JPS60201909A - Manufacture of multilayer stretch blown bottle - Google Patents

Abstract

PURPOSE:To obtain a desired multilayer stretch blown bottle by a method wherein the 1st injected preform is placed in a mold at temperatures distributed so that they are low on the injection gate side and high on the opposite side and thermoplastic resin on and after the 2nd stage is injected and molded. CONSTITUTION:Gas barrier resin is applied to the outer surface of the primary molded article manufactured by the 1st stage injection molding of polyester and dried to make a coated article. The primary preform coated article 13' controlled so that the injection gate side 14 is low in temperature and the opposite side 15 is high is held by the core 17 and the gripper 18 and inserted into the cavity 20 of the molds 19a, 19b. In the secondary injection process polyester resin is injected from the gate at the bottom of the mold to the clearance between the cavity 20 and the coated article 13' to manufacture a multilayer preform with a bottom. This multilayer perform takes finally a bottle shape at a stretch blowing process. It becomes possible to manufacture the desired multilayer stretch blown bottle by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer stretched blow bottle, and more specifically, the present invention relates to a method for manufacturing a multilayer stretched blow bottle. The present invention relates to a method for manufacturing a multilayer stretched blow bottle with excellent uniform distribution of.

In the method of manufacturing a stretched blow bottle, a method of forming a bottomed preform by injection molding a stretchable thermoplastic resin and performing a stretching blow bottle using this preform is as follows:
Axial stretching by pushing in a stretching rod and blow stretching in the circumferential direction are possible at the same time, and the resulting product has advantages such as a well-balanced molecular orientation in the biaxial directions. It is widely used in the production of stretched blown bottles.

Expanded polyethylene terephthalate (pET) bottles are currently used overseas for carbonated soft drinks, beer, whiskey, etc., and in Japan for food products such as soy sauce, sauces, dressings, and cooking oil, as well as non-food products such as synthetic detergents and cosmetics. There is. Recently, its use has been expanding both domestically and internationally, including beer, carbonated soft drinks, and fruit juice.

Stretched PET bottles have excellent features such as transparency, strength, and light weight, as well as gas barrier properties and gas pressure resistance, which are factors that have expanded their use. However, even among plastic containers, even stretched PET bottles, which have excellent properties, are still plastic and have some gas permeability, whereas metal containers and glass bottles are completely gas impermeable. For example, there is a limit to the shelf life of various types of carbonated beverages that are filled and sealed, which inevitably limits the distribution period of the product, which poses a considerable hindrance to product sales plans. The reality is that the E7 has arrived.

In this case, the greater the carbon dioxide pressure and the smaller the capacity of the container, the greater the damage.

To solve the gas permeation problem in stretched bottles,
1 for an oriented resin layer such as polyester. Therefore, it has been proposed to laminate gas barrier resin layers such as non-vinyl alcohol copolymer, vinylidene chloride resin, etc., and these known methods prevent the influence of humidity etc. on the gas barrier resin layer. In order to avoid this, a laminated structure is generally adopted in which a gas barrier resin layer is sandwiched between inner and outer layers of moisture-resistant resin capable of molecular orientation.

In manufacturing this multilayer stretched bottle, each of the resin layers described above is coextruded to form a laminated structure with an adhesive resin interposed as needed. There is also a method of subjecting the film to sequential biaxial stretching, which consists of
There is a risk that the gas barrier resin system will fibrillate in the first stage of stretching, and that problems such as cracks will occur during the second stage of blow stretching.

From this point of view, polyjI′! for stretch-blow molding! J preform, it is desirable to manufacture a bottomed preform by multi-stage injection molding and to subject this brief yarn to biaxial stretching almost simultaneously.

However, when producing a bottomed multilayer preform for stretch molding using multi-stage injection molding, the resin injected in the second stage and subsequent stages does not completely surround the molded product in the first stage, resulting in a so-called short mold. [or the overall wall thickness is the same as that of the final cavity], the disadvantage is that the distribution of the wall thickness of each layer becomes extremely uneven, and as a result, the wall thickness of each layer of the final bottle becomes The thickness distribution was also unexpectedly poor.

This causes the inconvenience of being symmetrical.

Therefore, it is an object of the present invention to effectively eliminate the drawbacks of the conventional methods described above, and to produce a 1 m 7'
To provide a blow bottle (7) 'JJ a method using remodeling.

Another object of the present invention is to provide a method for molding a multilayer preform that does not cause the aforementioned short molding and can maintain the thickness of each resin layer at a set thickness over the entire preform.

