JPS6156086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat-resistant stretch blow-molded container using crystalline plastic.

In order to impart heat resistance to stretched hollow containers made of crystalline plastic, heat treatment can be applied to stretched hollow-formed containers in a short period of time while preserving the product shape.
Because its shape is a three-dimensional three-dimensional structure, it is extremely difficult to produce it compared to linear (one-dimensional) fibers, planar (two-dimensional) sheet films, and the like.

That is, when heat-treated, the stretched resin wall generates heat shrinkage stress, so some means is required to resist this stress and maintain its shape. In the heat treatment mold, the inventor blows gas into the container and pressurizes it from the inner wall of the container to form the mold, raises the mold temperature and performs heat treatment, and after treatment lowers the mold temperature to a temperature that does not cause deformation. Attempts were made to cool the mold down to a temperature and then release it from the mold, but this required a long time to raise and lower the mold temperature, resulting in a lack of substantial productivity, and the method could not be put to practical use. In addition, attempts have been made to fill the container with a fluid such as pressurized gas or liquid to prevent deformation due to heat shrinkage, and to heat-treat the molded product while keeping its shape, but the fluid filled in the container flows. This resulted in deformation of the molded product, making it impossible to obtain a normal product. Furthermore, we attempted to heat-treat the molded product while supporting the inner wall of the container with a solid shape-retaining device, but we were only able to obtain a product with a simple shape, and it was difficult to obtain a container with a complex shape, such as a concave ribbed product. It is difficult to obtain products such as bottles and narrow-mouthed containers.

The present invention eliminates these difficulties and makes it possible to manufacture heat-resistant plastic containers made of crystalline plastic that are characterized by rapid heat treatment and have excellent product shape uniformity.

The gist of the first invention is to carry out stretch hollow molding of crystalline plastic to obtain a stretch blow molded container, and then take out the molded container from the molding die and form a cavity having the same three-dimensional shape as the molded container. In addition, a cooling device is provided below the region of the cavity side surface that is in contact with the unstretched portion of the molded product, and a temperature regulating fluid circulates in the lower part of the other region of the cavity side surface. The molded container is placed in a heat treatment mold in which a fluid passage is provided, and the inner wall of the container is pressed with pressurized gas from inside the molded container to bring the container wall into close contact with the cavity side surface, thereby retaining the shape. Meanwhile, the region of the cavity side surface that is in contact with the unstretched portion of the molded product is cooled to below the crystallization temperature of the resin, while the other region of the cavity side surface is cooled to a constant temperature within the temperature regulating fluid passage. By circulating the temperature regulating fluid adjusted to the adjusted temperature, radiant energy is irradiated from inside the container to the inner wall surface of the container while maintaining the temperature below the melting point temperature of the crystalline plastic, and the temperature is lower than the adjusted temperature. After performing heat treatment at a temperature above the glass transition point and below the melting point of the high crystalline plastic, the radiant energy source is taken out from inside the container, and the temperature of the container wall is lowered to around the adjustment temperature, and then The method for manufacturing a heat-resistant molded container is characterized in that the pressurized gas is evacuated, and then the heat-treated molded container is released from the heat treatment mold.

Next, the gist of the second invention is that a cooling device is provided at the lower part of the region of the cavity side surface of the stretch blow molding mold that is in contact with the unstretched resin wall of the molded product, and the lower part of the other region of the cavity side surface is After a stretch blow-molded container is obtained by stretch blow-molding the crystalline plastic using a dual-purpose forming and heat-treating mold provided with a temperature-regulating fluid passage through which a temperature-regulating fluid circulates, Hold the stretched hollow-molded container, and press the inner wall surface of the container with pressurized gas from inside the molded container to bring the container wall surface into close contact with the cavity side surface, and while maintaining the shape, unstretch the molded product on the cavity side surface. The area facing the part is cooled to below the crystallization temperature of the resin by the cooling device, while the other area on the cavity side surface is provided with a temperature adjusting fluid adjusted to a constant temperature in the temperature adjusting fluid passage. By ring-cycling, while maintaining the temperature at the melting point of the crystalline plastic or lower, radiant energy is irradiated from the inside of the container onto the inner wall surface of the container to raise the temperature at or above the glass transition point of the crystalline plastic, which is higher than the adjustment temperature. After heat treatment at a temperature below the melting point temperature, the radiant energy source is taken out from inside the container, the temperature of the container wall is lowered to around the adjustment temperature, the pressurized gas is evacuated, and then, The method for manufacturing a heat-resistant molded container is characterized in that the heat-treated molded container is released from the mold for molding and heat treatment.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

First, crystalline plastic is stretch-hollow-molded,
A stretch blow-molded container 1 as shown in the first figure is obtained.

