JP6614440B2 - Blow molding method - Google Patents

Description

  The present invention relates to a blow molding method for performing biaxial stretching blow by combining a preform and a tubular molded body.

  As a method for molding a plastic container (bottle), a blow molding method is widely used. An injection molded preform is set in a mold, and air is blown to form a mold cavity 2 An axial stretch blow molding method or the like is known.

  In recent years, in the field of plastic containers, various functions and performances are often required, and ingenuity is required for the materials and molding methods used. For example, when a gas barrier property, a light shielding property, a heat retaining property, etc. are required, a material to be used has a gas barrier property, or a colorant or an ultraviolet absorber is added to a plastic material.

  However, there is a limit to the contrivance of materials, and various functions are imparted by multilayering plastic containers. By optimizing the constituent materials of each layer, it is expected that a plastic container having a composite function such as a light shielding container excellent in gas barrier properties can be realized.

  In order to mold a multilayer plastic container, it is considered that a multilayer preform may be injection-molded and blow-molded, and various methods for molding a multilayer preform have been proposed. However, there is a problem in terms of cost, for example, because advanced technology is required for molding a multilayer preform, and a large amount of equipment investment is required for the molding apparatus.

  From such a situation, it has been proposed to form a composite container by mounting a preform cover separately molded on the outside of the preform and blow-molding it (see Patent Document 1, Patent Document 2, etc.) ). By using the preform cover, it is considered unnecessary to form a multilayer preform, leading to cost reduction and the like.

  In Patent Document 1, an outer shrink member is provided on the outer side of the preform, a composite preform having a preform and an outer shrink member in close contact with the outer side of the preform is manufactured, and the composite preform is formed in a blow mold. A blow molding method is disclosed in which a preform of a composite preform and an outer contracting member are expanded together by performing blow molding on the reform. By forming the outer contraction member with a material having a gas barrier property or a light barrier property, for example, a composite container having these functions can be formed.

  Patent Document 2 discloses a blow molding method in which an inner label member is provided on the outer side of a preform, and the preform and the inner label member are expanded integrally as in Patent Document 1. Thereby, it is possible to realize a blow molding method capable of eliminating the step of applying a label by a labeler.

Japanese Patent Laying-Open No. 2015-9493 Japanese Patent Laying-Open No. 2015-9487

  By the way, with the method of molding a composite container by attaching a preform cover to the outside of the preform and blow molding it, it is not possible to impart functionality to the entire container, which is a requirement for diversification of plastic containers. The fact is that it is not always possible.

  When forming a plastic container by biaxially stretching blow-molding the preform, a screw portion for screwing the cap onto the outer peripheral surface of the mouth of the preform corresponding to the cap attached to the plastic container And various flange portions are often formed. In the method of attaching the preform cover to the outside of the preform in such a form, it is difficult to cover the preform mouth with the preform cover, and it is difficult to impart functionality to the entire container.

  The present invention has been proposed in view of such conventional circumstances, and it is possible to provide a blow molding method capable of imparting functionality to the entire container, for example, to easily produce a delamination container. The purpose is to provide.

In order to achieve the above-mentioned object, the blow molding method of the present invention loads a pre-blow-molded tube-shaped molded body inside a pre-molded preform and the tube-shaped molded body inside the preform. It is characterized by performing biaxial stretching blow molding in a state where the layers are stacked to form a delamination container .

  On the inner surface of the preform, there is no unevenness corresponding to the screw portion or various flange portions, and the surface is a smooth surface. Therefore, the tubular molded body can be loaded in close contact with the preform even at the mouth portion of the preform. If a tube-shaped molded body that reaches the opening end of the preform is loaded and biaxial stretch blow molding is performed, the entire inner surface of the container is molded with the tubular molded body, and functionality is added to the entire container. Is done.

  According to the blow molding method of the present invention, the entire container can have a double structure, and various functions can be imparted to the entire container. Moreover, it is also possible to easily produce a so-called delamination container as a double-structure container.

It is a schematic perspective view which shows an example of the manufacturing process of a composite container, and shows the attachment process of the tubular molded object to a preform. It is a schematic sectional drawing which shows the state which loaded the tubular molded object to the preform. It is a schematic side view which shows a partially broken composite container. It is a figure which shows an example of the method of latching the opening edge part of a tubular molded object to the opening edge part of a preform, (a) shows the bending process by a jig | tool, (b) is engagement of a tubular molded object. It shows a stop state. It is a figure which shows an example of the tubular molded object which curved the opening part outside. It is a schematic side view of the tube-shaped molded object shape | molded in the connected state. It is a schematic sectional drawing which shows an example of the blow molding method of a tube-shaped molded object, and shows a parison extrusion process. It is a schematic sectional drawing which shows a parison sandwiching process. It is a schematic sectional drawing which shows the state after an air blow. It is a longitudinal cross-sectional view which shows typically the form of the parison in 1 piece blow molding. It is a cross-sectional view in the XX line of FIG. 5A. It is a longitudinal cross-sectional view which shows typically the form of the parison in two-piece blow molding. It is a cross-sectional view in the YY line of FIG. 5A.

