JP7131122B2 - Preform, preform manufacturing method and plastic bottle manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a preform, a method for manufacturing a preform, and a method for manufacturing a plastic bottle, and more particularly to a method for manufacturing a multilayer plastic bottle, a preform, and a method for manufacturing a preform.

Plastic bottles, especially PET (PolyEthylene Terephthalate) bottles, are often used as containers for beverages and the like. The market for multi-layered bottles laminated with other materials to compensate for the lack of functionality in polyethylene terephthalate, which is the base material of PET bottles, is also expanding.

Patent Document 1 discloses a low-crystalline ethylene terephthalate having inner and outer layers made of an ethylene terephthalate-based polyester resin and at least one intermediate layer made of at least a low-crystalline ethylene terephthalate-based polyester resin and an aromatic polyamide-based gas barrier resin. A multi-layer preform is disclosed in which the polyester resin contains 7.5 to 15 mol % of isophthalic acid in the dicarboxylic acid component and the haze of the portion where the multi-layer structure is formed is 5% or more. Further, Patent Literature 1 discloses a multilayer stretch blow molded container obtained by biaxially stretch blow molding a multilayer preform and having a body portion haze of 3% or less.

JP 2015-157469 A JP-A-1-254539 Japanese Unexamined Patent Application Publication No. 2010-12605

According to Patent Document 1, by forming the inner and outer layers from a crystalline ethylene terephthalate-based polyester resin, it is possible to impart a uniform draw ratio to the intermediate layer using a low-crystalline polyester resin with poor stretching properties. It is said that it is possible to provide a multilayer stretch blow molded container having excellent mechanical strength. Further, it is said that the multilayer stretch-blown container obtained from the multilayer preform of Patent Document 1 can prevent delamination due to drop impact or the like.

Patent Document 2 discloses a preform obtained by using a co-injection method, in which the mouth and bottom of the preform are substantially made of polyester, and the rest of the preform is made of a laminate of polyester inner and outer layers and a gas-barrier thermoplastic resin. is disclosed. Furthermore, by removing the gas-barrier thermoplastic resin layer from the mouth portion and the center portion of the bottom portion and forming these portions from a single layer of polyester, these portions can be sufficiently thermally crystallized, and the hot water It is said that deformation and expansion of these parts can be almost completely suppressed during sterilization or sterilization.

Patent Document 3 describes a test-tube-shaped synthetic resin laminated preform in which at least one intermediate layer is laminated on a base layer made of a main material resin, and the mouth part and the bottom are areas where the intermediate layer is not laminated. It is said that it is possible to effectively prevent the problem of impairing the sealing performance of the cap at the neck portion or impairing the uprightness of the bottle at the bottom.

However, when the gas-barrier intermediate layer is applied to the upper end of the drinking spout of the mouth portion, there is a problem that cracks occur and it is not suitable for drinking. Also, when an intermediate layer is applied to the bottom surface, there is also the problem that cracks are likely to occur. Another reason is that since the bottom surface is relatively thick due to the low stretching ratio, the gas barrier intermediate layer is unnecessary.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a low-cost preform that has a gas barrier property in the body, a method for manufacturing the preform, and a method for manufacturing a plastic bottle by blow-molding the preform. to do.

In order to solve the above problems, the present invention provides an annular support ring having a mouth, a body, and a bottom, projecting outward from the mouth, and an annular support ring projecting outward above the support ring. In the multi-layered preform having a turnip of , the intermediate layer starts from a position 10 mm from the upper end of the mouth, to a position 3 to 20 mm from the bottom, and from a position intermediate between the support ring and the turnip to the body surrounded by and continuously provided with a substrate layer in the intermediate layer is a mixed material of nylon and a metal complex, and the ratio of the nylon and the metal complex is from 11:1 to 20:1 characterized by

Further, the intermediate layer is characterized by having gas barrier properties.

Further, the weight of the intermediate layer is 2% to 7% by weight with respect to the weight of the entire preform.

Furthermore, the present invention provides a preform manufacturing method according to the present invention, which is a preform manufacturing method by co-injection molding in which one material is injected and another material is injected, wherein the first molding material is injected at the start of injection. to the end of injection, and after the start of injection of the first molding material, the second molding material is injected for a predetermined time, and the second molding material is injected into the first molding material. It is characterized by being sandwiched between molding materials and injected.

Furthermore, there is provided a method for manufacturing a plastic bottle, characterized by molding the preform described above by blow molding.

The present invention is a multi-layered preform having a mouth portion, a body portion and a bottom portion, and having an annular support ring projecting outward from the mouth portion and an annular turnip projecting outward above the support ring. , the intermediate layer is surrounded by the base material layer in the body from the intermediate position between the support ring and the turnip, and is provided continuously from the position 10 mm from the top of the mouth to the position 3 to 20 mm from the bottom. , the intermediate layer is a mixed material of nylon and metal complex, characterized in that the ratio of nylon and metal complex is from 11:1 to 20:1, so that there is no intermediate layer at the mouth and bottom, It is possible to provide a plastic bottle in which cracks do not occur in each of these portions. In this way, the intermediate layer is applied to the portion to be stretched during blow molding, but the injection molding method described later provides an excellent preform that is less likely to lose its shape due to unevenness of the material during stretching. can be done.

In addition, since the intermediate layer is characterized by having gas barrier properties, it is possible to prevent oxidation and reduction of carbon dioxide in beverages and the like contained in the plastic bottle, and to provide a plastic bottle having excellent storability. can be done.

