Manufacturing method for container

Abstract

To provide a technology capable of suppressing occurrence of a molding defect even when a preform formed by direct blow molding is used.SOLUTION: There is provided a method for manufacturing a container, comprising a biaxially stretching blow molding step of manufacturing a container body by biaxially stretching blow molding a preform. In the biaxially stretching blow molding step, the preform is biaxially stretched and blow-molded into a shape of the container body in a state where the preform is attached to a blow core such that an insertion portion of the blow core is positioned within the preform. The preform is a direct blow molded article at a portion facing the insertion portion. When the preform is attached to the blow core, if a minimum allowable value of an inner diameter of the direct blow molded article at a component part constituting a closest part where a distance between the insertion portion and the direct blow molded article is smallest is Dmin, and an outer diameter of the insertion portion is Db, then Db>Dmin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a container by biaxially stretched blow molding. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a container by biaxially stretching and blow molding a preform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-130735 Summary of the Invention [Problem to be solved by the invention]

[0004] In one example, biaxially stretched blow molding is performed by placing a blow core inside a preform and blowing air through through holes in the blow core. Conventionally, to prevent interference between the blow core and the preform, the outer diameter of the blow core was set to a dimension that would prevent the blow core from interfering with the preform, and the blow core was not press-fit into the preform. In biaxially stretched blow molding using preforms formed by injection molding, setting the outer diameter of the blow core as described above did not cause any problems during mass production.

[0005] On the other hand, when mass production trials were carried out using a blow core with an outer diameter designed with a similar concept in biaxial stretch blow molding using a preform formed by direct blow molding, it was found that the incidence of molding defects was significantly higher than when using a preform formed by injection molding.

[0006] The present invention has been made in view of the above circumstances, and provides a technique that can suppress the occurrence of molding defects even when a preform formed by direct blow molding is used. [Means for solving the problem]

[0007] According to the present invention, the following inventions are provided. [1] A method for manufacturing a container, comprising a biaxially stretched blow molding process for manufacturing a container body by biaxially stretching blow molding a preform, wherein in the biaxially stretched blow molding process, the preform is attached to a blow core so that an insert portion of the blow core is positioned within the preform, and the preform is biaxially stretched blow molded into the shape of the container body, wherein the portion of the preform facing the insert portion is a direct blow molded body, and where Dmin is the minimum allowable value of the inner diameter of the direct blow molded body at the constituent part that constitutes the closest part where the gap between the insert portion and the direct blow molded body is smallest when the preform is attached to the blow core, and Db is the outer diameter of the insert portion, Db>Dmin. [2] The method according to [1], wherein Db≧Dmid is satisfied, where Dmax is the maximum allowable inner diameter of the direct blow-molded body at the component part, and Dmid is the midpoint between Dmin and Dmax. [3] The method according to [2], wherein Db≧Dmax. [4] A method according to any one of [1] to [3], wherein, when the inner diameter of the direct blow molded body at the closest portion is Di, Db>Di, and the insertion portion is press-fitted into the direct blow molded body. [5] A method for manufacturing a container, comprising a biaxially stretched blow molding process for manufacturing a container body by biaxially stretching blow molding a preform, wherein in the biaxially stretched blow molding process, the preform is attached to a blow core so that an insertion portion of the blow core is positioned within the preform, and the preform is biaxially stretched blow molded into the shape of the container body, and the portion of the preform facing the insertion portion is a direct blow molded body, and the insertion portion is pressed into the direct blow molded body. [6] A method according to [5], wherein the insertion portion has a tapered portion that reduces in diameter toward the tip of the blow core, and the open end of the preform expands in diameter along the tapered portion during the press-fitting. [7] The method according to any one of [1] to [6], wherein the direct blow-molded article comprises a polyolefin layer. [8] The method according to any one of [1] to [7], wherein the preform is constructed by covering an outer preform on an inner preform, and the inner preform is the direct blow molded article. [9] The method according to [8], wherein the inner preform has a protruding portion protruding from the open end of the outer preform, and a component portion that forms the closest portion at which the gap between the insertion portion and the direct blow molded article is smallest when the preform is attached to the blow core is provided on the protruding portion. [Effects of the Invention]

