JP2000117778A - Injection molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a sinkmark from being generated on the first surface of a molded product corresponding to a gate position and a foil-decorated sheet damage such as the run of an ink layer of the foil-decorated sheet from occurring by providing a gate as an injection hole for a resin into a cavity, in a rib on the second surface of the molded product. SOLUTION: A gate 3 is formed in a rub 7 by using the rib 7 formed on the second surface of a molded product 1. Then a fluid resin is made to pass through a runner 2 from a sprue and thereby is packed into a cavity with the rib 7 from the gate 3. In addition, even when the molded product 1 is of such a type that no rib 7 is present on the second surface of the molded product 1, but the rib 7 is formed on the outer periphery, as the back side, of the molded product 1, the rib 7 is used. In addition, the gate 3 is formed on the rib 7 overhanging behind the outer periphery of the molded product 1. The rib 7 may be formed as one serving as the gate 3, when it is considered that this structure does not bring about a difficulty to the use of the molded product 1. Thus it is possible to prevent a sinkmark from being generated on the first surface corresponding to the position of the gate 3 and a foil-decorated sheet damage such as the run of an ink layer due to shear heat generation when the resin is injected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold used in a simultaneous painting method for injection molding. In particular, the present invention relates to an injection mold that can prevent sinks from occurring on a product surface of a gate portion.

[0002]

2. Description of the Related Art Conventionally, there are various injection molding simultaneous painting methods in which a pattern or the like is formed on the outer surface of a molded article simultaneously with the molding of the molded article. For example, in Japanese Patent Publication No. 50-19132, after a picture-formed sheet made of a thermoplastic resin is vacuum-formed by using a female mold having a vent hole for vacuum molding, both the male and female molds are clamped to melt the molten resin. There is disclosed a method of injecting into a cavity formed by both molds and integrating a painting sheet with an outer surface of a molded article simultaneously with injection molding. The simultaneous injection molding painting method of this aspect is a method in which vacuum molding and injection molding are combined, and a complicated curved surface can be patterned. Note that there are two types of painted sheets: a laminate type and a transfer type. In the former, the painted sheet itself is laminated on a molded product for painting, and in the latter, only the base sheet of the painted sheet is peeled off to form the transfer layer. Transfer to the product and paint.

[0003]

By the way, the injection resin is filled from the gate into the cavity. However, depending on the shape of the molded product, the gate position, and the like, the surface of the molded product near the gate is depressed. May occur. Also,
In the simultaneous painting method of injection molding, the surface of the molded product is painted with a painted sheet, the gate is usually provided on the back side of the molded product, and the resin is injected from the back side, so the heat resistance of the painted sheet is low. If it is not enough, the molten resin immediately after filling into the cavity from the gate on the back side touches the back side which will be the adhesive surface of the painted sheet, and the painted sheet will melt or soften, and the painted sheet will break. It may flow. Further, even when the heat resistance of the ink layer formed by printing to impart a pattern or the like to the back side of the painted sheet is not sufficient, the ink layer may melt or soften and flow for the same reason.
When the ink layer flows, the picture is distorted or disappears. In particular, in a portion where the resin is filled into the cavity through the gate, the cross-sectional area of the flow path is small, so that there is also an effect due to the heat generated by shearing of the resin. For this reason, as shown in FIG. 3, a circular thick portion 4 may be provided on the back surface of the molded product around the gate 3 to reduce the influence of heat applied to the painted sheet or its ink layer. Since the thick part has a large thickness, sink marks become severe and the appearance of the molded product may be poor. In this way, in the case of the simultaneous painting method of injection molding, the use of a painted sheet requires special heat resistance and the shape of the molded product to prevent sink marks and prevent the painted sheet from being damaged by the heat of the injection resin. We had to devise something.

[0004]

Therefore, in order to solve the above-mentioned problems, in the injection molding die of the present invention, after the painting sheet is supplied between the male and female dies of the injection molding, the two dies are clamped to form a flow. Inject the resin in the state into the cavity formed by both molds,
In the mold used in the simultaneous injection molding and painting method for producing a painted product, a gate, which is a hole for injecting the resin into the cavity, is provided in a rib on the back side of the molded product. As a result, sink does not occur on the surface of the molded product corresponding to the gate position. In addition, since the painted sheet is far from the portion where the resin generates heat upon filling, damage to the painted sheet such as the flow of the ink layer of the painted sheet can be prevented.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an injection mold according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view for comparing and explaining a case where an injection mold is according to the present invention and a case where it is conventional. It should be noted that the drawing is based on the resin filled in the mold, that is, a cross-sectional view of the molded product.

