JPH06226785A - Apparatus and method for manufacturing multilayer preform - Google Patents

Abstract

PURPOSE:To provide an apparatus for manufacturing a multilayer preform to be co-injection molded without unevenness of flow of resin. CONSTITUTION:An apparatus for manufacturing a multilayer preform comprises (a) an injection mold 2 having a cavity corresponding to the piece and a gate at a position corresponding to its bottom, and (b) a hot-runner nozzle 1 communicating with the mold 2, wherein the nozzle 1 has a linear channel A1, double spiral channels B1, C1 provided at a periphery of the channel A1 and a cylindrical channel A2. The channels A1, A2 are branched from an inlet A, joined at a slight upstream of an injection port 15, the channels B1, C1 communicate with inlets B, C, extends toward the port without crossing, joins the channel A1 before a confluent point of the channels A1 and A2 in the apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a multilayer preform capable of providing a biaxially stretch blow molded bottle having a plurality of functions such as heat resistance, barrier property and light shielding property. More specifically, the present invention relates to a method and an apparatus for producing a multi-layer preform capable of co-injection molding without causing the resin to flow.

[0002]

BACKGROUND OF THE INVENTION Biaxially stretched blow molded bottles made of saturated polyester resin represented by polyethylene terephthalate have excellent transparency and surface gloss, and are beautiful and have a gas barrier. Excellent in water resistance, water impermeability, content resistance, and storage stability. In addition, it has many advantages such as no generation of toxic gas, little heat generation during combustion, and no damage to the furnace. Therefore, it is widely used in various drinking water, seasonings, bottles for alcoholic beverages and other foods.

Under such circumstances, various attempts have been made to further respond to diversifying needs by imparting functions such as heat resistance, gas barrier property, and light shielding property to a polyester bottle produced by biaxial stretch blow molding. Has been done.

For example, it has been attempted to provide a polyester bottle with heat resistance so that a so-called hot fill for filling a liquid at 80 to 95 ° C. or a bottle to which pasteurizing by hot shower can be applied. . Further, it has been attempted to use a bottle having excellent gas barrier properties as a bottle for juice that is easily affected by oxygen, a carbonated drink, and a food that needs to maintain freshness. Further, not only the gas barrier property, but also the moisture barrier property is required for the contents which are reluctant to mix in moisture from the outside world. In addition, in order to protect the contents from ultraviolet rays and visible rays, it has been attempted to add a function of blocking them.

Further, it is possible to add a plurality of functions to the above-mentioned various functions to make a bottle with high added value.

Among the methods generally used for imparting such various functions to bottles, there is a method in which the bottle wall or its mouth has a multi-layer structure composed of a resin expressing each function and polyester. There is. In this method, first, a functional resin and polyester are co-injected to form a multilayer preform, and then this is biaxially stretch blow molded to form a functionalized bottle.

Various structures of the multi-layer preformed product in this method are conceivable. For example, a multi-layer preformed product as shown in FIG. 4 is given as an example. The multilayer preform 4 shown in FIG. 4 has a multilayer structure including three resin layers a, a, a and two resin layers b, b in the mouth portion 41, and the body portion 42 and the bottom portion 43. Has a three-layer structure of resin layer b / resin layer c / resin layer b from the outside. If a heat-resistant resin is used for the resin layer a, a polyester resin is used for the resin layer b, and a resin having a function such as a barrier property, a light-shielding property, or an ultraviolet absorbing property is used for the resin layer c, the heat resistance is excellent. At the same time, it is possible to manufacture a bottle having any one or two functions of the barrier property, the light shielding property, and the ultraviolet absorbing property.

It should be noted that the reason why heat resistance is imparted to the mouth in particular is that the mouth is first exposed to the hot liquid in the hot fill, and the hot shower is poured from above the bottle even in the pasteurizing by the hot shower. This is because it is general, and the mouth portion is a portion that is not stretched in the biaxial stretch blow molding, and heat resistance is not imparted by the stretching effect.

On the other hand, the resin layer that imparts the barrier property, the light shielding property, the ultraviolet absorbing property, and the like is preferably arranged over the entire area of the shoulder, body, and bottom of the bottle. Thus, the function-imparting resin layer c is uniformly provided on the body portion 42 and the bottom portion 43 of the preform 4.

