JP2000263598A - Method for foil decoration simultaneously with injection molding and foil decoration mold therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of sink, the whitening of a painting sheet caused by the sink, and peeling in foil decoration simultaneously with injection molding. SOLUTION: A sink preventing slide part 4 which slides in the thickness direction of a molding is provided in a part of the cavity surface 3 of a mold Mb, which does not face a decoration sheet S, out of a pair of molding molds Ma, Mb for decorating corresponding to a thick-wall part in which sink is apt to occur by a boss 1 and others, and the slide part, in a process in which a packed resin is solidified by cooling and others, is slide to the side of the decoration sheet S by a drive part 5 to prevent the generation of sink in the surface of the molding on the side of the sheet S in the neighbourhood (a) of the slide part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simultaneous painting method for injection molding and a painting mold used for the method. In particular, the present invention relates to a method for preventing sink marks and a mold for painting using the method.

[0002]

2. Description of the Related Art Injection molding simultaneous painting methods in which a pattern or the like is provided on the outer surface of a molded article and painted simultaneously with the molding of the molded article have been conventionally performed in various modes. For example, Japanese Patent Publication No. 50-19
In JP-A-132, after a picture-formed sheet made of a thermoplastic resin is vacuum-formed using a female mold provided with air holes for vacuum molding, the male and female molds are clamped to form a molten resin in both molds. A method is disclosed in which a cavity is injected and filled, and simultaneously with injection molding, a painted sheet is integrated with the outer surface of a resin molded product. 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. The mode disclosed here is a mode in which vacuum molding and injection molding are combined, and is a method capable of patterning a complicated curved surface shape. Note that there are two types of painted sheets, a laminate type and a transfer type. In the former, the entire layer of the painted sheet is laminated on a molded product and painted, and in the latter, only the base sheet of the painted sheet is peeled off and the transfer layer is formed. Transfer to a molded product and paint.

[0003] When the drawing sheet has a small drawing, for example, as disclosed in JP-B-43-27488, the resin in a fluid state to be injected and filled into a cavity without performing preforming of the painting sheet. There is also an injection molding simultaneous painting method in which the painted sheet is formed along the cavity surface at the same time as the resin is injected by the above resin pressure.

[0004]

However, in general, in injection molding, sink is likely to occur in a thick portion of a molded product. This is because, due to the nature of the resin, the resin has a shrinkage ratio, which causes volume shrinkage in a solidification process due to cooling or the like after injection, and shrinks in the direction of decreasing the wall thickness. In particular, when there is a boss or a rib on the back surface, the thickness increases at that portion, so the amount of shrinkage increases, so-called “sink” where the surface of the molded product is dented.
The phenomenon occurs. The sink marks make the appearance of the molded article unsightly, and if the degree is large, the product becomes defective. Therefore, when designing a product, it is usual to take care to prevent sinks from occurring on the surface of a molded product due to a thick portion such as a boss. Incidentally, FIG. 2 shows a sink mark 7 generated on the front side of the molded product corresponding to the portion of the boss 1 on the back side of the molded product in the painted product P in which the painted sheet S is laminated on the surface of the resin molded product 6 and integrated. It is sectional drawing.

[0005] In particular, in the simultaneous injection molding and painting method for producing a molded article painted with a painted sheet, sink marks may be more conspicuous than ordinary injection molding without using a painted sheet. This is because, when the painted sheet is laminated on the surface of the molded product, if the injection resin breaks down during cooling, the painted sheet will be dented in the form dragged by it, so the painted sheet will whiten, or if it is severe, laminate it once. This was because the integrated painted sheet was peeled off from the resin molded product. The whitening of the painted sheet, when forming the painted sheet along the cavity surface of the painting mold, the painted sheet is heated to such an extent that the formability of the painted sheet can be sufficiently ensured, This is because, during the solidification process after the end of the injection, the painted sheet is not in such a heated state and is forcibly extended.

By the way, sink marks are a problem that is fundamentally caused by the shrinkage of the resin, and the shrinkage differs depending on the type of the injection resin. On the other hand, in recent years, especially in order to reduce the cost of products, even for products in which ABS (acrylonitrile-butadiene-styrene copolymer) resin or the like is conventionally used as an injection resin, inexpensive polyolefins such as polypropylene are used. The use of resin is required. However, crystalline polyolefin-based resins such as polyethylene and polypropylene are commonly used ABS resins,
Compared with amorphous resins such as AS (acrylonitrile-styrene copolymer) resin and styrene resin, the shrinkage is remarkably large, and problems such as whitening and peeling of the painted sheet due to sink mark occurred.

