixed material 21.
It has also been found that the conductivity is further improved (in other words, the volume specific resistance value is lower) than the sheet-shaped member of specification 2 in which No. 5 is arranged at a distance from each other.

Therefore, based on the experimental results shown in FIGS. 5 and 6, the solid material-containing resin molded article (sheet-shaped member of specification 1) molded by the molding method of the above embodiment was obtained by the conventional injection molding method. It has been confirmed that it has more suitable characteristics as an electromagnetic noise shielding material, a member for grounding, and the like than a solid material-containing resin molded product (sheet-shaped member of specification 2) molded by extrusion.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a molding method of a solid material-containing resin molded product of an example.

FIG. 2 is a longitudinal sectional view illustrating a molding method of a solid material-containing resin molded product as another example.

FIG. 3 is a longitudinal sectional view illustrating a molding method of a solid material-containing resin molded product as another example.

FIG. 4 is an explanatory diagram illustrating a method of measuring a volume specific resistance value of a sheet-like member (solid resin-containing resin molded product) molded in an experimental example.

FIG. 5 is a graph showing a measurement result of a volume specific resistance value of a sheet-shaped member of specification 1 molded in an experimental example.

FIG. 6 is a schematic diagram showing a distribution state of a conductive filler on a surface of a sheet member having two specifications formed in an experimental example.

[Explanation of symbols]

10: mold, 11: mold movable side, 12: mold fixed side, 1
5: cavity, 21: mixed material, 23: resin base material, 25
... conductive filler

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AA13 AA45 AB13 AB25 CA11 CB01 CK18 CK41 CK52 4F206 AA13 AA45 AB13 AB25 JA03 JA07 JN25 JQ81

Claims (5)

[Claims] 1. A method in which a volume of a cavity in a mold is made larger than a volume of a molded product, and a mixed material comprising a resin base material as a molten resin and a solid material mixed in the resin base material is mixed with the mixed material. An injection step of injecting the mixture into the cavity, and after the injection step, reducing the volume of the cavity to press and compress the mixture in the cavity to expose the solid material on the surface of the mixture. And a compression molding step. 2. The method according to claim 1, wherein the solid material is a conductive particle.
The method for molding a solid material-containing resin molded product according to claim 1, wherein the filler is a fibrous or flake filler. 3. The solid material has a volume resistivity of 10 ³ Ω.
The method for molding a solid material-containing resin molded product according to claim 2, wherein the molded product is not more than cm. 4. In the compression molding step, the volume of the cavity after pressurization / compression is 50% or more and less than 100% of the volume of the cavity before pressurization / compression. The method for molding a solid material-containing resin molded product according to any one of claims 1 to 3, wherein the mixed material is pressed and compressed. 5. In the compression molding step, the volume of the cavity after pressurization / compression is 75% or more and less than 100% of the volume of the cavity before pressurization / compression. The method for molding a solid material-containing resin molded product according to any one of claims 1 to 3, wherein the mixed material is pressed and compressed.