JP2021100823A - Resin molded article and manufacturing method of the same - Google Patents

Abstract

To provide a resin molded article capable of improving appearance and a manufacturing method of the same.SOLUTION: A resin molded article 10 includes: a first resin layer 21; and a second resin layer 22 integrally formed on a front side of the first resin layer 21. A recess 15 is provided at a portion close to an outer edge of the resin molded article 10 on a surface of the resin molded article 10 facing the back side. The recess 15 has an undercut shape in which a cross-sectional area increases toward the front side of the resin molded article 10.SELECTED DRAWING: Figure 3

Description

The present invention relates to a resin molded product having a first resin layer and a second resin layer, and a method for producing the same.

In Patent Document 1, as a conventional method for manufacturing a resin molded product, a first resin layer is formed by a common mold and a primary mold, and the common mold and the secondary mold are formed while the first resin layer is left in the common mold. A method of forming the second resin layer on the first resin layer is shown by the mold.

Japanese Unexamined Patent Publication No. 2001-26036 (Fig. 10)

However, in the conventional method for manufacturing a resin molded product described above, if the first resin layer is lifted or warped when the second resin layer is formed, the resin constituting the second resin layer is on the back side of the first resin layer. Wrap around to. As a result, there is a problem that the appearance of the back surface of the resin molded product is deteriorated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin molded product having an improved appearance and a method for producing the same.

The invention of claim 1 made to achieve the above object is a resin molded product having a first resin layer and a second resin layer integrally formed on the front side of the first resin layer. A recess is provided in a portion of the surface of the resin molded product facing the back side near the outer edge of the resin molded product, and the recess has an undercut shape in which the cross-sectional area increases toward the front side of the resin molded product. It has become.

According to the second aspect of the present invention, in the resin molded product according to the first aspect, the recess is formed so as not to penetrate the first resin layer.

The invention of claim 3 is the first resin constituting the first resin layer in the resin molded product according to claim 1 or 2, wherein the distance from the outer edge of the resin molded product to the recess is X1 (mm). When the shrinkage rate of is Y1, X1 · Y1 ≧ 0.2 (mm).

According to the invention of claim 4, in the resin molded product according to claim 3, X1 is 40 (mm) or less.

The invention of claim 5 is to inject the first resin into the first cavity formed between the common mold and the primary mold to form the first resin layer, and to form the first resin layer in the common mold. The primary mold is replaced with a secondary mold while leaving the above, and the second resin is injected into the second cavity formed between the common mold and the secondary mold, and the first resin is placed on the front side of the first resin layer. A method for manufacturing a resin molded product having two resin layers, wherein the common mold and the primary mold are opened and closed at a portion of the common mold that constitutes a portion near the outer edge of the first cavity. An undercut-shaped protrusion whose cross-sectional area increases toward the inside of the first cavity in the direction is provided, and when the first resin layer is formed, the protrusion provides a recess on the back surface of the first resin layer. The second resin layer is formed in a state where the protrusion and the recess are engaged with each other.

In the invention of claim 6, in the method for manufacturing a resin molded product according to claim 5, the distance from the outer edge of the first cavity to the protrusion is X2 (mm), and the shrinkage rate of the first resin is Y1. When, the protrusion is arranged so that X2 · Y1 ≧ 0.2 (mm).

According to the invention of claim 7, X2 is 40 (mm) or less in the method for producing a resin molded product according to claim 6.

[Inventions of Claims 1 to 4]
According to the configuration of the resin molded product according to the present invention, it is possible to mold the second resin layer in a state where the protrusion provided in the mold for forming the concave portion is engaged with the first resin layer. Become. Moreover, since the recess has an undercut shape, it is possible to fix the first resin layer to the engaging portion with the protrusion of the mold and suppress the warp of the first resin layer. As a result, the resin constituting the second resin layer is suppressed from wrapping around on the back side of the first resin layer, and the appearance of the resin molded product can be improved.

Further, when the recess is formed so as not to penetrate the first resin layer, it is possible to suppress the occurrence of spots corresponding to the recess on the front surface surface of the second resin layer (invention of claim 2).

