JPS62199425A - Manufacture of heat shrinkage resistant gas-barrier biaxially oriented polyester container - Google Patents

Abstract

PURPOSE:To perform rapid molding processing by enhancing heating and cooling efficiency at the time of molding to a large extent, by interposing an intermediate layer having a heat insulating property and a gas barrier property between inner and outer layers comprising a polyester resin. CONSTITUTION:An intermediate layer 4 (e.g., a nylon 6/nylon 66 copolymer layer) having a heat insulating property and a gas barrier property is interposed between inner and outer layer 2, 3 comprising a polyester resin and bottom neck parts 12, 13, 14 are further formed to obtain a multilayered preform 11. After this preform 11 was preheated, the heated preform 11 is stretched by a stretching rod 25 in a blow mold of which the cavity surface is heated to 145 deg.C and, at the same time, compressed gas is blown in the preform from a fluid passage 27 to perform blow molding. After molding, a cooling fluid (e.g., cooling nitrogen gas) is made to flow into a molded body 29 from the fluid passage 27. The inner layer 2 is rapidly cooled because of the presence of the intermediate layer 4 and shape holdability necessary for taking-out is immediately obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a heat-resistant multilayer stretched polyester container, and more specifically, a layer made of a thermoplastic polyester such as polyethylene terephthalate has a sparring property. The present invention relates to a method for efficiently manufacturing a multilayer stretched polyester container having excellent heat resistance and heat shrinkage resistance, including a layer made of resin, using only one type of mold.

(Prior art) Stretched bottles made of polyethylene terephthalate (PET) have advantages such as transparency, impact resistance (drop resistance), lightness, hygiene, appropriate gas barrier properties such as oxygen and carbon dioxide, and pressure resistance. Excellent for use in soy sauce, sauces, dressings, cooking oil, beer, cola, carbonated drinks such as cider, fruit juice drinks, mineral water, shampoo, detergents, cosmetics,
Widely used as packaging containers for wine, Kara 7, aerosol products, etc.

However, since stretched polyester bottles are also made of plastic, gas permeability can be considered to be equal to zero in completely sealed items such as glass bottles and metal cans, whereas stretched polyester bottles have a high gas permeability of oxygen and carbon dioxide. It has a slight permeability to substances such as beer, cola, cider, etc., and is inferior to cans and glass bottles in terms of food filling and storage stability. There is a clear limit on the shelf life, and fruit juice-containing beverages also have a limited shelf life due to the permeation of oxygen from the outside.

In addition, stretched polyester is significantly superior to other plastics in terms of transparency, gas barrier properties, and pressure resistance against gas-filled beverages, but the stretching and forming temperature is relatively low (80 to 110°C). ) and has no heat resistance due to the presence of non-stretched or low-stretched regions, so when it is filled with holatonoduck, the filling temperature must be 65°C or lower for practical use, which has the disadvantage of losing its shape retention. .

In order to eliminate this drawback, heat treatment (heat setting) of the non-stretched parts (e.g. neck and neck) and stretched parts (e.g. body) of polyester bottles has already been proposed.
There is a way to do this. This heat treatment method involves a so-called one-mold process in which a mold for stretch blow molding is maintained at a high temperature for heat treatment, heat treatment is performed within this mold following stretch blow molding, and the mold is cooled and removed from the mold. According to the method (for example, Japanese Patent Publication No. 59-6216), a mold for stretch blow molding is maintained at a high temperature for heat treatment, heat treatment is performed in this mold following stretch blow molding, and the blow molded product is taken out and then The so-called two-mold method (for example, Japanese Patent Application Laid-Open No. 57-533
No. 26) is known.

(Problems to be Solved by the Invention) However, although the conventional single-layer PET & ) film has moderate gas barrier properties, considering the current state of the art and taking economic efficiency into account, the type of content is limited. However, the distribution format is still not completely satisfactory. In order to improve the gas barrier properties of polyester, a method of forming multiple layers has been proposed.

It has not yet been put to practical use, and no material with excellent gas barrier properties, improved heat resistance, and heat deformability has been proposed.

In addition, when heat treatment is performed in one stretch blowing step, the molded product is cooled by passing cooling water into the mold to cool the blow mold, and the temperature of the molded product is brought to a temperature at which it can be removed from the blow mold. By cooling the bottle to a certain temperature and taking it out, a predetermined heat-treated polyester bottle is obtained.