[0008] The inventors investigated the causes of the high incidence of molding defects in mass-production trials and found that preforms formed by direct blow molding have greater variation in inner diameter than preforms formed by injection molding. When the inner diameter of a preform is large, the gap between the inner surface of the preform and the outer surface of the blow core becomes excessively large. The pressurized fluid injected during biaxial stretch blow molding leaks through this gap, resulting in insufficient internal pressure on the preform and molding defects. Based on this finding, the inventors arrived at the idea of ​​increasing the outer diameter of the blow core beyond the dimensions derived from conventional design concepts, thereby allowing the blow core to be pressurized into the preform. Using a blow core designed based on this concept eliminates or reduces the gap between the blow core and the preform, thereby preventing leakage of the pressurized fluid during biaxial stretch blow molding and, as a result, reducing molding defects. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a container 10 according to a first embodiment of the present invention. The dashed-dotted lines in the figure represent boundary lines along which the curvature of the faces that make up the surface shape changes. The same applies to the other figures. [Figure 2] FIG. 2 is a perspective view of the container body 2 in FIG. [Figure 3] FIG. 3 is an exploded perspective view of the vicinity of the open end 5c in FIG. 2. [Figure 4] FIG. 2 is a perspective view of the vicinity of an open end 3a of the outer shell 3. [Figure 5] FIG. 2 is a perspective view showing a state in which the inner preform 14 and the outer preform 13 are separated. [Figure 6] FIG. 1 is a perspective view of a preform 15 formed by covering an outer preform 13 on an inner preform 14. [Figure 7] 7A to 7C are a perspective view, a bottom view, and a cross-sectional view taken along CC of the blow core 21 of the first embodiment, respectively. [Figure 8]7C in a state where the blow core 21 and the preform 15 of the first embodiment are separated. FIG. [Figure 9] Fig. 9A is a cross-sectional view corresponding to Fig. 8, showing a state in which the insertion portion 21b of the blow core 21 of the first embodiment is press-fitted into the preform 15. Fig. 9B is an enlarged view of region B in Fig. 9A. [Figure 10] 1 is a cross-sectional view showing a state in which a preform 15 is attached to a blow core 21 of the first embodiment and brought close to a heater 32. FIG. [Figure 11] 11 is a cross-sectional view showing the state after the preform 15 has been transferred from the state of FIG. 10 to the molding die 23. FIG. [Figure 12] Fig. 12A is a cross-sectional view showing a state after the bottom support mold 22 supports the bottom 15c of the preform 15 from the state shown in Fig. 11. Fig. 12B is an enlarged view of region B in Fig. 12A. [Figure 13] 13 is a cross-sectional view showing the state after the stretching rod 25 is extended and the bottom support mold 22 is retracted from the state of FIG. 12 to stretch the preform 15 in the first axis. [Figure 14] 14A to 14C are a perspective view, a bottom view, and a cross-sectional view taken along CC of the blow core 21 of the second embodiment, respectively. [Figure 15] 14C in a state where the blow core 21 and the preform 15 of the second embodiment are separated. FIG. [Figure 16] Fig. 16A is a cross-sectional view corresponding to Fig. 15, showing a state in which the open end 15f of the preform 15 is in contact with the tapered portion 21f of the blow core 21 of the second embodiment. Fig. 16B is an enlarged view of region B in Fig. 16A. [Figure 17] Fig. 17A is a cross-sectional view corresponding to Fig. 15, showing a state in which the insertion portion 21b of the blow core 21 of the second embodiment is press-fitted into the preform 15. Fig. 17B is an enlarged view of region B in Fig. 17A. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently. Furthermore, in the following embodiments, elements not specified in the claims are optional elements and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400."

[0011] 1. First embodiment A first embodiment of the present invention will be described with reference to FIGS.

[0012] 1-1. Configuration of the container 10 <Basic configuration> As shown in FIG. 1, a container 10 according to a first embodiment of the present invention includes a container body 2 and a spout attachment member 8. The container 10 is a bottle-shaped container capable of holding beverages, seasonings, etc. The container 10 may be a single-walled container or a double-walled container. The following description will be given taking as an example a case in which the container 10 is a double-walled container.

[0013] As shown in Figures 2 and 3, the container body 2 has a mouth 5, a body 6, and a bottom 7. The mouth 5 is a tubular (preferably cylindrical) portion having an open end 5c. The open end 5c is the open end of the container body 2 and also the open end of the inner bag 4. The mouth 5 has an engaging portion 4m to which a mouth attachment member 8 can be attached. In this embodiment, the mouth attachment member 8 is a cap 8a, but it may also be a pump. The mouth 5 has a flange 5b. The flange 5b can be used to support the mouth 5 when the mouth attachment member 8 is attached to the mouth 5.

[0014] The body 6 is disposed adjacent to the mouth 5 on a side farther from the open end 5c than the mouth 5. In one example, the body 6 is located below the flange 5b. The body 6 has a larger outer diameter (in this specification, "outer diameter" means the equivalent circular diameter when the cross section is not circular) than the mouth 5. The body 6 is cylindrical, and the bottom 7 is provided at the lower end of the body 6 and closes the lower end of the body 6. The body 6 has a shoulder 6b whose outer diameter increases with increasing distance from the mouth 5. The body 6 also has a body main body 6c on the bottom 7 side of the shoulder 6b. The body main body 6c has a shape in which the outer diameter is approximately constant toward the bottom 7, or a shape in which the diameter decreases toward the bottom 7, for example.

