JP2008068633A - Injection molding mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a sink mark from appearing on the gate of the product surface and a printing sheet from being damaged by the heat of an injected resin in molding a printed molding by an in-mold printing method. <P>SOLUTION: The in-mold printing method comprises feeding a printing sheet in the middle of the male and female molds for injection molding, clamping the molds, injecting a fluidized resin into the cavity and obtaining a printed mold. The gate through which the resin is injected into the cavity of the mold used is arranged at the rib behind the molding. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injection mold used in an injection molding simultaneous painting method. In particular, the present invention relates to an injection mold that prevents the occurrence of sink marks on the product surface of the gate portion.

2. Description of the Related Art Conventionally, an injection molding simultaneous painting method in which a pattern or the like is provided on the outer surface simultaneously with molding of a molded product has been performed in various modes. For example, after a vacuum-formed sheet made of thermoplastic resin is formed using a female mold provided with a vent for vacuum forming, both the male and female molds are clamped and the molten resin is injected into a cavity formed by both molds. And the method of integrating a picture sheet | seat with the outer surface of a molded article simultaneously with injection molding is disclosed (for example, refer patent document 1). The injection molding simultaneous painting method of this aspect is a method in which vacuum molding and injection molding are combined, and a pattern can be formed on a complicated curved surface shape. In addition, there are two types of picture sheets: a laminate type and a transfer type. In the former, the picture sheet itself is laminated on the molded product and painted, and in the latter, only the base sheet of the picture sheet is peeled off and the transfer layer is formed. I transfer it to the product and paint it.
Japanese Patent Publication No. 50-19132

  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, a so-called sink may occur in which the surface of the molded product near the gate portion is recessed. In the injection molding simultaneous painting method, the front side of the molded product is painted with a painted sheet, and the gate is usually provided on the back side of the molded product, and the resin is injected from the back side. If the properties are not sufficient, the molten resin immediately after filling the cavity from the gate on the back side touches the back surface, which becomes the adhesive surface of the painted sheet, and the painted sheet melts and softens, causing the painted sheet to break There are times when it flows. Further, even when the heat resistance of the ink layer printed and formed for imparting a pattern or the like to the back side of the picture sheet is insufficient, the ink layer may flow after being melted or softened for the same reason. When the ink layer flows, the pattern is distorted or disappears. In particular, in the portion where the resin begins to fill into the cavity through the gate, the flow path has a small cross-sectional area, which is also affected by the shear heat generation of the resin. For this reason, as shown in FIG. 3, there is a case where a circular thick portion 4 is provided on the back surface of the molded product around the gate 3 to reduce the influence of heat applied to the picture sheet or its ink layer. Since the thickness of the thick part is thick, sink marks become severe, and the appearance of the molded product may be deteriorated. In this way, in the case of the injection molding simultaneous painting method, because the painting sheet is used, depending on its heat resistance and the shape of the molded product, special treatments such as prevention of sink marks and damage to the painting sheet due to the heat of the injection resin It was necessary to devise.

  Therefore, in order to solve the above-described problems, in the injection mold of the present invention, after supplying the sheet with a picture between both the male and female molds of injection molding, both molds are clamped to form a fluid resin in both molds. In the mold used in the injection molding simultaneous painting method for producing a painted product by injecting into a cavity, a gate as an injection hole into the resin cavity is provided on the rib on the back side of the molded product. did. As a result, no sink marks are generated on the side surface of the molded product corresponding to the gate position. In addition, since the picture sheet is far from the portion where the resin shears and generates heat during filling, damage to the picture sheet such as the flow of the ink layer of the picture sheet can be prevented.

