JP5830319B2 - Mold for vacuum forming and method for producing resin molded product - Google Patents

Description

The present invention relates to a vacuum forming mold and a method for producing a resin molded product, and more specifically, a vacuum forming mold used for vacuum forming a thermoplastic resin sheet, and such a vacuum forming mold. Relates to a method for producing a resin molded product obtained by vacuum molding a thermoplastic resin sheet.

Conventionally, resin trays such as food trays and lids for food trays have been produced using raw rolls obtained by winding thermoplastic resin sheets such as foam sheets and transparent films made of thermoplastic resins into rolls. ing.
For example, a heating zone that heats a thermoplastic resin sheet so that it can be deformed and a molding zone that includes a molding die for thermoforming the thermoplastic resin sheet softened in the heating zone, and the molding A strip-shaped thermoplastic resin fed from the raw roll to a production facility having a punching zone for separating a product and a portion outside the product by punching a thermoplastic resin sheet having a product shape formed by a mold with a Thomson blade mold or the like Conventionally, continuous production of resin molded products by supplying sheets has been widely performed.

In addition, as the mold, a mold having a molding recess corresponding to the product shape is usually used, and in the thermoforming, the softened thermoplastic resin sheet and the mold are brought into contact with each other, The inside of the molding recess is evacuated (vacuum molding), the thermoplastic resin sheet is pressurized from the side opposite to the molding recess (pressure forming), or the vacuum molding with the pressurization (so-called “vacuum”)・ Pressurized molding ”) is performed to deform the thermoplastic resin sheet along the shape of the inner surface of the molding recess, and the thermoplastic resin sheet is brought into contact with the inner surface of the molding recess to be removed from the mold. Cooling the thermoplastic resin sheet to a level at which the shape can be sufficiently maintained even if the mold is separated is performed.
In addition, usually, in the punching with the Thomson blade mold, a thermoplastic resin sheet is cut one size larger than the portion formed by the molding recess, and a product having a flange on the outer periphery is manufactured. In addition, during the thermoforming, not only the portion in contact with the molding recess but also the portion that becomes the flange is sufficiently cooled.

By the way, in the continuous production of such a resin molded product, the time required for thermoforming in the molding zone is generally rate-determining to determine the line speed.
In other words, the heating zone can secure the necessary heating capacity even if the line speed increases by increasing the set temperature or lengthening the zone length, and the punching zone also has a punching speed of Thomson blade type. While it is easy to improve to some extent according to the speed, in the molding zone, if the thermoplastic resin sheet softened in the heating zone is brought into contact with the surface of the mold and not cooled sufficiently, the product may be deformed. In general, the time required for cooling the thermoplastic resin sheet in this molding zone is the rate-limiting factor for continuous production of resin molded products.

  For this reason, for example, in Patent Document 1 below, it has been studied to improve the cooling capacity by circulating cooling water through a vacuum forming mold.

JP-A-6-47804

In the production of a resin molded product, if the above-described vacuum forming mold is used, the thermoplastic resin sheet softened in the heating zone can be quickly cooled, and the production speed of the resin molded product can be improved and the production efficiency can be improved. Can be improved.
However, even if the mold used for vacuum forming is sufficiently cooled, the effect is greatly impaired if the thermoplastic resin sheet does not sufficiently contact the surface of the vacuum forming mold.

As a result of extensive studies by the inventor of the present invention, the contact state of the thermoplastic resin sheet around the molding recess is usually not sufficient in vacuum forming compared to the contact state in the molding recess. It has been found that the thermoplastic resin sheet is slightly lifted from the surface of the mold around the recess for molding and is not sufficiently cooled.
In addition, when cooling around the molding recess is insufficient, there is a risk of causing “swells” or “wrinkles” in the thermoplastic resin sheet when the thermoplastic resin sheet is deformed along the molding recess. It was found that the obtained resin molded product may be defective.

  An object of the present invention is to provide a vacuum forming mold capable of satisfactorily contacting a thermoplastic resin sheet over the entire range used as a product during vacuum forming. Therefore, it is an object to improve the production efficiency of the resin molded product.

  The present invention relating to a vacuum forming mold for solving the above-mentioned problems is used for vacuum forming of a thermoplastic resin sheet, and has a forming recess corresponding to a product shape to be formed on the thermoplastic resin sheet. A molding die further comprising a groove portion surrounding the molding recess, the groove portion being provided to form a groove in the thermoplastic resin sheet in a portion outside the product, and in the vacuum forming It is characterized by being evacuated.