[0015] As shown in Fig. 3, the container body 2 includes an inner bag 4 and an outer shell 3 arranged to cover the inner bag 4. The inner bag 4 has an inner bag body 4d other than a protruding portion 4c housed within the outer shell 3. In the following description, the portions of the inner bag 4 that correspond to the mouth 5, body 6, and bottom 7 of the container body 2 will be referred to as the mouth 5, body 6, and bottom 7 of the inner bag 4, respectively. The same applies to the outer shell 3.

[0016] <Detailed structure of outer shell 3 and inner bag 4> 2 to 4, inner bag 4 has a protruding portion 4c protruding from open end 3a of outer shell 3. Protruding portion 4c has a protruding tube 4c1, an engaging protrusion 4c2, an annular protrusion 4c5, and an abutting protrusion 4v.

[0017] The annular protrusion 4c5 engages with the spout mounting member 8 in the axial direction. The engaging protrusion 4c2 engages with the spout mounting member 8 in the circumferential direction. The engaging protrusion 4c2 and the annular protrusion 4c5 form the engaging portion 4m. The engaging portion 4m is positioned closer to the open end 5c of the inner bag 4 than the abutting protrusion 4v. In this specification, the "axial direction" refers to the direction in which the central axis C of the spout 5 extends, in other words, the direction in which the inner bag 4 is pulled out from the container body 2. The "circumferential direction" refers to the direction in which the spout 5 rotates around the central axis C, in other words, the direction in which the inner bag 4 rotates at the spout 5 relative to the outer shell 3.

[0018] The engaging protrusions 4c2 are preferably provided at multiple locations (eight locations in this embodiment) spaced apart in the circumferential direction. The engaging protrusions 4c2 are arranged on the annular protrusion 4c5 and are provided so as to protrude radially outward from the annular protrusion 4c5. The annular protrusion 4c5 and the engaging protrusions 4c2 have tapered portions 4c8 on their upper surfaces. This makes it easier for the annular protrusion provided on the nozzle mounting member 8 to climb over the annular protrusion 4c5 and the engaging protrusions 4c2.

[0019] The contact protrusion 4v is disposed at a position where it contacts the outer shell 3 (in this embodiment, the opening end 3a) and is a portion that protrudes radially outward from the protruding tube 4c1. The contact protrusion 4v contacts the outer shell 3, thereby preventing the inner bag 4 from falling into the outer shell 3.

[0020] In one example, the container body 2 is a molded body produced by biaxially stretching blow molding a preform 15 (shown in Figures 5 and 6) which is formed by covering an outer preform 13 on an inner preform 14 formed by direct blow molding.

[0021] 3, a ridge 4g is provided on the outer peripheral surface of the inner bag 4 (more specifically, the inner bag main body 4d). The lower surface of the ridge 4g is inclined counterclockwise when viewed from the opening end 5c of the mouth portion 5 so as to approach the opening end 5c.

[0022] As shown in Figures 3 and 4, a cam rail 3l is provided on the inner peripheral surface of the outer shell 3. A recess 3m that can engage with the protrusion 4g is provided in a portion of the cam rail 3l. The recess 3m is preferably provided at the end of the cam rail 3l. The upper surface of the cam rail 3l is inclined so as to approach the open end 3a as it progresses in the counterclockwise direction. The protrusion 4g and the recess 3m are configured to be engageable with each other by rotating the inner bag 4 clockwise relative to the outer shell 3, and to be disengageable by rotating the inner bag 4 counterclockwise relative to the outer shell 3.

[0023] Before the inner bag 4 is pulled out of the container body 2, the lower surface of the ridge 4g abuts against the upper surface of the cam rail 3l. The ridge 4g and the cam rail 3l form a cam mechanism 31. When the inner bag 4 is rotated counterclockwise relative to the outer shell 3, the cam mechanism 31 causes the inner bag 4 to displace in a direction that allows it to come out of the container body 2. At this time, the inner bag 4 is twisted and its diameter is reduced. The cam mechanism 31 has an inclined structure that is inclined in the same direction as a right-handed screw.

[0024] <Attaching the mouth attachment member 8 and removing the inner bag 4> The mouth attachment member 8 is preferably of a stopper type and is configured to be attachable to the mouth 5 of the container body 2, and by placing the mouth attachment member 8 over the mouth 5 and pressing the mouth attachment member 8 in the direction of the bottom 7, the mouth attachment member 8 can be engaged with and attached to the mouth 5.