In the case of a conventional injection molding die, for example, in the case of a submarine gate, as shown in FIG. 1A, a gate 3 is provided on a boss 6 provided on the back surface of the molded product 1. In addition to this boss 6 being provided only for resin filling,
It may be provided for other purposes. On the other hand, in the injection molding die of the present invention, as illustrated in FIG. 1 (B), the gate 3 is provided on the rib 7 by utilizing the rib 7 provided on the back surface of the molded product 1. Provide. FIG. 1 (B)
Is an example in which a pinpoint gate is provided at the tip of the rib 7. As shown in FIG. 1 (A), when the molded article 1 has a rib 7 on the back surface, a sink is prevented by providing a gate on the rib.
The resin in a flowing state is supplied from a sprue (not shown) to a runner 2.
To fill the cavity having the ribs 7 from the gate 3.

FIGS. 1 (A) and 1 (B) show the case where there is a rib on the back surface of the molded product 1. However, even if there is no rib on the back surface of the molded product 1, as shown in FIG. 1 (C). When the rib 7 is located on the outer periphery of the molded product as the back side of the molded product, the rib 7 may be used. That is, as shown in FIG. 1 (D), the gate 3 may be provided on the rib 7 projecting rearward on the outer periphery of the molded product. The gate 3 illustrated in FIGS. 1C and 1D
Is a case using a submarine gate (tunnel gate), but of course, in this case, the invention is not limited to the submarine gate.

As described above, in the injection mold of the present invention, since the gate is provided on the rib, sink does not occur. Also, since the painted sheet is far from the portion where the resin generates heat by shearing during filling, the painted sheet is less likely to be damaged such as the ink layer of the painted sheet flowing. Note that the rib provided with the gate may be a rib originally provided, but a rib may be newly provided for the gate if there is no problem in using the molded product. In the above description, the type of the gate is the pinpoint gate and the submarine gate. However, the type of the gate is not limited to this, and various other known gates may be used. Further, the mold material of the injection mold is not particularly limited. For example, S50C, S5
As a mold material such as 5C, SCM3, and SCM4, besides various conventionally known steel materials, other metals and metal alloys such as copper, and nonmetal materials such as ceramics may be used, and may be appropriately selected and used.

[Injection Simultaneous Painting Method] A simultaneous injection molding simultaneous painting method in which the injection mold of the present invention can be used will be described here. The injection molding simultaneous painting method is described in JP-B-50-19132, JP-B-43-27488, JP-A-6-315950, and JP-B-2-420.
As described in Japanese Patent Publication No. 80, etc., after supplying a painted sheet between both male and female molds for injection molding, a resin in a fluid state is injected and filled into a cavity formed by both molds, thereby forming a resin molded product. At the same time, a painting sheet is laminated on the surface to produce a painting molded article painted by lamination or transfer.

There are various types of simultaneous injection molding painting methods.
For these various forms, the injection mold of the present invention can be used. As various forms of the injection molding simultaneous painting method,
For example, either a mode in which the preformed sheet is preformed or a mode in which the preformed step is not performed may be used. Also, the prepainted sheet may or may not be preheated. Note that the prepainted sheet is usually preheated during preforming. Of course, when the drawing sheet has a large drawing, it is preferable to perform preforming.
On the other hand, when the drawing sheet has a small amount of drawing, the drawing sheet can be formed by the resin pressure of the resin in the flowing state to be injected. At this time, if the drawing is shallow, the painted sheet may be formed only by the resin pressure of the resin in the flowing state filled into the mold at the same time as the resin injection without preforming. Further, even when the painted sheet is formed by the resin pressure, the painted sheet may utilize the heat of the injection resin without preheating. In addition, in the preforming of the painted sheet, usually, the injection molding die is also used as a vacuum molding die, but before supplying the painted sheet between the dies, the painted sheet is vacuum molded with another vacuum molding die outside the mold. Such preliminary molding may be used.
In addition, the vacuum forming includes vacuum pressure forming.

The injection molding simultaneous painting method will be described in one form with reference to the conceptual diagram of FIG. The embodiment described here is a mode in which the painted sheet is heated and softened between the molds, pre-molded by vacuum molding using an injection molding die, and then resin is injected by clamping before the mold is clamped. Further, since this conceptual diagram is a diagram for explaining the simultaneous painting method for injection molding itself, the position of the gate is not intentionally specified and is shown in a simplified manner. 1
As shown in (B) and (D), the gate is provided at the rib on the back side of the molded product.