However, in the former heat treatment method, heat treatment, and internal cooling are performed in the same blow mold, and each has its own processing time, so the time occupied in one mold is long. Nasi, normal / IJ Esther M
Since the molding time is 2 to 4 times longer than that of stretch blow molding, production efficiency is significantly lowered and manufacturing costs are increased. Furthermore, when the heat treatment temperature is increased, it takes a longer time to cool down the molded product to a temperature at which it can be removed from the mold, so there is a tendency to lower the natural heat treatment temperature. You will not be able to do so.

In addition, the latter heat treatment method requires two molds and a two-stage blowing operation, which increases the number of steps and equipment costs. In order to ensure that it enters the mold, the dimensions of the secondary blow-molded product must be smaller than those of the final molded product, taking into account the safety factor. Since stretching must be carried out to a certain degree, thermal contraction corresponding to this second stage expansion stretching occurs. Furthermore, this two-mold method has the problem that it is difficult to faithfully reproduce the shape of the mold cavity light surface on the surface of the blow-molded product during the secondary blowing process.

Therefore, the technical problem of the present invention is to solve the above-mentioned drawbacks in the conventional method for manufacturing a heat-set polyester biaxially stretched container, use only one type of metal, and reduce the time occupied by the blow molded product in the mold. To provide a method for manufacturing a biaxially oriented polyester container having an excellent combination of heat shrinkage resistance and gas barrier properties at a high production rate in a shortened time frame. (Means for solving the problems) The present invention According to the above, a multilayer preformed product comprising inner and outer layers made of polyester mainly composed of ethylene terephthalate units and at least one intermediate layer made of a gas barrier resin is preheated or controlled to an appropriate temperature for stretching, and the preform is The molded product is subjected to biaxial stretch blow molding in a mold maintained at a heat-fixing temperature range, and the blow molded body is also heat treated, after which the pressurized fluid for blow molding is switched to an internal cooling fluid, and By cooling the blow-molded body while bringing the gold into contact with the cavity surface to a temperature at which the blow-molded body does not lose its shape even if the blow-molded body is taken out of the mold, and then taking out the molded body from the mold,
A biaxially oriented polyester container with an excellent combination of heat shrinkage resistance and gas barrier properties can be manufactured at a high production rate and with a reduced number of steps.

(Function) The present invention is characterized in that the intermediate layer of the sparring resin in the multilayer blow molded product acts as a heat insulating layer during heat treatment and cooling removal of the blow molded product, and the blow molded product is cooled from the inside with a cooling fluid. This is based on the new finding that the shape retention required for removal can be quickly obtained.

In FIG. 1 for explaining the present invention in detail, a multilayer blow-molded body 1 is comprised of a polyester inner layer 2, a preester outer layer 3, and a gas-carrying resin intermediate layer 4 located between these layers. At the cooling stage after heat treatment,
4 The outer layer 3 of the reprocessed ester is heated by contacting the mold 5 heated to the heat setting temperature, while the inner layer 2 of the IJ ester is heated.
is in a cooled state in contact with the cooling fluid 6. In the present invention, since the gas barrier resin intermediate 114 acts as a heat transfer barrier layer, the polyester interior 12 is rapidly cooled to a temperature that is generally 60° C. or lower and can be taken out of the mold without losing its shape. An advantage is obtained that the temperature of the polyester outer layer 3 and the mold 5 in contact with it is not significantly lowered by this inner layer cooling operation.

Table 1 below shows the thermal conductivity of various resins.

No.1 vinylidene chloride resin 2.50~2.65EVOH
2,00-2.55 Stretched PET 6.40-7.80 Unstretched PE
T 4.90-5.5 From this result,
Ethylene-vinyl alcohol copolymer (l1lVOH)
It is clear that such gas barrier resins have low thermal conductivity, and in particular, exhibit only a thermal conductivity of A to just that of polyethylene terephthalate (PET). So, ethylene-
Vinyl alcohol copolymers not only have gas barrier properties, but also act as a barrier to heat conduction.

According to the present invention, the polyester inner layer is quickly cooled for removal from the mold so that it has sufficient shape retention, and the temperature of the mold surface required for heat treatment is not significantly lowered. , it becomes possible to rapidly heat-treat and cool a stretch-produced product for removal using a single mold.