  According to the injection mold of the present invention, when obtaining a painted product by simultaneous injection molding, there is no sink on the side surface of the molded product corresponding to the gate position. In addition, when the resin is filled in the cavity, the painting sheet does not exist in the gate or in the vicinity of the gate where the heat is easily generated. Therefore, the painting sheet is not damaged such as the ink layer flowing. By using the original ribs, it is possible to prevent sink marks and damaged sheets with pictures without changing the product design. In addition, to prevent damage to the painted sheet, the painted sheet is originally painted with a painted sheet without any design changes, such as providing a thick part specific to the use of the painted sheet. it can. Further, since the rib is provided with a gate, short shots and the like are unlikely to occur on the rib.

  Embodiments of an injection mold according to the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view for comparing and explaining the case where the injection mold is according to the present invention and the conventional case. In the figure, the resin filled in the mold is used as a reference, that is, in a sectional view of the molded product.

  For example, in the case of a submarine gate, a conventional injection mold has a structure in which a gate 3 is provided on a boss 6 provided on the back surface of a molded product 1 as shown in FIG. The boss 6 may be provided for other purposes in addition to being provided exclusively for resin filling. On the other hand, in the injection mold of the present invention, as exemplified in FIG. 1B, the rib 7 provided on the back surface of the molded product 1 is utilized to provide the gate 3 with the rib 7. Provide. FIG. 1B shows an example in which a pinpoint gate is provided at the tip of the rib 7. As shown in FIG. 1A, when the molded product 1 has ribs 7 on the back surface, sink marks can be prevented by providing gates on the ribs. The resin in a fluid state passes through the runner 2 from a sprue (not shown) and is filled into a cavity having ribs 7 from the gate 3.

  1 (A) and 1 (B) show the case where the ribs are provided on the back surface of the molded product 1, but the ribs 7 are not formed on the back surface of the molded product 1 as shown in FIG. When it is 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. 1D, the gate 3 may be provided on the rib 7 projecting rearward on the outer periphery of the molded product. Note that the gate 3 illustrated in FIGS. 1C and 1D is a submarine gate (tunnel gate), but of course, in this case, the gate 3 is not limited to the submarine gate.

  As described above, in the injection mold according to the present invention, since the gate is provided on the rib, sink does not occur. In addition, the picture sheet is also far from the portion where the resin shears and generates heat during filling, so that the picture sheet is less likely to be damaged, such as the ink layer of the picture sheet flowing. In addition, although the rib which originally provided may be utilized for the rib which provides a gate, if there is no trouble on use of a molded article, you may newly provide a rib for gates. Moreover, although the kind of gate demonstrated in the said description by the pinpoint gate and the submarine gate, it is not limited to this, Other well-known various gates may be sufficient. In addition, the mold material of the injection mold is not particularly limited. For example, other metal materials such as copper, other metal materials such as copper, metal alloys, ceramics, and the like are conventionally known as mold materials such as S50C, S55C, SCM3, and SCM4. A non-metallic material or the like may be used and may be appropriately selected and used.

  [Injection molding simultaneous painting method] The injection molding simultaneous painting method in which the injection mold of the present invention can be used will be described here. The method of simultaneous painting with injection molding is as follows: Japanese Patent Publication No. 50-19132, Japanese Patent Publication No. 43-27488, Japanese Patent Laid-Open No. 6-315950, Japanese Patent Publication No. 2-4080, etc. After being supplied 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, and simultaneously with the molding of the resin molded product, a picture sheet is laminated on the surface, This is a method for manufacturing a painted product that has been painted by transfer or transfer.

  The injection molding simultaneous painting method has various forms, and the injection mold of the present invention can be used for these various forms. Various forms of the injection molding simultaneous painting method may be, for example, a form in which a picture sheet is preformed or not. In addition, the picture sheet may or may not be preheated. In the pre-molding, the picture sheet is usually preheated. Of course, when the drawing sheet has a large aperture, it is preferable to perform preforming. On the other hand, when the drawing sheet has a small aperture, the drawing sheet can be formed by the resin pressure of the injected resin in a fluid state. At this time, if the drawing is shallow, the picture sheet may be formed only with the resin pressure of the resin in a fluid state filled in the mold at the same time as the resin injection without pre-molding. Even when a picture sheet is molded by resin pressure, the picture sheet may be preheated and use the heat of the injection resin. In addition, the pre-molding of a picture sheet is usually performed by using an injection mold as a vacuum mold, but before supplying the picture sheet between the molds, the picture sheet is vacuum-formed by another vacuum mold outside the mold. Various preforms may be used. The vacuum forming includes vacuum / pressure forming.