By the way, such a multilayer preform is
In principle, a hot runner nozzle 9 having a structure illustrated in FIG. 3 is used, and a polyester resin and a functional resin are injected into the flow paths D, E, and F of the hot runner nozzle 9, respectively, and both are injected. Can be manufactured by co-injecting while adjusting the timing. Here, the flow passage D has a linear flow passage D ₁ which linearly communicates with the gate portion 22 of the injection mold 2, and the flow passages E and F are respectively linear flow passages D.
₁ has a cylindrical channel E _1, and F ₁ which surrounds concentrically.

However, when a multilayer preform is manufactured using such a hot runner nozzle, the flow of the polyester or the functional resin in the cavity often occurs, and therefore the thickness of each resin layer is reduced. The bottle wall and mouth may not be symmetrical, or the inner layers may not be formed to the desired thickness and the inner resin layer may be too close to either of the walls forming the cavity of the injection mold. It was

Depending on how the resin flows, the temperature in the hot runner nozzle is not uniform (the temperature in the circumferential direction is not uniform with respect to the resin flowing direction), or the cross-sectional area of the flow path in the circumferential direction due to the minute bending of the resin flow path. It is considered to be due to non-uniformity or the like, but if such a flow pattern of the resin occurs, it is inconvenient because the function to be imparted cannot be sufficiently exhibited and the multilayer structure changes for each product.

Therefore, an object of the present invention is to have a plurality of functions such that the mouth portion has heat resistance and the shoulder portion, the body portion, and the bottom portion have a barrier property, a light shielding property, and the like. It is to provide a method for manufacturing a preform for giving a bottle and an apparatus capable of carrying out the method, and particularly to prevent the flow of resin from bending,
It is an object of the present invention to provide a method and an apparatus capable of accurately manufacturing a desired preform having a multilayer structure.

[0014]

As a result of earnest research in view of the above object, the present inventor has found that a linear flow passage and a concentric double spiral flow passage and a cylindrical flow passage are provided in that order in that order. With the hot runner nozzle formed, polyester resin is injected into the linear flow path and cylindrical flow path, and the first functional resin and the second functional resin are injected into the double spiral flow path, respectively. It was discovered that co-injection of a resin can prevent the resin from flowing, and a desired preform having a multi-layer structure can be produced. Thus, the present invention has been completed.

That is, the apparatus of the present invention for producing a bottomed cylindrical multilayer preform comprises (a) a cavity corresponding to the multilayer preform, and a position corresponding to the bottom of the multilayer preform. An injection mold with a gate at (b)
A hot runner nozzle communicating with the injection mold is provided, and the hot runner nozzle is one linear flow path, and a double spiral flow path and a cylinder that are concentrically provided around the linear flow path in order from the inside. A linear flow path, the linear flow path and the cylindrical flow path are joined from each other at a position slightly upstream of the injection port that branches from the first injection port and communicates with the gate portion of the injection molding die, The double spiral flow path communicates with the second and third injection ports, respectively, and advances toward the injection port without intersecting with each other, each of which is a confluence point of the linear flow path and the cylindrical flow path. It is characterized in that it joins the straight flow path in front.

The method of the present invention for producing a multilayer preform having a bottomed cylindrical shape by using the above-mentioned apparatus is such that the polyester resin is injected into the first injection port and the second and third Injecting heat-resistant resin and functional resin into the inlets respectively, (a) injecting the polyester resin from the linear flow path and the cylindrical flow path to fill the middle of the cavity with polyester, (b) the heat resistance Resin and the polyester resin are co-injected, (c) after the injection of the heat-resistant resin is stopped, the functional resin and the polyester resin are co-injected, so that the heat-resistant resin at the mouth of the molded body. In addition to being concentrated, the portion other than the mouth portion is substantially formed into a multilayer structure of polyester resin and functional resin.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an apparatus for manufacturing a multilayer preform according to an embodiment of the present invention, showing a state in which a hot runner nozzle 1 and an injection mold 2 are connected.

First, the hot runner nozzle 1 has three flow passages A, B, and C. The flow passage A further includes a central linear flow passage A ₁ and a cylindrical flow passage A provided outside thereof. Divided into _two . Further, the linear flow path A ₁ and the cylindrical flow path A ₂ join together slightly upstream of the injection port 15. The valve 13 provided upstream of the confluence point of the linear flow path A ₁ and the cylindrical flow path A ₂ is a rod-shaped operation valve, and moves vertically due to a change in resin pressure injected into the flow path A. Then, it is designed to open and close.

