MX2007016435A - Compression molding method and device therefor. - Google Patents

Abstract

A compression molding method in which the yield of a product can be enhanced by preventing mixing of abrasion powder produced through galling. In the compression molding method where a fixed die (2) and a movable die (3) are arranged oppositely, a sliding board (3d) connected with a movable mold plate on the movable die side through a spring (3c) is touched to the parting plane of the fixed die (2) with spring force, the movable die (3) is advanced furthermore after resin is injected into the cavity (4) in the die, and molding is performed by compressing resin R filling the cavity (4) by means of a core (3g) provided in the movable die (3) with the core penetrating the sliding board (3d), characterized in that a resin film F is arranged between the fixed die (2) and the sliding board (3d) and one side of the resin R in the cavity (4) is compressed by means of the core (3g) through the resin film F.

Description

METHOD OF COMPRESSION MOLDING AND DEVICE FOR THE SAME BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of compression molding using a central compression mold and a device therefor.

Description of the Related Art Conventionally, a central compression mold is used to mold glasses, optical lenses and the like. This type of mold consists of a fixed mold 50, a movable mold 51 and a movable plate 52 interposed therebetween, as shown in Figure 8. In the fixed mold 50, a runner 50a and a mold cavity 53 are formed which they communicate with the 50th corridor. In the mobile mold 51, a core 54 is provided which penetrates through the displaceable plate 52 on a position opposite to the mold cavity 53. The core 54 is adapted to move back and forth relative to the mold cavity. 53 corresponding to the movement of a central cylinder 55. In the case of molding using the central compression mold, the fastening is effected in a state that the core 54 is retracted to thereby cause a large clamping force to act on a dissociated face 54 where the fixed mold 50 and the displaceable plate 52 come into contact with each other. Next, the molten resin of an injector is injected into the mold cavity 53 through the corridor 50a. Then, the core 54 is advanced by operating a central cylinder 55 to compress the molten resin into the mold cavity 53 to thereby produce a molded product E (see, for example, Japanese Patent Publication, Open to the Public Not 11-179769). In the central compression mold, however, the sliding surfaces between the core 54 and the displaceable plate 52 can be worn to produce so-called "scratching". The scratching is classified according to the causes in a) abrasive wear, which is easily caused if the materials of the sliding components of the mold include differences in the hardness, b) adhesive wear in which the projections of the mold components collide each other, so that it is easily caused. Adhesion in the toughest contact part, and the adhesion is built to thereby form abrasion dusts, and c) fatigue wear in which the components wear and tear, for example. Scratching is caused due to several causes as described above, and if the abrasive dusts are contaminated in the molded products, they should be discarded as waste, causing a delay in the performance of the product and also damaging the mold. In addition, the space of the central sliding part is large, there is a problem that the resin is submerged in the central sliding part thereby producing burrs.

