JP4273791B2 - Preform, preform compression molding apparatus, and bottle formed by blow molding this preform - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a preform and a compression molding apparatus for molding the preform. More specifically, the present invention relates to a preform in which the strength of the thick-walled portion is remarkably improved, and compression molding for manufacturing the preform. Relates to the device.
[0002]
[Prior art]
As containers for filling beverages and the like, those made of a synthetic resin such as polyethylene terephthalate are widely used, and such containers are formed by injection molding of a synthetic resin to form a bottomed preform having a considerably smaller size than the final container. A method is employed in which the preform is preliminarily heated to its stretching temperature, stretched in the axial direction in a blow mold, and blow-stretched in the circumferential direction (see, for example, Patent Document 1).
As the shape of this preform, one having a neck and neck corresponding to the mouth and neck of a bottle and a bottomed cylindrical portion to be stretch blow molded is generally used. The mouth-neck portion has, for example, a sealing opening end and a means for engaging with the lid, and generally called a thick-walled portion, and an annular protrusion for supporting the container when filling the container with the contents or attaching the lid. It is formed on the outer peripheral surface. In addition, a gate portion that protrudes outward from the center of the bottom portion is always formed on the bottom portion because of the necessity of injection molding.
[0003]
However, in general, in the manufacture of a preform by injection molding, the melt-plasticized resin is injected into the cavity through a nozzle, a sprue, a runner, and a gate. A long stay in a simple molding machine may cause deterioration of the resin and may be inferior in strength at the bottom of the obtained bottle due to the presence of the gate formed at the bottom.
[0004]
It is also known to produce a bottomed preform by compression molding of a resin. A compression mold having a closed bottom and a cavity for forming a preform shape is prepared, and a thermoplastic resin is molded into a precursor and a precursor is prepared. The body is placed in a compression mold where the precursor is totally fixed and intimately seated in the cavity and the precursor does not completely fill the compression mold but before being compressed to the final shape. And having a shape that is supported in a predetermined manner in the cavity of the compression mold, heating the precursor prior to placing the precursor in the compression mold, and compressing the heated precursor in the compression mold There has been proposed a method for manufacturing a preform including molding (see Patent Document 2).
[0005]
However, there are the following problems to be solved in molding a preform by compression molding. That is, in the case of compression molding, the synthetic resin material may be supplied to the female mold means or the male mold means before the male mold means and the female mold means are closed and the mold space is defined between them. is necessary. The supply of the synthetic resin material is performed, for example, by extruding the softened and melted synthetic resin material from an extruder and separating the synthetic resin material from the extrusion port of the extruder. For this reason, it is extremely difficult to control the supply amount of the synthetic resin material with sufficient precision, and there is usually an error of about 0.5 to 1.0% in the supply amount of the synthetic resin material. If the main dimensions such as the height and inner and outer diameters of the neck and neck vary slightly due to such errors, the required sealability may not be obtained when the lid is attached to the neck and neck, or the lower surface of the thick part Various obstacles occur in the automatic lid mounting operation for mounting the lid on the mouth and neck due to the variation in height from the tip of the mouth to the neck.
[0006]
From such a point of view, the present inventors have proposed a preform in which an annular groove is formed in the inner peripheral edge of the lower surface of the thick wall portion (Patent Document 3). Even if there is an error in the amount, by adjusting the dimensions of the annular groove, it is possible to effectively prevent fluctuations in dimensions such as the inner diameter and height of the mouth and neck, and the height from the bottom of the thick wall to the tip of the mouth and neck. And a preform can be formed efficiently.
[0007]
[Patent Document 1]
JP-A-4-154535 [Patent Document 2]
International Publication No. 97/32706 Pamphlet [Patent Document 3]
JP-A-10-337769
[Problems to be solved by the invention]
However, in a preform provided with such an annular groove, wrinkles or vertical thin grooves are generated at the corners of the top surface of the annular groove, and the strength of the thick part is inferior due to the influence of the wrinkles or grooves. Problems arise.
That is, the resin supplied to the space formed by the female mold means and the male mold means causes volume shrinkage when changing from a molten state to a solidified state. For this reason, in compression molding, either the male mold means or the female mold means moves up and down according to the amount of shrinkage of the resin. At this time, the resin cooled on the lower side of the thick wall portion is pushed up and pushed up. The resin is pushed into the resin that forms the thick wall portion, but is not remelted, so that the resin is solidified in the corners of the top surface of the annular groove as it is in wrinkles or vertically narrow grooves. Such wrinkles or grooves formed at the corners of the top surface of the annular groove are not preferable because they cause a decrease in the strength of the thick portion.