  With reference to the conceptual diagram of FIG. 2, the injection molding simultaneous painting method will be described in one form. In addition, the form demonstrated here is a form which heats and softens a picture sheet between molds, pre-molds it with an injection molding die by vacuum molding, and injects resin after mold clamping. Further, this conceptual diagram is a diagram for explaining the injection molding simultaneous painting method itself, and therefore, the position of the gate is not specified intentionally, but is simply illustrated. As shown in 1 (B) and (D), the gate is provided at the rib on the back side of the molded product.

First, as shown in FIG. 2A, the injection mold includes a mold Ma having a runner and a gate communicating with the injection nozzle, and a mold Mb having a suction hole 41 on the mold surface and also serving as a sheet preforming mold. A pair of molds is used. These molds are made of metal such as iron or ceramics. In the mold open state, a picture sheet S is supplied between both molds Ma and Mb, and the picture sheet S is fixed to the mold Mb by pressing it with a frame-shaped sheet clamp 42. In this case, it goes without saying that the adhesive surface side of the picture sheet is the injection resin side on the right side of the drawing. Next, the picture sheet is softened by heating with a heater inserted between both molds as appropriate. The heating is, for example, non-contact radiation heating, but may be contact heating. Then, vacuum suction is performed through the suction holes, and the picture sheet is preformed along the cavity surface of the mold Mb. Note that the vacuum forming may be vacuum / pressure forming using pressure air together, and includes this. Next, the heater is retracted from between both molds, both molds are clamped as shown in FIG. 2B, and a resin formed in a fluid state such as a heat-melted state is filled in a cavity formed by both molds. And after resin solidifies by cooling etc., a mold is opened and a molding is taken out. In the case where the picture sheet is a laminate sheet, if there is an unnecessary portion of the picture sheet, trimming is appropriately performed to obtain a picture-molded article in which the picture sheets are laminated on the resin molded product. When the picture sheet is a transfer sheet, the molded product is taken out with the base sheet left on the mold Mb side, or the molded sheet is taken out with the whole picture sheet laminated, and then the base sheet Is peeled off to obtain a painted product in which only the transfer layer is laminated and painted.

In addition, when performing the injection molding simultaneous painting using the injection mold of the present invention, as the resin to be injection molded, those conventionally known in the injection molding simultaneous painting method can be used and there is no particular limitation. The injection molding resin is selected according to the required physical properties and cost of the product. For example, if it is a thermoplastic resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, styrene resin, vinyl chloride resin, acrylic resin, polycarbonate resin, polyethylene, polypropylene , Polyolefin resins such as polybutene, polymethylpentene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, and olefin-based thermoplastic elastomer. Moreover, if it is curable resin, the material conventionally known for injection molding simultaneous painting of uncured resin liquids, such as two-component curable resin, for example, urethane resin, unsaturated polyester resin, epoxy resin, etc. Can be used. The thermoplastic resin is melted by heating and injected in a fluid state, and the curable resin is injected in a fluid state at room temperature or appropriately heated. However, the advantage of the injection mold of the present invention is that the resin that is particularly utilized is a resin that is heated and injected, and in particular, a thermoplastic resin that is injected in a fluidized state by heating and melting.