THE INVENTION The present invention has been developed considering the problems in the conventional compression molding method using a central compression mold as described above. Therefore, it is an object of the present invention to provide a method of compression molding and a device therefor, capable of preventing contamination of the abrasion dusts caused by scratching to thereby improve the performance of the product, and increase even more service life of the central compression mold. A method of compression molding of the present invention to achieve the aforementioned objective is a method that includes a fixed mold and a movable mold arranged opposite each other, comprising the steps of contacting the sliding board connected with a mobile die plate on the side of the mobile mold via the spring with a mold separation face fixed by the force of the spring; further advancing a movable mold after supplying resin to a cavity within the mold; and compress and mold the filled resin in the cavity by a core, provided in the mobile mold, which penetrates through the sliding side. The method is characterized in that the thermoplastic resin film is placed between the fixed mold and the movable mold, and a surface of the resin in the cavity is compressed by the core via the thermoplastic resin film. According to the compression molding method of the present invention, when the resin film is interposed between the fixed mold and the moving mold and the resin is supplied to the cavity in a state where the core is lowered, and the resin provided press the resin film to adhere to the core. Then, when the core advances while the spring contracts by advancing the movable mold further, the molded resin is compressed by the core which is covered with the thermoplastic resin film. That is to say, that the resin molding is effected without being influenced by abrasive powders generated in the slidable part, since the Thermoplastic resin film is provided between the slidable core and the molded resin as a divider. In the compression molding method, it is preferable to use the polyester film having a thickness of 20 to 200 μm as the thermoplastic resin film. In the compression molding method, a base film of a transfer film may be used on which a design was formed as in the thermoplastic resin film. In that case, the design can be transferred on the decorative face by arranging the transfer film, so that the design is oriented towards the side of the fixed mold, and after placing the resin to be supplied to the cavity and the design of the Transfer film, provide the resin to the cavity in the mold and compress the face of the decorative resin filled in the cavity by the core via the transfer film. Therefore, it is actually possible to prevent abrasion dusts generated in the slidable part of the core from being mixed, as well as being transferred to the design. In the compression molding method, it is preferable to supply the resin in the cavity after causing the thermoplastic resin film placed between the fixed mold and the mobile mold to be absorbed into the face. of compression of the nucleus. In addition, a compression molding device of the present invention is a device having a fixed mold and a mobile mold arranged opposite each other, in which a sliding board connected on a movable matrix plate on the side of the mobile mold via a The spring comes into contact with a stationary separating face of the mold by the spring force, and the moving mold further advances after the resin supplied to a cavity within the mold, and the filled cavity is compressed and molded by a core, provided in the mobile mold in a state of penetration through the sliding board. The device is characterized in that it is configured so that a surface of the resin in the cavity and the core is divided with a thermoplastic resin film when molding compression molding. In the compression molding device, the thermoplastic resin film can be formed of a band-shaped resin film, and can be configured to unwind from a roll and to pass through the mold intermittently. According to the compression molding method and the compression molding device of the present invention, it is possible to avoid contamination of the abrasion dusts generated by scratching to improve both the performance of the product, and also to increase the service life of the mold.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a configuration diagram of a mold used in a compression molding method according to the present invention; Figures 2a to 2e are process diagrams to explain the compression molding method according to the present invention; Figure 3 is a cross-sectional view of a transfer film used in the present invention; Figures 4a to 4e are process diagrams for explaining a method of compression molding using the transfer film; Figures 5a and 5b are images of the molded product, molded by means of a conventional compression molding method, in which Figure 5a is a micrograph taken with a magnification value of 50 times, and Figure 5b is a micrograph taken with an amplification value of 500 times; Figure 6 is a micrograph in which Figure 5b was further amplified 3500 times; Figures 7a and 7b are images of a product molding, molded by means of the compression molding method according to the present invention, in which in Figure 7a is a micrograph taken with a magnification value of 50 times, and Figure 7b is a micrograph taken with a value of 500 times amplification; and Figure 8 is a sectional view showing the configuration of a conventional compression mold.