[0025] The mouth attachment member 8 is engaged with the mouth 5 of the inner bag 4 in the circumferential and axial directions, and is configured so that the inner bag 4 rotates relative to the outer shell 3 as the mouth attachment member 8 rotates. The action of a cam mechanism 31 provided between the inner bag 4 and the outer shell 3 causes the inner bag 4 to move in a direction that allows it to come out of the container body 2 as the inner bag 4 rotates.

[0026] With this configuration, by rotating the mouth attachment member 8, the inner bag 4 can be twisted and moved in a direction that allows it to come out of the container body 2, and then by pulling the mouth attachment member 8, the inner bag 4 can be pulled out of the container body 2.

[0027] 1-2. Manufacturing method of container 10 The container body 2 can be manufactured by a method including a biaxially stretch blow molding process in which a preform 15 shown in Fig. 6 is biaxially stretch blow molded. In addition, the container 10 can be manufactured by attaching a mouth attachment member 8 to the container body 2.

[0028] <Configuration of inner preform 14, outer preform 13, and preform 15> The preform 15 includes an inner preform 14 that will become the inner bag 4 and an outer preform 13 that will become the outer shell 3.

[0029] As shown in Fig. 5, the inner preform 14 is cylindrical with a bottom and includes a mouth portion 14a, a body portion 14b, and a bottom portion 14c. A protrusion 14d is provided on the mouth portion 14a. As shown in Fig. 6, the protrusion 14d is a portion of the preform 15 that protrudes from the open end 13f of the outer preform 13. The protrusion 14d does not deform during molding and remains in its original shape to become the protrusion 4c. The protrusion 14d is provided with an engagement portion 14m that becomes the engagement portion 4m. The bottom portion 14c is provided to close the lower end of the body portion 14b.

[0030] 5, the outer preform 13 is cylindrical with a bottom and includes a mouth portion 13a, a body portion 13b, and a bottom portion 13c. The bottom portion 13c is provided so as to close the lower end of the body portion 13b. The bottom portion 13c is provided with an annular protrusion 13d.

[0031] 6, a preform 15 can be formed by covering an inner preform 14 with an outer preform 13. In the preform 15, the mouth portion 14a faces the mouth portion 13a, and the body portion 14b faces the body portion 13b.

[0032] The mouth portions 13a and 14a become the mouth portion 15a of the preform 15, the body portions 13b and 14b become the body portion 15b of the preform 15, and the bottom portions 13c and 14c become the bottom portion 15c of the preform 15. The body portion 15b and the bottom portion 15c (in this embodiment, the portion closer to the bottom portion 15c than the flange 15e) are mainly stretched in the biaxial stretch blow molding. The mouth portion 15a is hardly deformed during molding and becomes the mouth portion 5 of the container body 2. The above-mentioned contents regarding the configuration included in the mouth portion 5 can also be applied to the configuration included in the mouth portion 15a, as long as it is not contrary to the spirit thereof.

[0033] <Materials and manufacturing methods for inner preform 14, outer preform 13, and preform 15> The inner preform 14 and the outer preform 13 can be formed from a thermoplastic resin such as polyester (e.g., PET) or polyolefin (e.g., polypropylene, polyethylene). The outer preform 13 can be formed by direct blow molding or injection molding. The inner preform 14 is formed by direct blow molding using a molten cylindrical parison. Direct blow molding has the advantage of easily achieving thinner walls and multi-layered structures compared to injection molding. A seal portion is formed on the bottom 14c of the inner preform 14 formed by direct blow molding, by welding the inner surfaces of the parison together. This seal portion has relatively low strength and is prone to tearing during biaxial stretch blow molding. Therefore, to increase the strength of the seal portion, it is preferable that the seal portion be a protruding seal portion 14t that protrudes from the bottom 14c of the inner preform 14.

[0034] <Biaxial stretch blow molding process> The biaxial stretch blow molding process will be described with reference to Figures 7 to 13. In the biaxial stretch blow molding process, the preform 15 is attached to the blow core 21 so that the insertion portion 21b of the blow core 21 is positioned within the preform 15, and the preform 15 is then biaxially stretch blow molded into the shape of the container body 2.

[0035] In one example, the biaxial stretch blow molding process includes a mounting step, a heating step, and a stretching step. Each step will be described below.