  Hereinafter, an embodiment of a blow molding method to which the present invention is applied will be described with reference to the drawings.

  In the blow molding method of this embodiment, a composite container is produced by performing biaxial stretching blow in a state where a tubular molded body is stacked inside a preform. In order to produce a composite container by the blow molding method of this embodiment, first, a preform 1 made of a plastic material is prepared. Examples of the molding method of the preform 1 include injection molding using an injection molding machine and extrusion molding.

  As a constituent material of the preform 1, any thermoplastic resin may be used, and it may be appropriately selected according to the use and performance of the composite container. Specific examples of the thermoplastic resin include PE (polyethylene), PP (polypropylene), PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and the like.

  Further, the preform 1 can have a multilayer structure. For example, a two-layer preform, a product name nylon MXD6, a product name nylon MXD6 + fatty acid salt, PGA (polyglycolic acid), EVOH (ethylene vinyl alcohol copolymer) or PEN (polyethylene naphthalate), etc. It is also possible to form a preform composed of three or more layers having a resin having a property as an intermediate layer.

  Next, as shown in FIG. 1A, a tubular molded body 2 is mounted inside the preform 1. The tubular molded body 2 has a bottomed cylindrical shape as a whole, and includes a cylindrical body portion and a bottom portion closed by pinch-off.

  When the tubular molded body 2 is loaded, the tubular molded body 2 is mounted so as to overlap the entire inner surface of the preform 1 including the neck and mouth of the preform 1. A convex portion 1a such as a screw portion or a flange portion for screwing the cap onto the molded container may be formed at a position corresponding to the container mouth portion of the preform 1, but these screws are formed on the inner surface. Neither a part nor a flange part is projected and formed. Therefore, there is no problem in loading the tubular molded body 2 up to the neck or mouth of the preform 1.

  The tubular molded body 2 is molded in advance by blow molding, but the outer surface of the tubular molded body 2 should have a slightly higher roughness to reduce friction during loading. For example, if the blasting process etc. are given with respect to the cavity surface of the metal mold | die used when shape | molding the tubular molded object 2, the outer surface of the tubular molded object 2 can be made into a rough surface.

  Moreover, the tube-shaped molded object 2 can select a material, an additive, etc. suitably according to the functionality to provide. Examples of the functionality to be imparted include low adsorptivity, oxygen barrier properties, and light shielding properties. By using a cyclic polyolefin resin or the like as the molding material of the tubular molded body 2, low adsorptivity can be realized. . Alternatively, oxygen barrier properties can be imparted by using EVOH (ethylene vinyl alcohol copolymer) as a molding material of the tubular molded body 2. In order to impart light-shielding properties, a colorant, an ultraviolet absorber, or the like may be added to the molding material of the tubular molded body 2.

  Next, the preform 1 to which the tubular molded body 2 is attached is preheated and set in a molding die. What is necessary is just to set the temperature of preheating according to the constituent material of the preform 1, etc., for example, it is about 90 to 130 degreeC.

  After preheating, the preform 1 to which the tubular molded body 2 is attached is set in a mold. The mold has a cavity corresponding to the shape of the composite container to be molded, and the preform 1 and the tubular molded body 2 are blown into the preform 1 (tubular molded body 2) softened by heating. Is stretched and shaped into the cavity shape of the mold.

  Thereby, the composite container 10 in which the inner side of the container body 11 formed by stretching the preform 1 is covered with the coating layer 12 formed by stretching the tubular molded body 2 is molded. . In the composite container 10 to be produced, since the tubular molded body 2 is formed by blow molding, the manufacturing cost can be reduced as compared with the case where the tubular molded body 2 is injection molded. Moreover, the coating layer 12 is formed so as to cover even the neck and mouth of the composite container 10, and the functionality of the coating layer 12 can be imparted to the entire composite container 10.

  In the above-described blow molding, when biaxial stretching blow is performed in a state where the preform 1 and the tubular molded body 2 are overlapped, the opening end of the tubular molded body 2 is stretched as the tubular molded body 2 is stretched. May fall back into the preform 1. If the open end of the tubular molded body 2 is retracted, the entire inner surface of the preform 1 cannot be covered with the tubular molded body 2.