Still another object of the present invention is to prevent the gas barrier resin layer from becoming thinner, especially at the bottom, and to
It is an object of the present invention to provide a method for manufacturing a multilayer stretched blow bottle that effectively prevents the occurrence of cracks or fissures due to stretching of a resin layer.

According to the present invention, a bottomed multilayer preform in which at least one resin is made of a thermoplastic resin capable of molecular orientation is manufactured by multistage injection molding of a thermoplastic resin17, and this multilayer preform is axially In a method for manufacturing a multilayer stretched blow bottle that involves blow stretching in the circumferential direction while stretching, the first stage injection molded preform or its coating is heated at a temperature distribution such that the injection gate side is at a low temperature and the opposite side of the gate is at a product temperature. , preferably with a temperature difference of at least 1 ocS% and at least 201" between the two in an injection mold, and the injection molding of the thermoplastic resin in the second and subsequent stages is performed. A method is provided, the method comprising:

The present invention will be described in detail below based on specific examples shown in the accompanying drawings.

In FIG. 1 showing a multilayer preform used in the present invention, this preform includes an open end 1, a screw 2 for engaging a cap, a step shoulder 6, and a support ring (neck ring).
4f: Consists of a neck 5 with a thick body 6 to be stretched and a closed bottom 7.

The neck portion 5 is made of polyester alone, while the body portion 6 and closed bottom portion 7 below the neck portion have a laminated structure of a polyester inner layer 8, a gas barrier resin intermediate layer 9, and a polyester outer layer 10. The neck portion 5 and the polyester inner layer are integrally formed, and the gas barrier resin intermediate layer 9 is provided by injection molding or coating so that one end thereof reaches just below the armor portion, and the outer layer 10 and the neck portion 5 The seam 11 is directly below the neck or through an intermediate layer.
is formed. ° One object of the present invention is to prevent non-uniformity in thickness due to thinning of the intermediate layer 9 and/or inner layer 8 in the closed bottom portion 7 and its vicinity, and to improve the throwing power of the outer layer 10 in this multilayer preform. The object of this invention is to use the above-mentioned means for this purpose.

In Figures 2-A to 2-G for detailed explanation of the present invention, first, in the first step (Figure 2-A), a primary molded product 12 is manufactured by first-stage injection molding of polyester. This second molded product 12 corresponds to the neck portion 5 and polyester inner layer 8 of the multilayer preform described above.

In the next process (Figure 2-8), this primary molded product 12
A gas barrier resin such as ethylene-vinyl alcohol copolymer or vinylidene chloride copolymer is applied in the form of a solution or latex to the outer surface of the film, and is dried to form a gas barrier resin coating layer 9.

In the present invention, as shown in FIG. 2-c, the injection gate side, that is, the bottom side 14 as measured in the figure, of this enriched material 16 is at a low temperature, and the opposite side, that is, the side 15 connected to the neck part is high temperature. The temperature of the covering 16 is controlled to achieve a temperature distribution. For this purpose, a shielding plate 16 is provided between the image parts 14 and 15,
While heating the upper part 15 with hot air or dielectric heating,
The lower portion 14 is cooled by means such as water cooling to form the temperature distribution described above.

Next, in FIG. 2-D, the neck 5 of the primary preform covering 16' having the above-described temperature distribution formed therein is gripped by the gripping fitting 18, and the core 17 is inserted into the neck portion 5 of the primary preform covering 16'.

In the second stage injection process shown in FIG. 2-E, with the primary preform covering 16' having a temperature distribution formed therein held by the core 17 and the gripping tool 18, the mold 1'? z, 19A
into the cavity 20 of.

Between the cavity 20 and the covering layer 9 there is a clearance corresponding to the outer layer 10 of the final pref Ohm. In this state, polyester is injected through the gate 21 of the mold. In the case of manufacturing a multilayer preform by multi-stage injection, the overall thickness is limited to less than the cutting thickness from the viewpoint of stretching workability and economical aspects. Generally, the thickness of the layer formed in the second stage injection molding is limited to a layer thinner than that thickness. If this thickness exceeds two throats,
Since there is no problem with the pressure inflow of the molten resin to be injected, the troubles described below do not occur.However, in actual second stage injection, the distance between the primary preform and the cavity is considerably thinner than the above thickness. It's refreshing.

