JP2013112399A - Resin-made cap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin-made cap that suppresses an outward appearance defect by a cold mark without cost increase.SOLUTION: There is provided a resin-made cap 1 including a cap body 5 molded in a compression molding method and comprising of a top plate 2 and a sidewall 3, and a pilfer-proof band 4 connected to an opening end of the cap body 5 through a plurality of rupturable bridges 11. A cold mark appearing on an outer surface g1 of the top plate 2 profiled in advance with molten resin 100 charged in a recessed metal mold 60 is made inconspicuous by controlling a surface roughness of the outer surface g1 to 1.3-6.0 μm in terms of R a value, and formation of the cold mark itself is suppressed.

Description

  The present invention relates to a resin cap that is attached to seal containers such as beverages and can suppress appearance defects due to cold marks.

  As a resin cap to be attached to a container such as a beverage, for example, a cap body composed of a disk-shaped top plate and a side wall extending from the peripheral edge of the top plate, and a plurality of bridges that can be broken at the open end of the cap body By using a pilfer proof band connected via a pin, one that can confirm the presence or absence of unauthorized opening is widely used. If consumers before purchase can confirm that they have been opened, they can prevent tampering and guarantee the quality of the contents.

  The above-mentioned resin cap is generally molded using an injection molding method or a compression molding method. In the injection molding method, since the molten resin is press-fitted, the orientation of the resin occurs, and the molded product is likely to be deformed. In particular, the deformation due to residual strain may be prominent in the vicinity of the gate. In addition, since the molten resin is loaded through a thin gate, there is a disadvantage that the molding time is increased accordingly. On the other hand, in the compression molding method, since the molten resin is directly loaded into the molding die, there is an advantage that the molded product is hardly deformed and the molding time can be shortened compared with the injection molding method. However, when the molten resin is loaded into the molding die, the molten resin at a high temperature comes into contact with the low-temperature molding die and a sudden temperature change occurs in the molten resin. For this reason, for example, in the resin cap 50 shown in FIG. 4, a wrinkle-like pattern (cold mark) 52 may appear on the outer surface 51a of the top plate 51 that is preliminarily molded, resulting in poor appearance.

  As a countermeasure, there is known a method in which a heating medium having a predetermined temperature is passed through a passage formed in a molding die for compression molding, and a molten resin is charged while raising the temperature of the molding die (see, for example, Patent Document 1). ).

Japanese Patent Publication No. 5-3373

  However, in the method of flowing the heating medium into the molding die as in Patent Document 1, it takes time to cool the molding die heated by the heating medium, so that the molding time can be reduced by using the compression molding method. The above-mentioned advantage that it can be shortened cannot be utilized. In addition, there is a cost for constructing equipment for flowing the heating medium and for maintaining it. As a result, there is a problem that the cost is increased.

  Accordingly, an object of the present invention is to provide a resin cap that can suppress an appearance defect due to a cold mark without incurring an increase in cost in view of the above-described problems of the prior art.

In order to achieve the above object, the following technical measures were taken.
The present invention is a resin cap having a top plate located at the opening end of the container mouth and a cylindrical side wall extending from the peripheral edge of the top plate to one side in the axial direction, and charging molten resin into a molding die In this case, the surface roughness of the outer surface of the molded part that was previously molded is 1.3 to 6.0 μm in terms of Ra value.

  According to the above-mentioned resin cap of the present invention, the surface roughness of the outer surface of the molding part that was previously molded when the molten resin was loaded into the molding die is 1.3 to 6.0 μm in Ra value. For this reason, the cold mark appearing on the outer surface of the molding site is canceled by the surface roughness, and is inconspicuous in the appearance of the product. Further, since the molding part is molded by a molding die having a rough surface in order to make the predetermined surface roughness appear, a sudden temperature change of the molten resin that contacts the molding die And the occurrence of cold marks on the outer surface of the molding site can be suppressed. By these, the appearance defect by the cold mark of the outer surface of the shaping | molding site | part shape | molded ahead can be suppressed. When molding the resin cap of the present invention, it is not necessary to cool the temperature rise by the heating medium in the molding die, and there is no need to construct a device for flowing the heating medium or to maintain it. . For this reason, it is possible to prevent an increase in cost.

  For example, in a general compression molding method, when the molten resin is loaded into a molding die, the molding part that is pre-molded is a top plate, and the surface roughness of the outer surface of the top plate is expressed by a Ra value. By setting it as 1.3-6.0 micrometers, the cold mark which appeared on the outer surface of the said top plate becomes inconspicuous on the appearance of a product. Since the molding die that molds the top plate has a rough surface in order to make the predetermined surface roughness appear, the occurrence of cold marks on the outer surface of the top plate itself can be suppressed.

  The above-mentioned resin cap of the present invention can be applied to various types of resin caps. For example, a cap body composed of the top plate and the side wall and a plurality of pieces that can be broken at the open end of the cap body. A pilfer proof band connected via a bridge, and the cap body and the pilfer proof band are separated from each other by breaking the plurality of bridges by an opening operation from a mounted state. There are types.

