JP2010188711A - Method for manufacturing bottomed cylindrical container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the weight and thickness of a cup-shape container manufactured by stretch blow molding. <P>SOLUTION: A plate-shape preform 10 made of a thermoplastic resin used for manufacturing the cup-shape container 1 by stretch blow molding has a plate-shape part 12 and a flange 13 formed in the outer fringe part of the same. The plate-shape part 12 is a stretched part becoming a container body part 2 of the cup-shape container 1 by being stretched an blown, the flange 13 is a not stretched and blown part not stretched and blown and becoming a container mouth part 3 of the cup-shape container 1. The front surface 12a of the plate-shape part 12 is a planar plane and the rear surface 12b of the same is regulated by a convex curbed surface whose center has the largest wall thickness. Deformation causing problem in the stretch blow molding when heating is not generated even though the wall thickness is small because the plate-shape preform 10 does not a 3D shape. Therefore, the lightweight cup-shape container can 1 be obtained by reducing the wall thickness of the plate-like preform. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a bottomed cylindrical container such as a cup-shaped container such as a cup-shaped container by stretch-blow-molding a preform, and in particular, thermoplasticity suitable for weight reduction of the bottomed cylindrical container. The present invention relates to the shape of a preform made of resin.

  As a cylindrical container with a bottom manufactured by biaxial stretch blow molding, a wide-mouthed cup-shaped container made of a thermoplastic resin used as a container for milk beverages is known. The wide-mouthed cup-shaped container includes a cylindrical body with a bottom and a mouth flange that extends outward from the upper end opening of the cylindrical body, and the diameter of the upper end opening is in addition to the cylindrical body. The shape is larger than the part. In general, after filling a cup-shaped container, a lid made of aluminum foil or synthetic resin paper is adhered to the surface of the mouth flange to seal the cup-shaped container. .

  As cup-shaped containers, injection-molded products, vacuum / pressure-formed products, and stretch blow-molded products of preforms (primary molded products) are known. The injection-molded cup is manufactured using a resin such as polypropylene or polystyrene, is thick with a thickness of about 0.5 mm, and has poor oxygen barrier performance. Vacuum / pneumatic molding cups are manufactured using single-layer sheets made of polyethylene terephthalate (PET) or multi-layer sheets of multiple types of resin, but there are many burrs and yields are low, and cracks occur during molding. Because it is easy, it is not suitable for forming a container with a deep bottom. Stretch blow molded cups do not generate burrs, have good oxygen barrier performance, and can form deep bottom containers. In the patent document 1, the present applicant has proposed a method for forming a stretch blow molded cup having excellent heat resistance and a preform for the method.

JP 2004-58602 A

  Here, it is very effective to reduce the weight of a bottomed cylindrical container such as a cup-shaped container in order to reduce the cost. However, it is difficult to reduce the weight of stretch blow molded containers.

  For example, the weight of a stretch blow molded cup currently on the market is about 11-14 g for a 200 ml cup. The shape of the preform used to manufacture the stretch blow molded cup is hemispherical, conical or bell-shaped, and is generally an injection molded product. In the stretch blow molding, it is necessary to heat the preform to a temperature suitable for stretch blow. In the case of a PET preform, the preform is heated to about 100 ° C. In order to reduce the weight of the stretch blow molded cup, it is only necessary to reduce the weight of the preform. In other words, the preform may be thin.

  However, if the preform is too thin, the self-holding property is likely to be impaired by heating, and the original shape cannot be maintained at the time of heating to a temperature suitable for stretch blow, and it will be deformed and crushed. There is a risk of hindering stretch blow molding. Therefore, it is necessary to make the wall thickness of the cup-shaped preform used for manufacturing the cup-shaped container greater than 2 mm, and there is a limit to reducing the thickness and weight. Therefore, there is a limit to the reduction in the thickness and weight of the cup-shaped container obtained by stretch blow molding, and a sufficient cost reduction cannot be achieved.