  The term “vacuum forming” in the present specification does not intend “vacuum forming” in a narrow sense in which only evacuation is performed from the mold side, but so-called “vacuum / pressure forming”. It is used in the meaning including the molding method called.

In the vacuum forming mold of the present invention, a groove is formed so as to surround the forming recess.
The groove portion can be formed in the thermoplastic resin sheet at a portion outside the product, and is provided in a state capable of being evacuated in vacuum forming.
Therefore, when vacuum forming is performed, tension can be generated in the thermoplastic resin sheet between the molding recess and the groove surrounding the molding recess.
That is, the contact state between the thermoplastic resin sheet and the mold can be improved not only in the concave portion for molding but also around the concave portion for molding, and the thermoplastic resin sheet can be efficiently cooled and wrinkled. It is possible to suppress the occurrence of defects due to.

The schematic perspective view which shows the resin molded product (container for cut tofu) manufactured with the shaping | molding die for vacuum forming which concerns on one Embodiment of this invention. The schematic plan view (a) which shows the shaping | molding die for vacuum forming of one Embodiment, and a schematic partial sectional view (b). The schematic plan view which shows the shaping | molding die for vacuum forming of other embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
Below, the shaping | molding die for vacuum forming for forming the container for cut tofu by vacuum forming is demonstrated.

FIG. 1 is a schematic perspective view of a cut tofu container that is a resin molded product manufactured by a vacuum forming mold according to the present embodiment. As shown in FIG. A housing recess 110 that houses cut tofu is formed by a substantially square bottom surface portion 111 and a peripheral side wall 112 erected along the outer periphery of the bottom surface portion 111.
The accommodation recess 110 of the cut tofu container 1 is opened so that the upper side thereof is a square slightly larger than the bottom surface portion 111, and is directed from the upper edge side of the peripheral side wall 112 toward the bottom surface portion 111. The cross-sectional shape is continuously reduced.
That is, the accommodation recess 110 has an accommodation space having an inverted square frustum shape.

The cut tofu container 100 according to the present embodiment further includes a flange 113 extending outward from the opening edge 110e (upper edge of the peripheral side wall 112) of the housing recess 110, and the flange 113 extends outward. The protruding length is made substantially constant around the opening edge.
Therefore, the contour shape of the cut tofu container 100 defined by the outer edge 113e of the flange 113 in a top view is a square that is slightly larger than the opening edge 110e of the housing recess 110.
In addition, the said collar part 113 does not have an unevenness | corrugation from the front-end | tip which defines the outer edge of the cut tofu container 100 to a base end (opening edge 110e of the accommodation recessed part 110), and has become a flat state. .
That is, the cut portion 113 is provided in the cut tofu container 100 so that the whole of the ridge portion 113 is substantially flush with the opening of the receiving recess 110.

The cut tofu container 1 in the present embodiment is formed by vacuum forming a non-foamed thermoplastic resin sheet (resin film), and a recess corresponding to the housing recess 110 in the resin film. Is formed by cutting the outside of the recess with a Thomson blade that is slightly larger than the recess.
More specifically, the cut tofu container 100 in the present embodiment is formed after a plurality of the concave portions are formed by a single vacuum forming with respect to the resin film having a large area compared to the cut tofu container 100, A plurality of Thomson blades are punched and formed by a Thomson blade mold mounted on the substrate in correspondence with the arrangement of the recesses.

FIG. 2 shows a schematic plan view (a) and a schematic partial sectional view (b) of a vacuum forming mold used for forming the cut tofu container 100. The partial sectional view (b) is shown in FIG. 1 shows a schematic cross-sectional structure in the direction of arrows AA ′ shown in the plan view (a).
As shown in this figure, the vacuum forming mold 1 (hereinafter also simply referred to as “molding die”) in the present embodiment has a total of 16 housing recesses 110 formed on a resin film by one vacuum forming. Four forming recesses 10 having a recess shape corresponding to the receiving recess 110 are arranged vertically and horizontally so that they can be formed.
Moreover, the said shaping | molding die 1 of this embodiment is equipped with the flat part 30 provided with the flat surface for forming the collar part 113 of the container 100 for cut tofu around each recessed part 10 for shaping | molding, and this flat A groove portion 20 is further provided to surround the molding recess 10 from the outside of the portion 30.

