JP6876935B2 - Double container molding method - Google Patents

Description

The present invention relates to a method for forming a double container in which an outer layer and an inner layer are combined to perform biaxial stretching blow, and more particularly to a technique for forming a through hole in the outer layer.

As a molding method for a plastic container (bottle), a blow molding method is widely used. An injection-molded preform is set in a mold, and air is blown into the mold to form the shape of the mold cavity. Axial stretch blow molding methods and the like are 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 gas barrier property, light shielding property, heat retention property, etc. are required, the material used is made to have gas barrier property, or a colorant or an ultraviolet absorber is added to a plastic material.

However, there is a limit to the device of the material, and various functions are given by making the plastic container multi-layered. By optimizing the constituent materials of each layer, it is expected that a plastic container having multiple functions, such as a light-shielding container having excellent gas barrier properties, can be realized.

In order to mold a multi-layer plastic container, it is considered that a multi-layer preform is injection-molded and then blow-molded, and various molding methods for the multi-layer preform have been proposed. However, molding of a multi-layer preform requires advanced technology, and a large amount of capital investment is required for the molding apparatus, and there are problems in terms of cost and the like.

Under such circumstances, it has been proposed to attach a separately molded preform cover to the outside of the preform and blow-mold it to form a composite container (see Patent Document 1 and Patent Document 2 and the like). ). By using the preform cover, it is not necessary to mold the multi-layer preform, which is considered to lead to cost reduction and the like.

In Patent Document 1, an outer shrinking member is provided on the outside of the preform, and a composite preform having the preform and the outer shrinking member in close contact with the outside of the preform is produced, and the composite preform is formed in a blow molding mold. A blow molding method is disclosed in which a preform of a composite preform and an outer shrinking member are integrally expanded by performing blow molding on the reform. By forming the outer shrinking member from, for example, a material having a gas barrier property or a light ray barrier property, it is possible to mold a composite container to which these functions are imparted.

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

Japanese Unexamined Patent Publication No. 2015-9493 Japanese Unexamined Patent Publication No. 2015-9487

In recent years, a double container (so-called laminated peeling container) in which the inner layer container shrinks with the discharge of the contents and the outer layer container maintains the shape has been proposed, and a multi-layer preform, a preform and an outer layer member, and an inner layer member have been proposed. It has been studied to form this kind of double container by blow molding in combination with each other.

In this case, it is necessary to form an air introduction hole in the outer layer container for introducing air between the inner layer container and the outer layer container, but it is necessary to study how to form the air introduction hole. For example, in order to obtain a highly transparent container, it is necessary to use polyethylene terephthalate or the like for the outer layer container, but since polyethylene terephthalate is a hard material, it is difficult to make a hole only in the outer layer container after blow molding.

When the multi-layer preform is blow-molded to form the above-mentioned double container, a technique of forming a through hole in the outer layer of the multi-layer preform and using this as an air introduction hole is also known. If the through hole is formed before, it is difficult to control the size and shape of the through hole, and the shape of the double container itself to be molded may be adversely affected. There is a problem that the shape of the heavy container becomes unclear.

The present invention has been proposed in view of such conventional circumstances, and a double container such as a laminated peeling container can be easily manufactured, and an air introduction hole having a predetermined shape can be used for molding the container. It is an object of the present invention to provide a method for forming a double container which can be formed without adversely affecting it.

In order to achieve the above-mentioned object, the method for forming a double container of the present invention is a method for forming a double container in which an outer layer and an inner layer are overlapped and biaxially stretch blow molding is performed . It is characterized in that a notch for cutting up to the middle position is made and a through hole is formed after biaxial stretching blow molding.

If a through hole is formed in the outer layer in advance and blow molding is performed in that state, the shape of the final through hole tends to be unclear. Further, if the through holes are formed in advance and blow molding is performed, the molding of the container is also adversely affected. In the present invention, a notch is made in the outer layer so that the notch is stretched to be in a penetrating state in the process of biaxial stretching blow molding, so that the shape of the through hole becomes clear, which affects the molding of the container. The impact is also minimized.

According to the method for molding a double container of the present invention, a double container such as a laminated peeling container can be easily manufactured, and an air introduction hole having a predetermined shape is formed without adversely affecting the molding of the container. It is possible.