  In view of this point, an object of the present invention is to propose a manufacturing method of a bottomed cylindrical container capable of forming a thin and light bottomed cylindrical container by stretching and blowing a preform. Another object is to propose a preform for use in the manufacturing method.

In order to solve the above problems, the present invention provides a bottomed cylindrical container manufacturing method in which a bottomed cylindrical container is stretch blow molded from a thermoplastic resin preform.
The bottomed cylindrical container includes a bottomed cylindrical container main body part, and a container mouth part formed at an opening edge of the cylindrical container main body part,
The preform includes a plate-like body portion and a flange formed on the outer peripheral edge of the plate-like body portion, and the flange has the same shape as the container mouth portion,
Stretching and blowing the plate-like body portion of the preform to form the cylindrical container body,
The flange of the preform is left as it is as the container mouth portion without being stretch-blown.

  The preform used in the production method of the present invention is not a three-dimensional shape as in the prior art, but a plate shape. Therefore, when the wall thickness is reduced, the central portion is slightly bent downward even when softened by heating, and deformation that hinders stretch blow molding does not occur. Therefore, the conventional problem that the self-holding property is lost and the three-dimensional shape is crushed and hinders stretch blow molding can be avoided, and the preform can be made thinner and lighter. As a result, it is possible to reduce the thickness and weight of the bottomed cylindrical container obtained by stretch blow molding, thereby achieving a significant cost reduction of the bottomed cylindrical container.

  Thus, since the preform used in the production method of the present invention is a plate-like preform, it can be produced not only by injection molding but also by compression molding. Moreover, since the shape is simple, the manufacturing cost of the preform molding die can be reduced, and it can be easily manufactured using various thermoplastic resins such as PP, PE, PEN, PS other than PET. Furthermore, since it is a plate-shaped preform, it is easy to laminate and form from the same resin or different resins, and it is easy to sandwich a coating film or film between each resin layer. It is also easy to sandwich a functional material having heat resistance, oxygen barrier properties and the like between them.

  Here, in the plate-like body portion (12) of the preform, at least one of the surface that becomes the inner peripheral surface of the cylindrical container main body and the rear surface that becomes the outer peripheral surface of the cylindrical container main body. Is preferably a flat surface. If it does in this way, since the shaping | molding surface of the shaping | molding die for preform shaping | molding will become a simple shape, manufacture of a shaping | molding die will become easy and the manufacturing cost can be reduced.

  In addition, by making one surface a flat surface and the other surface a curved surface (a curved surface having a single curvature or a composite curved surface composed of a plurality of curved surfaces having different curvatures), each part of the plate-like body portion is formed in a desired shape. Thickness can be set.

  Generally, the central portion of the plate-like body portion having the highest draw ratio may be set to be thicker than the outer peripheral side portion.

  Next, the mouth of a bottomed cylindrical container, for example, a cup-shaped container, is a flat flange having a constant width. In such a case, the flange of the preform has a constant thickness, and both the front surface portion and the back surface portion of the flange may be defined by a flat surface.

  Further, a rib that is bent and extended on the back surface side is formed continuously to the outer peripheral edge of the flange, and this rib is directly stretched and blow molded without being part of the mouth of the bottomed cylindrical container. It is desirable to do. By forming the rib, it is possible to prevent deformation of the preform that has become thin and easily deformed. Further, it is possible to prevent deformation of the mouth portion of the thin-walled cylindrical container with the bottom obtained by stretch-blow molding the preform.

  Next, in the manufacturing method of the present invention, in the heating step of heating the preform while being conveyed along a predetermined heating path, the preform is heated from at least one side in the thickness direction of the preform. do it.

  A conventional preform has a three-dimensional shape such as a test tube shape or a conical shape. In the heating process, a preform that is conveyed in an upright state is used to uniformly heat the entire circumference of the preform. It is necessary to heat from both sides or one side by a heater while rotating around the central axis. In addition, it is necessary to arrange 3 to 5 heaters on the upper and lower sides on both sides or one side so that the heating can be performed uniformly in the vertical direction (center axis direction). On the other hand, the plate-shaped or flat-type preform of the present invention can be heated by a heater from one side or both sides in the thickness direction, so that one or two heaters are sufficient. It is.