(Operations and Effects of the Invention) According to the present invention, since only one type of mold and a single blow operation are required, heat setting and 92-axis stretch blow molding can be performed with a small number of steps and a small equipment cost. Not only can the container be manufactured, but the time for heat treatment of the gold inside the mold and the cooling time for taking it out from the mold can be significantly shortened, the time occupied in the mold can be significantly shortened, and the heat shrinkage resistance and gas barrier properties can be improved. The combination is excellent and nine-biaxially stretched polyester containers can be manufactured at high production rates. Moreover, since the container obtained is produced using a one-stage blowing method, it has excellent surface shape reproducibility and also has excellent appearance characteristics such as aesthetic appearance and commercial value. In particular, in the two-molt method, two parting lines are placed on the left and right sides of the final container corresponding to the two split molds used, but according to the present invention, only one 74-parting line is placed on the left and right sides. It also has excellent characteristics.

(Description of preferred embodiments of the invention) In the present invention, thermoplastic polyesters include polyethylene terephthalate, copolyesters containing mainly ethylene terephthalate units, and a small amount of ester units for modification which are known per se. Used for the purposes of the present invention. It is sufficient that this 4-liester has a molecular weight sufficient to form a film.

In addition, as the gas barrier resin, a copolymer obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate is used. Considering moldability and barrier properties, the ethylene content is 15%. to 50 molti, 11
Those having a saponification degree of 96% or more are advantageously used. Other resins that can be used include vinylrizoin chloride resin, high nitrile resin, xylylene group-containing polyamide resin, and pipe resin polyester.

Although not required, any adhesive known per se can be used to enhance the adhesion between the polyester layer and the gas barrier resin layer. Copolyester adhesives, polyamide adhesives, polyester-ether adhesives, niboxy-modified thermoplastic resins, acid-modified thermoplastic resins, etc. are used for this purpose.

Next, as a method for manufacturing a multi-layer material including a thermoplastic polyester layer and a gas barrier resin layer, one method is to use a gas barrier resin as an inner layer and an outer layer, or a polyester resin as an inner layer and an outer layer, respectively. In this case, an adhesive layer is interposed between both horizontal layers, a pipe is formed by coextrusion, the multilayer pipe is cut to an appropriate length, one end of the pipe is fused and closed, and the bottom At the same time, a mouth and neck part having an opening and a fitting part or a threaded part on the outer periphery are formed in the upper part of the other end, and the multilayer preform is tossed.

In addition, using a co-injection molding machine equipped with two or more injection machines and a co-injection mold, the inner and outer layers are made of polyester resin, and one or more layers of barrier resin are inserted in the middle to cover the inner and outer layers. A multilayer preform having a bottom and an opening can be obtained depending on the main parts of the preform mold.

In addition, a multi-stage injection machine equipped with three or more injection machines is used to first form a first inner layer preform, then transfer it to a second mold, inject an intermediate layer, and then inject an outer layer in a third mold. It is also possible to obtain a multilayer preform by sequentially transferring multistage molds.

In order to impart heat resistance to the preform obtained in this way, the mouth and neck parts including the threaded parts, fitting parts, support rings, etc. are sometimes crystallized and whitened by heat treatment at the stage of the preform. After axial stretching blowing is completed, the mouth and neck of the unstretched portion may crystallize and turn white after completion of torling.

The temperature range is 85 to 115℃ by using the heat given to the preform of the prepared multilayer preform injection machine, that is, the residual heat.
The stretching temperature is adjusted to a temperature of 85 DEG to 115 DEG C., or in the case of a cold process, it is reheated and preheated to a stretching temperature of 85 DEG to 115 DEG C. 12 of our Shibrow Kanaya for biaxial stretching with metal blindness
The outer surface of the container wall of the multilayer preform is stretched and blown into a heated mold at 0 to 230°C, preferably 130 to 210°C.
Heat treatment (heat setting) is started at the same time as the PET comes into contact with the inner surface of the mold. After a predetermined heat treatment time, the blowing fluid is switched to the internal cooling fluid to start cooling the inner II PET. The heat treatment time varies depending on the thickness and temperature of the blow molded product, but generally speaking, it is 1.5 to 30 seconds.
It is on the order of 1IK2 to 20 seconds.

On the other hand, the cooling time also varies depending on the heat treatment temperature and the type of cooling fluid, but is generally on the order of K1 to 30 seconds, and particularly on the order of 2 to 20 seconds.

The cooling fluid may be a cooled gas, for example -4
In addition to nitrogen, air, carbon dioxide, etc. at 0°C to +10°C, chemically inert liquefied gases such as liquefied nitrogen gas, liquefied carbon dioxide, liquefied trichlorofluoromethane gas, liquefied dichlorodifluoromethane gas, and other liquefied aliphatic gases. Hydrocarbon gas etc. are also used. This cooling fluid may also contain a liquid mist having a large heat of vaporization, such as water. By using the cooling fluids described above, significantly greater cooling rates can be obtained.