On the other hand, the flow passages B and C are spiral flow passages B ₁ and C ₁ which go around the straight passage A _{1 from} the upstream portion thereof.
Is formed, and the spiral shape continues until just before the confluence of the linear flow path A ₁ and the cylindrical flow path A ₂ . Immediately before joining with the linear flow path A ₁ , short cylindrical flow path portions B ₂ and C ₂ are formed. The spiral flow path B ₁ and the spiral flow path C ₁ spirally advance around the straight flow path A _{1 in} the direction of the outlet without intersecting with each other, but both spiral flow paths are the same cylinder. The surface is formed in a double spiral shape.

However, when it is better to intentionally make a temperature difference between the resin flowing in the spiral flow passage B ₁ and the resin flowing in C ₁ , both spiral flow passages The diameter of the spiral may be changed appropriately. An example thereof is shown in FIG.

The injection mold 2 has a cavity 21 having a shape corresponding to that of the multilayer preform 4 shown in FIG. 4, and the injection port 15 of the hot runner nozzle 1 has the bottom center of the multilayer preform as a gate. Is in communication with. The multilayer preform 4 has a mouth portion including a screw tightening portion 44 and a support ring 45.
41, a body 42, and a bottom 43.

Next, a method of manufacturing a multilayer preform using the above apparatus will be described with reference to the accompanying drawings. 2 (a) to 2 (d) show that the mouth portion has three layers of functional resin (for example, heat-resistant resin), and the trunk portion and the bottom portion have one layer of functional resin (for example, barrier resin or FIG. 3 is a schematic cross-sectional view showing a co-injection step of producing a preform having a multilayer structure including a layer made of a light-shielding resin).

First, in the step of FIG. 2A, the linear flow path A ₁
And the polyester resin 30 is injected from the cylindrical flow path A ₂ ,
Fill a portion of cavity 21.

Next, the resin pressure in the flow passage B is increased to increase the linear flow passage A.
_The functional resin 31 is injected between ₁ and the polyester resin injected from the cylindrical flow path A ₂ (FIG. 2 (b)). If the sizes (cross-sectional areas) of the linear flow path A ₁ and the cylindrical flow path A ₂ are set appropriately, the functional resin 31 is the polyester resin 30.
Can flow in the center of. The functional resin 31 is
Polyester resin 30 without touching the inner wall of the injection mold
Since it goes through the interval, there is little decrease in the resin temperature and the fluidity is large. Therefore, it moves faster than the polyester resin 30. Here, since the functional resin 31 passes through the spiral flow path in the hot runner nozzle, the temperature of the resin can be kept uniform even if the hot runner nozzle is not partially soaked. , The center of the polyester resin 30 is flowed without causing a flow bias such that it approaches the inner wall surface of one of the cavities of the injection mold.

When a predetermined amount of the functional resin 31 is co-injected, the resin pressure in the flow passage B is lowered, and the linear flow passage A ₁ and the cylindrical flow passage A ₂ are injected.
Then, only the polyester resin is injected, and then the resin pressure in the flow path C is increased to provide another functional resin 32 between the polyester resins injected from the linear flow path A ₁ and the cylindrical flow path A _2. Inject (Fig. 2 (c)). Since the previously injected functional resin 31 flows inside the polyester resin, it advances faster than the polyester resin as described above, overtakes the polyester resin 30 as shown in FIG. 2 (c), and removes the tip of the fluid resin layer. Will occupy.

Furthermore, polyester resin 30 and functional resin 32
Are co-injected to fill the injection mold (FIG. 2 (d)), and finally the pressure in the injection mold is adjusted (holding pressure) to finish.

As described above, if the timings and injection amounts of the three types of resins are properly adjusted, the three functional resin layers (heat resistant resin layers) and the two polyester resin layers are formed at the mouth. It is possible to manufacture a preform having an alternating multilayer structure and having a three-layer structure of polyester layer / functional resin layer / polyester layer on the body and bottom from the outside. The outermost resin layer 31a and the innermost resin layer 31c of the functional resin are formed in the mouth portion because the functional resin 31 occupying the resin tip portion is injected as shown in FIG. 2 (c). This is because the functional resin at the portion in contact with the inner wall of the molding die lowers the fluidity at that portion in order to move inside the cavity by coming into contact with the inner wall of the molding die, and the polyester resin flowing inside moves faster.