[0036] <Installation process> In the mounting step, as shown in FIGS. 7 to 9, the preform 15 is mounted on the blow core 21 so that the insertion portion 21b of the blow core 21 is positioned within the preform 15. The blow core 21 has a base 21a, an insertion portion 21b, and a through hole 21c. The insertion portion 21b is provided so as to protrude from the base 21a. The insertion portion 21b is inserted into the preform 15. The insertion portion 21b is tapered, making it easier to insert the insertion portion 21b into the preform 15. In addition, the insertion portion 21b is provided with an expanded diameter portion 21e, and the gap between the insertion portion 21b and the preform 15 is narrowed in the expanded diameter portion 21e.

[0037] As shown in Figure 9, the base 21a abuts against the open end 15f of the preform 15. The open end 15f is also the open end of the inner preform 14. As shown in Figure 8, an expanded diameter portion 14n is provided at the open end 15f. The reduced diameter portion 14o between the expanded diameter portion 14n and the engaging portion 14m has a smaller inner diameter than the expanded diameter portion 14n and the engaging portion 14m. The reduced diameter portion 14o has a minimum inner diameter at the protruding portion 14d.

[0038] In this embodiment, the preform 15 is composed of an inner preform 14 and an outer preform 13 that covers it, and the insertion portion 21b is inserted into the inner preform 14. The inner preform 14 is a direct blow-molded article, and the inner preform 14 faces the insertion portion 21b. Therefore, the portion of the preform 15 that faces the insertion portion 21b (i.e., the inner preform 14) is the direct blow-molded article. In the following description, the "inner preform 14" can be read as "direct blow-molded article" as appropriate.

[0039] Incidentally, when the inner preform 14 is formed by direct blow molding, the outer surface shape of the inner preform 14 is defined by a mold and therefore has high precision, but the inner surface shape of the inner preform 14 is not defined by a mold and therefore tends to vary greatly in the inner surface shape of the inner preform 14. For this reason, the inner diameter of the inner preform 14 also tends to vary greatly.

[0040] Here, the portion where the gap between the insertion portion 21b and the inner preform 14 is smallest when the preform 15 is attached to the blow core 21 is defined as the closest portion 41. The closest portion 41 is made up of a component portion 41a on the inner preform 14 side and a component portion 41b on the blow core 21 side. In this embodiment, as shown in FIGS. 8 and 9, the closest portion 41 is the portion where the expanded diameter portion 21e and the reduced diameter portion 14o face each other, and the reduced diameter portion 14o and the expanded diameter portion 21e form the component portions 41a and 41b. In this specification, unless otherwise specified, the dimensions of the preform 15 and the blow core 21 refer to the dimensions when no external force is applied to the preform 15 and the blow core 21 (that is, when the preform 15 and the blow core 21 are separated, as shown in FIG. 8).

[0041] For example, when a large number of inner preforms 14 are manufactured under the condition that the reference dimension of the inner diameter Di of the inner preform 14 in the component part 41a is 27.5 mm, some inner preforms 14 will be manufactured with Di both smaller and larger than 27.5 mm. Typically, a predetermined tolerance is set so that those with Di that are too small or too large will be deemed defective. Di is measured for each inner preform 14, and those whose deviation from the reference dimension is within the tolerance range are deemed to be good products, while those whose deviation is outside the tolerance range are deemed to be defective products. While a smaller tolerance has the advantage of increasing the uniformity of good products, it also increases the proportion of products deemed to be defective and reduces the yield, so the tolerance is set by taking into account the balance between the uniformity of good products and the yield.

[0042] In direct blow molding, variation in Di is likely to be large, so if the tolerance is set to the same level as in injection molding, the yield will be too low, and so the tolerance must be set to a certain degree, for example, ±0.2 mm. In this case, the minimum allowable value of the inner diameter Di is 27.3 mm, and the maximum allowable value of the inner diameter Di is 27.7 mm. The minimum allowable value and maximum allowable value are the minimum and maximum values, respectively, when the tolerance is taken into consideration. The minimum allowable value and maximum allowable value of the inner diameter Di will be referred to as Dmin and Dmax hereinafter.

[0043] If the outer diameter of the insertion part 21b at the component part 41b is Db, in the present embodiment, Db is set such that Db > Dmin. According to the conventional design concept, since the dimension of the outer diameter of the insertion part of the blow core is determined so as not to interfere with the preform, the outer diameter Db is set such that Db < Dmin. Therefore, the blow core is not press-fitted into the preform.

[0044] On the other hand, when using the inner preform 14 formed by direct blow molding, if Db < Dmin, when Di is close to Dmax, the gap between the component parts 41a and 41b becomes too large, and the air blown in during biaxial stretch blow molding leaks from the above gap, resulting in a problem that the internal pressure applied to the preform 15 becomes insufficient and molding defects are likely to occur. Therefore, in the present embodiment, Db is made larger than the dimension derived from the conventional design concept, and by setting Db > Dmin, molding defects are suppressed.

