JP2004268486A - Preform, compression molding apparatus for preform, bottle obtained by blow-molding preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preform excellent in strength of a thick-wall part by effectively preventing wrinkles formed in an annular channel or the occurrence of the channel. <P>SOLUTION: In the preform composed of an annular mouth-neck part and a bottomed cylindrical barrel part suspended from the mouth-neck part, the thick-wall part protruding outward in the radius direction is arranged on the outside surface of the mouth-neck part, and the annular channel is formed in the inside edge part of the lower surface of the thick-wall part. The wrinkles and/or the groove are not formed in the angular part of the top surface of the annular groove. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a preform and a compression molding apparatus for molding the preform, and more particularly, to a preform in which the strength of a thick portion is significantly improved, and compression molding for producing the preform. Equipment related.
[0002]
[Prior art]
As containers for filling beverages and the like, containers made of synthetic resins such as polyethylene terephthalate are widely used, and such containers are manufactured by injection molding of synthetic resins to form bottomed preforms whose dimensions are considerably smaller than the final containers. A method in which the preform is preliminarily formed, the preform is preheated to the stretching temperature, and the preform is stretched in the blow mold in the axial direction and is stretched in the circumferential direction (for example, see Patent Document 1).
The preform generally has a neck and neck portion corresponding to the mouth and neck portion of a bottle and a bottomed cylindrical portion to be stretch-blow molded. On the mouth and neck, for example, means for engaging with a sealing opening end or a lid, and an annular projection generally called a thick portion for supporting the container when filling the container with the contents or mounting the lid, etc. It is formed on the outer peripheral surface. In addition, a gate portion protruding outward from the center of the bottom is necessarily formed at the bottom due to the necessity of injection molding.
[0003]
However, in the production of preforms by injection molding, generally, the melt-plasticized resin is injected into the cavity via a nozzle, a sprue, a runner, and a gate, so that the residence time of the resin in the injection molding machine is long. For a long period of time in a molding machine, the resin may deteriorate, and the strength of the bottom of the bottle may be poor due to the presence of the gate formed at the bottom.
[0004]
It is also known to manufacture a closed-end 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 formed into a precursor and the precursor is formed. The body is placed in a compression mold where the precursor is fixed and adhered entirely within the cavity, and the precursor is not completely filled in the compression mold but before being compressed to its final shape. In the compression mold, the precursor has a shape such that it is supported in a predetermined manner in the cavity, and the precursor is heated before the precursor is put into the compression mold, and the heated precursor is compressed in the compression mold. A method of manufacturing a preform by molding has been proposed (see Patent Document 2).
[0005]
However, there are the following problems to be solved also in the preform molding by compression molding. That is, in the case of compression molding, the synthetic resin material may be supplied to the female or male means before the male and female means are closed and a molding space is defined between them. is necessary. The supply of the synthetic resin material is performed, for example, by extruding a softened and molten synthetic resin material from an extruder and cutting off the synthetic resin material from an extrusion port of the extruder. Due to this, it is extremely difficult to control the supply amount of the synthetic resin material with sufficient precision, and usually, there is an error of about 0.5 to 1.0% in the supply amount of the synthetic resin material. Due to such an error, if the main dimensions such as the height and inner and outer diameters of the mouth and neck are slightly changed, a required sealing property cannot be obtained when the lid is attached to the mouth and neck, or the lower surface of the thick portion. Various obstacles occur in the automatic lid mounting operation for mounting the lid on the mouth and neck due to the variation of the height from the to the tip of the mouth and neck.
[0006]
From such a viewpoint, the present inventors have proposed a preform in which an annular groove is formed on the inner peripheral edge of the lower surface of the thick portion (Patent Document 3). Even if there is an error in the amount, by adjusting the size 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, the height from the bottom of the thick part to the tip of the mouth and neck, etc. Thus, a preform can be efficiently formed.
[0007]
[Patent Document 1]
JP-A-4-154535 [Patent Document 2]
WO 97/32706 pamphlet [Patent Document 3]
JP-A-10-337969
[Problems to be solved by the invention]
However, in the preform provided with such an annular groove, a wrinkle or a vertical thin groove is generated at the corner of the top surface of the annular groove, and the strength of the thick portion is inferior due to the influence of the wrinkle or the groove. Problems arise.