Accordingly, an object of the present invention is to provide a method for preventing a product defect due to sink from occurring even when a resin having a large shrinkage such as a polyolefin resin is used, and a molding die for painting used therefor. Is the thing.

[0008]

Therefore, in order to solve the above problems, in the simultaneous injection molding and painting method of the present invention, after inserting a painting sheet between a pair of molds, both molds are clamped and both molds are clamped. After filling the resin in the fluid state into the cavity formed by the mold and solidifying it, the painted sheet is brought into close contact with the surface of the resin molded article at the same time as the molding and laminated, then both molds are opened, and the lamination with the painted sheet is performed. In the simultaneous injection molding and painting method for producing a painted molded article with a resin molded article painted by transfer, during the solidification process after the end of injection, a part of the cavity surface of the mold that does not follow the painted sheet is molded. Sliding toward the painted sheet side in the thickness direction of the product prevents the occurrence of sink marks on the molded article surface on the painted sheet side near the sliding portion.

As described above, in the process of solidifying the resin by the cooling or curing reaction after the end of the injection, the mold that does not follow the painted sheet (usually because the painted sheet is along the female side, By sliding part of the cavity surface in the thickness direction of the molded product toward the painted sheet side, the thickness of that part is reduced in the solidification process, and the volume shrinkage of the resin that occurs in the solidification process is compensated for. As a result, the occurrence of sink marks on the surface of the molded article on the side of the painted sheet near the slide portion can be suppressed. For this reason, it is possible to suppress the occurrence of whitening and peeling of the painted sheet caused by sink marks on the surface of the molded product that has been thickened by the boss or the like.

The painting mold of the present invention is a mold useful for carrying out the simultaneous injection molding painting method as described above. That is, in the present molding die, the painted sheet is inserted between a pair of dies, then both dies are clamped, and the cavity formed by both dies is filled with a resin in a flowing state and solidified. After forming and attaching a painted sheet to the surface of the resin molded article at the same time as molding, the two molds are opened and used to manufacture a painted molded article on which the resin molded article is painted by lamination or transfer by the painted sheet. In the pair of molding dies, a part of the cavity surface of the mold that does not follow the painting sheet is provided with a slide portion for preventing sink marks that slides in the thickness direction of the molded product. By sliding the sheet toward the painted sheet during the solidification step, the occurrence of sink marks on the surface of the molded article on the painted sheet near the sliding portion can be suppressed.

As described above, the molding die for painting is formed on a part of the cavity surface of the mold on which the painting sheet is not placed (usually a male mold because the painting sheet is along the female mold side). Since it has a sink portion for preventing sink marks that slides in the thickness direction of the product, the slide portion is slid to the painted sheet side during the resin solidification process by a curing reaction after the injection is completed, so that the resin is solidified during the resin solidification process. To compensate for the volumetric shrinkage, and to suppress the occurrence of sink marks on the surface of the molded article on the side of the painted sheet near the slide portion.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the simultaneous injection molding painting method and the painting mold according to the present invention will be described with reference to the drawings.

First, FIG. 1 is an explanatory view (cross-sectional view) conceptually illustrating a molding die for painting of the present invention capable of implementing the simultaneous painting method of injection molding of the present invention. FIG. 1A is a cross-sectional view of a certain molded article P and a molded mold for painting that includes a pair of a male mold Ma and a female mold Mb for obtaining the same. The lower part) has a plurality of bosses 1 for mounting products. A gate 2 is provided at the center of the molded product on the male mold Ma side.
It has.

[0014] In the molding die for painting of the present invention, FIG.
As shown in one form in (B), the mold Ma that does not follow the painted sheet S (in this case, the mold that follows the painted sheet S is the female mold Mb, Is provided with a slide portion 4 for preventing sink marks that slides in the thickness direction of the molded product on a part of the cavity surface 3 of the mold Ma). FIG.
In the case of (B), the slide portion 4 is a rod-shaped block having a circular shape in a front view (as viewed from the cavity surface) which covers all the cavity portion for forming the boss 1 which causes sink marks. The part 4 has a structure that slides in the thickness direction of the molded product with respect to the mold Ma body. In addition, the slide part 4 may be a conventionally known mold material like the mold Ma main body.
It is formed of metal such as iron or ceramics.