  [Painted sheet] A sheet with a picture that can be used for simultaneous painting by injection molding using an injection mold as described above can be a transfer type or a laminate type, and a conventionally known sheet with a picture can be used. Not. However, in the injection mold according to the present invention, since the influence of the heat of the gate portion is reduced, it is possible to use a sheet with a picture having a lower heat resistance than before. Therefore, I will explain the sheets with pictures.

  A transfer-type picture sheet (transfer sheet) has a configuration in which a peelable sheet is used as a base sheet, and a transfer layer is laminated on the base sheet. The transfer layer is made of, for example, a decoration layer or an adhesive layer. There is also 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. A laminate-type picture sheet (laminate sheet) has a configuration in which, for example, a decorative layer and an adhesive layer are sequentially laminated on a base sheet. Note that the adhesive layer may be omitted for both the transfer type and the laminate type.

(Substrate sheet) As the substrate sheet, a resin sheet having moldability is typically used. Examples of the resin sheet include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, olefin resins such as olefin thermoplastic elastomer, polybutylene terephthalate, ethylene terephthalate isophthalate copolymer. Polyester resins such as vinyl chloride resin, acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, polyamide resin, urethane-based other thermoplastic elastomers, etc. A single layer of a thermoplastic resin sheet or a laminate of two or more layers of different materials is used. Moreover, if the moldability is satisfied, a sheet obtained by impregnating a resin into a cloth such as a nonwoven fabric or a woven fabric, or a laminate in which the resin sheet is laminated on the sheet is used. In addition, in a transfer type, in order to improve the peelability from the transfer layer on the transfer layer side of the base sheet, a base sheet having a release layer is provided as necessary. The release layer is separated and removed from the transfer layer together with the base sheet when the base sheet is peeled off. For the release layer, for example, a single substance or a mixture of two or more of a silicone resin, a melamine resin, a polyamide resin, a urethane resin, a polyolefin resin, a wax, or the like is used. In the laminate type, a coloring agent such as a pigment is kneaded in the base sheet resin, and the base sheet may be subjected to a decoration treatment such as colored transparent or colored opaque or colorless transparent or colorless opaque. In this case, the base sheet itself may form a decorative layer and become a picture-attached sheet having only the base sheet.

  (Decoration layer) The decoration layer is a conventionally known method such as gravure printing, silk screen printing, offset printing, a pattern layer (ink layer) obtained by printing a pattern or the like with a material, a known vapor deposition method using a metal such as aluminum or chromium, etc. The metal thin film layer etc. which were formed in the part or the whole. The pattern may be any pattern such as a wood grain pattern such as a grain or a grain, a stone pattern such as marble or granite, a tile-like pattern, a brick-like pattern, a texture pattern, a character, a geometric pattern, or a solid pattern. The pattern layer ink is composed of a vehicle composed of a binder, a colorant such as a pigment or a dye, and various additives appropriately added thereto. The binder includes chlorinated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, polyester resins, thermoplastic urethane resins, acrylic resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, cellulose resins and other thermoplastic resins, A thermosetting resin such as a thermosetting urethane resin or an epoxy resin is used as a single substance or a mixture of these resins. As colorants such as pigments or dyes, titanium white, carbon black, petal, cobalt blue, chrome lead, phthalocyanine blue, isoindolinone, quinacridone, aluminum powder and other metallic pigments, pearlescent (pearl) pigments, etc. are used. It is done.

  (Adhesive layer) In order to improve the adhesion to the injection resin, an adhesive layer such as a corona discharge treatment or various known primer coatings or a heat-sensitive adhesive layer may be applied to the back surface of the sheet with a picture. . For the adhesive layer, a known resin such as a thermoplastic resin or a thermosetting resin is used. For example, for thermoplastic resins, styrene resins or styrene copolymers such as polystyrene and poly-α-methylstyrene, acrylics such as poly (meth) methyl acrylate, poly (meth) ethyl acrylate, poly (meth) butyl acrylate, etc. 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 type or a mixture of two or more types such as a rubber-based resin such as acrylonitrile rubber and a thermoplastic resin such as polyamide resin is used. In the thermosetting resin, a urethane resin, an epoxy resin, or the like is used.

