JP2005035191A - Method for giving heat resistance to cup-shaped vessel and manufacturing method for heat-resistant cup-shaped vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To give heat resistance to a cup-shaped vessel. <P>SOLUTION: A primary vessel 11 is fitted on a male 50 having a forming surface 51 corresponding to the internal shape of a heat-resistant cup-shaped vessel 11 made of plastic. In this state, the primary vessel 11 is heated by a quartz-sheathed heater or the like from outside. The heating makes the vessel 11 shrink thermally and it is brought to close fitting on the forming surface 51 of the male 50. Since a heat medium circulates inside the male 50 and the forming surface is kept thereby at a prescribed temperature, the primary vessel 11 is cooled by the male 50. The flat bottom portion of the vessel 11 is press-formed in a three-dimensional shape by a bottom tool and thus the heat-resistant cup-shaped vessel 11 in the final shape is obtained. This vessel 11 is removed from the male 50 and made to radiate heat naturally. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for imparting heat resistance to a plastic cup-shaped container, and a method for producing a heat-resistant cup-shaped container using the method.

  Wide-mouthed cup-shaped containers are used as beverage containers for dairy products. The cup-shaped container has a shape including a cylindrical barrel portion with a bottom and a flange that spreads outward from the opening edge of the cylindrical barrel portion. Moreover, generally the cylindrical trunk | drum is carrying out the truncated cone shape spread toward the opening edge.

  The cup-shaped container is formed from a plastic sheet made of a thermoplastic resin such as polyethylene terephthalate (PET) or polystyrene (PS) by a pressure forming method or a vacuum forming method. That is, the plastic sheet fed from the plastic roll sheet is heated to a suitable molding temperature. Next, a plastic sheet is three-dimensionally molded using a mold in which concave portions or convex portions corresponding to the cup-shaped container are formed in a matrix shape. The individual flanged cup-shaped containers are then punched out of the plastic sheet. However, such a method is unsuitable for forming a cup-shaped container having a depth.

  Therefore, a method of manufacturing a cup-shaped container using a biaxial stretch blow molding method has been proposed in Patent Document 1 below. A cup-shaped container formed by biaxial stretching blow is thin and transparent and has high strength, and can be used as a general beverage container or food container.

However, since the conventional cup-shaped container has poor heat resistance, it is not suitable for use as a container that must be sterilized at a high temperature before filling the contents. For example, in order to use as a beverage container for coffee or the like, it is necessary to perform steam sterilization for several seconds at 168 ° C., and the cup-shaped container may be thermally deformed by such high temperature sterilization.
Japanese Utility Model Publication 4-20012

  An object of the present invention is to propose a method for imparting heat resistance to a cup-shaped container so that thermal deformation does not occur.

  Another object of the present invention is to propose a method for producing a heat-resistant cup-shaped container using such a new method.

In order to solve the above problems, the method for imparting heat resistance to the cup-shaped container of the present invention is as follows.
A mounting step of mounting the cup-shaped container on a male mold having a molding surface corresponding to the inner surface shape of the plastic cup-shaped container;
A heat treatment step of heating the cup-shaped container from the outside and closely contacting the molding surface of the male mold by heat shrinkage;
A cooling step of cooling the cup-shaped container by the closely attached male mold;
A mold release step of removing the cup-shaped container from the male mold;
including.

  In the method of the present invention, heat setting is performed while the cup-shaped container is heated from the outside and brought into close contact with the male mold. Accordingly, the cup-shaped container can be formed into a target shape by the male mold and at the same time heat resistance can be imparted to the cup-shaped container, so that a target-shaped cup-shaped container having heat resistance can be obtained. .

  Here, if the gap between the cup-shaped container and the male mold is too wide, the cup-shaped container may not be in close contact with the male mold even if the cup-shaped container is thermally contracted. Otherwise, irregularities and wrinkles will occur in the cup-shaped container, resulting in a defective product. Therefore, it is desirable that the gap between the inner surface of the cup-shaped container and the molding surface of the male mold be 6 mm or less. If it is 2 mm or less, it is more desirable.

  Next, the heating temperature in the heat treatment step is preferably in the range of 80 to 230 ° C. This is because if the temperature is lower than the lower limit, there is a problem that the heat resistance is low, and if it is higher than the upper limit, the problem of crystallization and white turbidity occurs.

  In the heat treatment step, the cup-shaped container can be heated using a quartz tube heater, heated air, heated and pressurized water vapor, or a carbon dioxide gas laser having a center wavelength of 10.6 microns.