It shows an example of the manufacturing process of a composite container, and is the schematic perspective view which shows the process of attaching a tubular molded body to a preform. It is the schematic cross-sectional view which shows the state which the tubular molded body is loaded in the preform. It is the schematic sectional drawing which shows the molded composite container with a part enlarged view. It is a figure which shows an example of the method of locking the open end of a tubular molded body with the open end of a preform, (a) shows the bending process by a jig, and (b) is the engagement of a tubular molded body. It indicates a stopped state. It is a schematic side view of the tubular molded body molded in a connected state. It shows an example of the blow molding method of a tubular molded body, and is the schematic cross-sectional view which shows the parison extrusion process. It is the schematic sectional drawing which shows the parison sandwiching process. It is schematic cross-sectional view which shows the state after air blow. It is a vertical cross-sectional view which shows typically the form of the parison in the blow molding of one piece. 6 is a cross-sectional view taken along the line XX of FIG. 6A. It is a vertical cross-sectional view which shows typically the form of the parison in the blow molding of two pieces. 6 is a cross-sectional view taken along the line YY of FIG. 6A.

Hereinafter, embodiments of a method for forming a double container to which the present invention is applied will be described with reference to the drawings.

In the method for forming a double container of the present embodiment, a double container is produced by performing biaxial stretching blow with a tubular molded body stacked inside the preform. In order to produce a double container by the molding method of the present 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, extrusion molding, and the like.

Examples of the constituent material of the preform 1 include any thermoplastic resin, which may be appropriately selected depending on 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.

It is also possible to form the preform 1 in a multi-layer structure. For example, two-layer preform, gas barrier properties such as brand name nylon MXD6, trade name nylon MXD6 + fatty acid salt, PGA (polyglycolic acid), EVOH (ethylene vinyl alcohol copolymer) or PEN (polyethylene naphthalate), and light shielding. It is also possible to make a preform composed of three or more layers having a property resin as an intermediate layer.

In the case of a so-called laminated peeling container, it is necessary to form an air introduction hole in the outer layer, and in the present embodiment, a circular notch 3 is made at the formation position of the air introduction hole in the above-mentioned preform 1. This notch 3 cuts up to the middle position of the thickness of the preform 1 which is the outer layer, and by leaving the uncut portion, the region inside the notch 3 is combined with the preform 1 at this stage. It is maintained in a state.

Next, as shown in FIG. 2, the tubular molded body 2 is mounted inside the preform 1. The tubular molded body 2 has a bottomed cylindrical shape as a whole, and has 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 portion and the mouth portion of the preform 1. Convex portions 1a such as a screw portion and a flange portion for screwing the cap into the molded container may be formed at a position corresponding to the container mouth portion of the preform 1, and these screws are formed on the inner surface. No portion or flange portion is formed so as to protrude. Therefore, there is no problem in loading the tubular molded body 2 into the neck and mouth of the preform 1.

The tubular molded body 2 is molded in advance by blow molding, but the outer surface thereof should have a slightly higher roughness in order to reduce friction during loading. For example, if the cavity surface of the mold used for molding the tubular molded body 2 is subjected to a blast treatment or the like, the outer surface of the tubular molded body 2 can be made a rough surface.

Further, for the tubular molded body 2, the material, additives and the like can be appropriately selected according to the functionality to be imparted. Examples of the functionality to be imparted include low adsorptivity, oxygen barrier property, light-shielding property, and the like, and low adsorptivity can be realized by using a cyclic polyolefin resin or the like as a molding material for the tubular molded body 2. .. Alternatively, by using EVOH (ethylene vinyl alcohol copolymer) as the molding material for the tubular molded body 2, oxygen barrier properties can be imparted. In order to impart light-shielding properties, a coloring material, an ultraviolet absorber, or the like may be added to the molding material of the tubular molded body 2. If the innermost layer is EVOH, it is possible to prevent the adsorption of citrus components.

The ratio of the thickness of the preform 1 to be the outer layer and the tubular molded body 2 to be the inner layer is, for example, outer layer / inner layer = 90 to 80% / 10 to 20%.

Next, the preform 1 to which the tubular molded body 2 is mounted is preheated and set in the molding die. The temperature of the preheating may be set to an appropriate temperature according to the constituent materials of the preform 1, for example, about 90 ° C to 130 ° C.

