JP2014136391A - Mold for blow molding and blow molding container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for blow molding capable of sharpening a cubic inscribed part and securing impact strength even in the case a container is thinned, and to provide a blow molding container.SOLUTION: Provided is a mold for blow molding formed with a fine recessed part for forming a cubic inscribed part. At least a region to be formed with the fine recessed part is formed by a porous metal. The depth of the fine recessed part is 0.2 mm or less. The porous metal, e.g., being porous aluminum (porous aluminum).

Description

  TECHNICAL FIELD The present invention relates to a blow molding die capable of forming a three-dimensional notation portion as a minute convex portion, and a blow molding container formed using the same, and in particular, a blow molding die capable of forming a clear three-dimensional notation portion. The present invention relates to a mold and a blow molded container.

  Plastic containers made of polyolefin resin and the like are widely used as containers for various foods, beverages, chemicals, and the like because they have high moisture resistance, are relatively soft, and have excellent transparency and moldability. As the molding method, blow molding is the mainstream because the container can be efficiently molded and is advantageous in terms of manufacturing cost.

  By the way, in this type of blow-molded container, there are cases where three-dimensional notation such as characters and figures is performed by forming minute convex portions. At this time, a blow molding die used for molding is provided with a minute concave portion corresponding to the minute convex portion, and the resin material enters the concave portion during molding to form the minute convex portion, thereby realizing the three-dimensional notation. Is done.

  In this case, how to clearly form the three-dimensional notation becomes a big problem. For example, in the above-described blow molding, air may remain between the parison and the mold during molding, and air tends to remain particularly in minute recesses such as the three-dimensional notation. If air remains between the parison and the mold, the transfer of the minute concave portions of the mold to the container surface becomes insufficient, and the three-dimensional notation portion is not clear.

  Therefore, for the purpose of eliminating such an inconvenience, the present applicant has proposed that the air vent is formed in a mold and the three-dimensional notation portion is made clear (see Patent Document 1). The blow molding die described in Patent Document 1 intends to eliminate the residual air by providing an air vent for removing air between the split die and the parison.

JP 2011-73365 A

  However, even if the blow molding die described in Patent Document 1 is used, it is not always sufficient to cope with the clearness of the three-dimensional notation and the thinning of the container. For example, by providing an air vent, it is possible to remove air between the parison and the mold to some extent, but it is not possible to completely prevent air from remaining in the corners of the recess, and the three-dimensional notation formed There is a possibility that the portion lacks clarity. In order to clearly transfer the three-dimensional notation portion, it is thought that the depth of the concave portion formed in the mold may be deepened. However, if the concave portion is deepened, the resin is stretched and locally thinned. There is a risk that the impact strength of the resulting container will be greatly reduced.

  In addition, the installation of air vents is limited to several locations of minute recesses, and it is not realistic in terms of mold configuration to form too many. Therefore, air can be excluded only in the vicinity of the air vent, and it is difficult to clarify the entire three-dimensional notation such as figures and characters.

  The present invention has been proposed for the purpose of solving such problems of the prior art, the entire three-dimensional notation can be clarified, and the impact strength is reduced even when the container is thinned. It aims at providing the metal mold | die for blow molding which does not do, and also aims at providing a blow molding container.

In order to achieve the above-mentioned object, the blow molding die of the present invention is a blow molding die in which a minute recess for forming a three-dimensional notation is formed, and at least the minute recess is formed. The region is formed of a porous metal. The blow-molded container of the present invention is a blow-molded container molded by the blow molding die, and has a three-dimensional notation portion formed as a minute convex portion at a predetermined location.

  In the blow molding die, if the region where the minute recesses for forming the three-dimensional notation are formed of porous metal, the air remaining in the minute recesses in the entire three-dimensional notation is eliminated. As a result, even if the depth of the minute concave portion is shallow, the three-dimensional notation portion is sharpened, and it is not necessary to deepen the minute concave portion, so that the resin is not stretched and locally thinned. .