Then, the molded container 1 is taken out from inside the molding die, and as shown in the second figure, the molded container 1 is placed between the support molds 3a, 3b of the heat treatment mold 2, the mouth insert molds 4, 4',
The bottom nesting mold 5 and the mandrel 6 are closed and formed. Cavity 7 with the same three-dimensional shape as the molded container
Pressurized gas is blown into the container through the gap between the mandrel 6 and the heater 8, and the pressurized gas presses the inner wall of the container from inside the container to bring the container wall into close contact with the surface of the cavity 7 of the heat treatment mold 2. do.

Here, a cooling pipe 9 is provided inside the mouth part nesting mold 4, 4' and the bottom part nesting mold 5, which are in contact with the unstretched part of the molded product of the heat treatment mold 2. The mouth insert molds 4, 4' and the bottom insert mold 5 are cooled by the action of the cooling water passing through the cooling water, and the container wall of the molded container 1 that is in contact with them is cooled to below the crystallization temperature of the resin. This prevents spherical crystallization from occurring in the unstretched resin portion during the heat treatment performed.

On the other hand, a temperature regulating fluid passage 1 in which a temperature regulating fluid circulates at a depth as close as possible to the cavity side surfaces of the support molds 3a and 3b of the heat treatment mold 2.
0 is provided, and by circulating the temperature regulating fluid adjusted to a constant temperature in the temperature regulating fluid passage 10, the cavity side surfaces of the support molds 3a and 3b are brought to the optimum temperature for heat treatment (hereinafter referred to as base). (referred to as temperature) at all times.

FIG. 3 shows an enlarged view of the supporting mold surface part, and in the figure, 11 is a resin layer, 12 is a supporting mold surface layer,
13 is radiant energy. At this stage, a temperature distribution as shown by the curve ( ) in the graph shown in FIG. 4 is obtained.

Here, the base temperature does not need to be fixed, and is set depending on processing conditions such as the intensity of heating by radiation from inside the container and heat treatment time, which will be described later.
It may be lower than the melting point temperature of the resin.

Next, in this state, the heater 8 is inserted into the container.

Here, the heater 8 has the function of radiating electromagnetic waves in the absorption band of the resin forming the container 1.

As the heater 8 is inserted, the wall of the container 1 absorbs radiant energy from the inner wall surface and is heated, causing the temperature of the container wall to rise rapidly.

On the other hand, the cavity-side surfaces of the support molds 3a and 3b are not directly heated because the resin portion interposed between the heater 8 and the cavity-side surfaces of the support molds 3a and 3b shields the radiant energy.
Due to the temperature gradient that occurs as a result of the temperature rise in the resin part and the heat conduction at the contact surfaces of the support molds 3a and 3b with the resin part, the temperature rises later than from the inside of the container. As a result, a temperature distribution as shown by the curve () in the graph shown in FIG. It is heated to an average temperature T ₂ by the cooling effect of the support type surface layer 12 facing the outside of the container wall, and at this temperature stress strain is relaxed, crystallization progresses, and under the oriented state,
Microcrystallization progresses and heat treatment is performed.

Next, when the heater 8 is taken out of the container 1 and heating is stopped, the temperature distribution becomes as shown by the curve of the graph shown in Figure 4 due to the cooling effect of the temperature regulating fluid circulating in the temperature regulating fluid passage 10, and the support type cavity is heated. The side surface layer 12 and the resin layer 11 are rapidly cooled.
After the temperature of the resin part 11 drops to near the base temperature _T0 , the pressurized gas is vented, and the heat treatment mold 2
Open the container 1 and release it from the mold. In the cooling process, the temperature is raised and lowered only to the resin layer 11 itself to be heat treated and the cavity side surface portions 12 of the support molds 3a and 3b, so the heat capacity of the target parts to be raised and lowered is reduced. This can significantly reduce the heat treatment time.

In FIG. 2, 14 is a heat insulating wall, and 15 is silicone packing to eliminate air leakage.