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

As a result, a double container 10 is formed in which the inside of the container body 11 formed by stretching the preform 1 is covered with a coating layer 12 formed by stretching the tubular molded body 2. To. In the double container 10 to be manufactured, 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. .. Further, the coating layer 12 is formed so as to cover the neck and the mouth of the double container 10, and the functionality of the coating layer 12 can be imparted to the entire double container 10, and the coating layer 12 is the content. It can be a laminated peeling type double container that shrinks when an object is discharged.

In the blow molding, the uncut portion of the circular notch 3 is also stretched along with the stretching of the preform 1, and after molding, this uncut portion is also in a cut state, and the cut pieces in the notch 3 fall off. , A through hole 13 is formed corresponding to the notch 3. By using this through hole 13 as an air introduction hole, air is introduced between the outer layer (container body 11) and the inner layer (coating layer 12), and the inner layer (coating layer 12) contracts as the contents are discharged. On the other hand, after discharging, the outer layer (container body 11) returns to its original shape.

A through hole 13 is formed in a clear shape by making a notch 3 in the preform 1 as in the present embodiment and stretching it by blow molding to bring it into a penetrating state. Generally, if a hole is opened during molding, the shape becomes unclear. However, in the molding method of the present embodiment, since the tubular molded body 2 which is the inner layer is in contact, the through hole 13 having the same shape as the mold is formed. Is obtained. Further, the influence of the formation of the through hole 13 on the molding of the double container 10 can be suppressed.

In the above-mentioned blow molding, when the biaxial stretching blow is performed with the preform 1 and the tubular molded body 2 overlapped with each other, the open end portion of the tubular molded body 2 accompanies the stretching of the tubular molded body 2. May recede into 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 inconvenience, in the case of biaxial stretching blow, for example, the open end of the preform 1 may be stacked so as to support the open end of the tubular molded body 2. FIG. 4 shows an example of a process for supporting the open end of the tubular molded body 2 with the open end of the preform 1. In this example, the open end 2a of the tubular molded body 2 is formed by extending from the open end of the preform 1, and as shown in FIG. 4A, the shape of the open end of the preform 1 is formed. The open end 2a of the tubular molded body 2 is folded back with a jig 20 having the combined recesses to perform habit. As a result, as shown in FIG. 4B, the top surface of the open end portion of the preform 1 supports the open end portion 2a of the folded tubular molded body 2, and the tubular molded body 2 is formed. It is possible to prevent the open end portion 2a of the above from being drawn into the preform 1.

Further, when the tubular molded body 2 is blow-molded, the form of the molded body is a form in which a plurality of tubular molded bodies are connected, and only the ends of the tubular molded bodies on both ends on the non-connected side are pinched off. Then, it is preferable to blow-mold a plurality of tubular molded bodies at once. As a result, a tubular molded product having excellent thickness uniformity in the circumferential direction can be molded, and the reliability of the composite container molded using the tubular molded product can be improved.

That is, in the blow molding method of a tubular molded body, a plurality of tubular molded bodies are joined so as to be connected in series in a so-called multiple-taken state, and blow molding is performed. The number of tube-shaped molded bodies to be molded in a batch may be two or three, and four or more can be used. However, the larger the number of tube-shaped molded bodies to be molded in a batch, the larger the mold. It is necessary to make it. Further, when three or more pieces are molded at once, the shape of each tubular molded body is limited to those in which both ends are open. Therefore, the number of molded bodies to be molded at once may be appropriately set according to the required shape of the tubular molded body, the scale of the equipment, and the like.

In the following, a case where two tubular molded bodies are collectively formed will be described as an example. In the case of two pieces, the two tubular molded bodies are connected at one end side, and only the end portion of each tubular molded body on the unconnected side is pinched off to collectively combine the two tubular molded bodies. Blow molding. That is, the parison is sandwiched between the molds only at the end portion of each tubular molded product on the unconnected side, but the parison is not sandwiched between the molds at other parts.

FIG. 5 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 a pinch-off portion 32a and 33a and being closed and the other end side being open. There is.

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 portion of each of the tubular molded bodies 32 and 33. Here, the diameter of the connecting portion 34 is set to be smaller than the diameter of the body portions of the tubular molded bodies 32 and 33 by installing the blowing needle at this position, and during blow molding, the blowing needle to the parison is set. This is for smooth insertion.