Furthermore, with such a configuration, the intermediate layer is not exposed on the mouth surface. In other words, the top surface is covered with the base material layer, and the intermediate layer is provided from a position separated from the top surface by 5 to 20 mm toward the bottom. With such a configuration, when the preform of the present invention is molded into a plastic bottle, a safe plastic bottle for beverages can be obtained.
In addition, by adopting a configuration in which the top surface is covered with the base material layer, peeling of the base layer and the intermediate layer can be prevented more than when the intermediate layer is exposed on the top surface of the mouth. When the mouth part is detached due to an impact or the like on the mouth part, for example, when the preform of the present invention is used for a PET bottle for beverages, the mouth part comes into contact with a person's mouth. From this, it is possible to provide a preform that is the basis of a safer plastic bottle by adopting a structure in which the base material layer covers the mouth surface.

In addition, since the maximum value of the intermediate layer at the mouth of 20 mm is smaller than the height of the mouth of 21 mm, the intermediate layer exists at least over the entire shoulder portion below the mouth, resulting in uneven stretchability in the circumferential direction during blow molding. has the effect of eliminating

In addition, since there is no intermediate layer in the range of 3 to 20 mm from the bottom, the PET bottle is more stable. That is, if there is an intermediate layer on the bottom, the intermediate layer may trigger cracking due to impact during transportation. If the bottom is cracked, the PET bottle will not be able to stand up stably. Therefore, according to the present invention, since there is no intermediate layer in the bottom portion, the bottom portion is less likely to be cracked, so that a highly stable PET bottle can be provided.

Furthermore, since the weight of the intermediate layer is 2% to 7% by weight with respect to the entire preform, the amount of the gas barrier material in the intermediate layer is small, making it the basis of plastic bottles with excellent recyclability. Preforms can be provided.

Further, the manufacturing method of the present invention is a preform manufacturing method by co-injection molding in which one material is injected and another material is injected, wherein the first molding material is constantly injected from the start of injection to the end of injection. After the start of injection of the first molding material, the second molding material is injected for a predetermined time, and the second molding material is injected while being sandwiched between the first molding materials. Characterized by This method enables efficient production of the preform of the present invention.

Furthermore, since the preform of the present invention is blow-molded to form a plastic bottle, there is provided a method for producing an excellent plastic bottle that has excellent gas barrier properties, high safety, little deformation and little liquid leakage from the mouth. be able to.

It is a sectional view showing an example of preform concerning this embodiment. 1 is a schematic cross-sectional view of a hot runner nozzle of an injection molding apparatus as an example of a preform manufacturing apparatus; FIG. 4 is a graph schematically showing the relationship between the injection rate of each co-injected molding material and time. FIG. 4 is a cross-sectional view schematically showing a state (step S1) in which each molding material flows from a hot runner nozzle to a cavity; FIG. 4 is a cross-sectional view schematically showing a state in which each molding material flows from a hot runner nozzle to a cavity (step S3); FIG. 4 is a cross-sectional view schematically showing a state in which each molding material flows from a hot runner nozzle to a cavity (step S3); FIG. 4 is a cross-sectional view schematically showing a state in which each molding material flows from a hot runner nozzle to a cavity (step S5); 1 is a cross-sectional view schematically showing a preform and a PET bottle after blow molding; FIG. 1 is a front view showing a PET bottle formed from a preform according to this embodiment; FIG. FIG. 10 is a cross-sectional view of the PET bottle of FIG. 9; FIG. 10 is a perspective view of the PET bottle of FIG. 9 as seen from the bottom side;

Hereinafter, details of embodiments of the present invention will be described with reference to the drawings. First, the configuration of a preform 1 (preformed body) for PET (PolyEthylene Terephthalate) bottle molding according to the present embodiment will be described in detail. FIG. 1 is a sectional view showing an example of a preform 1 according to this embodiment. The preform 1 has a cylindrical shape with a bottom, and is provided with a mouth portion 10, a body portion 16, and a bottom portion 17 in order in the axial direction. The preform 1 is drawn into a bottle shape. At this time, it is preferable to use a known blow molding technique. FIG. 1 shows a plane cut at the center of the preform 1 parallel to the axial direction from the mouth portion 10 to the bottom portion 17 .

In the following, for convenience of explanation, the direction of the opening 10 with respect to the bottom 17 in the preform 1 in the state of FIG.

The mouth 10 has a circularly open opening 11 at its upper axial end. The opening 11 has an annular top surface 15 and a circular hole 11a. The mouth portion 10 has an external thread 12, a turnip 13, and a support ring 14 on its outer peripheral surface. A male thread 12 for attaching a lid (not shown) protrudes spirally outward in the radial direction of the preform 1 from the outer peripheral surface of the mouth portion 10 . The turnip 13 protrudes radially outward in a circular manner below the male thread 12 . The support ring 14 is circular below the turnip 13 and protrudes radially outward beyond the turnip 13 .

In general, when the preform 1 is formed into a bottle shape, the shape of the portion axially above the support ring 14 does not change. On the other hand, even the maximum 20 mm range below the support ring 14 is hardly stretched when it is molded into a bottle shape. Preferably, this range is 10 mm. Therefore, here, the opening 10 is defined as a range in which the shape of the preform 1 is hardly changed when the preform 1 is molded into a bottle shape. As illustrated in FIG. 1, the mouth portion 10 has a substantially perfect cylindrical shape in which the inner diameter at a portion axially lower than the support ring 14 and the outer diameter are substantially the same in the upper and lower axial directions. Also good.