  Furthermore, the cup-shaped container may be sealed by heat-sealing a sealing material to the flange surface after filling the contents. In this case, if the flange surface is crystallized to give heat resistance, the sealing material cannot be reliably heat-sealed. Therefore, in such a case, in the heat treatment step, heating may be performed from the outside in a state where the flange spreading outward from the opening edge of the cylindrical body portion in the cup-shaped container is covered.

  Furthermore, in order to heat the cup-shaped container uniformly, in the heat treatment step, it is desirable to heat the cup-shaped container while rotating the cup-shaped container around its central axis by the male mold.

  Next, at least in the heat treatment step and the cooling step, it is desirable to adjust the temperature of the molding surface of the male mold to be in a temperature range of 50 to 120 ° C. In order to obtain a cup-shaped container with high heat resistance, it is necessary to increase the male mold temperature. However, when the temperature exceeds 120 ° C, the oligomer gradually accumulates on the male mold surface (molded surface) and adheres to the cup-shaped container. The gloss and transparency of the inner surface of the container are impaired. On the contrary, when the male mold temperature is too low as less than 50 ° C., the heat treatment of the cup-shaped container becomes insufficient, the distortion of the cup-shaped container cannot be removed, and the heat resistance of the cup-shaped container is insufficient.

  Next, in the mold release step, the cup-shaped container may be removed from the male mold by pushing the flange of the cup-shaped container in the axial direction of the cup-shaped container.

  Further, the higher the temperature of the male mold, the worse the mold-releasing property of the cup-shaped container. Therefore, air may be blown from the molding surface of the male mold in the mold releasing step.

  In this case, a slit having a width of 0.05 to 1 mm or a hole having an inner diameter of 1 mm or less may be formed on the molding surface of the male mold, and air may be blown out therefrom.

  Next, in the method of the present invention, the cup-shaped container having a flat bottom surface is prepared, and the bottom surface of the cup-shaped container has a three-dimensional shape during the period from the heat treatment step to the cooling step. A molding process for press molding may be included.

  Examples of the material for the cup-shaped container include PET, PP, and PEN.

  Next, the present invention relates to a method for producing a heat-resistant cup-shaped container, and a molding process for forming a cup-shaped container by biaxially stretching and blowing a preform, And a heat-resistant step for imparting the property.

  In the method of the present invention, the cup-shaped container attached to the male mold is heated from the outside to be thermally contracted, and the cup-shaped container is cooled by the closely adhered male mold to impart heat resistance of the cup-shaped container. Yes. Therefore, it is possible to obtain a heat-resistant cup-shaped container molded into a target shape.

  Below, with reference to drawings, the manufacturing method of the cup-shaped container to which this invention is applied is demonstrated.

  FIG. 1 is a side view showing a preform used for biaxial stretch blow molding of a cup-shaped container in an inverted state. The preform 1 has an annular mouth flange 2, a cylindrical neck portion 3 extending perpendicularly from the inner peripheral edge of the mouth flange 2 to the back surface side, and a bowl-shaped body portion 4 continuous with the neck portion 3. It has. In this example, the preform 1 having this shape is biaxially stretched and blown to form a primary container having an approximate shape to the cup-shaped container that is the final product.

  FIG. 2 is a side view showing the primary container obtained by biaxially stretching and blowing the preform 1 in an inverted state. The primary container 11 includes a mouth flange 12 that is left without being stretched by the mouth flange 2 of the preform 1, and a neck 13 that is obtained by biaxially stretching and blowing the neck 3 of the preform 1. The bowl-shaped body 4 of the preform 1 has a truncated cone-shaped cylindrical body 14 having a flat bottom surface portion 15 obtained by biaxial stretching blow.

  FIG. 3 is a side view showing the final heat-resistant cup-shaped container obtained by molding the primary container 11 in an inverted state. The heat-resistant cup-shaped container 21 includes a mouth flange 22 in which the mouth flange 12 of the primary container 11 remains as it is, and a cylindrical neck 23 in which the neck 13 of the primary container 11 remains as it is. And a cylindrical body portion 24 having a size slightly smaller than the cylindrical body portion 14 of the primary container 11 and a bottom surface portion 25 that is three-dimensionally molded so that the center portion is convex inward.

  4 to 7 are schematic configuration diagrams showing the configuration and operation of a molding apparatus used for molding the primary container 11 into the heat-resistant cup-shaped container 21. FIG. The molding apparatus 30 includes a carrier 40 that is transported at a constant pitch along a predetermined transport line, and a male mold 50 that is supported coaxially by each carrier 40. Moreover, it has the heating station 60 arrange | positioned along a conveyance line, and heat sources, such as the several quartz tube heater 61, are arrange | positioned in the heating station 60 at the one side of a conveyance line. Furthermore, a bottom mold 70 is disposed at a position above the downstream portion of the heating station 60.