In the present invention described above, by blowing pressurized cooling gas into the container after stopping the radiant heating by the heater, cooling can be accelerated and the processing cycle can be shortened.

As the supporting mold for the heat treatment mold used in the above manufacturing method of the present invention, a mold whose cavity side surface is made of a metal with good thermal conductivity, such as an aluminum alloy or a beryllium alloy, is recommended. It is optimal because it has a fast response time.
Further, the temperature regulating fluid passage 10 is desirably provided at a depth as close as possible from the cavity side surface of the mold in consideration of the thermal conductivity of the temperature regulating fluid to the mold cavity side surface. When the support type cavity side surface layer is made of hard chrome plated iron alloy S50C, the thickness is preferably 20 mm or less.

Next, as the heater used in the present invention, one that generates electromagnetic waves that match the absorption spectrum of the resin part, for example, a high frequency heating device that generates electromagnetic waves in the microwave range with a wavelength of 1 mm to 1 m can be applied. In addition, the medium wavelength is 0.8μm to 1
Cast-in heaters and infrared heaters in which a resistor such as a nichrome wire that generates electromagnetic waves in the infrared region of mm is built into a metal tube such as brass or stainless steel can be used. Among these, infrared lamps and quartz tube heaters that emit infrared rays with a peak wavelength of 1 to 3 microns, and infrared heaters having a welded ceramic layer that generates infrared rays with long wavelengths of 3 to 60 microns are most suitable. When using a tungsten lamp etc. that generates electromagnetic waves in the visible range, the resin part has poor absorption of electromagnetic waves in the visible range, so apply chrome plating etc. to the mold surface to make it mirror-like and reflective. There is a need to increase absorption by the resin part.

However, because the radiant energy is large,
The use of electromagnetic waves in the visible light range is effective.

When using a shorter wavelength range,
It is sufficient to select and use a radiation intensity that does not rapidly heat the irradiated surface of the resin and cause whitening. Furthermore, it is desirable to use a heater whose shape is changed depending on the shape of the container to be heat-treated so that the radiation can be applied uniformly to all the inner walls of the container. For example, if the container to be heat treated is a narrow cylindrical container, it is desirable to use a rod-shaped infrared heater.

Next, as the crystalline plastics used in the present invention, all crystalline plastics that crystallize in a temperature range above the glass transition point Tg and below the melting point Tm can be applied, and examples of these resins include polypropylene, polyethylene, and polyamide. ,
Examples include polyethylene terephthalate.
These resins are stretched from an amorphous state at a temperature higher than the glass transition point Tg, and in an oriented state, they are stretched at an appropriate temperature within the temperature range from the glass transition point Tg to the melting point Tm while maintaining their shape. When heat treatment is performed, stress and strain are removed, and microcrystalization progresses in the oriented and constrained state of molecules due to stretching, and the density increases without losing transparency, making it suitable for use as a container. A heat-resistant container is formed that has increased buckling strength and impact resistance and does not deform at temperatures lower than the temperature at which it was heat treated.

In the present invention, the difference between the base temperature T ₀ and the average temperature T ₂ of the resin layer during heat treatment is preferably 5° C. or more when polyethylene terephthalate resin is used as the crystalline plastic, for example.

Figure 5 shows that a cooling device is provided at the bottom of the area on the cavity side surface of a blow molding die that is in contact with the unstretched resin wall of the molded product, and a temperature regulating fluid is circulated at the bottom of the other cavity side surface area. This figure shows a state in which heat treatment is being performed using a mold for both molding and heat treatment, which is provided with a surrounding temperature-adjusting fluid passage. Also, FIGS. 6 and 7 show a rod heater. 5, 16 is a molding and heat treatment mold, 1
7a and 17b are molding and supporting molds that can be used as blow molding molds and supporting molds for stretched blow molded containers during heat treatment; 18 is a rod heater that can be used as a rod and a heater; 19 is a mold in the ceramic layer. A tubular infrared heater with a built-in nichrome wire, 20 a heater support tube, 21 a ceramic layer, 22 a nichrome wire, 23 a stretching rod used for biaxial stretching blow molding, 24 a rod body,
25 is the rod head. Further, 26 is a pressurized gas passage defined by a groove carved on the circumferential surface of the rod and the inner wall of the heater support tube 20, and 27 is a pressurized gas passage defined by a groove carved in the top of the heater support tube and the rod head 25. The pressurized gas passage 28 is a pressurized gas passage provided through the tube wall of the heater support tube. In the rod heater 18, only the rod 23 can be inserted into the cavity, and the heater 1
It is also possible to move the rod 9 out of the cavity in advance of the rod 23.