The outer layer of the blow molded product taken out from the mold is allowed to cool,
Alternatively, the outer layer PET is cooled by blowing cold air.

In the present invention, the gas barrier intermediate layer should have an average thickness of at least 5 μm when used as a container in terms of heat transfer insulation, but if it exceeds 300 μm, stretch formability tends to decrease. Generally, a range of 20 to 80 μm is preferred. From the point of view of shape retention during cooling and removal, the PET inner layer should have a thickness of at least 25 μm, and a range of 25 to 70 μm is suitable. The inner layer/outer layer thickness ratio is preferably in the range of 1/3 to 1/1.

However, this is not the case depending on the manufacturing method.

Next, according to the drawing, the thermoplastic polyester y3 according to the present invention? ) The manufacturing method of the mol is explained below.

FIG. 2 shows a multilayer preform molded by co-extrusion molding or co-injection molding.
2, threaded part 13, support ring (neck ring) 14
, a long cylindrical portion 15 and a bottom portion 16.

FIG. 3 shows a wall cross-section of a poly/ii f IJ foam, comprising an inner layer 2 and an outer layer 3 of thermoplastic polyester;
Gas barrier such as ethylene-vinyl alcohol copolymer
The intermediate layer 4 is made of a synthetic resin, and the adhesive layers 10m and 10b are interposed between these layers.

The preform shown in FIG. 2 is electrically heated by hot air heating, infrared heating, high frequency heating, etc. to a temperature suitable for stretching.

In this case the temperature range is 85-115°C, preferably 90-115°C.
The temperature is 110°C.

Next, the stretching blowing step (heat treatment step) will be explained using FIGS. 4 and 5.

The mouth and neck of the preform 11 has a lip cavity 21.
a e 2 l b, and the other parts of the preform 11 are heated to a desired heat treatment temperature by a heater 2.
A mandrel 26 equipped with a stretching rod 25 is inserted through the mouth of the preform 11. The stretching rod 25 is vertically movable and a fluid passage 17 is provided between the stretching rod 25 and the mandrel 26.

In the present invention, the blow metal W23a, 23b is 110~
The preform 21, which has been heated to the desired heat treatment temperature of 230° C. and whose temperature has been adjusted to the drawing temperature, is set in this mold, and the tip of the drawing rod 25 is pressed against the inside of the bottom of the preform 21 in the axial direction. and the fluid passageway 27
The preform is expanded and stretched in the circumferential direction by blowing compressed gas into the preform to form a blow-molded product 28 (FIG. 4).

The stretching ratio is not particularly limited, but in the axial direction 1c 1.5
It is approximately 3 to 3 times larger, and 3 to 5 times larger in the circumferential direction.

The molded blow-molded body continues to be exposed to the cavity surface 24a while the internal pressure of the compressed fluid is applied.

A heat treatment is performed in contact with 24b. Next, the compressed blowing fluid is switched to the cooling fluid, and the inside 29 of the molded body is filled with the cooling fluid through the fluid passage 27 to perform cooling for removal.

The final molded product obtained in this way has no heat deformation or shrinkage even when subjected to hot filling at a high temperature of 80°C or higher, has heat resistance, heat shrinkage resistance, transparency, and gas barrier properties.
This results in a multi-layer structure with excellent properties.

(Applications of the Invention) The container according to the present invention is a hot-filling (hot-hack) product at a high temperature of 80°C or higher, and is a product that contains carbon dioxide gas such as fruit juice or lager beer whose shelf life is desired to be extended, and is heat-treated (. It is particularly useful as a packaging container for contents that require pressure resistance and heat resistance.

(Example) The invention is illustrated by the following examples.

Example 1 Polyethylene terephthalate) (P
ET, temperature conductivity = 5.55 x 10-' m2
/hr -) ethylene-vinyl alcohol copolymer with an ethylene content of 30 mol and vinyl alcohol and t of 70 mol (EVOH, temperature rl conductivity = 2.00)
X10-'m2/hr.
A multilayer pipe was constructed with temperature conductivity = 2.85×10 m /hr·), a bottom neck was formed, and a multilayer preform with a weight of 599 was obtained.

The layer thickness ratio during pipe forming is PET (outer fl)/Ao/Evou/AD/pgT (
inner layer) = 1010.2/110.215. However, AD means an adhesive layer.