  The male mold 50 includes a molding surface 51 corresponding to the inner surface of the heat-resistant cup-shaped container 21 having the final shape. In the center of the male mold 50, a heat medium circulation path 52 for adjusting the male mold temperature is formed in the axial direction. A compressed air supply path 53 is formed inside the male mold 50, and the compressed air supply path 53 communicates with an air blowing hole 54 formed at a predetermined interval on the molding surface 51. The air blowing hole 54 has an inner diameter of 1 mm or less. Instead of the air blowing holes 54, slits having a predetermined length of 0.05 to 1 mm may be formed at predetermined intervals.

  The carrier 40 carrying the male mold 50 has a male carrying surface 41, and a heat medium supply pipe 43 is inserted into a center hole 42 extending therethrough. The heat medium supply pipe 43 is inserted into the heat medium circulation path 52 of the male mold 50. Further, a compressed air supply path 44 is formed in the carrier 40, and this communicates with the compressed air supply path 53 of the male mold 50. Further, the eject ring 45 is disposed so as to surround the outer peripheral surface of the lower end of the male mold 50 so that the flange 12 of the primary container 11 mounted on the male mold 50 is on the annular upper end surface 45 a of the eject ring 45. It has become. Furthermore, the eject ring 45 can be moved up and down by a lifting mechanism (not shown). A flange cover 46 is disposed so as to surround the eject ring 45. The flange cover 46 covers and hides the flange 22 of the primary container 21 attached to the male mold 50. The flange cover 46 can be opened and closed by an opening / closing mechanism (not shown) (see FIG. 7).

  A driven side gear 47 is coaxially attached to the bottom surface of the carrier 40, and the carrier 40 transported through the heating station 60 is transmitted with rotational force from the side of the rotary drive shaft 48 to the driven side gear 47, and its central axis line It is conveyed while rotating around 40a. Therefore, the male mold 50 is also conveyed while rotating around the central axis 50a.

  The operation of the molding apparatus 30 having this configuration will be described. As shown in FIG. 4, the primary container 11 is mounted on the male mold 50 carried on the carrier 40. Here, the primary container 11 is biaxially stretch blow molded so that the gap between the inner surface of the primary container 11 and the molding surface 51 of the male mold 50 is 6 mm or less. This gap is desirably 2 mm or less. After the primary container 11 is mounted, the primary container 11 is sent to the heating station 60 and heated by the quartz tube heater 61 disposed on the side. Since the male mold 50 rotates around its central axis 50a, the entire circumference is uniformly heated by the quartz tube heater 61 while the primary container 11 also rotates around its central axis. The heating temperature may be in the range of 80 to 230 ° C.

  The primary container 11 is heated to cause heat shrinkage, and comes into close contact with the molding surface 51 of the male mold 50 as shown in FIG. Since the bottom portion 15 of the primary container 11 is a flat surface, only this portion is separated from the concave bottom mold portion of the male mold 50. Moreover, since the flange 12 of the primary container 11 is covered with the flange cover 46, it is not heated to a predetermined temperature or higher.

  When the primary container 11 is thermally contracted and comes into close contact with the molding surface of the male mold 50, the primary container 11 is cooled by the male mold 50. The primary container 11 has a heat medium circulating therein, and the molding surface is held at a predetermined temperature by the heat medium. This temperature is preferably a value within the range of 50 ° C. to 120 ° C., more preferably a value within the range of 50 ° C. to 100 ° C.

  After the primary container 11 is heat-shrinked and closely contacts the male mold 50, the bottom mold 70 is lowered and the flat bottom surface portion of the primary container 11 is pressed against the molding surface of the male mold 50 as shown in FIG. The three-dimensional bottom portion is press-molded. Thereby, the heat-resistant cup-shaped container 21 having the final shape is obtained.

  Thereafter, as shown in FIG. 7, after the bottom mold 70 is raised and retracted, the flange cover 46 is opened, and the heat-resistant cup-shaped container 21 is pushed up by the eject ring 45 and removed from the male mold 50. Here, the compressed air is blown out from the compressed air blowing holes 54 formed in the molding surface 51 of the male mold 50 so that the mold release can be easily performed. After the mold release, the heat-resistant cup-shaped container 21 is regulated in the atmosphere and naturally contracts to stabilize its shape.