DESCRIPTION OF THE PREFERRED MODALITY Hereinafter, the present invention will be explained in detail on the basis of a modality shown in the drawings. Figure 1 shows the configuration of a core compression mold (here abbreviated later as a mold) used in a compression molding method according to the present invention. In Figure 1, a mold 1 includes a fixed mold 2 and a moving mold 3. A mold mounting board 2a of the fixed mold 2 is provided with a fixed die plate 2c via a spacer block 2b, and the fixed die plate 2c is provided with a hot runner 2d. In a toothed part defined by the fixed matrix plate 2c and a sliding table 3d described below, a nested M block divided into left and right parts by a separating face P. On the side of the fixed mold of the nested block M, a side of a cavity 4 in which fused resin is filled is formed as a first cavity 2e, with which the nozzle 2f of the 2d hot runner is communicated. Note that the reference number 2g denotes an ejector pin. In addition, it can be provided if an inclined pin (not shown) is required to form a cut-off part in the form of a ratchet. This is due to the fact that an inclined pin and a core 3g described below will not interfere with each other in the present configuration. The movable mold 3 is fixed to the fixed opposing mold 2, and a mold mounting base 3a of the moving mold 3 is provided with a moving die plate 3b. The mobile die plate 3b is provided with the sliding board, 3d via the spring 3c. In the sliding table 3d, a second cavity 3e is formed opposite to the first cavity 2e. The reference numeral 3f indicates a compression tolerance adjusting screw which is arranged coaxially with the spring 3c. In addition, the sliding table 3d is provided with the core 3g which penetrates through a sliding table 3d in the direction from left to right. The rear end of the core 3g is fixed to the movable matrix plate 3b via fastening screws of the 3h core. When the slide board 3d moves in a direction of the arrow A against the thrust force of the springs 3c and 3d to adhere close to the fixed die plate 2c, the slide board 3d retracts in a direction of the arrow B through As the core 3g is relatively advanced, the molten resin fills the cavity 4 when it is compressed. Note that the compression interval for the core 3g can be part or all of the cavity 4. The thermoplastic resin film (here abbreviated later as film), described below, is deposited between the fixed matrix plate 2c and the sliding 3d board of the mold 1. The film is formed of one in a band unrolling from a roll. Each time the compression molding is carried out it moves intermittently with a predetermined length to be fed into the mold 1. The film provided for the molding must be sent out of the mold after the release of the mold and rolled up by a roll of winding (not shown). In addition, in the moving mold 3, the suction passages 3i and 3j are formed, which communicate with a space in the slidable part of the core C; The suction passage 3j penetrates through the movable matrix plate 3b and is connected with a vacuum pump (not shown) outside the movable mold 3. therefore, when suction is carried out through the suction passages 3i and 3j, the film placed between the fixed mold 2 and the mobile mold 3 can adhere closely to the compression face of the core 3g , to avoid wrinkles caused by the surface of the resin to be molded. Note that the reference number 3k, in the Figure, denotes a sealing member consisting of an annular seal at 0, for example, which allows suction even if the moving matrix plate 3b and the 3d sliding board are separated. As a film material, it is preferable to specifically use a heat-resistant polyester film, especially PET (polyethylene terephthalate), but it is not limited to this material. A single layer film selected from polycarbonate resin, polyamide resin, polyimide resin, polyester resin, acrylate resin, olefin resin, urethane resin, acrylonitrile-butadiene-styrene resin, vinyl chloride resin and Similar, or a laminated film or a copolymer film made in less than two types of resin selected from those mentioned above can be used. When the resin molded into the cavity 4 is compressed by the core 3g, the breaking force acts on the film. Therefore, the thickness of the film can be selected so that it would counteract the breaking force. As a film thickness capable of counteracting the breaking force, one having 20 μm or more can be used, but since a thickness of resin to be formed is affected if the thickness exceeds 200 μm, it is preferable to select the thickness in a range from 20 to 200 μm. In addition, it is preferable to select a thickness in the range of 20 to 100 μm for high accuracy molding. As the molten resin to be filled in the mold 1, a resin is shown for general purposes as a polystyrene type resin, polyolefin type resin, ABS resin, AS resin, AN resin or the like. In addition, a resin designed for general purposes such as a polyphenylene oxide and polystyrene resin, polycarbonate type resin, polyacetal type resin, acrylic resin, polyphenylene ether modified with polycarbonate resin, and polybutylene terephthalate resin may be used. , and a super-modified resin such as polysulfone resin, polyphenylene sulfide type resin, polyphenylene oxide type resin, polyallylate resin, polyether imide resin, polyimide resin, liquid crystalline polyester resin, and resin heat resistant of the polyallyl type. Note that a composite resin to which reinforcing material has been added such as fiberglass or an inorganic filler is also included in the molten resin. Next, a method of compression molding using a film with reference to the main diagrams of Figures 2a to 2e will be described. In Figures 2a to 2e, step (a) shows a state of disposition of the film, step (b) shows a state of contact of the molding, step (c) shows the state of injection / filling of the resin in the molding, step (d) shows the state of compression, and step (e) shows a state of mold removal, respectively. In step (a), a film F is inserted between the fixed mold 2 and the sliding board 3d from the moving mold 3. Next, as shown in step (b), the mobile mold 3 moves to the side of the fixed mold 2, and the sliding board 3d comes into contact with the fixed die plate 2c by means of the force of the spring. The compression tolerance of the springs 3c and 3c is set at 0.3 mm, for example. Then, as shown in step (c) -, the molten resin R is filled into the cavity 4 from the nozzle 2f. At this time, the movie F is in close contact with the compression face of the core 3g. Then, as shown in step (d), the movable mold 3 moves so that the compression tolerance S2 of the spring is returned to 0 mm, therefore the 3d sliding board comes into close contact with the die plate 3b mobile At this time, corresponding to the sliding table 3d that is retracting in a direction of the arrow D, the core 3g advances towards an opposite direction in the direction of the arrow D relatively, and the end face of the front side (compressed face) press the molten resin R via the film F. Then, when the molten resin R hardens, the movable mold 3 is separated from the fixed mold 2 to separate a molded product R 'from the mold, as shown in step (e). In compression molding, the film F is interposed between the core 3g and the molded surface of the resin, so that even if abrasive powders are generated in the slidable part of the core C where the core 3g and the sliding table 3d are they move slightly towards each other, it is possible to prevent abrasion dusts from contaminating the molded resin R. As described above, effecting compression molding in a state where the film F between the fixed mold 2 and the mobile mold 3, it is possible to safely solve a reduction in the performance affected by the abrasion powders generated in the sliding part of the core C. In addition, in compression molding, when the film F softens with heat, it also becomes adherent at the same time. Therefore, the abrasion powders adhere easily to the hot film F, and when the film F is sent out of the compression mold after being separated from the mold, the abrasion powders will be discharged from the mold 1 together with the film F Consequently, each time the compression molding is carried out, the abrasion dusts generated in the sliding part of the core C are discharged out of the compression mold 1, so that the service life of the mold can be longer. . In addition, since it is possible to prevent the resin from entering the sliding part of the core C, the occurrence of burrs can be resolved. The film F used in the embodiment described above can be replaced with a transfer film. In that case, it is possible to solve a reduction in the performance caused by abrasion dusts and also to decorate the molded product at the same time.