  In order to eliminate such an inconvenience, the biaxial stretching blow may be performed so that, for example, the opening end of the preform 1 is supported by the opening end of the preform 1. FIG. 2 shows an example of a process for supporting the open end of the tubular molded body 2 at the open end of the preform 1. In this example, the opening end 2a of the tubular molded body 2 is formed to extend from the opening end of the preform 1, and the shape of the opening end of the preform 1 is formed as shown in FIG. The open end 2a of the tube-shaped molded body 2 is folded back with the jig 20 having the combined recesses, and is subjected to staking. As a result, as shown in FIG. 2 (b), the top end of the opening end of the preform 1 is supported on the opening end 2 a of the folded tube-shaped body 2. Can be prevented from being drawn into the preform 1.

  When the opening end 2a of the tubular molded body 2 is folded as described above, it is preferable to mold the opening end 2a so as to curve outward when the tubular molded body 2 is molded. For example, as shown in FIG. 3, on the opening end side of the tubular molded body 2, the opening diameter is increased and the opening end 2 a is bent outward. Then, if it cut | disconnects in a dashed-dotted line position, it will become the shape which the opening edge part 2a of the tubular molded object 2 spreads outside, and the said return | folding will become easy.

  Moreover, it is also a preferable form to form an air vent hole 2b at the bottom of the tubular molded body 2 to be molded. If the air vent hole 2b is formed at the bottom of the tube-shaped molded body 2, air does not remain between the tube-shaped molded body 2 and the preform 1, so that the tube-shaped molded body 2 and the preform 1 are separated. Molded in close contact.

  Further, when blow-molding the tubular molded body 2, the molded body is formed by connecting a plurality of tubular molded bodies, and only the ends of the tubular molded bodies at both ends that are not connected are pinched off. Then, it is preferable to blow-mold a plurality of tubular molded bodies at once. As a result, it is possible to form a tube-shaped molded body having excellent thickness uniformity in the circumferential direction, and it is possible to improve the reliability of a composite container molded using the tube-shaped molded body.

  That is, in the blow-molding method of a tubular molded body, a plurality of tubular molded bodies are combined so as to be connected in series in a so-called multiple-piece state, and blow molding is performed. The number of tube-shaped molded bodies formed at one time may be two or three, and may be four or more. However, the larger the number of tube-shaped molded bodies formed at one time, the larger the mold. It is necessary to make it. Moreover, when shape | molding 3 or more collectively, each tube-shaped molded object is limited to what has both ends open | released as a shape. Therefore, the number of molded bodies to be molded at a time may be appropriately set according to the required shape of the tubular molded body, the scale of equipment, and the like.

  Below, the case where two tube-shaped molded objects are formed collectively will be described as an example. In the case of taking two pieces, it is assumed that two tubular molded bodies are connected at one end side, and only the end portion of each tubular molded body that is not connected is pinched off to bundle the two tubular molded bodies together. Blow molding. That is, the parison is sandwiched between the molds only at the end portion of each tubular molded body that is not connected, but the parison is not sandwiched between the molds at other portions.

  FIG. 4 shows the form of the molded body 31 to be molded. The molded body 31 molded in this example has a form in which two tubular molded bodies 32 and 33 are connected in series. Each of the tubular molded bodies 32 and 33 is formed by being integrally connected to each other via a connecting portion 34 with one end side being closed by pinch-off portions 32a and 33a and the other end side being opened. Yes. In addition, as a form of each tube-shaped molded object 32 and 33, as shown, for example in FIG. 3, the shape by which the opening edge part was curved outward may be sufficient.

  The connecting portion 34 that connects the tubular molded bodies 32 and 33 is formed with a diameter slightly smaller than the diameter of the body of each tubular molded body 32 and 33. Here, the diameter of the connecting portion 34 is set to be smaller than the diameter of the body portion of the tubular molded bodies 32 and 33. The blowing needle is installed at this position, and the blow needle is inserted into the parison during blow molding. This is for smooth insertion.

  Next, a blow molding method of the molded body of FIG. 5 will be described. In order to blow-mold the molded body 31, as shown in FIG. 5A, a cylindrical parison 41 is extruded from a die of an extruder 42, and is sandwiched between a pair of split molds 43 and 44 as shown in FIG. 5B.