Further, the recess so that the product X1 and Y1 of the distance X1 (mm) from the outer edge of the resin molded product to the recess and the shrinkage rate Y1 of the first resin constituting the first resin layer is 0.2 (mm) or more. Is arranged, when the second resin layer is molded, a gap of 0.2 mm or more can be formed between the outer peripheral surface of the first resin layer and the mold due to the shrinkage of the first resin layer. .. Here, in resin molding, generally, if there is a gap of 0.2 mm or more, the resin easily enters the gap. Therefore, it is possible to allow the resin constituting the second resin layer to enter the gap between the outer peripheral surface of the first resin layer and the mold, and to cover the entire outer peripheral surface of the first resin layer with the resin. .. As a result, on the outer peripheral surface of the resin molded product, it is possible to prevent the outer peripheral surface of the first resin layer from being partially covered by the resin constituting the second resin layer, and the appearance of the resin molded product can be improved (claimed). Item 3). The distance X1 is preferably 40 (mm) or less (invention of claim 4). If the distance X1 exceeds 40 (mm), there may be a problem that the first resin layer tends to warp.

[Invention of claims 5 to 7]
In the method for producing a resin molded product according to the present invention, the second resin layer is molded in a state where the protrusions provided in the common mold are engaged with the first resin layer. Here, since the protrusion has an undercut shape, it is possible to fix the first resin layer to the engaging portion with the protrusion of the common type and suppress the warp of the first resin layer. As a result, the resin constituting the second resin layer is suppressed from wrapping around on the back side of the first resin layer, and the appearance of the resin molded product can be improved.

By the way, when the second resin layer is formed, the shrinkage of the first resin layer causes a gap between the first resin layer and the outer edge of the second cavity. Here, in general, in resin molding, if there is a gap of 0.2 mm or more, the resin easily enters the gap. In the present invention, as described above, since the first resin layer is fixed to the engaging portion with the common type protrusion, the distance X2 (mm) from the portion forming the outer edge of the first cavity to the protrusion is set. By arranging the protrusions so that the product X2 and Y2 with the shrinkage rate Y1 of the first resin is 0.2 (mm) or more, 0.2 mm is provided between the first resin layer and the outer edge of the second cavity. The above gap can be formed. Then, the second resin can be allowed to enter the gap, and the entire outer peripheral surface of the first resin layer can be covered with the second resin. As a result, on the outer peripheral surface of the resin molded product, it is possible to prevent the outer peripheral surface of the first resin layer from being partially covered by the resin constituting the second resin layer, and the appearance of the resin molded product can be improved (claimed). Item 6). The distance X2 is preferably 40 (mm) or less (invention of claim 7). If the distance X2 exceeds 40 (mm), there may be a problem that the first resin layer tends to warp.

Side view of a motorcycle provided with a resin molded product according to an embodiment of the present invention as a cover member. (A) side view, (B) rear view of resin molded product (A) side cross-sectional view of the resin molded product, (B) side cross-section around the outer edge (A) Cross-sectional view of the molding die when the primary mold is used, (B) Cross-sectional view of the molding die when the secondary mold is used. (A) Cross-sectional view of the molding die when the primary mold is closed, (B) Cross-sectional view of the molding die when the first resin layer is molded. (A) Cross-sectional view of the molding die when the secondary mold is closed, (B) Cross-sectional view when the second resin layer is molded. (A) Enlarged view of the periphery of the outer edge of the first resin layer in FIG. 6 (A), (B) Enlarged view of the periphery of the outer edge of the first resin layer in FIG. 6 (B). (A) A perspective photograph of the resin molded product of Experimental Example 1 seen from the back side, (B) Side sectional view of the resin molded product of Experimental Example 1 around the outer edge. (A) A perspective photograph of the resin molded product of Experimental Example 2 seen from the back side, (B) A side sectional view of the resin molded product of Experimental Example 2 around the outer edge. (A) A perspective photograph of the resin molded product of Experimental Example 3 seen from the back side, and (B) a side sectional view of the resin molded product of Experimental Example 3 around the outer edge. (A) A perspective photograph of the resin molded product of Experimental Example 4 seen from the back side, (B) Side sectional view of the outer edge of the resin molded product of Experimental Example 4 Side sectional view of the resin molded product according to another embodiment

Hereinafter, an embodiment in which the present invention is applied to vehicle parts will be described with reference to the drawings. As shown in FIG. 1, the resin molded product 10 of the present embodiment is a cover member 93 of the glove box 92 provided in the lower part of the handle 91 in the motorcycle 90. In the following, in the resin molded product 10, the design surface side of the cover member 93 is referred to as the front side, and the side opposite to the design surface of the cover member 93 is referred to as the back side.

As shown in FIG. 2A, the resin molded product 10 includes a cover main body portion 11 and a leg portion 12. The cover main body 11 is formed in the shape of a "<"-shaped plate. The legs 12 project from the back surface of the cover main body 11 and are fixed to the case member 94 (FIG. 1) of the glove box 92.