Figure 3 shows the configuration of a transfer film. The transfer film 21 consists of a base film 22, a separation layer 23, a release layer 24, a design layer 25 and an adhesive layer 26. Note that in the following explanation, the release layer 24, the layer of the design 25 and the adhesive layer 26 can be collectively called the decorative layer 27. As a material of the base film 22, PET (polyethylene terephthalate) excellent in its heat resistance is shown, but is not limited to this material. A single layer film selected from polycarbonate resin, polyamide resin, polyimide resin, polyester ream, acrylic resin, olefin resin, urethane resin, acrylonitrile-butadiene-styrene resin, vinyl chloride resin and the like , or a laminated film or a copolymer film consisting of less than 2 types of resins selected from those mentioned above can be used. As for the thickness of the base film 22, it was confirmed that one having a thickness of 38 μm will not break at the compression amount of 0.3 mm, and one having a thickness of 50 μm will not break up to an amount of 0.5 mm compression. Therefore, when it is carried After printing on the mold using the mold 1, the thickness of the base film 22 can be decided within the range of 38 to 50 μm corresponding to the amount of compression, but when handling capacity is considered, it is preferable to use one that have 38 μm. The release layer 24 forms the outermost face after the design is transferred and the base film 22 is peeled off, and serves as a protective layer for the design. The materials of the release layer 24 include resins of the acrylic type, resin of the nitrocellulose type, resin of the polyurethane type, resin of the chlorinated rubber type, and resin of the vinyl chloride / vinyl acetate copolymer type, resin of the polyamide type, polyester type resin, epoxy type resin, polycarbonate type resin, olefin type resin, and acrylonitrile-butadiene-styrene resin. The thickness of the film of the release layer 24 is preferably in a range of 0.5 to 50 μm. The separation layer 23 is a layer in which the processing of the surface is carried out in the base film 22. This is for a uniform detachment in the base film 22 and the release layer 24. Therefore, the separation layer 23 can be omitted if the detachment can be effected only with the base film 22 and a release layer 24. The material of the separation layer 23 can be constituted like the release layer 24. The design layer 25 which includes characters, symbols, patterns, and Coating patterns are enclosed between the release layer 24 and the adhesive layer 26. The materials of the design layer 25 include resin of the acrylic type, resin of the nitrocellulose type, a resin of the polyurethane type, resin of the rubber type chlorinated, resin of the type of vinyl chloride copolymer and a vinyl acetate, resin of the polyamide type, resin of the polyester type and epoxy type resin. The design layer 25 is not limited to the resin described above. It may consist of a metallic film such as aluminum, chromium, copper, nickel, indium, tin and silicon oxide with vacuum vapor deposition, electrodeposition or the like. Note that the thickness of the film of the design layer 25 is preferably set at a range of 0.5 to 50 μm to obtain a sufficient design property. In the case of consisting of a metallic film layer, a range of 50 Á to 1200 Á is preferable. The adhesive layer 26 is for attaching the design layer 25 to the surface of a molded product. The materials therefore include acrylic resin, resin of nitrocellulose type, resin of polyurethane type, resin of chlorinated rubber type, resin type of vinyl chloride-vinyl acetate copolymer, resin of polyamide type, resin of polyester type, epoxy resin , polycarbonate type resin, olefin type resin, and acrylonitrile-butadiene styrene resin. The thickness of the film of the adhesive layer 26 is preferably in the range of 0.5 to 50 μm. The design layer 25 can be printed on the release layer 24 by the well-known gravure printing. Engraving printing is an impression in which the ink is held in thin cavities of a plate, and printing is effected by transferring the ink to the release layer 24 with a pressure of a printing cylinder. The ink to be used is basically of the solvent type, which has the advantage that the adhesive property is excellent even with respect to a plastic film with web wettability as the release layer 24. In addition, since the surface of a Plastic film does not absorb ink and is very smooth, it is possible to create a precise design using printing by engraving with excellent ink with the release layer 24.

