JPS5935333B2 - Method for manufacturing polyester containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a biaxially oriented polyester container molded from a thermoplastic polyester having ethylene terephthalate as the main repeating unit, and more particularly relates to a method for manufacturing a biaxially oriented polyester container having excellent mechanical properties, gas barrier properties, The present invention relates to a method for producing a transparent polyester container which has excellent heat stability, has excellent properties such as durability and chemical resistance, and has excellent protection performance for contents, and has extremely low deformation and shrinkage when filled with high-temperature contents.

Thermoplastic polyester, which is mainly composed of polyethylene terephthalate, has been attracting attention for its excellent mechanical properties, gas barrier properties, chemical resistance, fragrance retention, transparency, hygiene, etc., and has been used for various containers, films, It is processed into sheets and is widely used as packaging material.

Recent advances in blow molding technology, especially biaxial stretch blow molding technology, have made remarkable progress in the use of hollow containers such as bottles and cans. In biaxial stretch blow molding using polyethylene terephthalate, a geometric form (hereinafter referred to as a parison) having a cylindrical shape with an expandable upper end opening and a bottom (hereinafter referred to as a parison) made of amorphous material is generally formed by injection molding or extrusion molding. The parison is then heated to a temperature range that allows orientation, e.g., above the glass transition temperature (Tg) and below the melting point (Tm), and connected to a spindle in a blow mold having the desired volumetric structure of the container. Stretching is carried out in the axial direction using an extruded rod and in the circumferential direction by blowing compressed gas.

During this stretching process, the molecular chains of the crystalline polymer are stretched in both the axial and circumferential directions, and the accompanying generation of oriented crystallized substances improves the physical properties of the bottle, such as mechanical properties such as tensile strength and impact strength, and gas permeation resistance. Sexuality etc. are significantly improved. However, in biaxially oriented bottles obtained by ordinary stretch-molding methods, various problems arise due to the distortion generated during the stretching process. When stored in a humid atmosphere, the bottle may gradually shrink and its internal volume may fluctuate, or when filled with high-temperature contents near the glass transition temperature of polyester, e.g. 60°C or higher, during light filling or light filling. This has the fatal disadvantage of shrinking afterwards, making it impossible to fill the contents accurately, and causing deformation of the bottle, making it impossible to maintain its original shape, which greatly reduces the commercial value of the bottle. As a result, the range of applications is currently severely restricted. Generally, in polyethylene terephthalate molded products such as threads with a one-dimensional structure or films with a two-dimensional structure, a heat treatment called heat setting is performed after stretching and forming to improve heat resistance.

The purpose of this is to change the microcrystals generated during stretching into a crystalline structure that is more stable against heat, fixing it in that alignment state, and alleviating residual strain during stretching. Molded products subjected to this treatment The heat resistance of is significantly improved.

Based on the same idea, a method for heat-setting a stretched or oriented container in order to improve its heat resistance has been developed. It is disclosed in Publication No.-264 and the like. However, with a stretch-oriented container molded by the normal blow molding method, it is impossible to finish the entire container with a uniform stretching ratio no matter what shape the container is formed into, and it is impossible to finish the entire container with a uniform stretching ratio. It is a one-piece molded product consisting of a plug part, a neck to shoulder part and a bottom part with a low stretching ratio, and a body part with a high stretching ratio.
In the heat setting at 140 to 220°C described in Publication No. 73, the body consisting of the highly stretched portion is heat set without any loss of aesthetic appearance, but the spout and neck portion consisting of the unstretched and low stretched portions are heat set. The temperature from 140 to 220 degrees Celsius for the area from the top to the shoulders and the bottom.
At such temperatures, whitening due to thermal crystallization is likely to occur, resulting in a fatal drawback of impairing the aesthetic appearance of the container.

In addition, the method described in JP-A-52-126376 uses a mold that can provide temperature distribution according to the stretching ratio of each part to heat fixation, that is, low-stretched parts are set at a low temperature, and high-stretched parts are set at a low temperature. attempts to prevent the whitening phenomenon by heat-setting at high temperatures, but not only does it require a complicated special mold, but it is also difficult to obtain a heat treatment effect that will give the low-stretched areas sufficient heat resistance. If this method is used, the area will turn white, and conversely, if an attempt is made to avoid the whitening of the area, the light effect will not be obtained, so even if this method is used, a transparent polyester container with satisfactory heat resistance cannot be obtained. I can't get it.