[0009]
Accordingly, an object of the present invention is to provide a preform that is effectively prevented from generating wrinkles or grooves formed in the annular groove and has an excellent strength at the thick portion.
Another object of the present invention is to provide a compression molding apparatus for molding a preform in which generation of wrinkles or grooves in the annular groove of the preform is effectively prevented.
Another object of the present invention is to provide a bottle excellent in the strength of the thick portion molded from the preform.
[0010]
[Means for Solving the Problems]
According to the present invention, it is composed of an annular mouth and neck and a bottomed cylindrical body that hangs down from the mouth and neck, and the outer peripheral surface of the mouth and neck is provided with a thick portion projecting radially outward, In the preform in which an annular groove is formed in the inner peripheral edge of the lower surface of the thick wall portion, either the male means or the female means is contracted by the resin at the corner of the top surface of the annular groove. Accordingly, there is provided a preform characterized by the absence of wrinkles and / or grooves that occur when moving up and down in response .
[0011]
According to the present invention, it is also composed of an annular mouth-neck portion and a bottomed cylindrical body portion that hangs from the mouth-neck portion. A compression molding apparatus for molding a preform in which an annular groove is formed in the inner peripheral edge of the lower surface of the thick wall portion, and moves in a direction approaching each other, and cooperates to form a molding space. It is set in a prescribed closed state, and moves up and down according to the shrinkage amount of the resin, and includes a male means and a female means that move in a direction away from each other to an open state, and the female means includes: A concave portion defining the outer surface of the cylindrical body portion; and an annular ridge defining an annular groove in the mouth-neck portion together with an upper outer surface of the cylindrical body portion, wherein the male means is at least an inner surface of the cylindrical body portion And a core member that defines the inner peripheral surface of the mouth and neck, and at least a radially movable member that defines the outer peripheral surface of the mouth and neck Consists mold member, portion defining a thick lower surface except for the annular groove of the該割type member, a compression molding apparatus characterized by comprising a material having a lower thermal conductivity than other portions of the split mold members Is provided.
In this compression molding device,
1. The portion that defines the lower surface of the thick part is a nesting that can be fitted to the split mold member,
2. The tip surface of the annular ridge of the female means is inclined upward by 1 to 80 ° radially outward,
Is preferred.
[0012]
According to the invention, the bottle characterized by the formation Turkey by biaxial stretch blow molding the preform is provided.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the preform of the present invention, an annular groove is formed on the lower surface of the thick-walled portion in order to prevent the dimensional accuracy of the neck and neck from being impaired due to an error in the amount of resin supplied during preform molding. It is an important feature that there is no generation of wrinkles or thin grooves at the corners of the top surface of the annular groove and the mechanical strength of the thick-walled portion is excellent.
That is, as will be described later, the density of the molten resin supplied into the compression molding machine changes when it changes to a solidified state. At this time, the cooled resin is pushed up on the lower surface side of the thick wall portion in contact with the male means. Since the pushed-up resin is pushed into the top surface side of the annular groove and solidified without being remelted, wrinkles or fine grooves are generated at the corners of the top surface of the annular groove.
In the present invention, from such a point of view, male means are used to prevent cooling and solidification of the resin that is pushed up and pushed into the top surface side of the annular groove, which causes wrinkles in the corners of the top surface of the annular groove. By forming the part of the split mold member in contact with the resin from a material having a lower thermal conductivity than other parts, the resin pushed up to the top surface side of the annular groove forms a mouth and neck part Together, it is possible to effectively prevent the generation of wrinkles and grooves, and to provide a preform and a bottle excellent in mechanical strength of the thick wall portion.
[0014]
Next, the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the preform of the present invention is formed by compression-molding a synthetic resin such as polyethylene terephthalate. It is comprised from the bottomed cylindrical blow molding part 3 drooping from the cyclic | annular opening neck part 2. As shown in FIG.
The mouth-and-neck portion 2 has a substantially cylindrical shape as a whole, and the inner peripheral surface thereof extends substantially vertically except for the upper end portion. A screw 4 that is screwed into a cap (not shown) is formed on the upper portion of the outer peripheral surface of the mouth-and-neck portion 2. An annular thick portion 5 is formed in the lower part of the outer peripheral surface of the mouth-and-neck portion 2 so as to project outward in the radial direction. The outer peripheral surface 6 of the thick portion 5 extends substantially vertically, and the lower surface 7 is formed substantially horizontally.
The bottomed cylindrical blow molding part 3 following the mouth and neck part is composed of a body part 8 and a hemispherical bottom part 9.