As shown in FIG. 3, the cover main body 11 of the resin molded product 10 has a laminated structure in which the first resin layer 21 made of the first resin and the second resin layer 22 made of the second resin are laminated. There is. The surface of the cover body 11 facing the front side is composed of the second resin layer 22, and the surface of the cover body 11 facing the back side is composed of the first resin layer 21. That is, the second resin layer 22 constitutes the design surface of the cover member 93. The leg portion 12 is integrally formed with the first resin layer 21.

As shown in FIG. 2 (B), a plurality of recesses 15 are formed in a portion near the outer edge on the back surface of the cover main body 11. The plurality of recesses 15 extend linearly along the outer edge of the cover main body 11. Further, as shown in FIG. 3A, the plurality of recesses 15 do not penetrate the first resin layer 21 and are formed only in the first resin layer 21.

As shown in FIG. 3A, the depth direction of the recess 15 coincides with the extending direction of the leg portion 12. Further, the recess 15 is formed in an undercut shape in which the cross-sectional area increases toward the front side of the cover main body 11. Specifically, the inner surface of the recess 15 is slightly inclined with respect to the extending direction of the leg portion 12. In FIG. 3A, the axis J1 parallel to the extending direction of the leg portion 12 is indicated by a alternate long and short dash line, and the surface M1 extending the inner surface of the concave portion 15 is indicated by a alternate long and short dash line.

In the resin molded product 10 of the present embodiment, the distance X1 (mm) from the outer edge of the cover main body 11 to the recess 15 is 40 (mm) or less (FIG. 2). Further, when the shrinkage rate of the first resin constituting the first resin layer 21 is Y1, the recesses 15 are arranged so as to satisfy the relationship of X1 · Y1 ≧ 0.2 (mm).

As shown in FIG. 3B, the outer peripheral surface of the first resin layer 21 is covered with the resin constituting the second resin layer 22. Specifically, the resin constituting the second resin layer 22 covers the entire outer peripheral surface of the first resin layer 21, and does not wrap around the back side of the first resin layer 21.

The resin molded product 10 is manufactured using the molding die 30 shown in FIGS. 4 (A) and 4 (B). The molding die 30 is a die for two-color molding, and has a common mold 31, a primary mold 32, and a secondary mold 33. As shown in the change from FIG. 4 (A) to FIG. 4 (B), the primary type 32 and the secondary type 33 are interchangeable with each other. A common recess 31A is formed on the surface of the common mold 31 facing the primary mold 32 or the secondary mold 33. Further, a first recess 32A is formed on the surface of the primary mold 32 facing the common mold 31, and a second recess 33A is formed on the surface of the secondary mold 33 facing the common mold 31. Has been done.

As shown in FIG. 5A, when the common mold 31 and the primary mold 32 are closed, the first resin layer 21 is formed by the common recess 31A of the common mold 31 and the first recess 32A of the primary mold 32. The first cavity 32C having a shape corresponding to the above is formed. Further, as shown in FIG. 6A, when the common mold 31 and the secondary mold 33 are closed, the resin molded product is formed by the common recess 31A of the common mold 31 and the second recess 33A of the secondary mold 33. A second cavity 33C having a shape corresponding to 10 is formed.

As shown in FIGS. 4 (A) and 4 (A), a plurality of protrusions 31T (the same figure) protruding in the opening / closing direction of the molding die 30 are located near the outer edge of the bottom surface of the common recess 31A in the common mold 31. Is provided with only one protrusion 31T). The protrusion 31T is formed in an undercut shape in which the cross-sectional area increases toward the inside of the first cavity 32C. Specifically, the outer surface of the protrusion 31T is slightly inclined with respect to the opening / closing direction of the molding die 30.

The protrusion 31T is arranged so that the distance X2 (mm) from the outer edge of the common recess 31A of the common mold 31 to the protrusion 31T is 40 (mm) or less (FIG. 4 (A)). Further, assuming that the shrinkage rate of the first resin is Y1, the protrusions 31T are arranged so as to satisfy the relationship of X2 · Y1 ≧ 0.2 (mm).

In order to manufacture the resin molded product 10 using the molding die 30, first, the common mold 31 and the primary mold 32 are closed (FIG. 5A), and the first resin is injected into the first cavity 32C. The first resin layer 21 is formed (FIG. 5 (B)). At this time, the recess 15 is formed in the first resin layer 21 by the protrusion 31T of the common mold 31.