[0045] Among the large number of good inner preforms 14 manufactured during mass production (hereinafter, "good products during mass production"), those with Di less than Db are included. For such inner preforms 14, the insertion part 21b is press-fitted into the inner preform 14. That is, while the component part 41b on the blow core 21 side expands the component part 41a on the inner preform 1, the insertion part 21b is inserted into the inner preform 14. On the other hand, when Db < Dmax, among the good products during mass production, there may be those with Di > Db. In such cases, the insertion part 21b is not press-fitted into the inner preform 14, and a gap is formed between the component parts 41a and 41b. In one example, Db = 27.5 mm. In this case, for the inner preform 14 with Di = 27.4 mm, the insertion part 21b is press-fitted, and for the inner preform 14 with Di = 27.6 mm, the insertion part 21b is not press-fitted. However, even in this case, since the gap between the component parts 41a and 41b becomes small, molding defects are suppressed.

[0046] If the average value of Dmin and Dmax is the intermediate value Dmid, then Db is preferably set so that Db≧Dmid or Db>Dmid. In the above example, Dmid is 27.5 mm, and Db is set to, for example, 27.6 mm. In this case, even if Di is a value close to Dmax, the gap between the component parts 41a and 41b becomes relatively small, further suppressing molding defects.

[0047] Preferably, Db is set so that Db≧Dmax or Db>Dmax. In the above example, Dmax is 27.7 mm, so Db is set to, for example, 27.8 mm. In this case, regardless of the value of Di, no gap is formed between the component parts 41a and 41b, further suppressing molding defects.

[0048] If (Dmax - Dmin) is the allowable dimensional difference Ddif, Ddif is, for example, 0.20 to 1.0 mm, and preferably 0.30 to 0.60 mm. Specific examples of Ddif are 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, and 1.00 mm, and may be in a range between any two of the values ​​exemplified here.

[0049] If (Db - Dmin) is the maximum interference amount Pmax, Pmax is, for example, 0.01 to 1.0 mm. Pmax refers to the amount of interference between the components 41a and 41b when Di is Dmin. Specific examples of Pmax are 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, and 1.00 mm, and may be in a range between any two of the values ​​exemplified here.

[0050] Alternatively, Pmax is α×Ddif. α is, for example, 0.05 to 2. When Db=Dmid, α=0.5, and when Db=Dmax, α=1. Specific examples of α are 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0, and may be in a range between any two of the numerical values ​​exemplified here.

[0051] The inner preform 14 preferably includes a polyolefin layer. If the inner preform 14 is formed of a highly rigid resin such as PET, the inner preform 14 may not deform sufficiently when inserting the insertion portion 21b, making it difficult to insert the insertion portion 21b or to pull out the insertion portion 21b from the inner preform 14. Therefore, it is preferable to provide a layer of a resin with relatively low rigidity such as polyolefin. The polyolefin layer is preferably provided in the innermost layer of the inner preform 14. This is because the innermost layer is the layer that comes into contact with the insertion portion 21b when the insertion portion 21b is press-fitted, and therefore it is desirable for the innermost layer to be easily deformed.

[0052] The ratio of the polyolefin layer (if multiple polyolefin layers are provided, the total of all polyolefin layers) to the thickness of the inner preform 14 at the component part 41a is, for example, 50 to 100%, preferably 80 to 100%, and specifically, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100%, or may be in the range between any two of the numerical values ​​exemplified here. Layers other than the polyolefin layer that make up the inner preform 14 include gas barrier layers such as EVOH and nylon.

[0053] The thickness of the inner preform 14 at the component part 41a is, for example, 0.40 to 1.20 mm, preferably 0.50 to 1.00 mm, and specifically, for example, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, or 1.20 mm, or may be in a range between any two of the numerical values ​​exemplified here.

[0054] The component part 41a is preferably provided on the protruding part 14d because the periphery of the protruding part 14d is not covered with the outer preform 13, and therefore the deformation of the inner preform 14 is not hindered by the outer preform 13.

[0055] <Heating process> The heating process can be performed using a heating device 35 shown in FIG. 10. In the heating process, the preform 15 is heated and softened to a softened state. In one example, the heating process can be performed by placing the preform 15 near a heater 32 while the preform 15 is attached to a blow core 21, as shown in FIG. 10. The heating process is performed by heating the body portion 15b and bottom portion 15c while the flange 15e provided on the preform 15 is covered with a heat shield 33. This softens the body portion 15b and bottom portion 15c. On the other hand, the flange 15e and the mouth portion 15a covered with the heat shield 33 receive little or no heat from the heater 32 and are not softened. In one example, the preform 15 can be heated while being rotated. In one example, the heater 32 is composed of multiple rod-shaped heaters arranged along the side of the preform 15, but other configurations are also possible.