[0015]
As described above, an annular groove 10 is formed on the inner peripheral edge of the lower surface of the thick portion 5 of the mouth / neck portion 2 to reduce the influence on the dimensional accuracy of the mouth / neck portion due to an error in the amount of resin supplied. . In other words, in the mouth and neck, when the amount of resin supplied varies, the depth of the annular groove varies and the error in the resin amount is adjusted, and it is effectively prevented that the dimensions of the parts other than the annular groove in the mouth and neck vary. ing.
In the present invention, it is an important feature that no wrinkles and / or grooves are formed in the corners 11 of the top surface of the annular groove 10. If the wrinkles and grooves are formed in the corners 11 of the top surface of the annular groove, the strength of the thick portion becomes inferior. However, in the present invention, the occurrence of such wrinkles is effectively prevented. It is possible to provide a preform and a bottle excellent in strength of the part.
[0016]
A preform having such characteristics can be molded by a compression molding apparatus shown below.
FIG. 2 is a schematic cross-sectional view of the compression molding apparatus of the present invention, in which the left half shows the closed state of the mold when the supplied synthetic resin is in a molten state, the right half is solidified and the female is solidified. The closed state of the mold when the mold means is raised is shown.
The compression molding apparatus generally indicated by 20 comprises a male mold means 21 and a female mold means 22, and the male mold means 21 and the female mold means 22 are moved relative to each other in a direction toward and away from each other and opened and closed. The In the specific example shown in the figure, the male means is lowered to the closed state. In this closed state, the mold means 21 and the female means 22 define a mold space for compression molding into a preform, but the synthetic resin is changed from a molten state to a solidified state in the mold space. Although the reform is formed, volume shrinkage occurs at this time, so that the female mold means 22 rises according to the shrinkage amount of the resin.
[0017]
The male mold means 21 comprises a core member 23 and a split mold member 24. The core member 23 has a columnar portion 25 having a relatively larger diameter than the inner diameter of the preform, and a plug positioned below the columnar portion 25. The neck portion 2 of the reform, the columnar portion 26 that defines the inner diameter of the blow molding portion 3, and the hemispherical portion 27 located at the lower end. An annular recess 28 is formed on the lower surface of the columnar portion 25, and the upper end surface 12 of the mouth and neck portion 2 is defined by the inner surface of the annular recess 28.
[0018]
The split mold member 24 includes two split mold pieces 30. Each of the split mold pieces 30 has a semi-annular shape, and in the closed state, they cooperate to form an annular shape, which are in the radial direction. It moves outward and is separated from each other to be in an open state.
The split mold piece 30 defines the portion of the lower surface 7 of the thick portion 5 excluding the annular groove 10 together with the outer peripheral surface 13 of the mouth-and-neck portion 2, but in the present invention, the portion of the thick portion 5 excluding the annular groove 10 is defined. It is an important feature that the portion 31 defining the lower surface 7 is made of a material having a lower thermal conductivity than the other portions of the split piece. In the specific example shown in the figure, a nesting 31 made of a material having low thermal conductivity is fitted to the main portion 32 of the split piece.
[0019]
The material having a lower thermal conductivity than the other split mold pieces used for the portion defining the lower surface of the thick wall portion excluding the annular groove is, for example, ceramic or the like when the split mold pieces are made of stainless steel or the like. A material having a thermal conductivity in the range of 1 to 5 W / (m · K) can be preferably used.
In addition, as described above, the nesting that forms only the portion of the split mold piece is formed from a material having low thermal conductivity, and this nesting is combined with the main portion to form the split mold piece. What coated the surface with the raw material of low heat conductivity etc. can also be used.
[0020]
The female means 22 has a substantially cylindrical shape as a whole, and a concave portion 41 is formed at the center thereof. The female means 22 is formed with an annular ridge 42 that projects upward from the outer peripheral edge of the recess 41 and that defines the outer peripheral surface of the annular groove. The outer diameter of the upper end portion of the annular protrusion 42 corresponds to the inner diameter of the nesting portion 31 of the split member 30 of the male means 21, and when the male means 21 and the female means 22 are closed, the annular protrusion 42. The upper end portion of the inner wall 31 enters the lower end portion of the split member 24 along the inner peripheral surface of the nesting portion 31 to define the annular groove 10 of the preform 1. Further, the inner peripheral surface of the annular protrusion 42 defines the outer surface of the blow molding portion 3 together with the concave portion 41 of the female mold means.
[0021]
Further, as is apparent from FIG. 2, it is particularly preferable that the tip end face 43 of the annular protrusion 42 of the female means described above is inclined upward in the radial direction. In this manner, the tip portion 43 of the annular ridge 42 of the female mold means is inclined upward in the radial direction so that the resin is pushed up when the annular ridge 42 enters the lower end of the split member 24. Is caused to flow outward from the annular groove 10, so that it is possible to prevent the flow orientation of the resin from being formed at the position of the annular groove of the thick wall portion where mechanical strength is a problem. Mechanical strength can be improved. Although the inclination angle varies depending on the width of the annular groove and the thickness of the thick portion, it is preferably within the range of 1 to 80 ° in order to improve the strength of the thick portion. .