In this way, the mouth portion 10 does not change its shape even after being molded by the blow molding machine. Here, there is no particular limitation on the dimensions of each portion such as the inner diameter and outer diameter (corresponding to the root diameter) of the mouth portion 10 of the preform 1 and the thread diameter. However, it is preferable that the dimensions be those that are normally used for beverage bottles, in that the versatility of existing lids and the sealing performance of beverage bottles can be ensured. For this reason, it is preferable that the opening 10 has dimensions corresponding to, for example, the PCO1810 standard and the PCO1881 standard.

The trunk portion 16 is configured in a substantially true cylindrical shape with an inner diameter and an outer diameter that are substantially the same in the vertical direction in the axial direction. However, the body portion 16 may be provided with a draft which is an inclination for facilitating removal from the mold used for manufacturing the preform 1, that is, releasing from the mold. Furthermore, the inner diameter and the outer diameter of the trunk portion 16 may slightly change vertically in the axial direction. Furthermore, the outer diameter of the trunk portion 16 can be substantially the same in the vertical direction in the axial direction.

The bottom portion 17 is configured in a substantially hemispherical shape curved outward. The bottom portion 17 may have a conical shape, a cylindrical shape with rounded corners, or other shapes.

It should be noted that the outer diameter of the trunk portion 16 is preferably 12 mm or more and 30 mm or less, in that an existing device can be used. Furthermore, it is preferable that the length from the lower surface of the support ring 14 to the lower end of the bottom portion 17 is 35 mm or more and 105 mm or less, in that an existing device, particularly a blow molding machine, can be used.

The preform 1 has a body portion 16 composed of multiple layers, and has an intermediate layer 20a between an outer layer 18a and an inner layer 19a. The preform 1 illustrated in FIG. 1 has an intermediate layer 20a in a region from the vicinity of the support ring 14 to the front of the bottom portion 17. As shown in FIG. A region with a height H1 from the top surface 15 (H1=5 to 20 mm) and a region with a height H2 from the bottom of the bottom portion 17 (H2=3 to 20 mm) have no intermediate layer 20a. there is By adopting such a configuration in which the region above the support ring of the mouth portion does not have an intermediate layer, cracking of the mouth portion can be prevented. In addition, cracking can be prevented by adopting a configuration in which the bottom portion does not have an intermediate layer. Since the bottom part has a low draw ratio and is thick, it also has the characteristic of ensuring, for example, gas barrier properties.

The preform 1 does not have an adhesive layer or an adhesive between the intermediate layer 20a and each of the outer layer 18a and the inner layer 19a. Therefore, after the preform 1 is used, recycling is not hindered. On the other hand, since the layers are not firmly adhered to each other, delamination may occur due to an external force. Therefore, since the intermediate layer 20a is configured so as not to extend to the end of the mouth portion 10, the end of the interface of each layer, which is likely to be the starting point of breakage, is not exposed on the mouth top surface 15, so that delamination is less likely to occur. .

In the preform 1, as illustrated in FIG. 1, the intermediate layer 20a is provided continuously from the height H1 near the support ring of the mouth portion 10 to the height H2 of the bottom portion. At this time, if the intermediate layer 20a has, for example, gas barrier properties, a plastic bottle with excellent gas barrier properties can be provided.

The thickness of the intermediate layer 20a is uniform. Even if the substrate layer is deformed due to the application of heat, it is less distorted due to the uniform provision. However, an intermediate layer 20 a may be provided in the base material layer of the support ring 14 of the mouth portion 10 so as to project radially from the mouth portion 10 . By doing so, the preform 1 can be manufactured more easily. As for the structure of the mouth portion 10, it is surrounded by the base material layer, and the intermediate layer is provided to protrude into the base material layer of the support ring 14 like a flange. You may have the structure that it is.

The weight of the intermediate layer 20a is preferably 2% to 7% by weight in the preform 1 for a 280 ml PET bottle with respect to the total weight divided by the weight of the intermediate layer 20a. As a result, the recyclability of the PET bottle 2 obtained by molding the preform 1 by blow molding or the like is improved. This ratio can vary depending on the size of the PET bottle. Even for a 2-liter PET bottle, if it is 3% by weight, the recyclability is the same as that of the preform 1 for a 280-ml PET bottle.

A material that exhibits various functions can be selected for the intermediate layer 20a. For example, the intermediate layer 20a can be made of a material that blocks light such as ultraviolet rays and provides gas barrier properties such as water vapor. It is preferable to use a gas barrier material for the intermediate layer 20a here. Here, the gas barrier material is a mixed material of nylon and a metal complex, and a material having a ratio of nylon to metal complex of 11:1 to 20:1 may be used. A thermoplastic polyester resin having excellent heat resistance can also be used as the material for the intermediate layer 20a of the present invention.

Examples of materials for the outer layer 18a and the inner layer 19a of the base layer of the illustrated preform 1 include polyolefins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and polypropylene, and ethylene-vinyl alcohol. Various thermoplastic resins that can be blow-molded, such as copolymers and polylactic acid made from plants, can be used. However, the outer layer 18a and the inner layer 19a are preferably made of PET layers mainly composed of polyester such as polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyarylate, particularly polyethylene terephthalate. In addition, various additives such as colorants, ultraviolet absorbers, release agents, lubricants, nucleating agents, antioxidants, and antistatic agents are added to the above-described resin within a range that does not impair the quality of the molded product. be able to.