Next, a blow molding method for the molded product of FIG. 6 will be described. To blow-mold the molded body 31, as shown in FIG. 6A, the cylindrical parison 41 is extruded from the die of the extruder 42 and sandwiched between a pair of split dies 43 and 44 as shown in FIG. 6B.

As described above, the parison 41 is formed by extruding the melt-kneaded raw material resin from the die of the extruder 42, and any thermoplastic resin can be used as the raw material resin. For example, polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, polyamide resins such as trade name nylon, and ethylene-vinyl alcohol resins having excellent gas barrier properties are not limited to these, of course. It may be appropriately selected from various resins according to the performance, function and the like required for the tubular molded body 2.

The split dies 43 and 44 have two cavities 43a and 44a corresponding to the shapes of the tubular molded bodies 32 and 33, respectively, and the cavities 43a and 44a corresponding to the shapes of the tubular molded bodies 32 and 33. Protruding portions 43b and 44b for forming a connecting portion 34 having a slightly smaller diameter are formed between them. Further, pinch-off portions 43c and 44c are provided at the ends of the cavities 43a and 44a on the side opposite to the side connected by the connecting portions 34. When the split dies 43 and 44 are butted against each other, the pinch-off portions 43c and 44c abut and both ends of the parison 41 are crushed to form a closed state.

As shown in FIG. 6B, the mold is closed, the parison 41 is sandwiched between the pair of split molds 43 and 44, and then the blow needle 45 is inserted into the parison 41 at the protruding portion 43b corresponding to the connecting portion 34 to blow air. I do. In the protruding portion 43b corresponding to the connecting portion 34, the distance between the parison 41 and the split mold 43 is larger than the distance between the parison 41 and the split mold 43 in the cavities 43a and 44a according to the shapes of the tubular molded bodies 32 and 33. Is also small, and the blow needle 45 can be easily inserted into the parison 41.

When blowing air, it is necessary to insert the blowing needle 45 with the parison 41 in close contact with the mold by vacuum suction. It is difficult to insert the blow needle 45 into the parison 41 when the parison 41 is attracted to the mold and is not in close contact with the mold, that is, when the parison 41 is separated from the mold. 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 making the connecting portion 34 a diameter smaller than the diameter of the body portions of the tubular molded bodies 32 and 33, the mold portion corresponding to the connecting portion 34 is projected more than the mold portion corresponding to the body portion. As a result, the mold portion corresponding to the connecting portion 34 and the parison 41 come close to each other.

The inner diameter of the mold portion corresponding to the connecting portion 34 is preferably substantially equal to the outer diameter of the extruded parison, and specifically, the inner diameter of the mold portion is 0 to 2 mm larger than the outer diameter of the parison. Is preferable. In order to prevent the parison from being pinched in the mold portion, it is preferable that the inner diameter of the portion is 0.5 mm or more larger than the outer diameter of the parison.

In this example, the blowing needle 45 is installed in the protruding portion 43b, which is the protruding mold portion 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 in the protruding portion 43b, 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. This vacuum suction attracts the parison 41 to the mold (protruding portion 43b). Since the distance between the protrusion 43b and the parison 41 is short, the parison 41 is quickly attracted to the protrusion 43b and comes into close contact with the protrusion 43b. Therefore, the blowing needle 45 can be smoothly inserted into the parison 41.

It should be noted that not only when a needle hole for projecting the blowing needle 45 is provided in the projecting portion 43b which is a protruding mold portion corresponding to the connecting portion 34, a recess is locally provided in the projecting portion 43b. A needle hole may be provided in the recess, and a plurality of suction holes for sucking the parison may be arranged side by side so as to surround the needle hole around the needle hole in the recess. For example, the protruding portion 13b is provided with a circular recess having a diameter of about 4 to 6 mm and a depth of about 2 to 4 mm, a needle hole having a diameter of 2 to 3 mm is provided in the center of the recess, and the needle hole is 45 ° around the center. Eight suction holes may be arranged around the needle holes at intervals. In this case, since the periphery of the recess is close to the parison, when the parison is sucked through the suction hole in the recess, the parison partially enters the recess, and the parison can be firmly held in the inserted portion. As a result, the blowing needle 45 can be more reliably inserted into the parison 41.