  Using a rotary biaxial stretch blow molding machine, a primary container 11 having a flange diameter of 71 mm, a weight of 12 g, and an internal volume of 250 ml was formed. A heat-resistant cup-shaped container 21 was formed by subjecting this primary container to a heat treatment with a quartz tube heater using a male mold 50 having a maximum clearance of about 1 mm.

  The obtained heat-resistant cup-shaped container 21 was filled with hot water to evaluate heat resistance. As an evaluation method, a shrinkage ratio calculated by measuring a volume before and after filling and a change in appearance by visual observation were adopted. The results are shown in Table 1.

It is a side view which shows the preform used in order to carry out biaxial stretch blow molding of the primary container in an inverted state. It is a side view which shows a primary container in an inverted state. It is a side view which shows the heat-resistant cup-shaped container of the last shape in an inverted state. It is a schematic block diagram which shows the example of the shaping | molding apparatus which provides heat resistance with the method of this invention. It is explanatory drawing which shows the state which the primary container contact | adhered to the male type | mold by heat contraction. It is explanatory drawing which shows the state which press-molded the bottom face part with the bottom type | mold. It is explanatory drawing which shows mold release operation | movement of a heat resistant cup-shaped container.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Preform 11 Primary container 12 Flange 13 Neck part 14 Body part 15 Bottom part 21 Heat resistant cup-shaped container 22 Flange 23 Neck part 24 Body part 25 Bottom part 30 Molding apparatus 40 Carrier 45 Eject ring 46 Flange cover 50 Male mold 51 Molding surface 52 Heat medium circulation path 54 Compressed air blowing hole 60 Heating station 61 Quartz tube heater 70 Bottom mold

Claims (13)

A mounting step of mounting the cup-shaped container on a male mold having a molding surface corresponding to the inner surface shape of the plastic cup-shaped container;
A heat treatment step of heating the cup-shaped container from the outside and closely contacting the molding surface of the male mold by heat shrinkage;
A cooling step of cooling the cup-shaped container by the closely attached male mold;
A mold release step of removing the cup-shaped container from the male mold;
A method for imparting heat resistance to a cup-shaped container comprising In claim 1,
A method of imparting heat resistance to a cup-shaped container on which the molding surface is formed such that a gap between the inner surface of the cup-shaped container and the molding surface of the male mold is 6 mm or less.   A method of imparting heat resistance to a cup-shaped container in which the heating temperature in the heat treatment step is in the range of 80 to 230 ° C. In any one of claims 1 to 3,
In the heat treatment step, heat resistance is imparted to a cup-shaped container using a quartz tube heater, heated air, heated and pressurized water vapor, or a carbon dioxide laser having a center wavelength of 10.6 microns. In any one of claims 1 to 4,
In the heat treatment step, heat resistance is imparted to the cup-shaped container that is heated from the outside in a state of covering a flange that spreads outward from the opening edge of the cylindrical body portion in the cup-shaped container. In any one of claims 1 to 5,
In the heat treatment step, heat resistance is imparted to the cup-shaped container that is heated while rotating the cup-shaped container around its central axis by the male mold. In any one of claims 1 to 6,
A method of imparting heat resistance to a cup-shaped container that adjusts the temperature of the molding surface of the male mold to be in the temperature range of 50 to 120 ° C. at least in the heat treatment step and the cooling step. In any one of claims 1 to 7,
In the mold releasing step, the cup-shaped container is removed from the male mold by pressing the flange of the cup-shaped container in the axial direction of the cup-shaped container, thereby imparting heat resistance to the cup-shaped container. In any one of claims 1 to 8,
A method of imparting heat resistance to a cup-shaped container that blows air from the molding surface of the male mold in the mold release step. In claim 9,
A method of imparting heat resistance to a cup-shaped container that blows air from a 0.05 to 1 mm wide slit or a hole having an inner diameter of 1 mm or less formed on the molding surface of the male mold. In any one of claims 1 to 10,
Prepare a cup-shaped container with a flat bottom surface,
A method of imparting heat resistance to a cup-shaped container including a molding step of press-molding the bottom surface of the cup-shaped container into a three-dimensional shape during a period from the heat treatment step to the cooling step. In any one of claims 1 to 11,
A method for imparting heat resistance to a cup-shaped container in which the material of the cup-shaped container is PET, PP or PEN. A molding step of forming a cup-shaped container by biaxially stretching and blowing the preform;
A heat-resisting step of imparting heat resistance to the cup-shaped container by the method according to claims 1 to 12,
Of manufacturing a heat-resistant cup-shaped container.

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