As the ethylene terephthalate-based thermoplastic resin constituting the outer layer 18a and the inner layer 19a of the preform 1, ethylene terephthalate units account for most of the repeating ester portions, generally 70 mol % or more, and the glass transition point (Tg) is is 50° C. or higher and 90° C. or lower, and the melting point (Tm) is in the range of 200° C. or higher and 275° C. or lower. Among ethylene terephthalate-based thermoplastic polyesters, polyethylene terephthalate is particularly excellent in terms of pressure resistance and the like. Copolyesters containing minor amounts of ester units can also be used.

Polyethylene terephthalate has the largest production volume among thermoplastic synthetic resins. Polyethylene terephthalate resin has various properties such as excellent heat resistance, cold resistance, chemical resistance, and abrasion resistance. Furthermore, polyethylene terephthalate resin has a lower petroleum content than other plastics and can be recycled. Thus, according to the structure having polyethylene terephthalate as a main component, it is possible to use a material that is produced in large quantities and to utilize its excellent various properties.

Polyethylene terephthalate is obtained by condensation polymerization of ethylene glycol (ethane-1,2-diol) and purified terephthalic acid. At least one of a germanium compound, a titanium compound, and an aluminum compound is preferably used as a polymerization catalyst for polyethylene terephthalate. By using these catalysts, it is possible to form a container having higher transparency and superior heat resistance than when an antimony compound is used.

If the amount of the intermediate layer 20a with respect to the entire preform 1 is too large, recycling of the preform 1 after use will be hindered. On the other hand, if the amount of the intermediate layer 20a with respect to the entire preform 1 is too small, the injection moldability will deteriorate. More specifically, it becomes difficult to fill the intermediate layer 20a when molding the preform 1, and if the intermediate layer 20a is forced into the preform 1, deterioration and uneven thickness will occur, which is undesirable. Therefore, the ratio of the intermediate layer 20a to the entire preform 1 must be at least 0.5% by weight. More preferably, it is between 2 weight percent and 7 weight percent.

Note that the intermediate layer 20a is not limited to a single layer and may be composed of multiple layers. For example, the intermediate layer 20a may be composed of a plurality of heat-resistant layers in addition to a gas barrier layer containing an oxygen absorbing material. For example, the preform 1 may have a five-layer structure (PET layer (outer layer 18a)/oxygen barrier layer/heat-resistant layer/oxygen barrier layer/PET layer (inner layer 19a)). The number of layers of the intermediate layer 20a may be further increased, and the preform 1 may have a maximum of seven layers. By configuring the intermediate layer 20a in multiple layers, the function of the intermediate layer 20a can be enhanced, or the intermediate layer 20a can have multiple functions.

Therefore, an example of the method for manufacturing the preform 1 will now be described in detail. FIG. 2 is a schematic cross-sectional view of a hot runner nozzle 31 of an injection molding apparatus as an example of a preform 1 manufacturing apparatus. The injection molding apparatus includes a heating cylinder (not shown) having a screw therein, a hot runner nozzle 31 and a mold 32 . The injection molding apparatus is configured such that a molding material is melted and plasticized by being heated to, for example, 270° C. to 300° C. by a heating cylinder, and fed to a mold 32 through a hot runner nozzle 31 by a screw. ing.

The hot runner nozzle 31 has an axially long configuration. The hot runner nozzle 31 has a linear channel 33a, a first cylindrical channel 33b, a second cylindrical channel 34, and a check valve 35, which is an example of an on-off valve. Each channel extends substantially in the axial direction. Hot runner nozzle 31 further includes a first inlet 36 , a second inlet 37 and an outlet 38 .

An injection port 38 is formed in the center of one end of the hot runner nozzle 31 . The injection port 38 communicates with the mold 32 . On the other hand, the first injection port 36 and the second injection port 37 are formed on the side surface of the hot runner nozzle 31 near the other end. Each of the first injection port 36 and the second injection port 37 is connected to separate heating cylinders. That is, the hot runner nozzle 31 is configured such that the first molding material and the second molding material can be injected from the first injection port 36 and the second injection port 37, respectively. Molding material flows from the first inlet 36 and the second inlet 37 towards the injection outlet 38 .

The linear flow path 33 a communicates with a flow path extending radially from the first injection port 36 and extends linearly through the central portion of the hot runner nozzle 31 to the injection port 38 . After branching from the linear flow path 33a, the first cylindrical flow path 33b passes radially outward of the linear flow path 33a and joins the linear flow path 33a at a first junction 39a near the injection port 38. merges with The second cylindrical channel 34 communicates with the channel extending radially from the second injection port 37 and extends between the linear channel 33a and the first cylindrical channel 33b to form the first merges with the linear flow path 33a at a second merge point 39b upstream of the merge point 39a.

The hot runner nozzle 31 has a check valve 35 that closes the second cylindrical channel 34 at the second junction 39b. The check valve 35 is opened according to the difference in injection pressure between the first molding material passing through the linear flow path 33a and the second molding material passing through the second cylindrical flow path 34 at the second junction 39b. and is configured to move axially. The check valve 35 is configured to open the second cylindrical flow path 34 when the injection pressure of the second molding material is high. The check valve 35 may have another configuration as long as it achieves such an action.