The method for manufacturing a multilayer preform by the apparatus of the present invention has been described above. As shown in FIG. 2 (d), the multilayer structure having the functional resin layer 32 covered with the polyester layers 30a and 30b is used. If a preformed product is used, for example, even if a mixture of polyester and an ultraviolet absorber is used as the functional resin layer 32, the ultraviolet absorber blooms.
This is advantageous because it can prevent Further, when a polyester containing carbon is used as the functional resin layer 32 for the purpose of shielding light, the black color of carbon can be prevented from being seen by coloring the outer polyester layer 30a with another color. . Furthermore, for example, if the inner functional resin layer 32 has a light-shielding property and the outer polyester layer has a barrier property, it is possible to add two more functions to the bottle in addition to the heat resistance of the mouth. Becomes

As the polyester resin which can be used, there is a thermoplastic resin containing a saturated dicarboxylic acid and a saturated dihydric alcohol. Examples of the saturated dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenyl ether-
4,4′-dicarboxylic acid, diphenyldicarboxylic acids, aromatic dicarboxylic acids such as diphenoxyethanediethanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, and aliphatic dicarboxylic acids such as decane-1,10-dicarboxylic acid, Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used. As the saturated dihydric alcohol, ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol,
Aliphatic glycols such as polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol, neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) )
Propane and other aromatic diols can be used. A preferred polyester is polyethylene terephthalate consisting of terephthalic acid and ethylene glycol.

The polyester resin used for producing the multilayer preform has an intrinsic viscosity of 0.5 to 1.2, preferably 0.7 to 0.9.
Has a value in the range of. In addition, such polyester,
Manufactured by melt polymerization and heat-treated under a reduced pressure or an inert gas atmosphere at a temperature of 180 to 250 ° C, or solid phase polymerized to reduce the content of low molecular weight oligomers and acetaldehyde. Is preferred.

As the heat resistant resin, a polyester resin having a high heat distortion temperature such as polyarylate, polycarbonate, polyacetal, polysulfone, polyetheretherketone, polyethersulfone, polyetherimide, polyphenylene sulfide, polyethylene naphthalate, and the like. A blend polymer of these resins and polyethylene terephthalate, a blend polymer between the above heat resistant resins, and a blend polymer of two or more kinds of the above heat resistant resins and polyethylene terephthalate, U polymer (manufactured by Unitika Ltd., A blend polymer of polyarylate and polyethylene terephthalate), THERMX (manufactured by EASTMAN, cyclohexadimethanol modified copolyester) and the like can be used.

Next, as the barrier resin, ethylene vinyl alcohol copolymer resin, high nitrile resin, polyacrylonitrile, copolymer of acrylonitrile, methyl acrylate and butadiene (commercial product), which has excellent gas barrier properties against oxygen, carbon dioxide gas, etc. Name: Barex), polyvinyl chloride, nylon MXD6 consisting of metaxylylenediamine and adipic acid, polyethylene isophthalate copolymer, isophthalic acid or terephthalic acid, ethylene glycol and 1,3-bis (2-hydroxyethoxy) benzene And a liquid crystal polyester of various types. Specifically, XYDAR (made by Dartco), VECTRA (made by Celanese Polyplastics)
, Econor (Sumitomo Chemical Co., Ltd.), Rod Run (Unitika Co., Ltd.), EPE (Mitsubishi Kasei Co., Ltd.), X7G (Eastman), ULTRAX (BASF). A blend polymer of the above barrier resin and polyethylene terephthalate may be used.

Further, as a material excellent in both gas barrier property and water barrier property, a blend polymer of a polyethylene copolymer (PETG) comprising terephthalic acid, ethylene glycol and cyclohexanedimethanol and an ethylene vinyl alcohol copolymer, A blend polymer of PETG and polyvinyl alcohol described above can be used.

Polyolefin, vinyl chloride resin and the like are suitable for forming a bottle excellent in moisture resistance.

Next, as the ultraviolet absorbing resin, a resin such as polyethylene terephthalate or a blend polymer of polyarylate and polyethylene terephthalate, which is previously kneaded with an ultraviolet absorbing agent such as a benzophenone type or a benzotriazole type, can be used.

Further, in order to obtain a light-shielding property or to color the bottle from the viewpoint of fashionability, a colored resin is used. As such a colored resin, a desired resin is used, as is usually done. The thing colored by adding the coloring agent which has a color tone can be used. Considering the adhesiveness between resin layers and the moldability, it is preferable to use the polyester resin as described above as a base and convert the colorant into the base. There are mainly dyes and pigments as colorants, but heat resistance, light resistance,
Considering color transfer resistance, etc., it is preferable to use a pigment,
It is preferable to knead this with a polyester resin to obtain a colored resin.

The polyester resin used in the present invention,
Additives such as stabilizers, pigments, antioxidants, heat deterioration inhibitors, UV deterioration prevention agents, antistatic agents, antibacterial agents and the like in heat resistant resins or colored resins within the range not impairing the object of the present invention. An appropriate amount of resin can be added.