Pressurized gas is directed down the cavity through passages 26 and 28 and up the cavity through passages 26 and 27.

Incidentally, in FIG. 5, parts common to those of the heat treatment mold shown in FIG. 2 are given the same numbers.

First, a parison (not shown) 23 is inserted into the cavity 7 of the mold 16 for forming and heat treatment, and the crystalline plastic is stretch-hollow-molded to obtain the stretch-hollow-molded container 1. This stretch blow-molded container 1 is held inside the molded container 1, and the inner wall surface of the container 1 is pressed with pressurized gas from inside the molded container 1 as described above, so that the wall surface of the container 1 is brought into close contact with the surface of the cavity 7 side of the molding and supporting molds 17a and 17b. Then, while maintaining the shape, the heater 19 is raised and inserted into the container 1 along the rod body 24, and heat treatment is performed.

When the mold shown in Figure 5 is used, molding and heat treatment can be performed in one step.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 Volume 1000 obtained by biaxial stretch blow molding using polyethylene terephthal resin with IV of 0.7
cc A ribbed cylindrical container with an average wall thickness of 0.4 mm was used as the container to be treated, and the supporting type was heat-treated in a mold made of aluminum alloy with the same shape as the container, with a base temperature of 120°C, a bottom nested type and a mouth nested type. The temperature was set at 50℃, the pressurized air pressure was set at 7Kg/ ^cm2 , and a 500W ceramic infrared heater was used to irradiate for 20 seconds.The heater was then removed from the container and cooled for 20 seconds, then the vent mold was opened at the same time. I went there and released the container.

Through this heat treatment, a heat-resistant container was obtained which had a volume shrinkage of 1% or less after being filled with hot water at 90°C, left on a wooden desk at room temperature without being capped, and cooled for 60 minutes. Furthermore, the cylindrical shape with a diameter of 80 mm before heat treatment did not undergo any deformation. Furthermore, transparency was not lost by heat treatment.

Example 2 A polyethylene terephthal resin with an rv of 0.7 was injection molded by combining a molding and heat treatment mold made of an aluminum alloy, the push-up rod for longitudinal stretching shown in Fig. 5, and a 500W tubular ceramic infrared heater. At the same time, the bottomed parison was stretched in the longitudinal direction, and at the same time, 10 kg/cm ² of pressurized air was blown into it to form a biaxially stretched hollow mold.The heater tube was then irradiated with infrared rays for 20 seconds while keeping its shape in the mold, and then the heater tube was inserted into the mold. The container was moved out of the container by sliding it along a domandrel, and the container was further cooled for 20 seconds, the pressurized air was removed, and the mold was opened at the same time to release the container. During the treatment, the heat treatment base temperature of the support mold is 120℃ and the mouth and bottom nested mold are
The temperature was set at 50°C. Through this heat treatment, a transparent heat-resistant container with a volumetric shrinkage of 1% or less after being filled with hot water at 95°C and left at room temperature on a wooden desk for 60 minutes without being capped is produced. Obtained.

Comparative Example Heat treatment was carried out without heating the container with a heater from inside the container and without cooling the mouth and bottom inserts according to the present invention.