  [Others] “Painting” as used in the present invention refers to an invisible pattern, a hard coating film, or a conductive film, other than simply providing a visible pattern such as a pattern, character, or figure to a molded product. It also includes providing a functional layer such as. As a visible pattern, known patterns such as a pattern layer formed by printing, a metal thin film layer formed by vacuum deposition, etc. are examples of patterns that are not visible. A fluorescent ink pattern that emits fluorescence is used.

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

  As the injection mold of the present invention, a mold for molding a molded product for a console box of an automobile was prepared. The size of the picture-molded product is a rectangle with a front of 200 mm in width and a length of 500 mm, an average thickness of 3 mm, and a drawing sheet with a maximum drawing depth of 40 mm. As shown in FIG. 1B, the gate is provided with a gade 3 at the tip of the rib 7 on the back surface of the molded product 1. The rib 7 had a width of 0.7 mm and the gate was a pinpoint gate having a diameter of 2.5 mm.

  On the other hand, for a sheet with a picture, a mixed resin system of an acrylic resin and a vinyl chloride-vinyl acetate copolymer is bonded to the back surface (molded product side) of a base sheet made of a transparent acrylic resin film having a thickness of 125 μm. The pattern layer of the wood grain design is formed by gravure printing using a colored ink containing a colored pigment mainly composed of a petal, and further combined with vinyl chloride-vinyl acetate. An adhesive layer (4 μm thick) made of a polymer was formed by two-layer coating by gravure coating and prepared.

  Then, by using the above-mentioned picture sheet, simultaneous injection painting was performed as described in the conceptual diagram of FIG. 2, and a picture-molded article in which the picture sheet was laminated was manufactured. First, after supplying the sheet with a picture between the male and female molds with the pattern layer facing the gate side of the male mold, an infrared radiation heating type heating plate heated to a surface temperature of 350 ° C. Insert between the molds and heat the picture sheet for 3 seconds without contact, then use the female mold as a vacuum mold and start vacuuming to pre-form the picture sheet by vacuum forming. Molded into a shape along the cavity surface of the mold. Thereafter, 5 seconds after the start of evacuation, the hot platen was retracted to the retracted position outside the mold, and both molds were clamped. Next, the heat-resistant ABS resin was injected into a cavity formed by both molds under the conditions of a resin temperature of 240 ° C. and a mold temperature of 60 ° C. Then, after the resin was cooled and solidified, the mold was opened to obtain a painted product.

  As a result, no sink marks were observed on the front side of the molded product. Further, the picture sheet withstood the heat of the resin at the time of injection, and neither the base sheet nor the pattern layer was broken or flowed. In addition, since there is a gate on the rib, even if the injection resin pressure is low, a short shot (not filled with resin in the rib) does not result in a short shot, so that stable injection molding simultaneous painting with no burr has been achieved.

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

  As a result, the picture sheet withstood the heat of the resin at the time of injection, but as shown in FIG. 3, sink marks 5 occurred in the gate 3 portion on the front side of the molded product 1. Then, in order to correct the sink, the injection resin pressure was increased and re-molding was performed, but burr was generated around the molded product.

Explanatory drawing which illustrates notionally the injection mold of this invention and the conventional injection mold by the shape of a molded article. The conceptual diagram explaining the injection molding simultaneous painting method by a certain example. Explanatory drawing which illustrates notionally other examples of the conventional injection molding die by a molded article shape.

Explanation of symbols

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

Claims (1)

At the same time of injection molding, a picture sheet is supplied between both male and female molds for injection molding, and then both molds are clamped to inject a fluid resin into a cavity formed by both molds. An injection mold in which a gate, which is an injection hole into a resin cavity, is provided on a rib on the back side of a molded product in a mold used for a painting method.

Images