In view of these circumstances, the inventors of the present invention have conducted extensive research on polyester containers that have good appearance, transparency, and excellent heat resistance, and have developed the method for manufacturing polyester containers of the present invention. I've reached it.

That is, in the present invention, a bottomed parison made of a thermoplastic polyester having ethylene terephthalate as a main repeating unit is biaxially stretched and blown using a compressed gas and a stretching rod at the stretching temperature of the polyester, thereby removing the unstretched portion and the stretched parison. Forming a container consisting of a portion and a portion in which the stretching ratio changes continuously from the unstretched portion to the stretched portion,
In the method for producing a polyester container that is then heat-set, when the parison is brought to a stretching temperature, the temperature of the parison portion corresponding to the neck or the shoulder and bottom of the target container is lowered to the temperature of the parison corresponding to the body of the container. After giving the temperature distribution so that it is 1 to 20 degrees Celsius higher than the temperature of the part,
After biaxial stretch blow molding using a mold, stretching rod, and compressed gas at a temperature lower than the stretching temperature, heat treatment is performed at a temperature range that is 20°C or more higher than the glass transition temperature of polyester and 20°C or more lower than the melting point. A method for producing a transparent polyester container characterized by a volumetric shrinkage rate of 2% or less when filled with boiling water. The polyester container obtained by the method of the present invention can be easily obtained by heat-setting a specific polyester container obtained by improving a conventionally known stretch blow molding mold and changing the molding conditions. It is economical and has excellent transparency and heat resistance stability against high-temperature light filling, as well as significantly improved mechanical properties, gas barrier properties, protection against the contents to be filled, chemical resistance, etc. This is an innovative container with many excellent practical features.

To explain in detail the structural and shape characteristics of the polyester container obtained by the method of the present invention, the container consists of an unstretched part, a stretched part, and a part in which the stretching ratio changes continuously from the unstretched part to the stretched part. .

Then, in a portion where the stretching ratio changes continuously from the unstretched portion to the stretched portion, the density ρ. The distance d (CIIL) from the stretching start point of the unstretched part with (9/C7l) to the position of the stretched part whose density ρ(9/d) is exceeded for the first time and the density rise (ρ-ρo) between A container having a ratio expressed by the following formula [1] can be easily provided. d/ρ−ρo〈
25・・・・・・・・・[1] However, ρ≧ρo+0.0
36 For example, taking the narrow-mouth bottle manufactured in Example as an example, in the longitudinal cross-sectional schematic diagram (Fig. 1) cut in the axial direction along the parting line of the blow mold, the size of the bottle is The part consists of a stretched part a with a thermally stable structure from the shoulder to the bottom, an unstretched part c at the spout and the center of the bottom, and a very small part from the neck to the shoulder of the bottle and the bottom. It has a structure in which a boundary part b between an unstretched part and a stretched part, that is, a part b where the stretching ratio changes continuously, exists in a very small part from the center to the corner.

The unstretched portion c is a substantially non-oriented portion, and when polyethylene terephthalate is taken as an example, it usually has a thickness of 1.342 to 1.
This part has density islands of about 3449/d.

Further, the stretched portion a has a high density due to the orientation in stretch blow molding, the crystal ratio, and the heat setting treatment after molding. The stretched portion a is usually ρ. From 0.0369/C
This is a portion that has a density ρ higher than fll, preferably 0.0389/ or higher, and an oriented pattern can be seen when subjected to X-ray diffraction, and is a thermally stable portion. Furthermore, it is particularly preferable that the density ρ of the stretched portion a in the polyethylene terephthalate container is 1.3809/~ or more. Further, the portion b where the stretching ratio continuously changes refers to a portion accompanied by a morphological change such as a change in thickness, and is a portion where no oriented pattern is observed by X-ray diffraction. In the container obtained by the method of the present invention, this part forms the boundary between the unstretched part and the stretched part, and is only present in a very small amount. The polyester container of the present invention is made of thermoplastic polyester having ethylene terephthalate as a main repeating unit, and is composed of an unstretched part, a stretched part, and a part in which the stretching ratio changes continuously from the unstretched part to the stretched part. Then, in the part where the stretching ratio changes, the density ρ(
Distance d (Cm) from the stretching start point of the unstretched part with 5 (fl/CTit) to the position of the stretched part that first exceeds the density ρ'' (9/~) and the density increase (ρ'' - ρ6) therebetween. It can be obtained by heat-treating a container whose ratio of