After preheating the core multilayer preform to 100℃, the inner volume of the cavity heated to 145℃ is 1580℃.
After biaxial stretching blowing and heat setting for 12 seconds in the blowing mold of Ce, the blowing fluid was switched to internal cooling fluid (air adjusted to +5℃) K, and fluid pressure was applied again for 9 seconds. Immediately take it out and leave it to cool.
Yes, the internal volume is 1500c8. &) le was molded.

Gas permeable product of this invention? Tor's oxygen permeability Q02 is 0.2cc shoulder 2
・day-atm, (Storage conditions 2? The humidity inside the tank is 1.
The outside humidity was 601 RH, and the storage temperature was 22° C.).

Oxygen permeability Q when a molded single-layer PET (same weight, same internal volume) was measured under the same conditions as above for comparison.
O was 4.4 cc/m @ day-atm.

Heat Resistance A kettle according to the present invention with an internal volume of 1500 cc was preliminarily measured for its internal volume, filled with hot water at 85°C, allowed to cool to room temperature, and the internal volume of the kettle was measured again. (Vlm).

The heat shrinkage rate of the kettle, S, is 5=(V,/Me-1)X100 When defined as , S was -0.21.

Moreover, no change was observed in terms of shape.

Example 2 The main injection machine was made of polyethylene terephthalate with an intrinsic viscosity of 0.75 (PET, the temperature conductivity was the same as in Example 1).
and meta-xylylene manufactured by Toyobo ■ to the sub-injection machine.
Adipamide resin (SM/nylon.

Temperature conductivity = 2.45X 10 m/hr), and in order to co-inject the multilayer preform, firstly, the primary injection was performed from the main injection machine at a pressure of about 60 kJi/m.
After that, the injection of the open core PET is stopped for 0.1 seconds, and the PET is started 1.4 seconds after the start of the nuclear PET injection.
pressure higher than the primary injection pressure (approximately 9/32 to 100)
A predetermined amount of molten SM/nylon is injected in 0.8 seconds from the sub-injection machine, and then the pressure is lower than the primary injection pressure from the main injection machine by 0.05 seconds after the end of injection of C8M/nylon. (approximately 30 kg/5!2) PET was injected to mold a multilayer preform with a wall thickness of approximately 5 mm. The tt of this preform is about 59.9, of which
The weight ratio of 8M nylon was approximately 4.5 inches.

The multilayer preform was subjected to biaxial stretching blowing in the same mold under the same conditions as in Example 1, and was simultaneously heat set and cooled to obtain a kettle with an internal volume of 1500 a.

Gas permeability The oxygen permeability, QO□, of yf) according to the present invention is 0.
9cc/m-day*aim, (Storage conditions were the same as in Example 1.) QO2 of the single-layer PETyK (same weight, same internal volume) conducted for comparison was 4. 4cc/m-day・a
tm・)・Heat resistance Example 1
A heat resistance test (kettle shrinkage rate measurement) was conducted using the same method as in the case of . The shrinkage rate (S) of the kettle was -0.1%.

Moreover, no deformation was observed in terms of shape.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of the manufacturing method of the present invention. Fig. 2 is a side sectional view of the preform used in the present invention, Fig. 3 is an enlarged sectional view showing the cross-sectional structure of the preform shown in Fig. 2, and Fig. 4 explains the drawing process. FIG. 5 is a side sectional view for explaining the heat setting and cooling steps. 1 is a multilayer blow-molded product, and 2 is a polyester inner layer. What about 3? A polyester outer layer, 4 a gas barrier resin intermediate layer, 5 a heated mold, 6 a cooling fluid, 11 a preform, 22 a heater, and 23 m. 23b is a mold, 25 is a drawing rod, and 27 is a passage for blowing fluid and cooling fluid. gFJ1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) A multilayer preformed product comprising inner and outer layers made of polyester mainly composed of ethylene terephthalate units and at least one intermediate layer made of gas barrier resin.
Preheat or adjust the temperature to the appropriate stretching temperature of 15°C, perform biaxial stretch blow molding on the preformed product in a mold maintained within the heat-fixing temperature range, and heat treat the blow molded product.
Thereafter, the pressurized fluid for blow molding is switched to the internal cooling fluid, and while the blow molded product is in contact with the surface of the mold cavity, it is cooled to a temperature at which the blow molded product does not lose its shape even if it is taken out of the mold, and then A method for producing a heat-shrinkable biaxially stretched container, which comprises removing a molded object from a mold.