[0056] <Stretching process> The stretching step can be performed using a blow molding device 36 shown in Figures 11 to 13. In the stretching step, the softened preform 15 is stretched to form the shape of the container body 2. In one example, the stretching step includes a first stretching step and a second stretching step.

[0057] <First stretching process> In the first stretching step, the preform 15 is stretched along a first axial direction (i.e., the vertical direction). The first axis is, for example, a direction parallel to the central axis C of the mouth portion 5, which is the vertical direction in FIG. 11. In one example, this step can be performed by setting the heated preform 15 in a molding die 23 as shown in FIG. 11, and then, with the bottom 15c of the preform 15 supported by a bottom support die 22 as shown in FIGS. 12 and 13, pressing a stretch rod 25 inserted through a through hole 21c provided in a blow core 21 against the inner bottom surface of the inner preform 14 to stretch it. At this time, it is preferable to retract the bottom support die 22 in synchronization with the stretching of the stretch rod 25. This allows the preform 15 to be stably stretched.

[0058] The preform 15 can be transferred from the heating device 35 to the blow molding device 36 while supported by the blow core 21. The molding die 23 is composed of a split mold that can be opened and closed, and includes a cavity surface 23a that corresponds to the outer surface shape of the container body 2, and a flange accommodating portion 23b that can accommodate the flange 15e. The preform 15 is set in the molding die 23 so that the flange 15e is disposed within the flange accommodating portion 23b. The first stretching step can be performed in a state where the flange 15e is pressed against the opposing surface 23c that faces the flange 15e in the first axial direction.

[0059] <Second stretching process> In the second stretching step, air is blown into the inner preform 14 from the state shown in Fig. 13 to stretch (i.e., expand) the preform 15 in the second axial direction (i.e., the lateral direction) and shape it into the shape of the cavity surface 23a, thereby obtaining the container body 2 shown in Fig. 2. Air can be blown in through the through holes 21c provided in the blow core 21.

[0060] 2. Second embodiment The second embodiment of the present invention will be described with reference to FIGS. 14 to 17. This embodiment is similar to the first embodiment, and the content described in the first embodiment is applicable to this embodiment as long as it does not conflict with the gist thereof. The main difference between this embodiment and the first embodiment is the difference in the shape of the blow core 21. Hereinafter, the description will focus on the differences.

[0061] As shown in FIG. 14, the blow core 21 of this embodiment is provided with a diameter-expanded portion 21e at the base end of the insertion portion 21b. As shown in FIG. 17, in the state where the preform 15 is attached to the blow core 21, at the diameter-expanded portion 21e, the interval between the insertion portion 21b and the inner preform 14 becomes the minimum, so the diameter-expanded portion 21e and the portion of the inner preform 14 facing the diameter-expanded portion 21e become the constituent parts 41b and 41a of the closest portion 41. In this embodiment, since the diameter-expanded portion 14n of the inner preform 14 faces the diameter-expanded portion 21e, the diameter-expanded portion 14n and the diameter-expanded portion 21e become the constituent parts 41a and 41b. Since the diameter-expanded portion 14n is provided at the opening end 15f, the inner diameter Di of the inner preform 14 at the constituent part 41a coincides with the inner diameter at the opening end 15f of the inner preform 14. Also, the outer diameter Db of the insertion portion 21b at the constituent part 41b coincides with the outer diameter of the diameter-expanded portion 21e.

[0062] A tapered portion 21f is provided on the tip side of the diameter-expanded portion 21e. The tapered portion 21f is provided such that the diameter-expanded portion 21e is reduced in diameter toward the tip. When the inner diameter at the opening end 15f is smaller than the outer diameter of the diameter-expanded portion 21e (that is, when Di < Db), when the insertion portion 21b is inserted into the inner preform 14, as shown in FIG. 16, the opening end 15f abuts against the tapered portion 21f. When a further force is applied to the insertion portion 21b from this state, as shown in FIG. 17, the opening end 15f is expanded along the tapered portion 21f while the insertion portion 21b is press-fitted.

[0063] With this configuration, air leakage from between the component parts 41a, 41b is suppressed, thereby suppressing molding defects. Furthermore, since the component part 41a is located at the opening end 15f, the inner preform 14 is likely to expand in diameter at the component part 41a. Furthermore, since the opening end 15f is expanded in diameter along the tapered portion 21f, the inner preform 14 is likely to expand in diameter at the component part 41a. Therefore, in this embodiment, it is easy to increase the maximum interference amount Pmax defined by (Db - Dmin), thereby further suppressing air leakage.