  As described above, the parison 41 is formed by extruding the melt-kneaded raw material resin from the die of the extruder 42. As the raw material resin, any thermoplastic resin can be used. For example, polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polyamide resins such as nylon under the trade name, ethylene-vinyl alcohol resins excellent in gas barrier properties, etc. Of course, but not limited thereto, What is necessary is just to select suitably from various resin according to the use of the preform covers 2 and 3, a required performance, a function, etc. In addition, various additives such as a colorant, a light-shielding agent, an ultraviolet absorber, and a lubricant, a filler, and the like can be added to the raw material resin, and the performance required for the tubular molded bodies 32 and 33 is also achieved. The material to be added may be appropriately selected depending on the function and the like.

  The split molds 43 and 44 have two cavities 43a and 44a respectively corresponding to the shapes of the tube-shaped molded bodies 32 and 33, and the cavities 43a and 44a corresponding to the shapes of the tube-shaped molded bodies 32 and 33, respectively. Projections 43b and 44b for forming a slightly small-diameter connecting portion 34 are formed between the two. Further, pinch-off portions 43c and 44c are provided at the ends of the cavities 43a and 44a opposite to the side connected by the connecting portion 34. When the divided molds 43 and 44 are brought into contact with each other, the pinch-off portions 43c and 44c come into contact with each other, and both ends of the parison 41 are crushed to be closed.

  As shown in FIG. 5B, after the mold is closed and the parison 41 is sandwiched between the pair of split dies 43 and 44, the blowing needle 45 is inserted into the parison 41 at the protrusion 43b corresponding to the connecting portion 34, and the air blow I do. In the protrusion 43 b corresponding to the connecting portion 34, the distance between the parison 41 and the split mold 43 is greater than the distance between the parison 41 and the split mold 43 in the cavities 43 a and 44 a according to the shape of the tubular molded bodies 32 and 33. The blowing needle 45 can be easily inserted into the parison 41.

  When blowing air, it is necessary to insert the blowing needle 45 in a state where the parison 41 is brought into close contact with the mold by vacuum suction. When the parison 41 is attracted to the mold and is not in close contact, that is, when the parison 41 is separated from the mold, it is difficult to insert the blowing needle 45 into the parison 41. Therefore, in order to quickly attract the parison 41 to the mold, it is advantageous that the distance between the parison 41 and the mold is small. By setting the connecting portion 34 to have a diameter smaller than the diameter of the body portion of the tubular molded bodies 32 and 33, the mold portion corresponding to the connecting portion 34 is protruded from the mold portion corresponding to the body portion. As a result, the mold part corresponding to the connecting portion 34 and the parison 41 come close to each other.

  The inner diameter of the mold part corresponding to the connecting portion 34 is preferably substantially equal to the outer diameter of the extruded parison. Specifically, the inner diameter of the mold part is 0 to 2 mm from the outer diameter of the parison. It is preferable. In order to surely prevent the parison from being caught in the mold part, the inner diameter of the part is preferably larger than the outer diameter of the parison by 0.5 mm or more.

  In this example, the blowing needle 45 is installed in the protruding portion 43b which is a mold portion protruding corresponding to the connecting portion 34, and the blowing needle 45 is inserted into the parison 41 and air blown. For example, the blowing needle 45 is installed on the protruding portion 43 b and a vacuum suction hole is provided around the blowing needle 45. When the blowing needle 45 is inserted into the parison 41, vacuum suction is performed through these vacuum suction holes. By this vacuum suction, the parison 41 is attracted to the mold (projecting portion 43b). Since the distance between the protrusion 43b and the parison 41 is short, the parison 41 is quickly attracted to and closely contacts the protrusion 43b. Therefore, the blowing needle 45 can be smoothly inserted into the parison 41.

  In addition, not only when providing the needle hole for projecting the blowing needle 45 in the protruding portion 43b which is a mold portion protruding corresponding to the connecting portion 34, a concave portion is locally provided in the protruding portion 43b. A needle hole may be provided in the recess, and a plurality of suction holes for sucking the parison may be arranged around the needle hole in the recess so as to surround the needle hole. For example, the protrusion 13b has a circular shape with a diameter of about 4 to 6 mm and a concave portion with a depth of about 2 to 4 mm, a needle hole with a diameter of 2 to 3 mm at the center of the concave portion, and a 45 ° angle around the needle hole. Eight suction holes may be arranged around the needle hole at intervals. In this case, when the periphery of the concave portion is close to the parison, when the parison is sucked by the suction hole in the concave portion, the parison partially enters the concave portion, and the parison can be firmly held in the portion where the parison has entered. Thereby, the blowing needle 45 can be more reliably inserted into the parison 41.