That is, using the same stretch blow molded container used in Example 1 as the container to be treated, the mold temperature was kept at 120°C by circulating silicone oil inside the aluminum alloy mold, and pressurized air of 7 kg/cm ² was applied for 40 seconds. After the container was heat-treated while maintaining its shape, the pressurized air was removed and the mold was opened at the same time to release the container. Containers obtained by such heat treatment had whitening at the bottom and mouth due to the formation of crystal spheres, resulting in a loss of transparency and a significant loss in the drop strength of the bottom. The cylindrical shape with a diameter of 80 mm before heat treatment has a long axis of 81.7 mm and a short axis.
It was deformed into an elliptical shape of 77.6 mm, and the volume shrinkage after heat treatment was 2.6%. However, the volume shrinkage of a heat-treated container after filling with hot water is 0.3 compared to the volume before filling with hot water.
%, no deformation was observed, and it is considered that heat resistance has been achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a stretch blow-molded container to be heat treated, FIG. 2 is a sectional view of a heat treatment mold used in the present invention, FIG. 3 is a sectional view of the surface layer of a supporting mold, and FIG.
The figure is a graph showing the temperature distribution during and before and after heat treatment, Figure 5 is a cross-sectional view of the mold for molding and heat treatment used in the present invention, Figures 6 and 7 are rod heaters, and Figure 6 is a longitudinal cross-section. 7 are cross-sectional views. 1... Stretch blow-molded container, 2... Heat treatment mold,
3a, 3b... Support type, 4, 4'... Mouth nested type, 5... Bottom nested type, 6... Mandrel, 7...
... Cavity, 8 ... Heater, 9 ... Cooling pipe, 10 ... Fluid passage for temperature adjustment, 11 ... Resin layer, 12 ... Support type surface layer, 13 ... Radiant energy, 16 ... Molding heat treatment dual-purpose type , 17a, 17
b... Molding/support mold, 18... Rod heater, 19... Heater, 22... Rod.

Claims (1)

[Scope of Claims] 1. After a crystalline plastic is stretch-hollow-molded to obtain a stretch-hollow-molded container, the molded container is taken out from a molding die and has a cavity having the same three-dimensional shape as the molded container. In addition, a cooling device is provided below the region of the cavity side surface that is in contact with the unstretched portion of the molded product, and a temperature regulating fluid circulates in the lower part of the other region of the cavity side surface. The molded container is placed in a heat treatment mold in which a fluid passage is provided, and the inner wall of the container is pressed with pressurized gas from inside the molded container to bring the container wall into close contact with the cavity side surface, thereby retaining the shape. Meanwhile, the region of the cavity side surface that is in contact with the unstretched portion of the molded product is cooled to below the crystallization temperature of the resin, while the other region of the cavity side surface is cooled to a constant temperature within the temperature regulating fluid passage. By circulating the temperature regulating fluid adjusted to the regulated temperature, the radiant energy is irradiated from inside the container to the inner wall surface of the container while maintaining the temperature below the melting point of the crystalline plastic to adjust the regulated temperature of the fluid. After performing heat treatment at a temperature higher than the glass transition point of the crystalline plastic and lower than the melting point temperature, the radiant energy source is taken out from inside the container, and the temperature of the container wall is lowered to around the adjustment temperature. . A method for manufacturing a heat-resistant molded container, comprising: releasing the pressurized gas, and then releasing the heat-treated molded container from the heat treatment mold. 2. The method for manufacturing a heat-resistant molded container according to claim 1, wherein polyethylene terephthalate resin is used as the crystalline plastic. 3. A cooling device is provided at the bottom of the region on the cavity side surface of the stretch hollow molding mold that is in contact with the unstretched resin wall of the molded product, and a temperature regulating fluid circulates in the bottom of the other region on the cavity side surface. A crystalline plastic is stretch-hollow-molded using a molding and heat-treating mold provided with a temperature-regulating fluid passage to obtain a stretch-hollow-molded container, and then the stretch-hollow-molded container is subsequently held in the mold to form the molded container. The inner wall surface of the container is pressed with pressurized gas from inside the container to bring the container wall surface into close contact with the cavity side surface, while maintaining the shape.
The region of the cavity-side surface that is in contact with the unstretched part of the molded product is cooled to below the crystallization temperature of the resin by the cooling device, while the other region of the cavity-side surface is kept within the temperature-adjusting fluid passage. By circulating the temperature regulating fluid adjusted to the regulated temperature, the radiant energy is irradiated from inside the container to the inner wall surface of the container while maintaining the temperature below the melting point of the crystalline plastic to adjust the regulated temperature of the fluid. After performing heat treatment at a temperature higher than the glass transition point of the crystalline plastic and lower than the melting point temperature, the radiant energy source was taken out from inside the container, and the temperature of the container wall was lowered to around the adjustment temperature. Afterwards, the pressurized gas is vented, and then,
A method for manufacturing a heat-resistant molded container, which comprises releasing the heat-treated molded container from the mold for molding and heat treatment. 4. The method for manufacturing a heat-resistant molded container according to claim 3, wherein polyethylene terephthalate resin is used as the crystalline plastic.