The mold 32 which is divided into a plurality of parts has a cavity 32 a which is a gap having a shape corresponding to the preform 1 and a gate 32 b at a position corresponding to the bottom 17 of the preform 1 . The cavity 32a communicates with the injection port 38 of the hot runner nozzle 31 through the gate 32b. The mold 32 is provided with a heater (not shown) for heating the mold 32 and a cooler (not shown) for cooling the mold 32 . The mold 32 is configured to mold the preform 1 by injecting a molten molding material into a cavity 32a heated by a heater, pressurizing it, and then cooling it by a cooler.

FIG. 3 is a graph schematically showing the relationship between the injection rate of each co-injected molding material and time. The injection rate is indicated by mass [g] of each molding material injected per unit time [s]. In FIG. 3, the first molding material a is indicated by a solid line and the second molding material b is indicated by a broken line. Here, polyethylene terephthalate (hereinafter referred to as PET resin a) is injected into the first molding material, and a mixture of nylon and a metal complex (hereinafter gas barrier resin b) is implanted. For example, as shown in FIG. 3, the method of manufacturing the preform 1 includes a step of injecting a first molding material (step S1), and injection of a second molding material at an injection rate higher than that of the first molding material. and a step of injecting the first molding material at a higher injection rate than the second molding material (step S5). Further, according to this method, the amount of molding material for the intermediate layer 20a can be reduced while ensuring the function of the intermediate layer 20a even after stretching the manufactured preform 1 . By performing injection molding according to the injection timing shown in this drawing, it is possible to mold one form of the preform of the present invention, in which the intermediate layer 20a exists in the body portion from the vicinity of the support ring.

First, PET resin a is injected (step S1). FIG. 4 is a cross-sectional view schematically showing a state (step S1) in which each molding material flows from the hot runner nozzle 31 to the cavity 32a. The PET resin a flows from the first injection port 36 (see FIG. 2) through either the linear channel 33a (PET resin a1) or the first cylindrical channel 33b (PET resin a2). They merge at the first confluence point 39a, then flow through the injection port 38 and the gate 32b in order to fill the cavity 32a. As exemplified in FIG. 4, the PET resin a flows through the linear flow path 33a (PET resin a1) and the first cylindrical flow path 33b (PET resin a2), respectively, into the PET resin layers A1, and the PET resin layer A2, and the PET resin layer A is filled in the cavity 32a.

At this stage, the gas barrier resin b is not injected, and the second cylindrical flow path 34 is closed by the check valve 35 which receives the injection pressure of the PET resin a1.

Next, the PET resin a is injected at a predetermined injection rate (step S2). This lowered injection rate is determined in consideration of the injection rate of the gas barrier resin b to be injected in the next step. Here, step S2 may be omitted if the injection of the PET resin a at the pre-lowered injection rate does not cause dimensional defects in the opening 10 or molding defects such as sink marks.

Next, the gas barrier resin b is injected at a higher injection rate than the PET resin a (step S3). FIG. 5 is a cross-sectional view schematically showing a state in which each molding material flows from the hot runner nozzle 31 to the cavity 32 (step S3). The check valve 35 is moved by the pressure with which the gas barrier resin b is injected, and the second cylindrical flow path 34 is opened. Then, as exemplified in FIG. 5, a gas barrier resin layer B is provided between the PET resin layer A1 passing through the linear channel 33a and the PET resin layer A2 passing through the first cylindrical channel 33b. formed. The gas-barrier resin layer B flows without coming into contact with the molding die, so that the temperature does not drop and the viscosity does not increase, so the gas-barrier resin layer B flows at a higher speed than the PET resin layers A1 and A2.

Next, the gas barrier resin b is injected while maintaining the same injection rate (step S3). FIG. 6 is a cross-sectional view schematically showing a state in which each molding material flows from the hot runner nozzle 31 to the cavity 32a (step S3).

Next, the gas barrier resin b is injected until the injection rate gradually decreases to zero and the injection rate of the PET resin a is gradually increased (step S4). As the injection rate of the gas-barrier resin b gradually decreases, the gas-barrier resin layer B is injected so as to become gradually thinner and then discontinued. Then, when the injection rate of the gas barrier resin b becomes zero, the check valve 35 is moved and the second cylindrical flow path 34 is closed.

Next, the PET resin a is injected while being maintained at a predetermined injection rate (step S5). FIG. 7 is a cross-sectional view schematically showing a state in which each molding material flows from the hot runner nozzle 31 to the cavity 32a (step S5). As illustrated in FIG. 7, the gas barrier resin layer B is pushed in by the PET resin layer A. As shown in FIG.

Finally, the PET resin a is injected until the inside of the cavity 32a is filled. The injection rate of the PET resin a gradually decreases, and when the inside of the cavity 32a is filled, the injection rate of the PET resin a becomes zero. ). After the molding material is cooled inside the cavity 32a, the mold 32 is opened and the molded preform 1 is taken out.

The pressure and injection rate for injecting each molding material are appropriately designed according to the difference in viscosity and the like.

As described above, the method for manufacturing the preform 1 according to the present embodiment includes a procedure for uniformly molding the intermediate layer 20a.

In addition, the manufacturing method may be another method. For example, the PET resin a, the gas barrier resin b, and the PET resin a are plasticized in this order and extruded to form a molten resin mass (billet) in which the gas barrier resin b is enclosed in a U shape, which is then compression molded. It may be a method by which the preform 1 is manufactured.