First, as shown in FIG. 2A, as an injection mold, a mold Ma having a runner and a gate communicating with an injection nozzle and a preforming mold for a sheet having a suction hole 41 on the mold surface are used. A pair of molds of the mold Mb is used. These molds are made of metal such as iron or ceramics. In the mold open state, the painting sheet S is supplied between the two molds Ma and Mb, and the painting sheet S is attached to the mold Mb by a frame-shaped sheet clamp 42.
Press to fix. At this time, it goes without saying that the adhesive surface side of the painted sheet is on the injection resin side on the right side of the drawing. Next, the painted sheet is appropriately heated and softened by a heater inserted between both molds. The heating is, for example, non-contact radiation heating, but may be contact heating. Then, the sheet is sucked from the suction hole and vacuum formed, and the prepainted sheet is preformed along the cavity surface of the mold Mb. In addition, vacuum forming may be vacuum press forming using both pressure and air, and this is also included. Next, the heater is retracted from between the two dies, the two dies are clamped as shown in FIG. 2B, and a cavity formed by the two dies is filled with a resin in a flowing state such as a heated and molten state. After the resin is solidified by cooling or the like, the mold is opened and the molded product is taken out. In the case where the painted sheet is a laminate sheet, if there is an unnecessary portion of the painted sheet, the trimmed sheet is appropriately trimmed to obtain a painted molded article in which the painted sheet is laminated on the resin molded article and painted. Further, when the painting sheet is a transfer sheet, the molded article is taken out with the base sheet left on the mold Mb side, or
Alternatively, after taking out the molded product in a state where the whole of the painting sheet is laminated, the base sheet is peeled off to obtain a painted molded product in which only the transfer layer is laminated and painted.

In the simultaneous painting by injection molding using the injection mold of the present invention, the resin to be injection-molded is not particularly limited, and any resin conventionally known in the method of simultaneous painting by injection molding can be used. The injection molding resin is selected according to the required physical properties and cost of the product. For example, in the case of a thermoplastic resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, styrene resin, vinyl chloride resin, acrylic resin, polycarbonate resin, polyethylene, or polypropylene And polyolefin resins such as polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, and olefin-based thermoplastic elastomer. In addition, in the case of a curable resin, a material which has been conventionally known as a two-part curable resin, such as an uncured resin liquid such as a urethane resin, an unsaturated polyester resin, or an epoxy resin, is used for simultaneous injection molding and painting. Can be used. The thermoplastic resin is melted by heating and injected in a fluid state, and the curable resin is injected at room temperature or appropriately heated and flowed. However, the advantage of the injection mold of the present invention is that the resin that can be particularly utilized is a resin that is injected by heating, and is particularly a thermoplastic resin that is injected in a fluid state by heating and melting.

[Painted sheet] As the painted sheet that can be used for simultaneous painting by injection molding using the above-described injection mold, a conventionally known painted sheet as a transfer type or a laminate type can be used. It is not done. However, in the injection molding die of the present invention, since the influence of heat at the gate portion is reduced, a painted sheet having lower heat resistance than the conventional one can be used. Therefore, the painting sheet will be briefly described.

Transfer type painting sheet (transfer sheet)
Has a configuration in which a releasable sheet is used as a base sheet and a transfer layer is laminated on the base sheet. The transfer layer includes, for example, a decorative layer, an adhesive layer, and the like. In addition, there is a configuration in which a release layer is appropriately provided as a component of the transfer layer on the base sheet side of the transfer layer. The laminate type painting sheet (laminated sheet) has a configuration in which, for example, a decorative layer and an adhesive layer are sequentially laminated on a base material sheet. The adhesive layer may be omitted in both the transfer type and the laminate type.