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the metal mold | die for blow molding which can clarify the whole three-dimensional description part and can eliminate the fall of the impact strength by resin becoming thin locally. Further, according to the present invention, it is possible to provide a blow molded container having a clear three-dimensional notation and excellent impact strength.

It is a schematic sectional drawing which shows the one aspect | mode of blow molding. It is a schematic sectional drawing of the metal mold | die for blow molding in the AA line position of FIG. It is a figure explaining the shape of a micro recessed part, (a) shows the example of the shape of the micro recessed part which can form a clear three-dimensional notation part, (b) is the shape of a micro recessed part where formation of a clear three-dimensional notation part is difficult An example is shown. It is a front view which shows an example of the blow molding container shape | molded. (A) is sectional drawing in the XX line of FIG. 4, (b) is sectional drawing in the YY line of FIG.

  Hereinafter, embodiments of a blow molding die to which the present invention is applied and a blow molded container molded using the same will be described in detail with reference to the drawings.

  FIG. 1 shows one embodiment of blow molding. In blow molding, a parison 2 formed in a cylindrical shape is supplied from the head 1, sandwiched between a pair of blow molding dies 3, 4, and blow molding dies 3 with the pressure of gas blown into the inside thereof. , 4 is pressed against the inner surface of the parison 2 to form a hollow container.

  Here, when providing the three-dimensional notation part which consists of a micro convex part on the surface of the container shape | molded, it is necessary to provide the micro recessed part 6 in the inner surface of the blow molding die 3 corresponding to a three-dimensional notation part, for example. In this embodiment, as shown in FIG.1 and FIG.2, the recessed part is formed in the micro recessed part formation area of the metal mold | die 3 for blow molding, and the insert piece 5 which consists of porous metals is fitted here. Thereby, the three-dimensional notation part formation surface of the metal mold | die 3 for blow molding is formed with a porous metal.

  As described above, it is possible to form a clear three-dimensional notation by forming the three-dimensional notation forming surface of the blow molding die 3 with a porous metal.

For example, a micro recess 6 is formed in the blow molding die 3 corresponding to the three-dimensional notation, and the parison 2 enters the micro recess 6 so that the three-dimensional notation is formed as a micro-projection. If the minute recess formation region is formed of a dense metal material without holes, air bleeding becomes insufficient and residual air stays in the minute recess 6. The remaining air expands due to heat, stretches the parison 2, and a thin portion is formed in the parison 2. Further, the parison 2 does not enter the minute recess 6 sufficiently, resulting in poor transfer, and the three-dimensional notation is unclear.

  On the other hand, when the minute recessed portion forming region is formed of a porous metal, the minute holes of the porous metal face the formation surface of the minute recessed portion 6, and air is quickly extracted from these minute holes. As a result, the parison 2 enters the minute recess 6 and is in close contact with the inner surface of the minute recess 6 so that the shape of the minute recess 6 is reliably transferred to the parison 2. Thereby, a clear three-dimensional notation part can be formed.

  Note that air venting in the minute recess 6 can also be realized by installing an air vent, but air is excluded only in the vicinity of the air vent, and sufficient air venting is performed at a position away from the air vent. Is difficult. Further, when an air vent is installed, the air vent shape may be transferred to the three-dimensional notation.

  The porous metal used in the blow mold is not limited as long as it is a porous metal material having fine open cells, but it is porous in terms of various properties such as thermal conductivity. Aluminum (so-called porous aluminum) is optimal. Moreover, although the size of the fine pores of the porous metal is arbitrary, it is preferable to have a fine pore structure having an average diameter of 20 μm or less. If the size of the holes is fine, the three-dimensional notation can be formed more clearly and cracking of the mold during molding can be suppressed. The porosity of the porous metal is also arbitrary, but in view of the above-described effects, it is preferably 5% to 20%, and more preferably 15% to 16%.