A drive section 5 is connected to the rear end (downward in the drawing) of the slide section 4 in order to advance (retreat) the slide section 4 in the thickness direction of the molded product (toward the picture sheet S) and back.
As the driving means of the driving unit 5, the driving unit is preferably such that the sliding unit does not retreat due to the injection pressure during the filling of the resin, and that the sliding unit can be advanced into the cavity in the thickness direction of the molded product during the cooling of the resin and press-fitted. There is no particular limitation as long as a force is applied and the forwardly moving slide portion can retreat to the original position before the next shot. For example, the driving unit may be driven by a hydraulic pressure such as a hydraulic cylinder. If the driving force is satisfied, air pressure may be used.

The portion where the slide portion 4 is provided may be a cavity on the mold Ma (usually a male mold) side of the cavity of the boss, the rib, or the other portion of the cavity where the thickness tends to be increased due to the product shape or the like. . The slide amount of the slide portion 4 varies depending on the degree of sink due to the injection resin, the injection conditions, the thickness, and the injection conditions such as the cavity area formed by the slide portion 4, but a small amount is sufficient. For example, 1
About 0 to 150 μm is sufficient. In addition, the slide part 4
May be a circle, a rectangle, other shapes, and a shape corresponding to the front view shape of the thick portion.

The shrinkage ratio of the resin which causes root sink is a crystalline polyolefin resin. For example, in the case of a polypropylene resin, it varies depending on the additive to be mixed, but it varies from 15/1000 to 7/1000. It is about. On the other hand, in the case of amorphous ABS resin, 5
/ 1000 is common and sink is unlikely to occur. Further, the amount of sink actually varies depending on, for example, the injection conditions, the holding pressure, the length of the cooling time, and the injection conditions of the temperature of the painting mold, and it is difficult to say unconditionally. Depending on the situation, a sink preventing structure with a slide portion may be adopted.

FIG. 1C shows a state in which the slide portion 4 is held at a position where the slide portion 4 is slid toward the painting sheet S during the solidification process after the end of the injection. As a result, the occurrence of sink marks on the surface of the molded product due to volume shrinkage at the time of solidification of the resin is suppressed in the thick portion due to the boss or the like. That is, FIG.
As shown in (C), sink marks 7 do not occur in the portion a near the slide portion which is the surface of the thick molded product.

There is no particular limitation on the mold material of the molding die for painting, and a conventionally known mold material such as a metal such as iron, carbon steel and various iron alloys, or a nonmetallic material such as ceramics may be appropriately selected and used.

The above description has been made mainly on the slide part, which is a key point of the painting mold of the present invention. However, the other parts of the painting mold of the present invention may be conventionally known in accordance with the intended use. Various structures in the painting mold may be employed. For example, a sheet clamp for fixing a painting sheet to a mold, a structure for using a painting mold as a vacuum molding mold to vacuum-mold a painting sheet, for example, a groove shape or a round hole opening on a cavity surface or a parting surface. It is a ventilation hole or the like having a shape or the like.
Note that these are not essential components of the painting mold of the present invention. For example, even if a sheet clamp is used for simultaneous injection molding painting, the sheet clamp may not be included in the painting mold and may be a component of the simultaneous injection molding painting apparatus. In addition, as a simultaneous painting apparatus for injection molding,
Although there is a case where the painting mold is considered including the painting mold, there is also a concept that the painting mold used to be replaced for each product is not included in the components of the injection molding simultaneous painting apparatus (not replaced for each product). By the way, as an injection molding simultaneous painting device,
A sheet supply device for supplying the painting sheet to the painting mold, a heating device for the painting sheet, a vacuum suction device, and the like are appropriately provided.

[Injection Simultaneous Painting Method] As the simultaneous injection molding painting method of the present invention, a painting mold having the above-mentioned structure may be preferably used. It can take various forms.

The method of simultaneous painting by injection molding 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 inserting a painted sheet between a pair of painting molds, both molds are closed, and a resin in a flowing state is injected into a cavity formed by both molds. After filling and solidifying, and attaching and laminating a painted sheet on the surface of the resin molded article at the same time as molding, open both molds, and paint or mold the resin molded article by lamination or transfer with the painted sheet. It is a method of manufacturing. In the case of laminate, the entire layer of the painted sheet was directly laminated to the resin molded product, and in the case of transfer, the base sheet of the painted sheet was then peeled off and only the transfer layer was laminated to the resin molded product. It shall be a molded article with pictures. Laminate and transfer are selected according to the use of the molded article with the picture and required specifications.