  As described above, the cold mark that appears on the outer surface of the molding part that is previously molded is not conspicuous on the product appearance, and can also suppress the occurrence of the cold mark on the outer surface of the molding part. Appearance defects due to cold marks can be suppressed. When molding the resin cap of the present invention, it is not necessary to cool the temperature rise by the heating medium in the molding die, and there is no need to construct an apparatus for flowing the heating medium or to maintain it. It is possible to prevent an increase in cost.

It is sectional drawing of the resin-made caps concerning one Embodiment of this invention. It is a perspective view of the resin caps of FIG. (A) is a schematic diagram showing the state by which a resin cap is shape | molded from molten resin with a shaping die, (b) is an enlarged schematic diagram showing the state in which molten resin is contacting the bottom face part of a concave mold. It is. It is a perspective view of the conventional resin cap with the cold mark appearing on the outer surface of the top plate.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a resin cap 1 according to an embodiment of the present invention, and FIG. 2 is a perspective view of the resin cap 1. The resin cap 1 is attached to a container mouth portion (not shown) and is integrally formed of polypropylene using a compression molding method. The resin cap 1 extends from the top 2 located at the opening end of the container mouth and the peripheral edge 2a of the top 2 toward the one side in the axial direction (downward in FIG. 1). And a pilfer proof band 4 connected to the lower end edge 3a of the side wall 3. In addition, the raw material which forms the resin-made caps 1 is not specifically limited, Polyethylene, polylactic acid, etc. other than the polypropylene used by this embodiment are used suitably.

  A cap body 5 is constituted by the top plate 2 and the side wall 3. The top plate 2 is formed in a disk shape having a required dimension, and an inner ring 6 extending inward and a radially outer side of the inner ring 6 are formed on the back surface 2b of the top plate 2. An annular protrusion 7 projecting inward and an outer ring 8 extending inward with a dimension shorter than that of the inner ring 6 on the radially outer side of the annular protrusion 7 are integrally formed. Yes. When the resin cap 1 is attached to the container mouth, the inner ring 6 is in close contact with the inner peripheral surface of the container mouth, and the outer ring 8 is in close contact with the outer peripheral surface of the container mouth. The annular protrusion 7 is brought into contact with the opening end surface of the container mouth and is deformed.

  The multiple seal structure due to the presence of the inner ring 6, the outer ring 8, and the annular protrusion 7 seals the container mouth well, so that the hermeticity of the container mouth is maintained high. The resin cap 1 of the present embodiment employs a one-piece structure that can seal the container mouth without providing packing as described above, but the form of the resin cap is not limited, and packing is provided. A two-piece resin cap may also be used.

  The side wall 3 is formed in the cylindrical shape which has a required dimension, The internal thread part 9 screwed by the container opening part is formed in the internal peripheral surface 3b. The female screw portion 9 is composed of a plurality of projecting portions 9A provided continuously at a predetermined interval in the circumferential direction. A knurled groove 10 extending in the vertical direction is formed on the outer peripheral surface 3 c of the side wall 3.

  A plurality of bridges 11 are formed at predetermined intervals along the circumferential direction at the boundary between the side wall 3 and the pilfer-proof band 4. The plurality of bridges 11 connect the cap body 5 and the pilfer proof band 4 to each other, and are broken when pulled by a predetermined force. A locking portion 12 is provided inside the pilfer proof band 4. The locking portion 12 is folded back obliquely inward from the lower end portion 4a of the pilfer proof band 4 and is formed continuously or intermittently along the circumferential direction. The locking part 12 can be elastically deformed inward, outward and downward. And this latching | locking part 12 is located under the bead part which is not shown in the container mouth part in the state which the resin cap 1 was mounted | worn, and is latched by the said bead part by opening operation. The

  When the resin cap 1 attached to the container mouth portion starts to turn in the opening direction, the latching portion 12 is latched to the bead portion of the container mouth portion, and a tensile force starts to act on the plurality of bridges 11. When the resin cap 1 is turned, the plurality of bridges 11 are greatly pulled and gradually become thin, leading to breakage. Thereby, the cap main body 5 which consists of the top plate 2 and the side wall 3 is isolate | separated from the pilfer proof band 4, and a container is opened.

  FIG. 3A is a schematic diagram showing a state in which the resin cap 1 is molded from the molten resin 100 with a molding die. The molding die includes a concave die 60 in which the molten resin 100 is loaded and a convex die 65 combined with the concave die 60. The bottom surface portion 61 of the concave mold 60 is a portion that molds the top plate 2 of the resin cap 1, and the side surface portion 62 is a portion that molds the side wall 3 and the pilfer proof band 4 of the cap 1. FIG. 3B is an enlarged schematic view showing a state where the molten resin 100 is in contact with the bottom surface portion 61 of the concave mold 60. When the molten resin 100 cut out by a blade (not shown) is loaded into the concave mold 60, the molten resin 100 first comes into contact with the bottom surface portion 61 and presses the convex mold 65 combined with the concave mold 60. The bottom plate 61 is pushed and spread over the whole by the pressure, and the top plate 2 is molded. Subsequently, the molten resin 100 spreads between the concave mold 60 and the convex mold 65, and the side wall 3 and the pill fur proof band 4 are molded.