As shown in FIG. 6C, the parison 41 is pressed against the inner walls of the cavities 43a and 44a of the split dies 43 and 44 by the air blow by the blowing needle 45, and is formed into the shapes of the cavities 43a and 44a. Next, the mold is opened and the molded product is taken out. The molded body to be molded is as shown in FIG. The taken-out molded body 31 is cut at the position of the broken line in FIG. 5 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. 6 is adopted for the blow molding of the tubular molded body will be described.

7A and 7B show the form of the parison 41 in blow molding in which the tubular molded body is a so-called single piece. In single-piece blow molding, one cavity 51a, 52a is formed in the split dies 51, 52 corresponding to one tubular molded body, and pinch-off portions 51b, 52b are provided at both ends thereof. Has been done.

When one piece is taken, as shown in FIG. 7A, the pinch-off portions 51b and 52b are provided on both sides of the tubular molded body (that is, the cavities 51a and 52a), and the distance L1 between the pinch-off portions 51b and 52b is increased. small. In the pinch-off portions 51b and 52b, a large force is applied to the parison 41 at the time of cutting off, which causes deformation of the parison 41. However, when the distance L1 is small, the influence extends to the entire tubular molded body.

FIG. 7B shows a cross section of the parison 41 when it is sandwiched between the split dies 51 and 52, and the parison 41 becomes flat due to the influence of the pinch-off portions 51b and 52b provided on both sides of the cavities 51a and 52a. The phenomenon of crushing can be seen. If the parison 41 is flattened, it will not be uniformly stretched when air blown, and the thickness variation in the circumferential direction will be large.

On the other hand, in the case of blow molding by so-called two-piece molding as in the blow molding method of this example, as shown in FIG. 8A, in the cavities 43a and 44a provided in two, the sides not connected to each other are on the side. The pinch-off portions 43c and 44c are provided only at the end portion, that is, the end portion on the side opposite to the side on which the projecting portions 43b and 44b for forming the connecting portion 34 are formed. Therefore, only the ends on both sides of the two tubular molded bodies that are far apart are pinched off (burrs), 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 doubled as compared with the case of the previous single picking, and the influence of the pinch-off portions 43c and 44c being cut off is greatly reduced. As a result, as shown in FIG. 8B, the cross-sectional shape of the parison 41 sandwiched between the split dies 43 and 44 is close to a circle. If the parison 41 is circular, it is evenly stretched in all directions during air blow and molded to a uniform thickness.

The tubular molded bodies 32 and 33 molded by the blow molding method of this example of the mold design are excellent in thickness uniformity in the circumferential direction, and a high-quality composite is made by utilizing this. It is possible to manufacture containers.

In the method for forming a double container of the present invention, as described above, a biaxially stretched blow is performed with a tubular molded body stacked inside the preform, whereby a so-called laminated peeling container can be easily produced. It is possible. In addition, an atmospheric insertion hole can be easily formed.

Although the embodiments to which the present invention is applied have been described above, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. It is possible. For example, the present invention can be applied to a method for forming a double container in which both the outer layer and the inner layer are injection-molded as a preform, and further, the double layer by a multi-layer preform in which the outer layer and the inner layer are integrally molded. It can also be applied to the method of molding a container.

1 Preform 2 Tube-shaped molded body 2a Open end 3 Notch 10 Double container 11 Container body 12 Coating layer 13 Through hole (atmosphere introduction hole)
31 Molded body 32, 33 Tube-shaped molded body 34 Connecting part 41 Parison 43,44 Divided mold 43a, 44a Cavity 43b, 44b Protruding part 43c, 44c Pinch-off part 45 Blowing needle

Claims (3)

This is a method for forming a double container in which biaxial stretching blow molding is performed with the outer layer and the inner layer overlapped.
A method for forming a double container, characterized in that a notch is made to cut up to an intermediate position in the thickness of the outer layer, and a through hole is formed after biaxial stretching blow molding. The method for molding a double container according to claim 1, wherein the outer layer is an injection-molded preform, and the inner layer is a blow-molded tubular molded body. The tubular molded body has a form in which a plurality of tubular molded bodies are connected, and only the ends of the tubular molded bodies on both ends on the non-connected side are pinched off to collectively combine the plurality of tubular molded bodies. The method for molding a double container according to claim 2, wherein the double container is blow-molded.

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