As various forms of the simultaneous painting method for injection molding, there are, for example, the following forms. 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 be preheated,
It is not necessary to do it. 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 only 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 by the resin pressure of the resin in a flowing state that is 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 a painted sheet, usually, the painting mold is also used as a vacuum forming die, but before supplying the painting sheet between the molds, the painted sheet is vacuum-formed with another vacuum forming die outside the mold. Preforming may be used. In addition, the vacuum forming includes vacuum pressure forming. Further, the painting sheet to be used may be either a single sheet or a continuous band. The injection molding machine used may be either a horizontal type or a vertical type.

The hot plate used for preheating the painted sheet at the time of vacuum molding is not generally a component of the painting mold, but a component of the injection molding simultaneous painting apparatus. Treated as A conventionally known hot plate may be appropriately selected and used. For example, an electric heater embedded in a block made of metal or ceramic, or a sheet-like so-called sheet heating element made of heat-resistant resin or metal may be used. Further, the hot plate may be provided with a vent hole for blowing out compressed air for forming the picture sheet into a vacuum compressed air. Further, the hot plate may be of a contact heating type in which heating is performed by conductive heat in close contact with the painting sheet, or a non-contact heating type in which heating is performed by radiant heat without contacting the painting sheet.

Next, a process of manufacturing a painted product by the simultaneous injection molding painting method of the present invention will be described in one form thereof.

First, as a sheet supply step, FIG.
In this example, a painting sheet S is supplied between the molds when both molds are in an open state by using a painting molding mold composed of a pair of male and female molds of a mold Ma (male mold) and a mold Mb (female mold). Then, the painted sheet S is pressed and fixed to the mold Mb by a frame-shaped sheet clamp (not shown). At this time, it goes without saying that the adhesive surface side of the painted sheet is on the injection resin side. Next, as a heating / softening step, a hot plate is inserted between the two dies from a retracted position outside the dies, and the painted sheet is heated and softened. Next, as a stretching step, the drawing sheet S is drawn through a ventilation hole (not shown) provided in the mold Mb and stretched to form a vacuum, thereby forming the drawing sheet S along the cavity surface of the mold Mb. Usually, the vacuum forming step includes at least the heat softening step and the stretching step. Next, as a mold clamping step, after the hot plate is retracted from the space between the two molds to a retracted position outside the mold, the molds are clamped. Next, as an injection step, a cavity formed by both molds is filled with a resin in a flowing state such as a heated and molten state. Next, in the solidification step, the process waits for the injected resin to be solidified by cooling, a curing reaction, or the like. Usually, during this period, the internal pressure of the cavity is maintained at an appropriate level as a pressure holding step. During this time, a part of the cavity surface is slid. Next, as a removal step, after the resin is solidified by cooling or the like, the mold is opened and a molded product is removed. When the painting sheet is a laminate sheet, if there is an unnecessary portion of the painting sheet, trimming is appropriately performed to obtain a painting molded article in which the painting sheet is laminated on the resin molded article and painted. When the painting sheet is a transfer sheet, the base sheet is formed into a mold M
The molded article was taken out while remaining on the b side, or the molded article was taken out in a state where all the layers of the painting sheet were laminated, then the base sheet was peeled off, and only the transfer layer was laminated and painted. Obtain a molded product with pictures.

In the simultaneous painting method of injection molding of the present invention, the above-mentioned painting mold of the present invention is used, for example,
During the solidification step, a part of the cavity surface of the mold that does not follow the painted sheet, corresponding to the part where sink marks are likely to occur,
The molded product is slid toward the painted sheet side in the thickness direction to reduce the thickness in the resin solidification process, thereby compensating for the volumetric shrinkage of the resin during the solidification process. As a result, the occurrence of sink marks on the surface of the molded article on the side of the painted sheet near the slid portion is suppressed.
For this reason, it becomes possible to suppress the whitening or peeling of the painted sheet from occurring on the surface of the molded product in the thick portion due to the boss or the like.