(Base Sheet) As the base sheet, a resin sheet having moldability is typically used. Examples of the resin sheet include olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, olefin-based thermoplastic elastomer, polybutylene terephthalate, and ethylene terephthalate isophthalate copolymer. Polyester resin, vinyl chloride resin, acrylic resin, etc.
Single layer or different types of thermoplastic resin sheets such as ABS (acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, polyamide resin, and other thermoplastic elastomers such as urethanes Is used. Also,
If the formability is satisfied, a sheet in which a resin such as a nonwoven fabric or a woven fabric is impregnated with a resin, a laminate obtained by laminating the resin sheet on the sheet, or the like can be used. In the transfer type, a base sheet having a release layer is provided on the transfer layer side of the base sheet, if necessary, in order to improve the releasability from the transfer layer. The release layer is separated from the transfer layer together with the base sheet when the base sheet is peeled, and is removed. For the release layer, for example, a simple substance such as silicone resin, melamine resin, polyamide resin, urethane resin, polyolefin resin, wax, or 2
Mixtures of more than one species are used. Further, in the case of a laminate type, a coloring agent such as a pigment is kneaded into a base sheet resin to perform a decoration process for making the base sheet colored transparent or colored opaque, or colorless transparent or colorless opaque.
In this case, the base sheet itself may form a decorative layer, and may be a picture sheet having a configuration of only the base sheet.

(Decoration Layer) The decoration layer may be formed by a conventionally known method such as gravure printing, silk screen printing, offset printing or the like, a picture layer (ink layer) on which a picture or the like is printed with a material, a metal such as aluminum or chromium. A metal thin film layer or the like formed on a part or the entire surface by a vapor deposition method or the like. The pattern is arbitrary, such as a grain pattern such as a plate grain or a straight grain, a grain pattern such as marble or granite, a tile pattern, a brick pattern, a cloth pattern, a character, a geometric pattern, and a solid surface. The picture layer ink comprises a vehicle such as a binder, a coloring agent such as a pigment or a dye, and various additives appropriately added thereto. For the binder, chlorinated polyethylene, chlorinated polyolefin such as chlorinated polypropylene, polyester resin, thermoplastic urethane resin,
Acrylic resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, thermoplastic resin such as cellulose resin, thermosetting urethane resin, thermosetting resin such as epoxy resin, etc., are used alone or as a mixture of these resins. . As a coloring agent such as a pigment or a dye, metal pigments such as titanium white, carbon black, red iron oxide, cobalt blue, graphite, phthalocyanine blue, isoindolinone, quinacridone, and aluminum powder, and pearlescent (pearl) pigments are used. Can be

(Adhesive layer) On the back side of the painted sheet, an adhesive layer such as a corona discharge treatment, a well-known various primer coating, etc., or a heat-sensitive adhesive layer is applied to improve the adhesiveness with the injection resin. Sometimes. Known resins such as a thermoplastic resin and a thermosetting resin are used for the adhesive layer. For example, in the case of a thermoplastic resin, a styrene resin such as polystyrene and poly-α-methylstyrene or a styrene copolymer, an acrylic resin such as poly (methyl) acrylate, ethyl poly (meth) acrylate, and butyl poly (meth) acrylate are used. Resin, chlorinated polyolefin resin such as chlorinated polypropylene, vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, vinyl polymer such as polyvinyl butyral, polyisoprene rubber, polyisobutyl rubber, styrene butadiene rubber, butadiene One or a mixture of two or more of a rubber-based resin such as acrylonitrile rubber and a thermoplastic resin such as a polyamide resin is used. In the case of thermosetting resin,
Urethane resin, epoxy resin and the like are used.

[Others] In the present invention, "painting"
The expression includes not only providing a visible pattern such as a pattern, a character, or a figure to a molded product, but also providing a pattern that is not visible or a functional layer such as a hard coating film or conductivity.
Known patterns such as a pattern layer formed by printing or the like and a metal thin film layer formed by vacuum evaporation or the like are examples of the pattern that can be visually observed. A pattern of fluorescent ink that emits fluorescence is used.

[0020]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Embodiment] As an injection mold of the present invention, a mold for molding a molded article for a console box of an automobile was prepared. The dimensions of the painted molded product are 200 m wide on the front
m, a rectangle having a length of 500 mm, an average thickness of 3 mm, and a maximum drawing depth of the painting sheet of 40 mm. As shown in FIG. 1 (B), the gate was provided with a gate 3 at the tip of a rib 7 on the back surface of the molded product 1. The width of the rib 7 was 0.7 mm, and the gate was a pinpoint gate having a diameter of 2.5 mm.