The molded preforms 1 may be boxed, so-called palletized, and temporarily stored in a warehouse or the like, or may be continued to the next step as they are. That is, a so-called cold parison method (two-stage method) in which the molding of the preform 1 and the blow molding are performed in separate places or devices may be used, and the molding of the preform 1 and the blow molding may be performed in the same manner. A so-called hot parison method (one-stage method), which is performed at a place or with an apparatus, may also be used. Furthermore, the manufacturing process from molding of the preform 1 to filling of contents may be continuous in-line.

Next, an example of a method of molding the preform 1 according to this embodiment into a bottle shape will be described in detail. When the preform 1 is molded into a bottle shape, the preform 1 is first heated.

The heating device includes a conveying device and a heater. The conveying device is configured to convey the preform while rotating it about its axis in order to uniformly heat the preform in the circumferential direction. The heater comprises a plurality of halogen lamps, for example, and is configured to heat the preform to a temperature suitable for blow molding, for example, 80.degree. C. to 140.degree. Furthermore, the heating device may include a reflector for reflecting heat from the heater to the preform, a shielding member for preventing the heat from the heater from escaping to the outside of the heating device, and the like.

The heated preform 1 is then molded into a plastic bottle, for example a PET bottle 2, by a blow molding machine. FIG. 8 is a cross-sectional view schematically showing the preform 1 and the PET bottle 2 after blow molding. A biaxial stretch blow molding device 50 as an example of a blow molding machine includes a mold 51, a stretching rod 52, a high pressure air supply device (not shown), and a control device (not shown) for controlling them. Although FIG. 8 illustrates a downward blow molding method, an upward blow molding method in which the material is less susceptible to gravity may be used.

Here, the PET bottle 2 has an upper portion 30 , a body portion 70 and a bottom portion 80 . Approximately before and after blow molding, the mouth 10 of the preform 1 corresponds to the top 30 of the PET bottle 2 and the bottom 17 of the preform 1 corresponds to the bottom 80 of the PET bottle 2 .

The mold 51 has a shape corresponding to the PET bottle 2 to be formed. 51b. The temperature of the surface of the mold 51 is configured to be controlled to, for example, 30.degree. C. to 130.degree.

The extension rod 52 is configured to extend and retract within the mold 51 . The stretching rod 52 is configured to stretch the body portion 16 of the preform 1 to which the mouth portion 10 is attached to the mold 51 in the longitudinal (axial) direction. The high-pressure air supply device is configured to blow out temperature-controlled high-pressure air h. The high-pressure air h may be supplied to the inside of the preform 1 attached to the mold 51 , may be blown from the stretching rod 52 , or may be blown from a member other than the stretching rod 52 . The high-pressure air h is configured to stretch the body portion 16 of the preform 1 in the lateral (diameter) direction and lower the surface temperature of the body portion 16 after stretching.

The heated preform 1 is attached to the mold 51 of the biaxial stretch blow molding device 50 . After that, the body 16 of the preform 1 mounted in the mold 51 is stretched in the longitudinal direction by the stretching rods 52 . At this time, the longitudinal draw ratio from the preform 1 to the PET bottle 2 is preferably 1.8 times or more and 4.0 times or less.

Here, the longitudinal draw ratio is the ratio of the length from the lower surface of the support ring 14 of the PET bottle 2 to the lower end of the bottom portion 80 to the length from the lower surface of the support ring 14 to the lower end of the bottom portion 17 of the preform 1. . Molecules of the preform 1 having an amorphous structure, which is an aggregate of amorphous parts and crystalline parts, are oriented and crystallized by stretching, and as a result, the strength, rigidity, heat resistance, etc. of the PET bottle 2 are increased. When the longitudinal draw ratio is less than 1.8, the orientation of the molecules of the PET bottle 2 (preform 1) does not increase. become difficult.

Furthermore, the longitudinally stretched body 16 of the preform 1 is stretched horizontally by the high-pressure air h until it hits the die 51 . At this time, the lateral stretching ratio from the preform 1 to the PET bottle 2 is preferably 1.5 times or more and 6.0 times or less.

Here, the transverse draw ratio is the ratio of the diameter of the body portion 70 of the PET bottle 2 to the diameter of the body portion 16 of the preform 1 . The diameter of the trunk portion 70 is defined as the distance between the centers of the wall thicknesses of the opposite wall surfaces of the trunk portion 70 . The molecules of the preform 1 are similarly oriented and crystallized by stretching in the horizontal direction, and as a result, the strength, rigidity, heat resistance, etc. of the PET bottle 2 are increased. When the lateral draw ratio is less than 1.5, the orientation of the molecules of the PET bottle 2 (preform 1) does not increase. become difficult.

Thus, the molding by the biaxial stretch blow molding device 50 has a longitudinal draw ratio of 1.8 times or more and 4.0 times or less and a transverse direction draw ratio of 1.5 times or more and 6.0 times or less. According to the configuration of biaxially stretched blow molding, the preform 1 can be molded into the PET bottle 2 with better blow moldability and reduced weight.

As described above, the PET bottle 2 according to this embodiment is formed by molding the preform 1 into a bottle shape by the biaxial stretch blow molding device 50 . By using the biaxially stretched blow molding apparatus 50, the preform 1 according to the present embodiment can be effectively molded into a lightweight PET bottle 2 with good blow moldability.

In addition, in this embodiment, the use of the molded PET bottle 2 is not limited. Therefore, the PET bottle 2 may be molded to have pressure resistance, oxygen barrier properties, and the like.