That is, when the resin supplied to the space formed by the female means and the male means changes from a molten state to a solidified state, the resin undergoes volume shrinkage. For this reason, in the compression molding, one of the male mold means and the female mold means moves up and down in accordance with the amount of shrinkage of the resin. At this time, the resin cooled on the lower side of the thick part is pushed up and this pushed up. Although the resin is pushed into the resin forming the thick portion, it is not re-melted, so that the corners of the top surface of the annular groove are wrinkled or solidified in a vertical thin groove. Such wrinkles or grooves formed at the corners of the top surface of the annular groove cause the strength of the thick portion to decrease, and are not preferable.
[0009]
Accordingly, an object of the present invention is to provide a preform in which wrinkles or grooves formed in the annular groove are effectively prevented and the strength of the thick portion is excellent.
Another object of the present invention is to provide a compression molding apparatus for molding a preform in which wrinkles or grooves are effectively prevented from being formed in an annular groove of the preform.
Another object of the present invention is to provide a bottle having excellent strength at a thick portion formed from the preform.
[0010]
[Means for Solving the Problems]
According to the present invention, it is constituted by an annular mouth and neck portion and a bottomed cylindrical torso hanging down from the mouth and neck portion, and a thick portion protruding radially outward is disposed on an outer peripheral surface of the mouth and neck portion, A preform in which an annular groove is formed on an inner peripheral edge of a lower surface of the thick portion, wherein the corner of a top surface of the annular groove has no wrinkles and / or grooves. You.
[0011]
According to the present invention, it is also composed of an annular mouth-neck portion and a bottomed cylindrical body hanging down from the mouth-neck portion, and a thick portion protruding radially outward is disposed on the outer peripheral surface of the mouth-neck portion. A compression molding device for molding a preform in which an annular groove is formed on an inner peripheral edge of a lower surface of the thick portion, wherein the compression molding device moves in a direction approaching each other and cooperates to form a molding space. A male member and a female member that are set to a defined closed state and move in a direction away from each other to be in an open state; and the female member includes a concave part that defines an outer surface of the cylindrical body. And an annular ridge defining an annular groove of the mouth and neck together with the upper outer surface of the cylindrical body, wherein the male means is a core that defines at least the inner surface of the cylindrical body and the inner peripheral surface of the mouth and neck. A member and a split mold member that is movable in the radial direction defining at least the outer peripheral surface of the mouth and neck portion, and the split mold member is Portion defining a thick lower surface is, compression molding apparatus characterized by comprising a material having a low thermal conductivity is provided than the rest of the split mold member.
In this compression molding machine,
1. The part that defines the thick part lower surface is a nest that can be fitted with the split mold member,
2. It is preferable that the distal end surface of the annular ridge of the female means is inclined upward by 1 to 80 ° toward the outside in the radial direction.
[0012]
According to the present invention, there is further provided a bottle obtained by biaxially stretch-blowing the preform, wherein the strength of a thick portion is improved.
[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 part in order to prevent the dimensional accuracy of the mouth and neck part 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 wrinkles or thin grooves at the corners of the top surface of the annular groove, and the thick portion has excellent mechanical strength.
That is, as described later, the molten resin supplied into the compression molding machine changes in density when it changes to a solidified state, and in order to respond to this, the compression molding is performed by the male or female means in accordance with the shrinkage of the resin. At this time, the cooled resin is pushed up on the lower surface side of the thick portion in contact with the male mold means. The pushed resin is pushed into the top surface of the annular groove and solidified without re-melting, so that a wrinkle or a thin groove is generated at a corner of the top surface of the annular groove.
In the present invention, from such a point of view, the male means is used to prevent the resin that is pushed up and pushed into the top surface side of the annular groove from cooling and solidifying, which causes wrinkles at the corners of the annular groove top surface. By forming the portion of the split mold member that comes into contact with such resin from a material having a lower thermal conductivity than other portions, the resin pushed up to the top surface side of the annular groove and the resin forming the mouth and neck portion As a whole, it is possible to effectively prevent the generation of wrinkles and grooves, and to provide a preform and a bottle having excellent mechanical strength in a thick 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. And a cylindrical blow-molded part 3 with a bottom that hangs down from the annular mouth and neck part 2.