The present invention will be described in more detail with reference to the following specific examples. Example 1 NEH2050 (manufactured by Unitika Ltd.) was used as the polyethylene terephthalate resin, and a blended polymer of polyethylene terephthalate and polyarylate (U polymer 8400, manufactured by Unitika Ltd.) (hereinafter referred to as U polymer) was used as the heat resistant resin. Further, MX nylon was used as a barrier resin to form a multi-layer preform by a co-injection molding method. As injection molding equipment, A manufactured by Nissei ASB Machinery Co., Ltd.
Using the SB50TH machine, the hot runner nozzle shown in FIG. 1 was connected, and the multi-layer preform was molded according to the co-injection process shown in FIG.

At this time, the injection barrel temperature on the polyethylene terephthalate side is 270 ° C., the injection barrel temperature on the U polymer side is 280 ° C., the injection barrel temperature on the MX nylon side is
The temperature was 270 ° C.

The obtained multilayer preform was cut in the axial direction and its cross section was observed. As a result, as shown in FIG. 2 (d), the mouth was found to have three heat resistant resin layers and two polyester resin layers. It has a multilayer structure in which layers alternate with each other, and a particularly thick layer or a thin layer was not formed in the circumferential direction in the resin layer constituting this multilayer structure. The cross-sections of the body and bottom are also very similar to the multi-layer structure shown in Fig. 2 (d), and the middle layer made of MX nylon is almost entirely in the polyester resin without depending on either the inner or outer wall surface of the preform. It was formed in the center. The above shows that the resin was co-injected without any tendency to flow.

[0041]

As described above in detail, when the apparatus of the present invention is used, three kinds of resins are co-injected without causing the flow of resin to be twisted, and a desired multi-layer structure (5 layers at the mouth, cylinder Part 3) preforms can be produced.

Therefore, by using the multilayer preform according to the present invention, a biaxially stretch blow molded polyester bottle having a plurality of functions can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an apparatus for manufacturing a multilayer preform according to an embodiment of the present invention.

2 (a) to (d) are schematic cross-sectional views showing a co-injection process for producing a preform having a multi-layered structure in its mouth.

FIG. 3 is a schematic cross-sectional view showing an example of a hot runner nozzle used in conventional co-injection molding.

FIG. 4 is a cross-sectional view showing an example of a layer structure of a multilayer preform.

FIG. 5 is a schematic sectional view showing an apparatus for manufacturing a multilayer preform according to another embodiment of the present invention.

[Explanation of symbols]

 1,9 Hot runner nozzle 2 Injection mold 4 Multilayer preform 15 Injection port 21 Cavity 30 Polyester resin 31, 32 Functional resin 41 Port 42 Body 43 Bottom A, B, C, D, E, F Flow path

Claims (3)

[Claims] 1. An apparatus for manufacturing a bottomed cylindrical multilayer preform, comprising: (a) a cavity corresponding to the multilayer preform, and at a position corresponding to the bottom of the multilayer preform. An injection molding die having a gate, and (b) a hot runner nozzle communicating with the injection molding die, wherein the hot runner nozzle is provided with one straight flow passage and a concentric circle in the order from the inside. Has a double spiral flow path and a cylindrical flow path, and the linear flow path and the cylindrical flow path branch from the first injection port and communicate with the gate portion of the injection mold. Merging slightly upstream of the injection port, the double spiral flow paths communicate with the second and third injection ports, respectively, and proceed in the direction of the injection port without crossing, and each of the linear flow paths The straight flow before the confluence of the channel and the cylindrical flow path. Multilayer preform manufacturing apparatus characterized by being joined to. 2. The apparatus according to claim 1, wherein each of the double spiral flow passages has a cylindrical space just before joining with the linear flow passage, where the double spiral flow passage becomes a cylindrical flow passage. An apparatus for manufacturing a multi-layer preform, characterized in that it merges with the linear flow path. 3. A method for producing a bottomed cylindrical multilayer preform using the apparatus according to claim 1 or 2, wherein a polyester resin is injected into the first injection port, and the second and Injecting a heat-resistant resin and a functional resin, respectively, into the third inlet, (a) injecting the polyester resin from the linear flow path and the cylindrical flow path to fill the polyester resin up to the middle of the cavity, b) co-injecting the heat-resistant resin and the polyester resin, (c) after stopping the injection of the heat-resistant resin, co-injecting the functional resin and the polyester resin, so that at the mouth of the molded body A method comprising concentrating a heat resistant resin and substantially forming a part other than a mouth part into a multilayer structure of a polyester resin and a functional resin.