Next, the configuration of the PET bottle 2 formed from the preform 1 according to this embodiment will be described in detail. FIG. 9 is a front view showing a PET bottle 2 formed from the preform 1 according to this embodiment. The PET bottle 2 exemplified in FIG. 9 is a round bottle whose cross-sectional view in the direction perpendicular to the axial direction is substantially circular. As mentioned above, the PET bottle 2 has an upper portion 30, a body portion 70 and a lower portion 80. As shown in FIG. And, as described above, the configuration of the upper portion 30 of the PET bottle 2 is similar to the configuration of the mouth portion 10 of the preform 1 .

The upper part 30 serves as a filling port and an outlet for contents, and the PET bottle 2 is hermetically sealed by attaching a lid (not shown) to the upper part 30 .

The trunk portion 70 has a substantially truncated cone shape with a portion adjacent to the upper portion expanding in diameter from above to below. In the barrel, the portion between the generally frusto-conical portion and the bottom has the shape of a cylinder. The body 70 may have pressure absorbing panels, lateral grooves, and longitudinal grooves.

The bottom portion 80 has its upper side connected to the lower side of the body portion 70 . The bottom 80 illustrated in FIG. 11 has a so-called petaloid shape. The bottom portion 80 has a concave portion 81, a leg portion 82, a valley portion 83, and the like. A concave portion 81 located in the radial center of the bottom portion 80 is configured to protrude toward the inside (upward in the axial direction) of the PET bottle 2 . The leg portions 82 radially extend radially outward from the recessed portion 81 and axially downward. The leg portion 82 serves as a contact surface of the PET bottle 2 . A valley portion 83 is formed between adjacent leg portions 82 . The valley portion 83 extends radially outward and axially upward from the recessed portion 81 . The configuration of the bottom portion 80 is not limited to that illustrated in FIG. 11, and may be a shape corresponding to the contents, for example, a shape provided with radial ribs.

10 is a cross-sectional view of the PET bottle 2. FIG. Furthermore, in FIG. 10, the region A of the upper portion 30 is shown enlarged. The PET bottle 2 has multiple layers from the vicinity of the support ring 14 to the body 70 and has an intermediate layer 20 between the outer layer 18 and the inner layer 19 . The middle layer starts near the support ring 14 15 mm below the top of the mouth, and the middle layer extends to the trunk.

By providing a gas-barrier intermediate layer in the body portion, a PET bottle capable of suppressing oxidation of the contents can be obtained, which is preferable.

The type, material, amount, layer structure, etc. of the intermediate layer 20 are the same as those of the preform 1 described above.

The shape of the PET bottle 2, particularly below the support ring 14, is not limited to the example shown in FIG. . For example, in this embodiment, the round bottle shown in FIG. 9 can be suitably formed. However, the plastic bottle formed in this embodiment is not limited to a round bottle, and may be a square bottle. Furthermore, the body portion 70 may have a shape in which the width expands downward. Also, the shape of the pressure-absorbing panel formed in the trunk portion 70 and the lateral grooves and vertical grooves can be freely designed.

The PET bottle 2 according to this embodiment is not limited by size, and can be applied to various sizes. For example, the PET bottle 2 may have a volume of 100 ml or more and 1000 ml or less, and is particularly suitable for a PET bottle 2 with a volume of 200 ml or more and 700 ml or less. The total height of the PET bottle 2 may be 120 mm or more and 260 mm or less, and the barrel diameter of the barrel portion 70 may be 40 mm or more and 75 mm or less.

Furthermore, the PET bottle 2 according to this embodiment can be suitably used as a lightweight bottle. The mass of the PET bottle 2 may be, for example, 8 g or more and less than 16 g for an internal volume of 200 ml, and 10 g or more and less than 20 g for an internal volume of 550 ml. In particular, from the viewpoint of maintaining the strength of the PET bottle 2 while ensuring lightness and ensuring the function of the intermediate layer 20, the ratio of the mass to the internal volume of the PET bottle 2 is 0.0180 g / ml or more, It is preferably 0.0800 g/ml or less.

A plastic bottle can be made by blow molding a preform 1 injection molded from the material described above. By using polyethylene terephthalate as a material, the PET bottle 2 as an example of the plastic bottle according to the present embodiment is produced. A filling body is composed of the PET bottle 2 and the liquid to be filled. The filled body is manufactured by filling the upper portion 30 of the PET bottle 2 with a liquid such as a beverage or a seasoning and sealing it with a lid (not shown) attached to the upper portion 30 .

The method of filling the PET bottle 2 with the contents is not limited either. Therefore, the PET bottle 2 may be used for hot filling or aseptic filling.

As described above, the PET bottle 2 has an upper portion 30, a body portion 70, and a bottom portion 80 in order in the axial direction. have According to such a configuration, the amount of molding material for the intermediate layer 20 can be reduced while ensuring the function of the intermediate layer 20 .

EXAMPLES Hereinafter, the present disclosure will be described in more detail and specifically by showing examples. However, the present disclosure is not limited to the following examples.

<Material and manufacturing method>
[Example 1]
Polyethylene terephthalate (PET resin a) is used for the outer layer 18 and the inner layer 19, and a mixture of nylon and a metal complex (gas barrier resin b) is used for the intermediate layer 20. A total of 22 g of preform 1 is used. It was made by the method shown in this specification, such as FIG. The ratio of the gas barrier resin b to the entire preform 1 was set to 3% by weight. The weight of the preform was 22g.

Then, from the preform 1, a PET bottle 2 having a full filling capacity of 295 ml as shown in FIG. 9 and the like was produced by blow molding. The PET bottle 2 was filled with 280 ml of water and then attached with a lid to prepare a filled body.