d/ρ7-ρ et al.〈100......[] (However, ρ5≧ρ et al. + 0.008) In polyester containers obtained by conventionally known molding methods, Areas with a high stretching effect, such as those shown in the drawings, do not whiten even when heat treated at high temperatures; It is impossible to obtain a polyester container that has both transparency and heat resistance because it easily whitens even when subjected to heat treatment.

In addition, the whitened portion has high gas permeability and poor mechanical properties, which causes a significant deterioration in the performance of the container. In order to improve heat resistance without impairing the appearance of the container by heat setting, the properties of the container before heat setting are particularly important. That is, in the present invention, the low-stretched portions (areas that are likely to whiten due to heat-setting treatment) that exist in the neck and bottom of the container where the stretching ratio changes continuously are minimized, and the By fixing the polyester in a limited area, whitening during the heat fixing treatment can be prevented and the polyester container of the present invention having excellent transparency and heat resistance can be successfully obtained. Note that d/ρ5−ρ is particularly preferably 85 or less. Further, the lower limit of d/ρ5-ρ6 is usually related to parison heating conditions, stretching speed, etc., but it is usually difficult to set it to 25 or less. The unstretched portion of the container before heat-setting treatment is of course a substantially unoriented portion,
Taking polyethylene terephthalate as an example, the density ρ is usually 1,340 to 13429/C7rL. The stretched portion has a density higher than that of the unstretched portion by 0.008 g/d or more, preferably 0.0139/CTII or more, and an oriented pattern can be obtained by X-ray diffraction. Furthermore, the part where the drawing ratio changes continuously is a part with morphological changes such as thickness change, and is a part where no orientation pattern is seen when X-ray diffraction is performed, and the density is ρS + 0.
．． It is a low stretching part that is less than 008 and is thermally unstable. In the present invention, a specific polyester container having the above-mentioned properties is heat-set.

The unstretched portion is unstable to high heat, and in order to avoid whitening, it is necessary to devise measures to prevent it from being subjected to the heat treatment effect, but there is no harm in subjecting it to heat that does not cause whitening. Taking polyethylene alephthalate as an example of a part where the stretching ratio changes continuously, the density after blow molding is 1.347.
The following parts will also whiten due to heat setting treatment, so it is necessary to take measures to prevent them from being affected by the heat treatment effect. At least 1.349 by blow forming in the case of polyethylene terephthalate
The heat resistance of the stretched portion having the above density can be improved by heat setting treatment without whitening. Therefore, in the present invention, the container of the present invention can be obtained by heat-setting the container so that the low stretch portion having a density of 1.347 or less does not exist as much as possible. Normally, the heat setting process is performed by loading the container into a mold and blowing pressurized gas into the container to apply internal pressure. The thermoplastic polyester having ethylene terephthalate as a main repeating unit in the present invention usually has an acid component of 80 mol% or more, preferably 90 mol% or more of terephthalic acid, and a glycol component of 80 mol%, preferably 90 mol%. The above refers to polyester that is ethylene glycol, and the remaining acid components include isophthalic acid and diphenyl ether 4,4
'-dicarboxylic acid, naphthalene 1,4- or 2,6-
Dicarboxylic acid, adipic acid, sebacic acid, decane 1,1
0-dicarboxylic acid, hexahydroterephthalic acid, and other glycol components such as propylene glycol, 1,4
-butanediol, neopentyl glycol, diethylene glycol, 1,6-hexylene glycol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane P- as mountain man or bovine silicic acid
It means a polyester containing oxybenzoic acid, P-hydroethoxybenzoic acid, etc.