  As shown in FIG. 5C, the parison 41 is pressed against the inner walls of the cavities 43a and 44a of the split molds 43 and 44 by air blowing by the blowing needle 45, and is formed into the cavities 43a and 44a. Next, the mold is opened and the molded body is taken out. The molded body to be molded is as shown in FIG. The molded body 31 taken out is cut at the position of the broken line in FIG. 4 and separated into individual tubular molded bodies 32 and 33.

  Hereinafter, the reason why the thicknesses of the tubular molded bodies 32 and 33 are made uniform when the blow molding method shown in FIG. 5 is adopted for blow molding of the tubular molded body will be described.

  FIG. 6A and FIG. 6B show the form of the parison 41 in blow molding in which a tubular molded body is so-called one piece. In the single blow molding, the cavities 51a and 52a are formed in the divided dies 51 and 52 corresponding to one tubular molded body, and pinch-off portions 51b and 52b are provided at both ends thereof. It has been.

  When one is taken, as shown in FIG. 6A, pinch-off portions 51b and 52b are provided on both sides of the tubular molded body (ie, cavities 51a and 52a), and the distance L1 between the pinch-off portions 51b and 52b is small. In the pinch-off portions 51b and 52b, a large force is applied to the parison 41 during biting, causing deformation of the parison 41. However, when the distance L1 is small, the influence reaches the entire tubular molded body.

  FIG. 6B shows a cross section of the parison 41 when sandwiched between the split molds 51 and 52. The parison 41 is flattened by the influence of the pinch-off portions 51b and 52b provided on both sides of the cavities 51a and 52a. The phenomenon of being crushed is seen. If the parison 41 is flattened, the parison 41 is not uniformly stretched when air blown, and the variation in thickness particularly in the circumferential direction increases.

  On the other hand, when so-called two-piece blow molding is performed as in the blow molding method of this example, as shown in FIG. 7A, in the two cavities 43a and 44a provided on the side not connected to each other. The pinch-off parts 43c and 44c are provided only at the end part, that is, the end part opposite to the side on which the projecting parts 43b and 44b for forming the connecting part 34 are formed. Accordingly, only the ends on both sides of the two tubular molded bodies that are far apart are pinched off (burr biting), and the connecting portion 34 is not pinched off.

  Here, the distance L2 between the pinch-off portions 43c and 44c at both ends is approximately twice as large as that in the case of the previous single piece picking, and the influence of the biting off at the pinch-off portions 43c and 44c is greatly reduced. As a result, as shown in FIG. 7B, the cross-sectional shape of the parison 41 sandwiched between the split molds 43 and 44 is nearly circular. If the parison 41 is circular, it is stretched evenly in all directions during air blowing and is formed with a uniform thickness.

  The tubular molded bodies 32 and 33 molded by the blow molding method of this example of such a mold design are excellent in thickness uniformity in the circumferential direction, and are used for high-quality composites. It is possible to produce a container.

  As described above, the blow molding method of the present invention performs biaxial stretching blow in a state in which a tubular molded body is stacked on the inner side of a preform, and this can impart functionality to the entire inner surface of the container. is there. In addition, a so-called delamination container can be easily produced.

  As mentioned above, although embodiment which applied this invention has been described, it cannot be overemphasized that this invention is not what is limited to the above-mentioned embodiment, In the range which does not deviate from the summary of this invention, a various change can be added. Is possible.

DESCRIPTION OF SYMBOLS 1 Preform 2 Tube-shaped molded object 2a Opening end part 31 Molded object 32, 33 Tube-shaped molded object 34 Connection part 41 Parison 43, 44 Split mold 43a, 44a Cavity 43b, 44b Projection part 43c, 44c Pinch-off part 45 Blow-in needle

Claims (4)

  A tube-shaped molded body that has been blow-molded in advance is loaded inside a preform that has been injection-molded in advance, and a biaxially stretched blow molding is performed in a state where the tube-shaped molded body is stacked on the inside of the preform. A blow molding method characterized by: Wherein upon loading the tubular shaped body, a blow molding method according to claim 1, wherein the engaging the open end of the tubular shaped body at the open end of the folded outwardly the preform.   3. The blow molding method according to claim 2, wherein when forming the tubular molded body, the opening end portion is bent outward so as to enlarge an opening diameter at the opening end portion.   The tube-shaped molded body has a form in which a plurality of tube-shaped molded bodies are connected, and only the ends of the tube-shaped molded bodies at both ends that are not connected are pinched off to collectively form the plurality of tube-shaped molded bodies. The blow molding method according to any one of claims 1 to 3, wherein the blow molding is performed.

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