  Further, in the embodiment shown in FIG. 1 and FIG. 2, the porous metal is fitted in the blow molding die 3 in the form of the insert piece 5, but the entire blow molding die 3 is formed of the porous metal. It is also possible. However, since porous metals such as porous aluminum have a problem of low strength, it is preferable to install them in the form of the insert piece 5.

  In order to ensure air bleeding, for example, an air vent or the like may be installed on the back surface of the insertion piece 5 made of porous metal. However, since the internal volume of the minute recess 6 is very small, no air vent or the like is installed. Both can be sufficiently absorbed by the space of the porous metal itself.

By forming the minute recess formation region with a porous metal, it becomes possible to form a clear three-dimensional notation portion, and in particular, even if the depth of the minute recess 6 is shallow, a clear three-dimensional notation portion can be formed. . When the depth of the minute recess 6 is deep, when the parison 2 enters the minute recess 6, the parison 2 is greatly extended, impact resistance is greatly reduced, and cracks occur in the molded container. There is a fear. Therefore, the depth of the minute recess 6 needs to be 0.2 mm or less. The micro concave portion 6 needs to have a certain depth, and therefore the optimum value of the depth of the micro concave portion 6 is 0.05 mm to 0.2 mm.

  As described above, by forming the micro unevenness formation region of the blow molding mold with a porous metal and making the depth of the micro recesses 0.2 mm or less, it is possible to form a clear three-dimensional notation, It is possible to mold containers with excellent impact resistance.

At this time, the shape of the minute recess 6 also affects the transferability, and affects the clarity of the three-dimensional notation. The shape of the minute recess 6 is preferably a shape having a corner, thereby increasing the clarity of the three-dimensional notation. Hereinafter, the shape of the minute recess 6 will be described.

  FIG. 3 schematically shows the minute recess 6. In the blow molding die of the present invention, as shown in FIG. 3A, it is preferable that the opening edge of the minute recess 6 has a corner. Generally, when forming a micro recessed part in a metal mold | die, the cutting tool called an end mill is used. The tip of the end mill has a spherical shape, and the shape of a groove (concave portion) formed using the end mill has an arcuate cross section. In this minute concave portion 6 having an arc shape in cross section, as shown in FIG. 3A, when the tangent line of the arc is drawn, if the tangent line s and the mold surface h form a predetermined angle α exceeding 0 °, It can be said that it has corners.

As shown in FIG. 3B, when the opening edge of the minute recess 6 does not have a corner and has a gentle shape, the tangent s and the mold surface h coincide (the angle α is 0 °). ) With such a shape, the contour of the minute convex portion to be molded becomes unclear, and it is not possible to form a clear three-dimensional notation portion. Preferably, the angle α formed by the tangent s and the mold surface h is 30 ° or more. If a clearer three-dimensional notation is desired, the angle α is more preferably 50 ° or more. In addition, since the shearing force acts on the parison as the angle α increases, it is preferable to reduce the angle α from the viewpoint of preventing cracking, and it is preferable to set it to 85 ° or less. When the minute convex portion is formed by the minute concave portion having the predetermined angle α, the molded minute convex portion rises at a corresponding angle. However, the starting point of the rising may not be completely transferred to the corners of the mold, and a fine R shape (arc shape) may be formed.

  An example of a container molded using the above-described blow molding mold is shown in FIG. The container 11 of this example has a mouth part at the upper end of the container body 12, and is a flexible container filled with mayonnaise, ketchup or the like. The body 12 of the container 11 has a recessed surface 13 inside the outer edge shape of the container 11, and a three-dimensional notation such as a manufacturer name and a logo mark is formed on the recessed surface 13.

  The average thickness of the container body 12 (the portion where the three-dimensional notation is not formed) is about 0.4 mm to 0.5 mm, and when the weight is reduced, the thickness may be 0.4 mm or less. is there. The thickness of the three-dimensional notation portion tends to be thinner than the thickness of the container body portion 12 where the three-dimensional notation portion is not formed. In particular, when the width of the minute concave portion of the mold for forming the minute convex portion of the three-dimensional notation is smaller than the average thickness of the container body (for example, 0.4 mm or less), The thickness tends to be thin.