[0022]
The preform compression molding process using the male means 21 and the female means 22 is as follows. As shown in FIG. 3A, when the male mold means 21 and the female mold means 22 are in the open state, the composite resin material 50 softened and melted is supplied to the recess 41 of the female mold means 22 in an appropriate manner. The Next, as shown in FIGS. 3B and 3C, the male means 21 gradually descends, and in response to this, the male means 21 is placed on the synthetic resin 50 present in the recess 41 of the female means 22. Acts, and the synthetic resin material 50 is compressed and flows. When the male mold means 21 is lowered to the position shown in FIG. 3C and the mold space defined between the male mold means 21 and the female mold means 22 is completely filled with the synthetic resin material 50, The mold means 21 stops without further descending, and the preform 1 having the shape of the mold space defined between the male mold means 21 and the female mold means 22 is molded.
[0023]
The formed preform is raised together with the male mold means when the male mold means is raised and separated from the female mold means, and then the core member is lifted and removed from the preform, and then the split mold of the male mold means is formed. The member is removed by moving radially outward.
[0024]
The preform thus molded is applied to a blow molding means known per se, and molded into a blow molded container as partially shown in FIG. 1 by a two-dot chain line.
[0025]
The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such embodiments, and various changes and modifications can be made without departing from the scope of the present invention. Needless to say. For example, in the illustrated embodiment, the synthetic resin material is supplied to the female means in a state where the male means is completely separated from the female means. After the synthetic resin material is injected into the space between the two in a partially closed state, the female means and the male means are completely closed and the synthetic resin material is compression-molded. You can also
[0026]
【The invention's effect】
According to the present invention, the portion defining the lower surface of the thick portion of the split mold member in the male mold means of the compression molding machine is made of a material having a lower thermal conductivity than the other portions of the split mold member. It was possible to effectively prevent the formation of wrinkles and grooves at the corners of the groove top surface and to form a preform having excellent mechanical strength at the thick wall portion by compression molding.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a preform and a blow molded bottle of the present invention.
FIG. 2 is a cross-sectional view schematically showing an example of a compression molding machine according to the present invention.
3 is a cross-sectional view showing a process of molding the preform shown in FIG. 1 using the compression molding machine shown in FIG.
[Explanation of symbols]
1: Preform 2: Mouth neck part 3: Bottomed cylindrical blow molding part 5: Thick part 10: Annular groove 11: Corner of the top surface of the annular groove 21: Male means 22: Female means 31: Nest 41 : Recess 42: Annular protrusion 50: Synthetic resin material

Claims (5)

It is composed of an annular mouth and neck and a bottomed cylindrical body that hangs down from the mouth and neck. A thick wall projecting radially outward is disposed on the outer peripheral surface of the mouth and neck, and the bottom surface of the thick wall In the preform in which an annular groove is formed in the inner peripheral edge of the ring , either the male means or the female means moves up and down at the corner of the top surface of the annular groove according to the contraction amount of the resin. A preform characterized by the absence of wrinkles and / or grooves. It is composed of an annular mouth and neck and a bottomed cylindrical body that hangs down from the mouth and neck. A thick wall projecting radially outward is disposed on the outer peripheral surface of the mouth and neck, and the bottom surface of the thick wall A compression molding apparatus for molding a preform in which an annular groove is formed in the inner peripheral edge of
A male mold that moves in a direction approaching each other, is set to a closed state that cooperates to define the molding space, moves up and down according to the amount of resin shrinkage, and moves in a direction away from each other to open. Means and female means,
The female means has a recess that defines the outer surface of the cylindrical body, and an annular ridge that defines an annular groove in the mouth and neck together with the upper outer surface of the cylindrical body,
The male means comprises a core member that defines at least the inner surface of the cylindrical body and the inner peripheral surface of the mouth and neck, and a split member that is movable in the radial direction and defines at least the outer surface of the neck and neck. A compression molding apparatus characterized in that a portion of the mold member that defines the lower surface of the thick portion excluding the annular groove is made of a material having a lower thermal conductivity than other portions of the split mold member.   The compression molding apparatus according to claim 2, wherein a portion defining the lower surface of the thick portion is a nest that can be fitted to the split mold member.   The compression molding apparatus according to claim 2 or 3, wherein a tip end surface of the annular ridge of the female mold means is inclined upward by 1 to 80 degrees radially outward. Bottle, wherein the deposition Turkey a preform according to claim 1, wherein by biaxial stretch blow molding.

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