In the molding die 1 of the present embodiment, the groove portions 20 are formed in a lattice shape, and extend in the lateral direction so as to be orthogonal to the five vertical grooves 21a extending in the vertical direction and the vertical grooves 21a. The groove portions 20 are formed in a lattice pattern by the five horizontal grooves 21b.
More specifically, in the mold 1 of the present embodiment, the groove portion 20 is configured by grooves 21a and 21b provided at equal intervals in the vertical direction and the horizontal direction, and these grooves 21a and 21b. Four square meshes surrounded by four sides are formed vertically and horizontally, and the molding recess 10 is provided at the center of each mesh so that the grooves 21a, 21b and the opening edge 10e are parallel to each other. .
The molding die 1 according to this embodiment has the flat surface between the molding recess 10 and the groove 20 surrounding the molding recess 10.

In addition, the distance between each groove | channel which comprises this groove part 20, and the said recessed part 10 for shaping | molding is longer than the protrusion length of the collar part 113 of the container 100 for cut tofu.
That is, of the resin film that comes into contact with the flat portion 30 during vacuum forming, the portion close to the molding recess 10 is used as the cut tofu container 100 but is located in the grooves 21a and 21b far from the molding recess 10. The close portion is out of the product including the portion where the groove shape is formed by the grooves 21a and 21b.

That is, the groove part 20 is provided so that a groove can be formed in the resin film outside the region (outside the product) used as the cut tofu container 100.
More specifically, the resin film vacuum-formed by the mold 1 of the present embodiment has a region indicated by a broken line 100x as a product by a Thomson blade when the portion located in the upper left of the front view of FIG. The remaining part other than the product region 100x is punched out, and the groove portion 20 is provided so that a groove can be formed in the punching bar serving as the outside region of the product.

The respective components of the mold 1 will be described in more detail. The molding recess 10 has vacuum holes AX opened at a plurality of locations along the outer periphery of the bottom surface 11 to evacuate the internal space during vacuum molding. The resin film is provided so that a portion that becomes the housing recess 100 of the cut tofu container 100 can be formed.
That is, the molding recess 10 has an opening edge 10e which is a square larger than the opening edge 110e of the cut tofu container 100 by the thickness of the resin film, and the bottom surface 11 and the outer edge of the bottom surface 11 An internal space having an inverted quadrangular pyramid shape that matches the shape of the outer surface of the housing recess 110 is defined by the side peripheral surface 12 that hangs down from the opening edge 10e.
Accordingly, the mold 1 of the present embodiment has a slight inclination with the side peripheral surface 12 not being a vertical surface, and the side peripheral surface 12 makes a draft (the angle “in FIG. 2B”). θ ”).

Moreover, the groove part 20 is recessed so that the cross-sectional shape at the time of cut | disconnecting in the depth direction of the recessed part 10 for shaping | molding may become a rectangle, and the recessed depth from the upper surface of a shaping | molding die is compared with the recessed part 10 for shaping | molding. It is shallow.
The groove portion 20 is used to suppress the occurrence of defects such as wrinkles in the cut tofu container 100 by generating a tension in the resin film between the groove portion 10 and the forming recess 10 during vacuum forming. Each of the grooves 21a and 21b is also provided with a vacuum hole AY at the bottom in the same manner as the molding recess 10 and can be evacuated in the vacuum molding.

Below, the inhibitory effect of the wrinkles etc. by this groove part 20 is demonstrated.
When vacuum forming is performed using the molding die 1 of the present embodiment, evacuation is performed from the vacuum hole AX opened on the outer periphery of the bottom surface of the molding recess 10 and the resin film is deformed while the resin film is deformed. As well as being drawn into the groove 20, vacuuming is performed also from the vacuum hole AY opened in the groove 20, and the resin film is also drawn into the groove.
Accordingly, the resin film is drawn into both the groove 20 and the molding recess 10, whereby tension can be generated in the resin film between the groove 20 and the molding recess 10. A contact state can be made favorable.
That is, the cooling efficiency of the resin film in the flat portion 30 can be improved.