  The surface roughness of the outer surface g1 of the top plate 2 molded by the bottom surface portion 61 of the concave mold 60 is 1.3 to 6.0 μm in Ra value. As shown in FIG. 3 (b), the molten resin 100 that contacts the bottom surface portion 61 whose surface roughness has been adjusted is not in surface contact with the bottom surface portion 61 but is in point contact with countless protruding portions, and gradually contacts. Expand the area. Therefore, it is difficult for a sudden temperature change to occur in the molten resin 100.

  In general, since the molten resin is in contact with the bottom of the concave mold for a long time, a cold mark is likely to occur on the top plate. Since the molten resin is suddenly spread out on the side surface portion of the concave mold, the temperature difference between the surface layer portion of the molten resin that is in contact with the side surface portion and the inside of the molten resin is reduced. Cold marks are unlikely to occur at the site. In the present embodiment, the molten resin 100 loaded in the concave mold 60 is unlikely to undergo a rapid temperature change at the bottom surface portion 61 of the concave mold 60 as described above. Is harder to cool than if it is mirror finished. As a result, it is possible to suppress the occurrence of cold marks on the top plate 2 that is molded by the bottom surface portion 61 of the concave mold 60.

  Moreover, since the surface roughness of the outer surface g1 of the top plate 2 is 1.3 to 6.0 μm in Ra value, even if a cold mark is generated on the outer surface g1 of the top plate 2, The level difference and the like constituting the cold mark is canceled by the unevenness of the outer surface g1 of the top plate 2 that is rough. Thereby, the cold mark which has appeared on the outer surface g1 of the top board 2 is not conspicuous in terms of the product appearance. From the above points, it is possible to suppress the appearance defect due to the cold mark of the top plate 2 that is previously molded.

  In the present embodiment, the molding part that is molded in advance in the resin cap 1 is the top plate 2. However, the molding part that is molded in advance is used as the side wall 3 or the pilfer proof band 4, and the outer surface g2 of the molding part is molded. The surface roughness may be 1.3 to 6.0 μm in terms of Ra value.

  The surface roughness of the outer surface of the molding part (for example, the top plate 2) to be molded in advance is preferably 1.3 to 6.0 μm, more preferably 2.0 to 3.0 μm in terms of Ra value. If the surface roughness of the outer surface is less than 1.3 μm in Ra value, the cold mark will not be canceled out and will become noticeable in appearance, or the cold mark will be in view of the contact area due to the surface roughness of the molding die. Will occur. If the surface roughness of the outer surface exceeds 6.0 μm in Ra value, problems such as poor printing such as poor printing will occur. That is, if the surface roughness of the outer surface of the molding site that is previously molded is outside the range of 1.3 to 6.0 μm in Ra value, a good appearance may not be obtained.

  Furthermore, when the resin cap 1 of the present embodiment is molded, it is not necessary to cool the temperature rise by the heating medium in the molding die, and it is necessary to construct a device for flowing the heating medium or to maintain it. It is not necessary to increase the cost. From the above points, appearance defects due to cold marks can be suppressed without incurring a cost increase.

  The embodiment disclosed above exemplifies the resin cap according to the present invention, and the shape, dimensions, and the like of each part are appropriately changed. Of course, it can be applied to a two-piece cap that seals the container mouth with a separate packing, and can also be applied to other resin caps that are not a pill fur proof type. The container to which the resin cap of the present invention is applied is not limited, and the shape of the container mouth is not limited. The resin cap of the present invention is not limited to the one formed by the compression molding method, and may be one molded using another molding method such as an injection molding method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. Five types of molding dies having different surface roughness at the bottom surface portion of the concave mold were prepared, and a plurality of resin caps were molded with each of the molding dies. Six samples from a plurality of resin caps molded with each molding die are sampled, and the surface roughness (arithmetic average roughness Ra) of the top surface of each sampled resin cap is measured, and the cold mark on the top plate In addition to visually determining the appearance defect due to, it was visually determined whether printing was performed on the top board. The results were as shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Resin cap 2 Top plate 3 Side wall 4 Pill fur proof band 5 Cap main body 50 Conventional resin cap 51 Top plate 52 Cold mark 60 Concave die 61 Bottom part 62 Side part 65 Convex die 100 Molten resin

Claims (3)

  A resin cap having a top plate located at the opening end of the container mouth and a cylindrical side wall extending from the peripheral edge of the top plate to one side in the axial direction, when the molten resin is loaded into a molding die A resin cap characterized in that the surface roughness of the outer surface of the molded part that has been molded is 1.3 to 6.0 μm in terms of Ra value.   The resin cap according to claim 1, wherein the molding part is the top plate.   A cap body composed of the top plate and the side wall; and a pilfer proof band connected to the opening end of the cap body via a plurality of breachable bridges. The resin cap according to claim 1 or 2, wherein the cap is a pilfer proof type in which the bridge is broken and the cap main body and the pilfer proof band are separated from each other.

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