  Here, a frame-shaped shielding member capable of covering the heating side surface in the heating step of the flange of the preform is prepared, and prior to the heating step, the flange of the preform is formed by the shielding member. Attach the shielding member to the preform so as to be covered, and in the stretch blow step, the preform is stretch blow molded with the shielding member attached to the preform, After the stretch blow molding step, it is desirable to remove the shielding member from the mouth of the bottomed cylindrical container.

  By attaching the shielding member, it is possible to prevent the flange on the outer peripheral edge side of the thinned preform from being heated, and by attaching the shielding member throughout the heating process and the stretch blow process, the thinned preform is prevented. The reform can be prevented from being deformed during the heating and stretching blow process.

  According to the manufacturing method of the present invention, a lightweight and thin preform that could not be used in the conventional method of manufacturing a cylindrical container with a bottom by stretch blow molding was used. Can produce a thin cylindrical container with a bottom. For example, the preform having a weight of 5 g to 8 g, a maximum wall thickness of 2 mm at the center portion, an inner volume of 200 ml and a maximum wall thickness of 0.5 mm is used. The said cylindrical container main-body part of a container can be shape | molded.

  Since the cup-shaped container of the present invention is manufactured using the above-described thin plate-shaped or flat-shaped preform, it has a thin-wall dimension that could not be obtained by conventional stretch blow molding, Compared to conventional cup-shaped containers, the weight can be greatly reduced, and a significant cost reduction can be achieved.

  In the method for manufacturing a cylindrical container with a bottom according to the present invention, since the preform has a plate shape or a flat shape, the three-dimensional shape heating in the case of using a conventional cylindrical or cup-shaped preform is used. Molding defects due to deformation can be avoided. Accordingly, the preform can be reduced in thickness and weight. As a result, a thin-walled cylindrical container with a bottom that cannot be obtained by the conventional stretch blow molding method can be obtained. Therefore, significant weight reduction and cost reduction of the bottomed cylindrical container manufactured by stretch blow molding can be realized.

(A) And (b) is the side view and longitudinal cross-sectional view which show an example of the cup-shaped container by this invention. (A), (b) and (c) are a side view, a cross-sectional view, and an enlarged half cross-section showing an example of a plate-like preform used for forming the cup-shaped container of FIG. 1 by biaxial stretching blow. FIG. (A)-(d) is explanatory drawing which shows the example of various cross-sectional shapes of a plate-shaped preform. It is explanatory drawing which shows the stretch blow molding method of the cup-shaped container using the preform of FIG. It is explanatory drawing which shows the stretch blow process in the stretch blow molding method of FIG. It is explanatory drawing which shows another example of a cylindrical container with a bottom, and a plate-shaped preform.

  Below, with reference to drawings, the cup-shaped container which concerns on embodiment of this invention, a plate-shaped preform, and the manufacturing method of a cup-shaped container are demonstrated.

(Cup-shaped container)
Referring to FIG. 1, a cup-shaped container 1 according to this embodiment includes a bottomed container body 2 and an annular container that spreads outward from the upper end opening edge of the container body 2. And a mouth 3. The container body 2 is a stretched portion that has been biaxially stretched and blown, and the container mouth 3 is a non-stretched portion that has not been biaxially stretched and blown.

  The container main body 2 has a wide cylindrical barrel 4 whose diameter gradually decreases from the top opening side to the bottom as a whole, and a circular bottom plate portion 5 that seals the lower end of the cylindrical barrel 4. And. The container mouth portion 3 has an annular flange body plate 6 extending outward from the upper end opening edge 4 a of the cylindrical body portion 4, and an annular shape bent at a right angle downward from the outer peripheral edge of the flange body plate 6. And an L-shaped cross section including the rib 7.