In addition, when cooling of the resin film in a flat part is inadequate, there exists a possibility that it may produce a "swell" and a "wrinkle" in a resin film by temperature variation etc., and a product may become inferior goods.
In addition, even when the force applied to the resin film becomes non-uniform when the resin film is not sufficiently cooled at the flat part, it is easy to cause “swells” and “wrinkles” on the resin film, and the product becomes a defective product. There is a risk of becoming.
For example, if the shape of the opening edge of the molding recess is close to a perfect circle, the force acting on the resin film during vacuum forming will be substantially constant over the entire circumference of the opening edge. In the case of having the square opening edge 10e as described above, the force acting on the resin film at the corner of the square and the force acting on the resin film at the side center are greatly different.
Therefore, when manufacturing a resin molded product such as the cut tofu container 100 exemplified in the present embodiment, if the resin film is not quickly cooled around the molding recess, “swell” or “ This is a situation where wrinkles are particularly likely to occur.
However, the mold 1 in the present embodiment is provided with the groove portion 20, and the resin film around the molding recess 10 can be brought into contact with the surface of the flat portion 30 at an early stage of vacuum molding to be cooled. Therefore, the occurrence of defects such as wrinkles can be suppressed.

In addition, even if there are no visually identifiable defects such as “swells” and “wrinkles”, if the heel part of the cut tofu container is made to have different cooling conditions depending on the location, the heel part is flat in the manufacturing stage. Even if it is obtained in such a state, for example, when heat sealing is performed using this collar, there is a risk of causing thermal distortion in the collar.
That is, by using the mold 1 of the present embodiment, it is possible to suppress the occurrence of the potential problems as described above, and it is possible to prevent the problems from becoming obvious when using the cut tofu container. can do.

  In addition, in the point which can improve the adhesiveness of the resin film in the flat part 30, and can demonstrate the above effects more notably, the shaping | molding die 1 of this embodiment is not only the vacuum drawing from the said shaping | molding die side. It is preferably used for vacuum forming called “vacuum / pressure forming” which simultaneously performs pressurization from the back side of the resin film.

And since the time required for the cooling of the resin film can be shortened by using the mold 1 of this embodiment at the time of such vacuum forming as compared with the case of using the conventional mold, a long strip-shaped resin film The line speed can be improved as compared with the conventional case in the case where the resin molded product is continuously produced using.
That is, by using the mold 1 of this embodiment, the number of resin molded products formed per unit time can be increased and the yield can be improved, so that the production efficiency can be improved.

The mold 1 of the present embodiment is not particularly limited to a resin film that is formed by vacuum forming. For example, a polyolefin resin film such as a polyethylene resin film or a polypropylene resin film; a polyethylene terephthalate resin film, a poly Polyester resin films such as butylene terephthalate resin films and polylactic acid resin films; polystyrene resin films; or laminated films in which a plurality of these are laminated, or one or more of these and other films Can be used for vacuum forming of a laminated film or the like laminated.
The resin film may be a stretched product or a non-stretched product.

  In addition, in the point which can improve the cooling efficiency of the resin film in the circumference | surroundings of the said recessed part 10 for shaping | molding, and can aim at the improvement of the manufacturing efficiency of a resin molded product, the said groove part etc. do not need special limitation. However, as illustrated in FIG. 2, the effect of suppressing the tension generated between the groove 20 and the molding recess 10 from becoming uneven on the outer periphery of the molding recess 10 can be further demonstrated. Further, it is preferable that the distance from the opening edge 11e of the molding recess 10 to the groove 20 is constant in the circumferential direction.

Further, the distance from the opening edge of the molding recess to the groove (“Lx” in FIG. 2B) varies depending on the type of resin film used and the shape of the resin molded product to be produced. If it is a case where it uses for the vacuum forming of the polypropylene-type resin film whose thickness is 0.2 mm-1.3 mm, generally it is preferable that the said distance (Lx) shall be 5 mm-15 mm.
Further, the size of the groove such as the width (Wx) and the depth (Dx) of the groove is not particularly limited. However, if the groove is used for vacuum forming of the polypropylene resin film as described above, the groove The width (Wx) is preferably 4.5 mm to 10 mm, and the groove depth (Dx) is preferably 1.5 mm to 5.5 mm.