Note that the method for forming the design layer 25 on the release layer 24 is not limited to engraving printing. For example, any printing method capable of attaching the design layer 25 to the release layer 24, such as transfer printing, screen printing or stenciling, coating or immersion, is applicable. Figures 4a to 4e show a method of effecting printing on the mold using the mold 1 shown in Figures 2a to 2e and the transfer film 21. In the following description, the same constitutional elements as those in Figures 2a a2e are denoted by the same reference numbers and the explanation of them was omitted. In Figures 4a to 4e, step (a) shows a state of placement of transfer film 21, step (b) shows a state of contact of the mold, step (c) shows an injection / filling state of the resin in the mold, step (d) shows a state of compression, and step (e) shows a state of mold removal, respectively. In the printing in "" "the mold, the transfer film 21 passes between the fixed mold 2 and the mobile mold 3. The transfer film 21 which passes through of both molds is positioned so that the decorative layer 27 is oriented towards the fixed mold 2. In the fixed die plate 2c, the hot runner 2d for injecting transparent resin is formed towards the transfer film 21. The hot runner 2d forming part connects to a nozzle of an injection molding device not shown. As shown in step (a), the transfer film 21 is fed between the fixed mold 2 and the moving mold 3 to thereby effect the positioning. That is to say, that the placement is effected so that the transparent resin formed upon being injected into the cavity 4 and the pattern formed on the transfer film 21 are arranged in a prescribed manner. As shown in step (b), when the placement of the transfer film 21 is complete, the movable mold 3 moves towards one side of the fixed mold 2, and the 3d sliding board comes into contact with the fixed die plate. 2c by means of spring force. The compression tolerance of springs 3c and 3d is set at 0.3 mm, for example. As shown in step (c), the transparent resin R is injected into the cavity 4. Then, as shown in step (d), the moving mold 3 is moved to set the tolerance of compression of the spring 3c by 0 mm, so that the sliding table 3d and the mobile die plate 3b are in loose contact. Then, after the clear resin was injected hardens, the fixed mold 2 and the movable mold 3 are opened as shown in step (e), and the base film 22 is peeled off since the release layer 24 is provided (see Figure 3), so that the molded product R 'remains on the side of the fixed die plate 2c. On the molded surface of the molded product R ', the design is transferred and integrated with the molded product R'. Then, the molded product R 'is separated from the fixed matrix plate 2c. In this way, by making the impression in the mold with a transfer film 21 being interposed between the fixed mold 2 and the mobile mold 3, it is possible to avoid a reduction in the performance affected by the abrasion powders generated in the slidable part of the core C, simultaneously making decoration by transfer simultaneously. Figures 5a and 5b show a surface (back face) of a molded product after a conventional compression molding, captured by an optical microscope, in which, Figure 5a shows the amplification 50 times, and Figure 5b shows a Amplification of 500 times As is obvious from Figure 5a, thousands of white spots caused by dots are generated on the surface of the molded product, and as is obvious from Figure 5b, the points generate holes. Figure 6 shows the orifice amplified 3500 times additionally, in which a strange article that generates the holes is clearly shown. Through the analysis of the foreign particle, Fe + Cr was detected and confirmed as an abrasion pow On the other hand, Figures 7a and 7b show a surface (back face) of a molded product, molded by the compression molding method of the present invention, captured unthe same conditions. As is obvious from Figure 7a, the white spots completely dissolved, and as is obvious from Figure 7b, holes were seldom generated. As described above, by effecting a compression molding with the film F or the transfer film 21 being interposed between the fixed mold 2 and the moving mold 3, it was confirmed that the molded product can be manufactured without being affected by the pow of abrasion generated in the sliding part of the core C. The compression molding method of the present invention is preferable for thin-walled moldings and 4 optical moldings using transparent resin, particularly. Specific examples of thin wall moldings include transparent display panels for mobile phones and PDAs (Personal Digital Assistants). Specific examples of optical pulleys include plastic lens components provided in mobile phone cameras, plastic lens components used in other electronic equipment, plastic lens components of optical equipment, and optical discs, in the middle of registers, such as CDs (Compact Disc) and DVD (Digital Versatile Disc).