The polyester in the present invention may contain additives such as colorants, ultraviolet absorbers, antistatic agents, thermal oxidative deterioration inhibitors, antibacterial agents, and lubricants in appropriate proportions, if necessary.

The thermoplastic polyester of the present invention needs to have an intrinsic viscosity of 0.55 or more, preferably 0.6 or more,
More preferably, it has an intrinsic viscosity of 0.7 to 1.4.

Fixed viscosity refers to a solution of polyester dissolved in a mixed solvent of phenol/tetrachloroethane (6/4 weight ratio).
Intrinsic viscosity measured at °C. Intrinsic viscosity is 0.5
If it is less than 5, it will be difficult to obtain a transparent amorphous molded product during parison molding, and the mechanical strength will also be insufficient. A polyester container satisfying the above formula [] can be manufactured, for example, from a substantially non-oriented and amorphous bottomed parison with an open top end by stretch blow molding under specific conditions.

That is, first, a substantially non-oriented and amorphous parison with an open top is formed from polyester by injection molding or by cutting an extrusion-molded pipe and sealing it by heating and pressing one end. The known method then stretches the parison in a skin heating device at a temperature such as the glass transition temperature T.
The container is manufactured by a method in which the container is heated to a temperature range of not less than Tm and not more than the melting point Tm, and then stretch-blow-molded using a stretching rod and pressurized gas in a blow mold having a desired volumetric structure.
Here, a preferred method for manufacturing a polyester container that satisfies the above formula (), which is suitable for manufacturing the polyester container of the present invention, that is, suitable for heat-setting treatment, is, for example, in manufacturing by such a known method, heating the parison to a stretching temperature. At this time, the temperature of the parison portion corresponding to the neck or neck to shoulder and bottom of the desired container shape is 1 to 20°C higher than the temperature of the parison portion corresponding to the body of the container.
After providing a temperature distribution that is preferably 1 to 15° C. higher, the relationship between the parison structure and the blow split mold structure is determined in advance, and when the parison is fitted into the parison fitting portion and the split mold is closed, Before carrying out the stretch blowing, a blow splitting mold is used which is designed so that the parison part of the neck of the container, preferably 311 tons or more, particularly preferably 5 inches or more, is in close contact with the corresponding part of the splitting mold. Then, the parison provided with the temperature distribution is biaxially stretched and blow-molded using a stretching rod and pressurized gas. The above is a blow molding method using a so-called cold parison, but in a blow molding method using a hot parison, the above temperature distribution may be given to the parison during the cooling process to the stretching temperature. The characteristic of the polyester container most suitable for heat setting is that it has a clear stretching start point between the unstretched part and the stretched part in order to counteract the stretching effect on the shoulders and bottom of the container where the stretching ratio is small. It is at the point where it was set.

Heating to bring the parison to the appropriate temperature for stretching is carried out in a heating oven equipped with a conventional heating element such as a block heater or an infrared heater.

Furthermore, various methods are used to impart temperature distribution to the parison by heating. For example, a parison is loaded onto a spindle that rotates and moves in a heating oven, and the parison is moved while rotating in the oven. At that time, an auxiliary heater may be installed in addition to the normal heating element only in the heating section of the oven that corresponds to the part of the parison where a temperature gradient should be created, so that the oven in that section can be heated to a higher temperature than other sections, or vice versa. Various methods are available, including a method of adjusting heating by installing a heat shield plate or a heat reflection plate in the oven section corresponding to the body of the parison, which has a relatively low temperature distribution, and a method of locally applying high-frequency heating or dielectric heating. However, there are no restrictions on the method of providing temperature distribution to the parison. In addition, the temperature distribution of the parison is given in the axial direction, and it is desirable that the temperature of the same circumferential soil is uniform in the circumferential direction. It is preferable to heat it while rotating it by a driving device. The stretching temperature of the parison (if stretch blow molding is carried out immediately after heating is almost equal to the heating temperature) is within the range of Tg or higher and Tm or lower of the polyester normally used, but the appropriate stretching temperature depends on the stretching speed and the polyester flame used. The temperature varies depending on the intrinsic viscosity and the like, and is usually preferably 80 to 170°C. Further explaining the stretch blow molding method, the parison, which has the above-mentioned temperature and has been adjusted to the stretching temperature by heating or cooling, is fitted into the parison fitting part of the stretch blow molding machine, and the blow split mold is closed.