The mouth and neck portion 2 has a substantially cylindrical shape as a whole, and its inner peripheral surface extends substantially vertically except for the upper end portion. A screw 4 for screwing with a cap (not shown) is formed on the upper part of the outer peripheral surface of the mouth and neck portion 2. An annular thick portion 5 that protrudes outward in the radial direction is formed at a lower portion of the outer peripheral surface of the mouth and neck portion 2. 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 molded part 3 following the mouth and neck comprises a body part 8 and a hemispherical bottom part 9.
[0015]
As described above, the annular groove 10 is formed on the inner peripheral edge of the lower surface of the thick portion 5 of the mouth and neck portion 2 to reduce the influence on the dimensional accuracy of the mouth and neck portion due to the error in the resin supply amount. . In other words, in the mouth and neck, when the supply amount of the resin fluctuates, the depth of the annular groove fluctuates to adjust the error in the amount of resin, and it is effectively prevented that the dimensions of the portion of the mouth and neck other than the annular groove fluctuate. ing.
An important feature of the present invention is that no wrinkles and / or grooves are formed in the corners 11 of the top surface of the annular groove 10. If wrinkles or grooves are formed at 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 and the like is effectively prevented. It is possible to provide a preform and a bottle excellent in part strength.
[0016]
A preform having such characteristics can be formed by a compression molding apparatus described below.
FIG. 2 is a schematic sectional view of the compression molding apparatus of the present invention, in which the left half shows the closed state of the molding die when the supplied synthetic resin is in a molten state, and the right half shows that the synthetic resin has solidified and It shows the closed state of the mold when the mold means is raised.
The compression molding apparatus generally designated 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 relatively opened and closed by moving relatively to and away from each other. You. In the specific example shown in the figure, the male means descends to the closed state. In this closed state, the molding die space for compression molding into a preform is defined by the male die means 21 and the female die means 22, but the synthetic resin changes from the molten state to the solidified state in the molding die space, The reform is formed. At this time, since the volume shrinks, the female mold means 22 rises according to the shrinkage amount of the resin.
[0017]
The male means 21 is composed of 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. It comprises a mouth-and-neck portion 2 of the reform, a columnar portion 26 for defining the inner diameter of the blow molding portion 3, and a hemispherical portion 27 located at the lower end. An annular concave portion 28 is formed on the lower surface of the columnar portion 25, and the upper surface 12 of the mouth and neck portion 2 is defined by the inner surface of the annular concave portion 28.
[0018]
The split mold member 24 is composed of two split mold pieces 30, each of which has a semi-annular shape, cooperates in a closed state to form an annular shape, and these are formed in a radial direction. It moves outward and separates from each other to open.
The split mold piece 30 defines a 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. 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 other portions of the split piece. In the specific example shown in the figure, a nest 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 pieces used for the portion defining the lower surface of the thick portion excluding the annular groove includes, for example, ceramics when the split pieces are made of stainless steel or the like. And those having a thermal conductivity in the range of 1 to 5 W / (m · K) can be suitably used.
Also, as described above, the nest forming only the relevant portion of the split mold piece is formed from a material having low thermal conductivity, and this nest is combined with the main portion to form the split mold piece. A material whose surface is coated with a material having low thermal conductivity may be used.
[0020]
The female means 22 has a substantially columnar shape as a whole, and has a concave portion 41 formed at the center thereof. An annular ridge 42 that protrudes upward from the outer peripheral edge of the concave portion 41 and that defines the outer peripheral surface of the annular groove is formed in the female mold means 22. The outer diameter of the upper end portion of the annular ridge 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 ridge 42 is closed. The upper end enters the lower end of the split mold member 24 along the inner peripheral surface of the nesting portion 31 to define the annular groove 10 of the preform 1. The inner peripheral surface of the annular projection 42, together with the concave portion 41 of the female mold means, defines the outer surface of the blow molded portion 3.
[0021]
As is apparent from FIG. 2, it is particularly preferable that the distal end face 43 of the annular ridge 42 of the above-mentioned female means is inclined upward in the radially outward direction. As described above, by inclining the distal end portion 43 of the annular ridge 42 of the female mold upward toward the outside in the radial direction, the resin is pushed up when the annular ridge 42 enters the lower end portion of the split mold member 24. Acts to flow outside the annular groove 10, so that the flow orientation of the resin is prevented from being formed at the position of the annular groove of the thick part where the mechanical strength is particularly problematic, and It is possible to improve the mechanical strength. The angle of inclination varies depending on the width of the annular groove, the thickness of the thick portion, etc., but is preferably in the range of 1 to 80 ° in order to improve the strength of the thick portion. .