[Injection Resin] The resin to be injection-molded is not particularly limited, and any resin known in the injection molding simultaneous painting method 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 and AS (acrylonitrile-
Styrene copolymer) resin, styrene resin, vinyl chloride resin, acrylic resin, polycarbonate resin, or polyethylene, polypropylene, polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, olefin-based heat And polyolefin resins such as plastic elastomers. 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 heated and melted and injected in a fluid state, and the curable resin is injected at room temperature or appropriately heated and flowed. Above all, the present invention is effective in preventing sink marks, a resin having a large shrinkage rate and easily causing sink marks is preferable, and can be adopted even in the case where conventional injection resin cannot be adopted due to sink marks. . For example,
Polyolefin resins such as polyethylene, polypropylene, polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, and olefin-based thermoplastic elastomer. Further, among the curable resins, a resin which undergoes a large volume shrinkage in a solidification process due to a curing reaction depending on the content of the uncured composition is preferable.

[Painting Sheet] The painting sheet that can be used may be a conventionally known painting sheet of a transfer type or a laminate type, and is not particularly limited. 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 side is the side in contact with the injection resin. On the other hand, a transfer type painting sheet (transfer sheet) has a configuration in which a release 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. 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. Acrylic resin such as thermoplastic polyester resin such as polymethyl (meth) acrylate, methyl (meth) acrylate-butyl (meth) acrylate copolymer [(meth)
Acrylate means acrylate or methacrylate], vinyl chloride resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, polyamide resin, and other thermoplastic elastomers such as urethanes. A single layer of a sheet of a thermoplastic resin such as, or a laminate of two or more layers of different materials is used. 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 in which the resin sheet is laminated on the sheet, or the like is used. In the case of a transfer type painting sheet, if the releasability from the transfer layer is insufficient with the base sheet as described above, the base sheet is used as a material sheet, and the transfer is performed on the transfer layer side of the material sheet. In order to improve the releasability from the layer, a base sheet having a release layer is provided. The release layer separates from the transfer layer and is removed as a part of the base sheet when the base sheet is separated. For the release layer, for example, a single substance or a mixture of two or more of silicone resin, melamine resin, polyamide resin, urethane resin, polyolefin resin, wax and the like 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 pattern layer (ink layer) on which a pattern 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, aluminum powder, and pearlescent (pearl) pigments are used. Can be In the case of the laminate type, the decorative layer is often on the back side (injection resin side) of the base sheet, but may be on the front side of the base sheet.

(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 or the like, 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.

[0034]

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

[Examples and Comparative Examples] As a molding die for painting according to the present invention, a mold for molding a panel for an automobile interior as a molding with painting was prepared. The mold includes a pair of a male mold such as a fixed mold Ma and a female mold such as a movable mold Mb that can obtain a molded article P as shown in the sectional view of FIG. 1A. It is. The dimensions of the picture-formed molded product P are 40 mm in width, 400 mm in length, and 3 mm in average thickness, and bosses 1 for mounting products protrude at 4 places on the back surface of the molded product with a length of 5 mm. The molding die for painting has a structure in which one of the two bosses far from the gate 2 provided substantially at the center of the molded product has a slide portion 4 as shown in FIG. The boss of the place is the same). Slide part 4
After the injection step was completed, the sheet was slid toward the 50 μm-painted sheet by the driving unit 5 driven by air pressure.
In addition, after the drawing sheet is squeezed to the mold Mb (female mold) side using the drawing mold as a vacuum forming die, it is laminated and integrated with an injection-molded resin molded product.

On the other hand, the painted sheet is made of a transparent acrylic resin film having a thickness of 125 μm as a base sheet, and a mixture of an acrylic resin and a vinyl chloride-vinyl acetate copolymer is formed on the back side (resin molding side). Using a resin based resin as the binder resin, using a colored ink containing a color pigment mainly composed of red-penetrated pattern, forming the pattern layer of the wood pattern design by three-color printing of gravure printing, and further, an adhesive made of urethane resin A sheet was used in which a layer (2 μm thick) and an adhesive layer (2 μm thick) made of chlorinated polypropylene were formed thereon by gravure coating with two layers.