The part of the parison that contacts the mold, corresponding to the neck of the container, is then rapidly cooled. Immediately thereafter, the parison is stretched in the axial direction, preferably by a factor of at least twice, by extrusion of a stretching rod connected to the parison fitting, and subsequently or almost simultaneously, preferably by 5 Kf/? More than 10K'/
It is stretched in the circumferential direction by a pressure gas of d or more, preferably by λ times (circumferential ratio to the parison) or more. Further, the area magnification of the stretching is usually 2.5 times or more, preferably 3 times or more, relative to the parison. In this method, the temperature distribution in the parison immediately after the drawing rod reaches the bottom of the parison is different from the temperature distribution in the temperature control stage by heating or cooling the parison, and the temperature distribution in the non-contact area immediately adjacent to the neck in contact with the mold and the drawing rod The temperature of the non-contact part, which is very close to the bottom in contact with the rod, is the highest, and the temperature of the part that comes into contact with the mold and stretching rod is rapidly cooled, so there is a large temperature gradient at the interface between the contact part and the non-contact part. is generated, and the material is stretched around this boundary surface in a state similar to a netting phenomenon, and at the same time, it is also stretched in the circumferential direction by blowing with a pressurized gas. In other words, the boundary surface having a steep temperature gradient at this time becomes the stretching fixing point. The contact between the parison part corresponding to the neck of the container and the mold not only creates a sharp temperature gradient in the neck part, but also has the effect of fixing the drawing point more clearly by mechanically gripping the parison at the contact part. have.

In this case, it is preferable that the bottom of the container is concave at the center as shown in FIG. 1, since this makes it easier to fix the stretching point. In the biaxially oriented polyester container thus obtained, the wall thickness suddenly becomes thinner in the immediate vicinity of the part that was in contact with the mold and the stretching rod, and the boundary between the stretched and unstretched parts is clearly formed. There is.

In addition, since the transition from the unstretched part to the stretched part is steep, the biaxially oriented polyester container can be subjected to the subsequent heat-setting treatment without forming a low-stretched part, which is most unstable against heat shrinkage. It can be obtained with good reproducibility and high productivity. The above has described a particularly preferable stretch blow molding in which the neck and the split mold are in contact with each other, but even if the parison structure and the split mold structure shown in FIGS. This objective can be achieved by fitting a ring made of aluminum or the like in advance to the parison portion corresponding to the neck portion of the parison and performing stretch blow molding.

As the blow mold used for manufacturing the polyester container of the present invention, for example, the blow mold shown in FIG. 2 is exemplified as a particularly preferable mold for manufacturing bottles.

That is, FIG. 2 is a schematic diagram showing the relationship between the parison structure and the blow mold that can be heat-set used in the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along a line. The blow mold has a spout part 31,
It consists of a split mold that constitutes the body part 33?5 and the bottom part 35,
It has a structure in which heat insulation blocks 32 and 34 are incorporated between each split mold. Furthermore, several stages of heaters 36 are arranged in a semicircular manner along the circumference of the bottle, and several cooling pipes 37 are arranged along the length of the bottle in the split mold 33 constituting the body. . FIG. 4 is an enlarged view of the parison structure in FIG. 2 and the opening, neck, and shoulder of the split mold, and the parison 29 heated to the stretching temperature has a portion corresponding to the neck of the bottle that is connected to the split mold. Blow molding is performed using pressurized gas in a close contact state. When the blowing step is completed, the water flow through the cooling pipe 37 disposed in the split mold 33 is stopped, and the heater 36 incorporated in the split mold 33 is energized to heat the mold to a heat-setting temperature. Thereafter, when the mold reaches a predetermined temperature, the normal current supply is automatically stopped, and water is passed through the cooling pipe 37 again to cool the mold until the mold temperature reaches the Tg of polyester or lower. Next, deaeration is performed, the mold is opened, and the polyester bottle of the present invention is taken out. In addition, it is preferable that the collar pipe 37 connects the earthen step and the lower step with a common annular connecting pipe 39.
When water stops flowing, a solenoid valve is activated to leak water, and the water is quickly removed from the mold. It is preferable that a cooling pipe 38 is disposed in the split mold forming the spout part 31 and the bottom part 35, and water can be routed to the body heater 36 by passing water to the cooling pipe 38 and by the presence of the heat insulating blocks 32 and 34. The spout and the unstretched bottom part of the bottle are designed so that they are not subjected to heat-setting treatment when the bottle is heated.As the heat treatment is performed under internal pressure, the molecules generated during the stretching process are A transparent container that has excellent physical and mechanical properties and is thermally stable can be obtained without impairing the effect of orientation. A polyester container that satisfies the formula (river) in the present invention can be heat-set. Although it is preferable to carry out heat setting by holding at a temperature for a predetermined period of time, a sufficient heat setting effect can also be obtained by a profile in which the temperature is raised to the heat setting treatment temperature and then cooled at the same time.