[0022]
The compression molding step of the preform using the male mold means 21 and the female mold means 22 is as follows. As shown in FIG. 3A, when the male means 21 and the female means 22 are in the open state, the soft resin material 50 which has been softened and melted is supplied to the recess 41 of the female means 22 in an appropriate manner. You. Then, as shown in FIGS. 3 (B) and 3 (C), the male means 21 gradually descends, and accordingly, the male means 21 is inserted into the synthetic resin 50 present in the concave portion 41 of the female means 22. Acts, and the synthetic resin material 50 is compressed and flows. When the male means 21 descends to the position shown in FIG. 3 (C) and the mold space defined between the male means 21 and the female means 22 is completely filled with the synthetic resin material 50, the male The mold means 21 stops without further lowering, and thus the preform 1 having the shape of the mold space defined between the male mold means 21 and the female mold means 22 is formed.
[0023]
The formed preform rises with the male means when the male means is raised and separated from the female means, and then the core member is lifted and pulled out of the preform. The member is removed by moving radially outward.
[0024]
The preform formed in this way is subjected to a blow molding means known per se, and is formed into a blow molded container partially shown by a two-dot chain line in FIG.
[0025]
As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments, and various changes and modifications can be made without departing from the scope of the present invention. Needless to say, there is. 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 parts in a partially closed state, the female mold means and the male mold means are completely closed and the synthetic resin material is compression-molded to form a preform by so-called injection compression molding. 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, so that The generation of wrinkles and grooves in the corners of the groove top surface can be effectively prevented, and a preform having excellent mechanical strength in the thick portion can be formed by compression molding.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a preform and a blow-molded bottle of the present invention.
FIG. 2 is a sectional view schematically showing an example of a compression molding machine of the present invention.
FIG. 3 is a sectional view showing a step of molding the preform shown in FIG. 1 using the compression molding machine shown in FIG. 2;
[Explanation of symbols]
1: Preform 2: mouth and neck 3: bottomed cylindrical blow molded part 5: thick part 10: annular groove 11: corner 21 of the top surface of annular groove 21: male means 22: female means 31: nest 41 : Recess 42: annular ridge 50: synthetic resin material

Claims (5)

An annular mouth-and-neck portion and a bottomed tubular body hanging down from the mouth-and-neck portion, a thick portion protruding radially outward on the outer peripheral surface of the mouth-and-neck portion, and a lower surface of the thick portion A preform in which an annular groove is formed at an inner peripheral edge of the preform, wherein a corner of a top surface of the annular groove has no wrinkles and / or grooves. An annular mouth-neck portion and a bottomed cylindrical body hanging down from the mouth-neck portion, a thick portion protruding radially outward on the outer peripheral surface of the mouth-neck portion, and a lower surface of the thick portion A compression molding apparatus for molding a preform in which an annular groove is formed on an inner peripheral edge of the preform,
It comprises a male means and a female means which move in a direction approaching each other, are set in a closed state which cooperate to define a molding space, move in a direction away from each other and become an open state,
The female means has a concave portion that defines an outer surface of the cylindrical body, and an annular ridge that defines an annular groove at the mouth and neck together with an upper outer surface of the cylindrical body.
The male means includes a core member that defines at least an inner surface of the tubular body and an inner peripheral surface of the mouth and neck, and a split mold member that is movable in a radial direction that defines at least an outer peripheral surface of the mouth and neck. A compression molding apparatus, wherein a portion of the mold member defining a lower surface of the thick portion is made of a material having a lower thermal conductivity than other portions of the split mold member. 3. The compression molding apparatus according to claim 2, wherein the portion defining the lower surface of the thick portion is a nest that can be fitted to the split mold member. 4. The compression molding apparatus according to claim 2, wherein the distal end surface of the annular ridge of the female means is inclined upward by 1 to 80 degrees outward in the radial direction. A bottle obtained by biaxially stretch-blow-molding the preform according to claim 1, wherein the strength of a thick portion is improved.

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