  For example, although the dimension of each part of the cup-shaped container 1 is as follows, the dimension of each part of the cup-shaped container of the present invention is not intended to be limited to these values. The cup-shaped container 1 has an inner volume of 200 milliliters, the inner diameter of the upper end opening edge 4b of the container body 2 is about 62 mm, the height is about 83 mm, and the average thickness of the cylindrical body 4 is about 0. .3 mm, and the average thickness of the bottom plate portion 5 is about 0.4 mm. Moreover, the thickness of the flange 6 of the container mouth part 3 is about 0.5 mm, and the thickness of the rib 7 is about 0.5 mm. The weight of the cup-shaped container 1 is about 7 g.

(Plate-shaped preform)
With reference to FIG. 2, the shape of the plate-shaped preform used in order to manufacture the cup-shaped container 1 by biaxial stretch blow molding is demonstrated. The plate-like preform 10 includes a plate-like body portion 12 made of a thermoplastic resin such as PET, and an annular flange 13 formed continuously on the outer peripheral edge portion of the plate-like body portion 12. . The plate-like body portion 12 is a stretched portion that becomes the container body 2 of the cup-shaped container 1 by stretch blow molding. The stretched part. Therefore, the flange 13 has the same shape as the container mouth portion 3 of the cup-shaped container 1 and has an L-shaped cross section including an annular flange body plate 16 and an annular rib 17.

  The surface 12a of the plate-like body portion 12 is defined by a flat surface. This surface 12a becomes the inner peripheral surface of the container body 2 of the cup-shaped container 1 by stretch blow molding. The back surface 12b of the plate-like body portion 12 is defined by a complex curved surface composed of curved surfaces having different curvatures. This back surface 12b becomes the outer peripheral surface of the container body 2 of the cup-shaped container 1 by stretch blow molding. The front surface portion 16a of the flange body plate 16 of the flange 13 is a flat surface located on the same plane as the front surface 12a, and the back surface portion 16b is also a flat surface, and is smoothly continuous with the back surface 12b. In this example, the outer peripheral side portion that is continuous with the rear surface portion 16a of the flange main body plate 16 on the rear surface 12b of the plate-like body portion 12 is defined by the curved surface 12b (1), and the inner portion of the curved surface 12b (1) is The curved surface 12b (1) is defined by the convex curved surface 12b (2) smoothly continuing, and the central portion of the plate-like body portion 12 having the highest draw ratio has the maximum thickness.

  For example, the maximum thickness of the central portion is set to about 2 mm. In the case of the plate-like preform 10 used for manufacturing a cylindrical or rectangular tube-shaped cup-shaped container having an internal volume of 200 ml, the maximum thickness is about 10% of the maximum width of the plate-like body portion 12. In this case, the outer diameter may be about 10% or less.

  In addition, as shown to Fig.3 (a), both surfaces of the plate-shaped body part 12 can be prescribed | regulated by a flat surface, and the whole plate-shaped body part 12 can also be made constant thickness. Further, as shown in FIG. 3 (b), the surface 12a of the plate-like body portion 12 can be defined by a curved surface, and the back surface 12b can be defined by a flat surface, as shown in FIG. 3 (c). It is also possible to define both sides by curved surfaces. Further, as the curved surface, it is possible to use an arc surface instead of a complex curved surface. Furthermore, in this example, the central portion of the plate-like body portion 12 has a maximum thickness. However, depending on the shape of the cup-shaped container 1, as shown in FIG. There may be a case where a ring-shaped maximum thickness portion is formed in the portion.

(Method for producing cup-shaped container)
With reference to FIG. 4, the example of the manufacturing method which manufactures the cup-shaped container 1 by biaxially stretching and blowing the plate-shaped preform 10 is demonstrated. As shown in the figure, the cup-shaped container manufacturing method S includes a preform supply step S1 for supplying the plate-shaped preforms 10 to the preform conveyance path 21 one by one. The preform conveyance path 21 is a circulation path that circulates the preform carrier 22 at a constant pitch. At the preform supply position 23 in the preform conveyance path 21, the plate-shaped preform 10 has a back surface (12b, 16b). It is put on the preform carrier 22 in a state of facing upward.