In this case, unless the temperature of the surface of the primary molded product is sufficiently high, the resin injected in the second stage will not completely cover the primary preform, which may result in a short mold. Even if the injected plastic is injected at a high temperature between the two, the temperature of the primary molded product corresponding to the core is low, and the temperature of the second stage cavity is low, and if the gap is narrow, the molten resin This is because the mold becomes short and solidifies without being able to fully rotate.

Therefore, in order to make it easier to perform the second stage injection into a narrow flare space, it is better to raise the temperature of the first molded product and the temperature of the second stage injection mold cavity appropriately. However, there are certain limits to it. 1. In other words, even if the resin in the second stage is injected, in order to be able to take out the molded product continuously from the mold,
・If the temperature of the tee is not below a certain temperature, the molded product will stick to the mold (Bucherocking), so the temperature of only the primary molded product must be controlled while keeping each temperature below a certain temperature.゛Also, when the second stage injection of extremely high temperature resin is performed on the primary molded product, the part of the primary molded product near the gate of the injection mold is exposed to high temperature and high pressure. The injection gate side, i.e., the lower end, will re-melt and become fluid and thin, or in extreme cases, the inner layer will flow out.1. There are even cases where it goes 1~. (7) Although it varies depending on the type of molten resin to be injected and the temperature of the resin, it is generally better to keep the lower part near the gate of the primary molded product (primary preform - inner layer) as cool as possible. Injection multilayering progresses smoothly.

As mentioned above, when the distance between the primary preform and the second stage cavity is thin and the passage is long, it is better to keep the temperature of the primary cedar crystals as high as possible. There is a contradictory requirement that it is better to keep the temperature as low as possible.

In the present invention, these conflicting requirements can be resolved by providing the above-mentioned temperature distribution to the preform, thereby eliminating short molding and preventing uneven thickness of the inner layer or intermediate layer of the preform.1. 2. It is possible to maintain each layer at a set thickness over the entire surface of the preform.

In the embodiment shown in the drawings, where the inner and outer layers are PET and the covering layer is an ethylene-vinyl alcohol copolymer layer, the temperature of the upper part 15 of the primary preform held in the mold cavity is about 40 to 80C. range, especially 40 to 6
DC, the temperature of the lower part 14 is below 30tT, especially -10'
If the temperature distribution is in the range of c to 20 tl'', it is possible to control each layer to a set thickness while preventing short molding.

In the second stage injection molding shown in FIG. 2-E, a multilayer preform having the cross-sectional structure shown in FIG. It is supported by a tool 18 and preheated to the stretching temperature of pET in a preheating step shown in FIG. 2-F.

Finally, in the stretch blowing step shown in FIG. 2-G, the preform 21 is placed in a blow molding die 22α.

22b and the mold is clamped, the stretching rod 26 is pushed in and stretched in the axial direction, and at the same time the blow hole 24 of the stretching rod is inserted.
A fluid is blown into the bottle to blow it in the circumferential direction to form the final bottle shape.

According to the stretch blow molding method of the present invention, the thickness of each layer in the bottomed multilayer preform, especially the gas barrier layer, can be maintained at a predetermined set thickness, and simultaneous 2T11 + blow stretching is possible, so cracks in the barrier layer can be maintained. This makes it possible to prevent the occurrence of , making it possible to obtain a bottle with excellent properties, especially gas barrier properties, transparency and other appearance properties, impact resistance, etc.

Although the present invention has been described with reference to an example of a multilayer bottle in which the inner and outer layers are made of polyethylene terephthalate, the present invention is also applicable to other resins whose molecules can be oriented by stretching, such as polypropylene, polycarbonate, polyarylate, polybutylene terephthalate, etc. It is equally applicable to plastic polyesters and the like.

Further, although the present invention has been described with respect to two-stage injection molding, it is natural that the present invention can be applied to multi-stage injection molding with three or more stages. For example, gas barrier resin is used in the second injection stage.
It is also possible to use an oriented resin such as polyester for the third injection stage, and to adopt the conditions described above for the second and subsequent injection stages.

The invention is illustrated by the following examples.

In the example, a primary preform (length 110, inner diameter 25φ, thickness 2.0
Q) is formed. The part below the neck ring of this preform is coated with a urethane adhesive solution (methyl ethyl ketone solution of tolylene diisocyanate and linear polyester).
The inside of the paint preform is dried with hot air at a temperature of 90U, and then the preform is coated with vinyl alcohol. After soaking in 85 molti ethylene-vinyl alcohol copolymer/7" o Hanol Φ water mixed solution and drying with hot air at a temperature of 100C, and further soaking in the urethane adhesive solution, 95t
While drying with hot air at a temperature of The polyethylene terephthalate is then cooled to the following temperature and the body is adjusted to a temperature that causes elastic deformation (e.g. 40 to 70C) and inserted into the injection mold (core). was injected to form a multilayer preform with a wall thickness of 5.5 m, and after heating this multilayer preform to a temperature of 95 iC, stretch blow molding was performed to obtain a body with an average wall thickness of 300 μm and an internal volume of 5 m.
A multilayer bottle of 0.00 CC was obtained.