[0064] The insertion portion 21b can be pressed into place at any timing before the completion (preferably before the start) of the step of blowing air into the inner preform 14. In one example, in the first stretching step, as shown in Fig. 12, the insertion portion 21b can be pressed into place by pressing the insertion portion 21b toward the inner preform 14, and the flange 15e can be pressed against the opposing surface 23c.

[0065] 3. Other embodiments In the above embodiment, the preform 15 is a two-body structure of the inner preform 14 and the outer preform 13, but it may also be an integrated structure. In this case, the entire preform 15 is made up of a direct blow-molded article. In addition, in this case, the description of the inner preform 14 in the above embodiment can be read as a description of the preform 15, as long as it does not contradict the spirit of the description. [Explanation of symbols]

[0066] 2: Container body 3: Outer shell 3a: Open end 3l: Cam rail 3m: Concave 4: Inner bag 4c:Protrusion 4c1:Protruding tube 4c2: Engagement convex part 4c5: Circular convex part 4c8: Tapered section 4d: Inner bag body 4g: Convex strip 4m: Engagement part 4v: Contact convex part 5: Mouth 5b: Flange 5c: Open end 6: Body 6b:Shoulder 6c: Body 7: Bottom 8: Mouth attachment member 8a: Cap 10: Container 13: Outer preform 13a: Mouth 13b: Torso 13c: Bottom 13d: Annular convex part 13f: Open end 14: Inner preform 14a: Mouth 14b: Torso 14c: Bottom 14d:Protrusion 14m: Engagement part 14n: Expanded diameter part 14o: Reduced diameter part 14t: Protruding seal part 15: Preform 15a: Mouth 15b: Body 15c: bottom 15e: Flange 15f: Open end 21: Blow Core 21a: Base 21b: Insertion part 21c: Through hole 21e: Expanded diameter part 21f: Tapered section 22: Bottom support type 23: Molding mold 23a: Cavity surface 23b: flange housing 23c: Opposite surface 25: Stretching rod 31: Cam mechanism 32: Heater 33: Heat shielding section 35: Heating device 36: Blow molding equipment 41: Nearest site 41a: Constituent part 41b: Constituent part C: Central axis Db:Outer diameter Di: Inner diameter

Claims

1. A manufacturing method of a container, comprising a biaxially stretch blow molding step of manufacturing a container body by biaxially stretch blow molding a preform, In the biaxially stretched blow molding step, the preform is attached to the blow core so that an insertion portion of the blow core is positioned within the preform, and the preform is biaxially stretched blow molded into the shape of the container body, the preform has a direct blow molded article at a portion facing the insertion portion, When the preform is attached to the blow core, the allowable minimum value of the inner diameter of the direct blow molded body at a constituent part constituting the closest part where the distance between the insertion part and the direct blow molded body is smallest is defined as Dmin, and the outer diameter of the insertion part is defined as Db. A method wherein Db>Dmin.

2. 10. The method of claim 1, Let Dmax be the maximum allowable inner diameter of the direct blow molded article at the component part, and let Dmid be the midpoint between Dmin and Dmax. A method wherein Db≧Dmid.

3. 3. The method of claim 2, A method wherein Db≧Dmax.

4. The method according to any one of claims 1 to 3, When the inner diameter of the direct blow-molded article at the closest portion is Di, Db>Di; The method wherein the insert is press-fit into the direct blow molded article.

5. A manufacturing method of a container, comprising a biaxially stretch blow molding step of manufacturing a container body by biaxially stretch blow molding a preform, In the biaxially stretched blow molding step, the preform is attached to the blow core so that an insertion portion of the blow core is positioned within the preform, and the preform is biaxially stretched blow molded into the shape of the container body, the preform has a direct blow molded article at a portion facing the insertion portion, The method wherein the insert is press-fit into the direct blow molded article.

6. 6. The method of claim 5, The insertion portion is provided with a tapered portion that reduces in diameter toward the tip of the blow core, The method, wherein the open end of the preform is expanded in diameter along the tapered portion during the press-fitting.

7. 10. The method of claim 1 or claim 5, The method, wherein the direct blow molded article comprises a polyolefin layer.

8. 10. The method of claim 1 or claim 5, The preform is configured by covering an outer preform with an inner preform, The method wherein the inner preform is the direct blow molded article.

9. 9. The method of claim 8, the inner preform has a protruding portion protruding from an open end of the outer preform, A method in which a component portion that forms a closest portion where the gap between the insert portion and the direct blow molded article is smallest when the preform is attached to the blow core is provided on the protrusion.

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