  The cup-shaped container manufacturing method S includes a shielding plate attaching step S2, and the preform carrier 22 carrying the plate-like preform 10 is conveyed along the preform conveying path 21, and a shielding ring attaching position in the middle thereof. In 24, a shielding ring 25 (shielding member) is attached to the plate-shaped preform 10. The shield ring 25 is a ring having a rectangular cross section, as indicated by an imaginary line in FIG. 2C, and the back surface portion 16 b of the flange body plate 16 and the inner peripheral surface portion 17 b of the rib 17 in the plate-shaped preform 10. It is attached in a state of covering up.

  The cup-shaped container manufacturing method S includes a preform heating step S3. The heating station 26 arranged along the preform conveying path 21 has heaters 27 arranged in one or two rows in the conveying direction on the top surface portion, and the plate of the plate-like preform 10 passing directly below. The body portion 12 is heated from the back surface 12b side to a temperature suitable for blow molding. For example, heating is performed while rotating the plate-shaped preform 10 around its central axis.

  The cup-shaped container manufacturing method S includes a stretch blow step S4 after the preform heating step S3. In the stretch blow step S4, the plate-like preform 10 heated to a temperature suitable for stretch blow molding through the preform heating step S3 is placed in a stretch blow mold, and the stretched portion 12 is subjected to biaxial stretch blow molding. The cup-shaped container 1 is formed.

  As shown in FIG. 5, the plate-like preform 10 is set in the stretch blow mold 30 while being held on the preform carrier 22. Further, the non-stretched portion 13 of the plate-shaped preform 10 is in a state where the shielding ring 25 is still attached. In this state, the stretch blow molding die 30 is clamped and stretch blow air is introduced from the lower side to stretch the plate-like body portion 12 upward. Further, the stretching rod 31 is pushed up at a predetermined timing to supply stretching blow air while stretching the plate-like body portion 12, and the plate-like body portion 12 is stretched in the biaxial direction as indicated by an imaginary line in the figure. Then, the molding surface shape of the stretch blow molding die 30 is applied to the plate-like body portion 12. As a result, the cup-shaped container 1 shown in FIG. 1 is obtained.

  Referring to FIG. 4 again, after the blow molding step S4 is completed, the stretch blow molding die 30 is opened, and the preform carrier 22 on which the cup-shaped container 1 is supported is then opened. The removal of the shielding ring 25 and the container collection step S5 for removing the cup-like container 1 from the preform carrier 22 and collecting it are performed. The preform carrier 22 after the cup-shaped container 1 is removed is conveyed along the preform conveyance path 21 and returns to the preform supply position 23 again, and the plate-shaped preform 10 is supplied.

(Other embodiments)
In addition, although said example is a manufacturing method of a wide-mouthed cup-shaped container, this invention can be used for manufacture of a cylindrical container with a bottom other than a cup-shaped container. For example, as shown in FIG. 6, the present invention can also be applied to the manufacture of a cylindrical container 1A with a bottom having a substantially constant outer diameter in which a male thread portion is formed in the mouth portion 3A. In this case, a plate-like preform 10A composed of a plate-like body portion 12A in which a flange 13A having the same shape as the mouth portion 3A is formed at the outer peripheral edge portion may be used.

DESCRIPTION OF SYMBOLS 1 Cup-shaped container 2 Container main-body part 3 Container port part 4 Cylindrical trunk | drum 5 Bottom plate part 6 Flange main-body board 7 Rib 10 Plate-shaped preform 12 Plate-shaped body part 12a Front surface 12b Back surface 12b (1) Curved surface 12b (2) Convex surface 13 Flange 16 Flange body plate 16a Surface portion 16b Back surface portion 17 Rib 17b Inner peripheral surface portion 21 Preform conveyance path 22 Preform carrier 23 Preform supply position 24 Shield ring attachment position 25 Shield ring 26 Heating station 27 Heating heater 30 Stretch blow mold 31 Stretch rod S Manufacturing method S1 of cylindrical container with bottom S1 Preform supply step S2 Shield plate attachment step S3 Preform heating step S4 Stretch blow step S5 Container recovery step