Next, while leaving the first resin layer 21 in the common mold 31, the primary mold 32 is replaced with the secondary mold 33, and the common mold 31 and the secondary mold 33 are closed (FIG. 6 (A)). At this time, the recess 15 of the first resin layer 21 engages with the protrusion 31T of the common mold 31, and the first resin layer 21 is fixed to the engagement portion with the protrusion 31T. Further, the first resin layer 21 undergoes heat shrinkage to form a gap 34 between the first resin layer 21 and the inner surface of the outer edge of the second cavity 33C (FIG. 7A). The width of the gap 34 is 0.2 mm or more due to the above-mentioned relationship of X2 · Y1 ≧ 0.2 (mm).

Next, the second resin is injected into the second cavity 33C to form the second resin layer 22 (FIG. 6 (B)). At this time, the second resin enters the gap 34 between the first resin layer 21 and the inner surface of the outer edge of the second cavity 33C and covers the entire outer peripheral surface of the first resin layer 21 (FIG. 7B). .. Further, since the first resin layer 21 is fixed to the common mold 31 by the engagement of the recess 15 and the protrusion 31T, the first resin layer 21 is lifted from the common mold 31 and the first resin layer 21 is warped. It is suppressed. As a result, it is possible to prevent the second resin from wrapping around the back side of the first resin layer 21.

Next, when the first resin layer 21 and the second resin layer 22 are removed from the molding die 30, the resin molded product 10 (FIGS. 2 to 3) is obtained.

The description of the resin molded product 10 of the present embodiment and the manufacturing method thereof has been described above. Next, the action and effect of this embodiment will be described.

In the present embodiment, the second resin layer 22 is formed in a state where the protrusion 31T provided on the common mold 31 is engaged with the first resin layer 21. Here, since the protrusion 31T has an undercut shape, the first resin layer 21 is fixed to the common mold 31 by engaging the recess 15 of the first resin layer 21 with the protrusion 31T of the common mold 31. It is possible to suppress warpage and floating of the first resin layer 21. As a result, the second resin is prevented from wrapping around to the back side of the first resin layer 21, and the appearance of the resin molded product 10 is improved.

Further, in the present embodiment, since the recess 15 does not penetrate the first resin layer 21, it is possible to prevent the occurrence of spots corresponding to the recess 15 on the front side surface of the second resin layer 22.

Further, in the present embodiment, when the second resin layer 22 is molded, a gap 34 of 0.2 mm or more is formed between the outer edge of the first resin layer 21 and the outer edge of the second cavity 33C. The second resin that has entered the gap 34 makes it possible to cover the entire outer peripheral surface of the first resin layer. As a result, it is possible to prevent the second resin from partially covering the outer peripheral surface of the first resin layer 21, and to improve the appearance of the resin molded product 10. Further, since the distance X2 (mm) from the outer edge of the common recess 31A to the protrusion 31T is 40 or less, the outer edge of the first resin layer 21 is warped when the second resin layer 22 is molded. Lifting is suppressed.

8 to 9 show the influence of the protrusion 31T (FIG. 4 (A)) of the common mold 31 on the appearance of the resin molded product 10 (in other words, the recesses 15 (FIGS. 2 (B) and 3 (A))). The results of Experimental Examples 1 to 4 performed to verify the effect on the appearance of the resin molded product 10) are shown. In Experimental Examples 1 to 4, a mixed resin containing a polypropylene resin, an elastomer and talc is used as the first resin, and an olefin-based elastomer is used as the second resin. Then, the shrinkage rate Y1 of the first resin is 0.7%. The thickness of the first resin layer 21 is 2.5 mm, and the thickness of the second resin layer 22 is 1.5 mm.

The details of each experimental example are as follows. In Experimental Example 1, the protrusion 31T is not provided in the common recess 31A. In Experimental Examples 2 to 4, the distance X2 (mm) from the outer edge of the common recess 31A to the protrusion 31T is different. In Experimental Example 2, X2 = 15 (mm), in Experimental Example 3, X2 = 25 (mm), and in Experimental Example 4, X2 = 30 (mm). In Experimental Examples 2 and 3, X2 · Y1 <0.2 (mm), and in Experimental Example 4, X2 · Y1> 0.2 (mm).

8 (A) to 11 (B) show the back surface and the side surface of the resin molded product 10 of each experimental example. The first resin constituting the first resin layer 21 is shown in gray, and the second resin constituting the second resin layer 22 is shown in black. The photographs shown in FIGS. 8 to 11 (A) are photographs of the resin molded product 10 taken from the direction Z shown in (B) of FIGS. 8 to 11, respectively.