  In addition, in the figure, the cross-sectional shape illustrates a rectangular groove, but in the function of generating an appropriate tension to the resin film between the molding recesses, the cross-sectional shape of the groove is not particularly different. Alternatively, grooves having various cross-sectional shapes such as an inverted trapezoid, an inverted triangle (V-shaped), and a semicircular shape can be used instead of the grooves having a rectangular cross section shown in the drawing.

  Moreover, although it is preferable that all the grooves constituting the groove portion 20 have the same size and the same shape, if necessary, one groove constituting the groove portion 20 and another groove may be combined. The size and shape may be different.

In addition, in this embodiment, in the point which can exhibit the effect of this invention more notably, the accommodation recessed part 110 for accommodating the cut tofu which is a to-be-contained object, and the opening edge 110e of this accommodation recessed part 110 outward. A mold for use in manufacturing a cut tofu container 100 having a flat flange 113 extending is illustrated, for forming the flange 13 on the outside of the molding recess 10 corresponding to the housing recess 110. Although the flat part 30 provided with the flat surface is formed and the groove part 20 exemplifies the molding die surrounding the concave part 10 for molding from the outside of the flat surface, the present invention describes the resin molded product to be manufactured. It is not limited to the container for cut tofu which has such a flat collar part.
That is, the vacuum forming mold of the present invention can be used for the production of a cut tofu container provided with unevenness in a portion corresponding to the flat portion and having a ridge portion having the uneven shape. Vacuum forming used for forming a container in which a plurality of ribs extending radially from the central part are formed in the collar part, or a container in which a rib that goes around the outside of the housing recess along the collar part is formed in the collar part. The molding die is also in the range intended as the vacuum molding die of the present invention.

  Also, in resin molded products other than cut tofu containers, as long as the vacuum forming mold of the present invention is used, there is no change in that it can be easily manufactured and excellent in quality, The vacuum forming mold used for the production of the resin molded product other than the cut tofu container is also within the range intended as the vacuum forming mold of the present invention.

  Furthermore, in the present embodiment, the grooves 20 are provided in a lattice shape to form a plurality of cells in that a large number of good products can be formed by one-shot vacuum forming, and each of the plurality of cells is molded. For example, the vacuum forming mold 1z provided with only one molding recess 1z as shown in FIG. 3 is also shown in FIG. As long as the groove 20z surrounding 1z is provided, it is within the range intended by the present invention.

Moreover, in this embodiment, the case where the resin film is used as the thermoplastic resin sheet is illustrated in that the effect of the present invention is more prominently exhibited, but the resin film and the resin foam sheet are laminated. The present invention is also intended to be used for vacuum forming of thermoplastic resin sheets such as laminated foam sheets and resin foam sheets.
Although no further detailed description will be given here, it goes without saying that conventionally known technical matters relating to a vacuum forming mold, a method for producing a resin molded product, and the like can be appropriately adopted in the present invention. It is a matter of.

1: vacuum forming mold, 10, 10z: molding recess, 20, 20z: groove, 30: flat part, 100: cut tofu container (resin molded product), 100x: product region, 110: housing recess, 113 : Buttocks

Claims (4)

A vacuum molding mold having a molding recess corresponding to a product shape used for vacuum molding of a thermoplastic resin sheet and formed on the thermoplastic resin sheet,
It further has a groove part surrounding the concave part for molding, and the groove part is provided to form a groove in the thermoplastic resin sheet in a part outside the product, and can be evacuated in the vacuum forming. A mold for vacuum forming characterized by   The container is used for manufacturing a container having an accommodating recess for accommodating an object to be accommodated and a flat flange extending outward from an opening edge of the accommodating recess, and the outer edge is defined by the tip of the flange A flat surface for forming the flange portion is formed outside the molding recess corresponding to the housing recess and used for manufacturing the container, and the groove portion extends from the outside of the flat surface to the molding recess. The vacuum forming mold according to claim 1, wherein the mold is enclosed.   The vacuum forming mold according to claim 1 or 2, wherein the groove portions are provided in a lattice shape to form a plurality of meshes, and the molding recesses are provided in the plurality of meshes. A method for producing a resin molded product using a vacuum molding die and vacuum-molding a thermoplastic resin sheet with the vacuum molding die to produce a resin molded product,
Examples mold for vacuum forming, method for producing a resin molded article, characterized in that there use a mold for vacuum forming according to any one of claims 1 to 3.

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