  In the case of the container 11 of this example, a geometric pattern is formed on the recessed surface 13 as a three-dimensional notation, and the three-dimensional notation has a cross-sectional shape as shown in FIG. It is composed of a geometric pattern in which a contour is formed by the linear minute convex portions 14 and a geometric pattern having a cross-sectional shape as shown in FIG. ing.

  In particular, when forming the micro-projections 14, if a blow molding die in which the micro-recess 6 is formed of a porous metal is used, a clear geometric pattern with a good transferability can be obtained. Formed as. Moreover, a thin part is not formed in the container 11 by formation of the micro convex part 14, and a crack does not generate | occur | produce in the three-dimensional notation part with thin thickness.

  Although the embodiment to which the present invention is applied has been described above, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications or improvements are made without departing from the gist of the present invention. It is possible.

  Hereinafter, the present invention will be described based on specific experimental results.

Difference by Blow Molding Mold A multilayer plastic container was molded by blow molding using polyethylene resin for inner and outer layers. The molded multilayer plastic container has a capacity of 500 ml and an average thickness at the container body of 0.4 mm or less.

  The multi-layer plastic container has a mold in which the surface for forming the three-dimensional notation portion is formed of porous aluminum (depth of minute recess 0.15 mm) (Example 1), a mold formed of ordinary aluminum (depth of micro recess) 0.15 mm) (Comparative Example 1), a mold made of ordinary aluminum (depth of the minute recess 0.3 mm) (Comparative Example 2), a mold made of ordinary aluminum and provided with an air vent (micro recess) The depth was 0.15 mm) (Comparative Example 3), and the clarity and drop resistance strength of the three-dimensional notation of the obtained container were evaluated. In addition, the width | variety of the micro recessed part was 0.4 mm or less. The results are shown in Table 1.

  As is clear from this table, as in Example 1, by forming the formation surface of the three-dimensional notation portion with porous aluminum, clear three-dimensional notation is possible and sufficient strength is ensured. On the other hand, in Comparative Example 1 using normal aluminum, the three-dimensional notation was lacking in clarity. In Comparative Example 2 in which the depth of the minute concave portion was increased in order to make the three-dimensional notation clear, the drop resistance strength was insufficient, and a crack occurred in the three-dimensional notation. In Comparative Example 3 in which the air vent was provided, a certain degree of clearness could be secured, but the outline was slightly unclear in the three-dimensional notation at a position away from the air vent.

Study on the depth of the minute recesses The depth of the minute recesses of the mold in which the formation surface of the three-dimensional notation portion is made of porous aluminum is 0.05 mm to 0.4 mm, and the average thickness in the container body is A multilayer plastic container of 0.4 mm or less was molded. Table 2 shows the clarity and drop resistance strength of the three-dimensional notation of the obtained container.

  When the depth of the minute recess exceeds 0.2 mm, the drop strength is reduced.

1 Head 2 Parison 3 and 4 Blow mold
5 Inserting piece 6 Minute concave portion 11 Container 12 Body portion 13 Depressed portion 14 Small convex portion 15 Convex portion

Claims (6)

A mold for blow molding in which a minute recess for forming a three-dimensional notation is formed,
A blow molding die characterized in that at least the region where the minute recesses are formed is formed of a porous metal.   The blow molding die according to claim 1, wherein the depth of the minute recess is 0.2 mm or less.   The blow mold according to claim 1 or 2, wherein the porous metal is porous aluminum. The blow mold according to any one of claims 1 to 3, wherein the porous metal has a microporous structure having an average diameter of 20 µm or less. A blow molded container formed by the blow molding die according to any one of claims 1 to 4.
A blow-molded container having a three-dimensional notation formed as a minute convex portion at a predetermined location. The average wall thickness is 0.4 mm or less,
The blow-molded container according to claim 5, wherein the height of the minute convex portion is 0.2 mm or less.

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