The intermediate layer 20 of the preform 1 according to Example 1 was continuously provided from a position approximately 10 mm from the top surface 15 to the body portion 70 .

[Comparative Example 1]
In Comparative Example 1, a single-layer preform was produced using only the PET resin a without using the gas barrier resin b. The weight of the preform was 22g. Then, a PET bottle 2 having a full filling volume of 295 ml as shown in FIG. 9 and the like was produced by blow molding. The PET bottle 2 was filled with 280 ml of water and then attached with a lid to prepare a filled body.

[Comparative Example 2]
In Comparative Example 2, the gas barrier resin b was used, and its proportion was 25% by weight. The intermediate layer 20 was continuously provided from a position about 10 mm from the top surface 15 to the body portion 70 .

[Comparative Example 3]
In Comparative Example 3, the gas barrier resin b was used and its proportion was 3% by weight. The intermediate layer 20 was continuously provided from a position about 2 mm from the top surface 15 to the body portion 70 .

<Evaluation method>
(Amount of gas barrier layer material used)
It was determined whether or not the amount used could be reduced depending on the mass of the material of the gas barrier layer used in each of the PET bottles of Example 1 and Comparative Examples 1-3. A threshold value was set for determining whether the amount of gas barrier resin b to be used was reduced, depending on whether the ratio of the gas barrier resin b to the entire PET bottle (each preform) was greater than or equal to 20 wt %. Table 1 shows the results of the evaluation of the reduction rate of the material usage of the gas barrier layer in each PET bottle. It is written.

(Gas barrier property)
It was determined whether or not the PET bottles of Example 1 and Comparative Examples 1 to 3 had sufficient gas barrier properties. For determination of gas barrier property, each PET bottle was filled with green tea, capped, and stored in a heat-retaining cabinet at 40°C for one month. After that, Table 1 shows the result of measuring the color difference ΔE. When the color difference is 5 or more, it is indicated by ×, and when it is less than 5, it is indicated by ◯.

(crack in mouth)
Green tea was filled into 100 PET bottles of each of Example 1 and Comparative Examples 1 to 3, and the capper was tightened. When there are no cracks, it is indicated by ◯, and when there are one or more cracks, it is indicated by ×.

(Comprehensive evaluation)
Based on the amount of material used for the gas barrier layer and the gas barrier properties described above, the PET bottles (each filling) of Example 1 and Comparative Examples 1 to 3 were comprehensively evaluated. Table 1 shows the results of comprehensive evaluation. Comprehensive evaluation is indicated by ⊚: extremely good, ∘: good, and x: unsuitable. Evaluation results for Example 1 and Comparative Examples 1 to 3 are shown. wt% is the amount used in the gas barrier layer and is expressed in percent by weight. t is the position from the opening of the gas barrier layer in units of mm.

INDUSTRIAL APPLICABILITY The present invention can be suitably applied to various plastic bottles filled with liquid as contents. However, the invention is not limited to the embodiments and examples described above. The plastic bottle of the present invention can be used for, for example, water, green tea, oolong tea, black tea, coffee, fruit juice, various non-carbonated drinks such as soft drinks, carbonated drinks, seasonings such as soy sauce, sauce, mirin, edible oil, and alcoholic beverages. It is useful for containing food, detergents, shampoos, cosmetics, medicines, and any other contents. Further, in the present disclosure, in particular, a gas barrier intermediate layer for preventing oxidation of the contents is provided, and a plastic bottle excellent in preventing oxidation of the contents and having high productivity can be provided.

1 preform 2 PET bottle (plastic bottle)
Reference Signs List 10 Mouth 14 Support ring 15 Mouth top 16 Body 17 Bottom 18 Outer layer of PET bottle 2 18a Outer layer of preform 1 19 Inner layer of PET bottle 2 19a Inner layer of preform 1 20 Intermediate layer of PET bottle 2 20a Preform 1 middle layer 30 upper part 31 hot runner nozzle 32 mold 32a cavity 32b gate 33a linear channel 33b first cylindrical channel 34 second cylindrical channel 35 check valve (on-off valve)
36 first injection port 37 second injection port 38 injection port 39a first junction 39b second junction 70 body 80 bottom

Claims (5)

Equipped with mouth, body and bottom,
A multi-layered preform having an annular support ring projecting outward from the mouth and an annular turnip projecting outward above the support ring,
The intermediate layer is surrounded by and continuous with the base material layer starting from a position 10 mm from the upper end of the mouth, to a position 3 to 20 mm from the bottom, from an intermediate position between the support ring and the turnip to the trunk. and
The preform, wherein the intermediate layer is a mixed material of nylon and a metal complex, and the ratio of the nylon to the metal complex is 11:1 to 20:1. The preform according to claim 1, wherein the intermediate layer has gas barrier properties. A preform according to claim 1 or 2 , characterized in that the weight of said intermediate layer is 2 to 7 weight percent with respect to the weight of the whole preform. In the preform according to any one of claims 1 to 3 ,
In a preform manufacturing method by co-injection molding in which one material is injected and another material is injected,
The first molding material is constantly injected from the start of injection to the end of injection,
After starting the injection of the first molding material, injecting the second molding material for a predetermined time,
The second molding material is sandwiched between the first molding materials and injected,
A method of manufacturing a preform. A method for manufacturing a plastic bottle, characterized in that the preform according to any one of claims 1 to 3 is molded by blow molding.

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