INDUSTRIAL APPLICABILITY The present invention is preferably for forming molded products, ie glasses and optical lenses in particular, in which the molding must be carried out while avoiding the abrasive dusts generated from the sliding face of the mold components contaminate the products.

Claims (8)

1. CLAIMS 1. Method of compression molding, which includes a fixed mold and a mobile mold arranged opposite each other, comprising the steps of: contacting the sliding board connected with a mobile matrix plate on the side of the mobile mold via a spring with a separating face of the mold fixed by the force of the spring; further advancing a movable mold after supplying resin to a cavity within the mold; and compressing and molding the filled resin in the cavity by a core, provided in the movable mold, which penetrates through the sliding board, where the thermoplastic resin film is placed between the fixed mold and the movable mold, and a surface of the resin in the cavity is compressed by the core via the thermoplastic resin film. The compression molding method according to claim 1, wherein a polyester film having a thickness of 20 to 200 μm is used as the thermoplastic resin film. The compression molding method according to claim 1, wherein a base film of a transfer film having a design as in the thermoplastic resin film and arranged so that the pattern is oriented towards a fixed mold side is used, the resin is supplied to the cavity inside the mold, a decorative face of the filled resin in the cavity is compressed by the core via the transfer film, and the design is transferred onto the decorated face. The compression molding method according to claim 1, wherein the resin is supplied to the cavity after the thermoplastic resin film deposited between the fixed mold and the movable mold is adsorbed to the compression face of the core. The compression molding method according to claim 3, wherein the resin is supplied to the cavity after the transfer film deposited between the fixed mold and the mobile mold is adsorbed to the compression face of the core. 6. Compression molding device including a fixed mold and a mobile mold arranged opposite one another, in which a sliding board connected to a mobile die plate on the side of the mobile mold via a spring enters. in contact with a separating face of the fixed mold by means of the force of a spring, and the moving mold further advances that the resin is supplied in a cavity within the mold; and the resin filled in the cavity compressed and molded by a core, provided in the movable mold, which. penetrates through the sliding board, where the device is configured so that a surface of the resin in the cavity and the core is divided with a thermoplastic resin film at the time of compression molding. The compression molding device according to claim 6, wherein the device includes a suction passage communicating with a space in the slidable part of the core within the movable mold and is configured so that the suction passage is connected to a vacuum pump, and the thermoplastic resin film placed between the fixed mold and the movable mold is tightly attached to the compression face of the core. The compression molding device according to claim 6, wherein the thermoplastic resin film is formed of a band-shaped resin film, and is configured to unwind from a roll and pass through the mold intermittently.