This bottle has an oxygen permeability of 2.1CC/11?・dL
'Lv・a, tm-37C, is 115 or less compared to a single polyethylene terephthalate bottle, and 1
No peeling between the layers was observed after 0 repeated drops.

Example 2 A preform of polyethylene terephthalate (intrinsic viscosity 0.7) having a length of 110°, an inner diameter of 25φ, and a wall thickness of 1.5B was molded by injection molding. After immersing this preform in vinylidene chloride-based aqueous latex, it was dried with hot air at a temperature of 1 oor, and then the neck and bottom parts of this painted preform were cooled to about 15C, and the other parts ( body) at a temperature at which it has elastic deformability (for example, 40
-70C) to A temperature [-2] and insert it into the injection mold (core),
The painted surface (outer surface) of this painted preform has an intrinsic viscosity of 0.
7 polyethylene terephthalate is injected to make the wall thickness 6.
A multilayer preform with five gates was molded, and this multilayer preform was heated to a temperature of 95C and then stretch blow molded to obtain a multilayer bottle with an average body wall thickness of 300 μm and an internal volume of 500 bottles.

This bottle has an oxygen permeability of 4.5 (L/lt?・da
y.atm.37tZ' was less than 1/3 of that of a single polyethylene terephthalate bottle, and no peeling between the layers was observed after 10 repeated drops.

In addition, the oxygen permeability of a single polyethylene terephthalate bottle is 15 CC/n? It was @day*atm-37C.

Example 3 Intrinsic viscosity 0.7, isophthalic acid content 8 moles 9!1
ethylene terephthalate copolymer is injection molded to produce a primary preform having a neck part with a neck ring (
The length is 110m, the inner diameter is 25φ, and the thickness is 2. The part of this preform below the neck ring is immersed in a urethane adhesive and dried with hot air at a temperature of 90C, and then this coated preform is coated with a vinyl alcohol-containing t 85 molar ethylene-vinyl alcohol copolymer/ After immersing in a furopanol/water mixed solution and further immersing in the urethane adhesive solution, 95C
The coating preform was dried with hot air at a temperature of 30C, the mouth and bottom of the preform was cooled to about 30C, and the body was heated to a temperature at which it could be elastically deformed, and the preform was inserted into an injection mold (core). , Polyethylene terephthalate with an intrinsic viscosity of 0.7 is injected onto the painted surface (outer surface) of this painted preform to form a multilayer preform with a wall thickness of 6.5R, and this multilayer preform is heated to a temperature of 95C. After that, biaxial stretch blow molding was performed to obtain a body with an average wall thickness of 0.3 mm and an internal volume of 50 mm.
A multi-J bottle of 0CC was obtained.

The oxygen permeability of this bottle is 2.3CC/-・day・α
tm@37C, it is 115 or less compared to a single polyethylene terephthalate bottle, and it is also
No peeling between the layers was observed after repeated drops.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multilayer preform used in the present invention, and FIGS. 2-A to 2-G are sectional views of each step of the present invention. 5... Neck, 6... Torso, 7...
...Bottom, 8...Inner layer, 9...Middle layer, 10...Outer layer, 12...-Next molded product, 13...・Coating, 16'...-Next preform coating, 16... Shielding plate, 17...
... Core, 19α, 19b ... Mold, 2
1...Multilayer preform, 22α, 22b...
...Blow 11. ．． 23...Stretching rod. Patent applicant: Toyo Seikan Co., Ltd. Figure 1 Figure 2-A Figure 2-8 Figure 1 Figure 2-C Figure 2-D Figure 1 8

Claims (1)

[Claims] (1) A bottomed multilayer preform in which at least one of the resins is composed of a thermoplastic resin capable of molecular orientation is manufactured by multistage injection molding of the thermoplastic resin, and this multilayer preform is stretched in the axial direction. In a method for producing a multilayer stretched blow bottle, which involves blow stretching in the circumferential direction while ... Method 0, characterized in that the thermoplastic resin is placed in an injection mold in a state in which the thermoplastic resin is injected in the second and subsequent stages.