As shown in FIGS. 8A and 8B, in Experimental Example 1, the second resin constituting the second resin layer 22 covers the entire outer peripheral surface of the first resin layer 21 and is the first. It wraps around to the back side of the resin layer 21. Further, as shown in FIGS. 9A and 9B, in Experimental Example 2, the second resin did not wrap around the back side of the first resin layer 21, and almost covered the outer peripheral surface of the first resin layer 21. Not done. As shown in FIGS. 10A and 10B, in Experimental Example 3, the second resin did not wrap around to the back side of the first resin layer 21, as in Experimental Example 2, but the first resin. It partially covers the outer peripheral surface of the layer 21. As shown in FIGS. 11A and 11B, in Experimental Example 4, the second resin covers the entire outer peripheral surface of the first resin layer 21 and wraps around the back side of the first resin layer 21. Not.

From the results of Experimental Example 1 and Experimental Examples 2 to 4, it can be seen that when the common mold 31 is provided with the protrusion 31T, the second resin is suppressed from wrapping around to the back side of the first resin layer 21. Further, from the results of Experimental Examples 2 to 4, it can be seen that as the values of X2 and Y1 increase, the area of the outer peripheral surface of the first resin layer 21 covered by the second resin increases. This is because as the values of X2 and Y1 increase, when the second resin is injected into the second cavity 33C (FIG. 6 (A)), it is between the first resin layer 21 and the outer edge of the second cavity 33C. This is because the width of the formed gap 34 (FIG. 7A) becomes large, and the second resin easily enters the gap 34. Then, when X2 · Y1 <0.2, the second resin cannot cover the entire outer peripheral surface of the first resin layer 21, and when X2 · Y1 ≧ 0.2, the second resin It can be seen that the resin covers the entire outer peripheral surface of the first resin layer 21.

As described above, from Experimental Examples 1 to 4, when the product X2 · Y1 of the distance X2 from the outer edge of the common recess 31A to the protrusion 31T and the shrinkage rate Y1 of the first resin is 0.2 or more, the first It was confirmed that while covering the entire resin layer 21 with the second resin, it was possible to prevent the second resin from wrapping around to the back side of the first resin layer 21.

[Other Embodiments]
The present invention is not limited to the above embodiments, and for example, embodiments as described below are also included in the technical scope of the present invention, and various other than the following, as long as they do not deviate from the gist. It can be changed and implemented.

(1) In the above embodiment, the cover member 91 provided in the motorcycle 90 is shown as an example of the resin molded product of the present invention, but the present invention is not limited thereto, and is used, for example, in a glove box or a console box of an automobile. It may be a member.

(2) In the above embodiment, the recesses 15 may be formed in dots and arranged along the outer edge of the resin molded product 10. Further, in the above embodiment, the recess 15 is provided in a straight line, but it may be provided in a curved shape along the outer edge of the first resin layer 21.

(3) In the above embodiment, the recess 15 does not penetrate the first resin layer 21, but as shown in FIG. 12, it may have a configuration that penetrates the first resin layer 21. In the example of FIG. 12, the depth of the recess 15 is the same as the thickness of the first resin layer 21.

10 Resin molded product 15 Recessed portion 21 First resin layer 22 Second resin layer 30 Molding mold 31 Common mold 31T Protrusion 32 Primary mold 33 Secondary mold

Claims (6)

A resin molded product having a first resin layer and a second resin layer integrally formed on the front side of the first resin layer.
A recess is provided on the surface of the resin molded product facing the back side.
A plurality of the recesses are formed along the outer edge of the resin molded product, and have an undercut shape in which the cross-sectional area increases toward the front side of the resin molded product. In the resin molded product according to claim 1,
The outer peripheral surface of the first resin layer is covered with the resin constituting the second resin layer. In the resin molded product according to claim 1 or 2.
The recess is formed so as not to penetrate the first resin layer. In the resin molded product according to any one of claims 1 to 3,
When the distance from the outer edge of the resin molded product to the recess is X1 (mm) and the shrinkage rate of the first resin constituting the first resin layer is Y1, X1 · Y1 ≧ 0.2 (mm). Is. In the resin molded product according to any one of claims 1 to 4.
The distance from the outer edge of the resin molded product to the recess is X1 (mm), and X1 is 40 (mm) or less. A cover member for a storage box for a vehicle, comprising the resin molded product according to any one of claims 1 to 5.

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