Using the above-mentioned painting mold and the above-mentioned painting sheet, the painting sheet is fixed to the above-mentioned painting mold as described above, then heated and softened to form a vacuum.
The painting was performed simultaneously with the injection molding to produce a painted molded product in which the painted sheet was laminated. That is, first, the sheet with the picture is inserted between the male and female molds in the mold opened state so that the picture layer faces the male gate side, and is pressed and fixed to the female parting surface with a sheet clamp to supply the sheet. did. Next, a hot plate of an infrared radiation heating method is inserted between the molds, and after a heating softening step of non-contact heating of the painted sheet, the female mold is used as a vacuum forming mold, and the painted sheet is preformed by vacuum forming, The softened picture sheet was formed into a shape along the cavity surface of the female mold, and the stretching step was completed. Then, as a mold clamping step, the hot plate is retracted to a retracted position outside the mold,
Both molds were clamped. Next, as an injection step, a polypropylene resin to which 20% by weight of an ethylene-propylene random copolymer rubber was added was formed on both molds under the conditions of a resin temperature of 220 ° C. and a mold temperature of 50 ° C. (both male and female molds). Injected into the cavity. After the injection step was completed with an injection time of 2 seconds, the slide portion was slid in a solidification step (cooling step). After the completion of the injection step, the slide is started at 900 kg / cm ² for 2 seconds and then 750 kg.
This was carried out in a solidification process after completing the pressure-holding step at 3 cm / cm ² for 3 seconds. And after the resin cools and solidifies in the solidification process,
In the take-out step, the mold was opened to obtain a picture-formed molded product in which the picture-sheet was laminated and integrated with the resin molded product.

As a result, on the surface of the molded product corresponding to one boss provided with a slide portion as an example, sink marks did not occur and the painted sheet had a good appearance without whitening or peeling. However, as a comparative example, among the molded product surfaces corresponding to the other three bosses without providing the slide portion,
At the two boss portions near the gate, there was some sink mark because the pressure was easily applied, but there was no whitening or peeling of the painted sheet, which was within the allowable range. However, in the portion of the boss far from the gate, as shown in FIG. 2, the sinking 7 occurred on the surface of the molded product corresponding to the boss 1, and the painted sheet S was pulled during the resin solidification process. Whitening occurred and the appearance was poor.

[0039]

According to the method for simultaneous painting by injection molding and the mold for painting of the present invention, the occurrence of sink marks can be suppressed even in a thick portion caused by a boss or the like, and the resulting whitening or peeling of the painted sheet can be prevented. . For this reason, even if it is inexpensive as an injection resin to be used but cannot be adopted due to large sink marks, it becomes easy to adopt a polyolefin-based resin such as polyethylene or polypropylene.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view conceptually illustrating one embodiment of an injection molding simultaneous painting method and a painting mold according to the present invention.

FIG. 2 is a cross-sectional view showing sink marks generated on the front side of the molded article corresponding to the boss portion on the back side of the molded article with pictures.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boss 2 Gate 3 Cavity surface 4 Slide part 5 Driving part 6 Resin molding 7 Sink a Close to slide part Ma type (male side of painting mold) Mb type (female side of painting mold) S Painting sheet P Painted product

Claims (2)

[Claims] 1. A sheet with a picture is inserted between a pair of dies, the dies are clamped, and a resin in a flowing state is injected into a cavity formed by the two dies, and solidified by molding. At the same time, a paint sheet is brought into close contact with the surface of the resin molded article, and after laminating, the two molds are opened, and a simultaneous molding method for injection molding is used to produce a painted article in which the resin molded article is painted by lamination or transfer by the painted sheet. During the solidification process after the end of the injection, by sliding a part of the cavity surface of the mold that does not follow the painted sheet toward the painted sheet side in the thickness direction of the molded product, the painted sheet near the sliding portion To suppress sink marks on the side of the molded product,
Injection molding simultaneous painting method. 2. After inserting a sheet with a picture between a pair of molds, both molds are clamped, and a cavity formed by both molds is filled with a resin in a flowing state and solidified. After the painted sheet is brought into close contact with and laminated on the surface of the resin molded product, the two molds are opened, and a pair of paintings used for manufacturing a painted molded product on which the resin molded product is painted by lamination or transfer with the painted sheet. In the molding die, a part of the cavity surface of the mold that does not follow the painted sheet is provided with a slide portion for preventing sink marks that slides in the thickness direction of the molded product. A molding die for painting, which is slid to the painting sheet side to suppress the occurrence of sink marks on the surface of the molding on the painting sheet side near the sliding portion.