Claims (11)

A method (S) for producing a bottomed cylindrical container (S) in which a bottomed cylindrical container (1) is stretch blow molded from a thermoplastic resin preform (10),
The bottomed cylindrical container (1) includes a bottomed cylindrical container body (2) and a container mouth (3) formed at the opening edge of the cylindrical container body (2). And
The preform (10) includes a plate-like body portion (12) and a flange (13) formed on the outer peripheral edge of the plate-like body portion (12). Part (3) and the same shape,
Stretching and blowing the plate-like body portion (12) of the preform (10) to form the cylindrical container body (2),
The manufacturing method (S) for a cylindrical container with a bottom, wherein the flange (13) of the preform is left as it is as the container opening (3) without being stretch-blown.   The plate-like body portion (12) of the preform (10) is formed on a surface (12a) which becomes an inner peripheral surface of the cylindrical container main body (2) and an outer peripheral surface of the cylindrical container main body (2). The manufacturing method (S) for a cylindrical container with a bottom according to claim 1, wherein at least one of the back surfaces (12b) is a flat surface.   One of the surface (12a) and the back surface (12b) of the plate-like body portion (12) of the preform (10) is a flat surface, and the other surface is defined by a curved surface. The manufacturing method (S) of the cylindrical container with a bottom of Claim 2 characterized by the above-mentioned.   The manufacturing method (S) of the cylindrical container with a bottom according to claim 3, wherein the plate-like body portion (12) of the preform (10) has a thickest central portion. The flange (13) of the preform (10) has a constant thickness;
Both the front surface portion (16a) continuous to the front surface (12a) of the plate-like body portion (12) and the back surface portion (16b) continuous to the rear surface (12b) of the flange (13) are flat surfaces. The method (S) for producing a cylindrical container with a bottom according to claim 4, wherein:   The flange (13) of the preform (10) is formed with a rib (17) that is bent and extended toward the back surface portion (16b) continuously from the outer peripheral edge thereof. The manufacturing method (S) of the cylindrical container with a bottom of Claim 5. A heating step (S3) of heating while conveying along a predetermined heating path;
A stretch blow step (S4) to obtain a cup-shaped container (1) by stretch blow molding the preform (10) heated to a temperature suitable for stretch blow molding through the heating step (S3);
The said heating (S3) WHEREIN: The said preform (10) is heated from at least one side of the surface (12a) and the back surface (12b) of the said preform (10), The manufacturing method (S) of the cylindrical container with a bottom as described in any one of thru | or 6. Preparing a frame-shaped shielding member (25) capable of covering the heating side surface (16a, 17b) in the heating step (S3) of the flange (13) of the preform (10);
Prior to the heating step (S3), the preform (10) is covered with the shielding member (10) so that the flange (13) of the preform (10) is covered with the shielding member (25). 25)
In the stretch blow step (S4), the preform (10) is stretch blow molded with the shielding member (25) being attached to the preform (10),
The bottomed cylindrical container according to claim 7, wherein the shielding member (25) is removed from the mouth flange (3) of the cup-shaped container (1) after the stretch blow molding step (S4). Manufacturing method (S). The weight of the preform (10) is 5g-8g,
The maximum thickness of the central portion is 2 mm;
The plate-like body portion (12) is stretched and blown to form the cylindrical container body (2) of the bottomed cylindrical container (1) having an internal volume of 200 ml and a maximum thickness of 0.5 mm. The method (S) for producing a cylindrical container with a bottom according to any one of claims 1 to 8, wherein:   The said preform (10) used for the manufacturing method of the cylindrical container with a bottom in any one of Claim 1 thru | or 9.   The said cylindrical container (1) with a bottom manufactured by the manufacturing method in any one of Claims 1 thru | or 9.

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