On the other hand, the painted sheet has an acrylic resin and a vinyl chloride film on the back side (molded article side) of a base sheet made of a transparent acrylic resin film having a thickness of 125 μm.
Using a mixed resin system with a vinyl acetate copolymer as a binder resin, and using a coloring ink containing a coloring pigment mainly consisting of a red stem, a pattern layer of a wood grain design is formed by gravure printing in three colors. After that, an adhesive layer (4 μm thick) made of a vinyl chloride-vinyl acetate copolymer was further formed by gravure coating to prepare a two-layer coating.

Then, simultaneous painting by injection molding is performed using the above-mentioned painting sheet as described in the conceptual diagram of FIG.
I tried to produce a painted molded product in which a painted sheet was laminated. First, after supplying the painted sheet between the male and female molds with the picture layer facing the gate side of the male mold and opening the mold, an infrared radiation heating type heating plate heated to a surface temperature of 350 ° C. After inserting between the molds and heating the painted sheet for 3 seconds in a non-contact manner, using the female mold as a vacuum forming mold, starting evacuation and preforming the painted sheet by vacuum forming, It was molded into a shape along the cavity surface of the mold. Then, 5 seconds after the start of evacuation, the hot plate was retracted to a retracted position outside the mold, and both molds were clamped. Next, the heat-resistant ABS resin was injected into the cavity formed by both molds at a resin temperature of 240 ° C. and a mold temperature of 60 ° C. After the resin was cooled and solidified, the mold was opened to obtain a painted molded product.

As a result, no sink marks were observed on the front side of the molded article. In addition, the painted sheet withstands the heat of the resin at the time of injection, and both the base sheet and the pattern layer break, flow,
Did not occur. In addition, even if the injection resin pressure is low, short shots (where the ribs are not filled with resin) do not occur due to the presence of the gates in the ribs, so that stable simultaneous injection molding painting without burrs can be performed.

[Comparative Example] With respect to the mold used in the example, the gate position was such that the gate 3 was directly provided on the back surface of the molded product 1 as shown in FIG. The gate was a 2.5 mm diameter pinpoint gate. However, around the gate 3 on the rear surface of the molded product, a thick portion 4 having a circular shape with a diameter of 10 mm and a thickness increased by 1 mm from 3 mm to 4 mm was provided. Other than this,
In the same manner as in the example, painting was performed simultaneously with injection molding to obtain a painted molded product.

As a result, the painted sheet withstood the heat of the resin at the time of injection, but as shown in FIG.
The sink 5 occurred at the gate 3. And in order to correct sink marks, I tried increasing the injection resin pressure and re-molding.
Burrs occurred around the molded product.

[0027]

According to the injection molding die of the present invention, when a painted product is obtained by simultaneous painting with injection molding, sink marks do not occur on the front surface of the molded product corresponding to the gate position.
Further, when the resin is filled in the cavity, the painted sheet is not present in the gate or in the vicinity of the gate where shear heat is liable to be generated, so that the painted sheet is not damaged such as the flow of the ink layer. Using the original ribs can prevent sink marks and damage to the painted sheet without changing the product design. In addition, since the painted sheet can be prevented from being damaged, painting with the painted sheet can be performed without changing the design, such as providing a thick part peculiar to the use of the painted sheet, for a molded product originally without painting using the painted sheet. it can. Furthermore, since a gate is provided on the rib, a short shot or the like at the rib is less likely to occur.

[Brief description of the drawings]

FIG. 1 is an explanatory view conceptually illustrating the injection mold of the present invention and a conventional injection mold in the form of a molded product.

FIG. 2 is a conceptual diagram illustrating an injection molding simultaneous painting method in one example.

FIG. 3 is an explanatory view conceptually illustrating another example of a conventional injection molding die in the form of a molded product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Runner 3 Gate 4 Thick part 5 Sink 6 Boss 7 Rib 41 Suction hole 42 Sheet clamp Ma Injection mold (male) Mb Injection mold (female) PL Parting line S Painting sheet

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F202 AA13 AD05 AD09 AG28 AH25 AJ02 AJ05 AM34 CA11 CB01 CB13 CB19 CB26 CK06 4F206 AA13 AD05 AD09 AG28 AH25 AJ02 AJ05 AM32 JA07 JB13 JB19 JB24 JE06 JE81 JF08

Claims (1)

[Claims] After supplying a painting sheet between both male and female molds for injection molding, both molds are clamped, and a resin in a fluid state is injected into a cavity formed by both the molds to form a painting molded article. A mold used in a simultaneous painting method for injection molding to be manufactured, wherein a gate, which is a hole for injecting resin into a cavity, is provided in a rib on the back side of a molded product.