The heat setting temperature is usually the glass transition temperature T of polyester.
The temperature range is from g+20°C to melting point Tm-20°C, preferably from 130 to 200°C. Further, blow molding and heat setting treatment do not necessarily need to be performed in one continuous step, but may be performed in separate separate steps.

For reference, FIG. 5 is an enlarged view showing the relationship between the parison structure and the blow split mold in the conventional method corresponding to FIG. 4. Hereinafter, the present invention will be explained in detail with reference to Examples.

The methods for evaluating and measuring the characteristic values of the bottles listed in Examples and Comparative Examples are as follows. (1) Cut the bottle in the axial direction along the parting line of the blow mold attached to the numbered bottle.

Numbers 1, 2, 3, etc. are numbered at intervals of one line along the shape of the bottle, as shown in Figure 1, starting just below the flange of the cut bottle. In the bottles manufactured in the examples, numbers 0 to 8 are the neck to shoulders, numbers 9 to 23 are the body, numbers 23 to 27 are the bottom, and number 28 is the center of the bottom. (11) Wall Thickness Measure the thickness at each position using a micrometer.

(111) Density The density at each position number of the bottle was measured using 5 specimens with a side of 1 to 5 mm cut from each position of the bottle.
This was carried out using a calcium nitrate monoaqueous density gradient tube.

The measurement temperature is 30°C. (IV Orientation Degree: Cut out a strip-shaped specimen with a width of 1 mm in the axial and circumferential directions from the side wall of the bottle, and irradiate X-rays from the thickness direction (Edge and E
nclvi-Ew), and the degree of orientation was calculated from the measurement of the orientation angle of the (100) crystal plane in each direction.

(V) Volume shrinkage due to boiling water light filling treatment Lightly fill a bottle with boiling water to the fullest and leave it for 5 minutes.

After 5 minutes, remove the hot water, fill it with 20°C water, measure the internal volume V after treatment, and measure the internal volume V before treatment.

By comparing with , the volumetric shrinkage rate Vs (%) is calculated using the following formula. (VO tensile properties A tampel size 8" test piece specified in JIS K-6301 was punched out from the cylindrical part of the maximum diameter of the bottle, and a tensile speed of 10 m7!L/?n was used using a Tensilon manufactured by Toyo Sokki Co., Ltd.
Measure the tension at yield and break, and convert it to stress per unit cross-sectional area of the original sample.

QIL) Drop test Fill a bottle with 1 ton of water, put a stopper on it, then drop it repeatedly from a height of 1.2 m onto a concrete floor with the bottom facing down, and check the number of drops until it breaks. .

Example 1 Pellets of polyethylene terephthalate with an intrinsic viscosity of 0.62 were dried to a moisture content of 0.01% or less under a reduced pressure of 130 points Cs and 0.1 mmHg for 16 hours, and then molded using N-95 injection molding manufactured by Nippon Steel Corporation. Using a machine, reduce the cylinder temperature from 250°C to 270°C to 280°C from one side of the hopper.
Injection pressure is 40K'/d1 gauge pressure, mold temperature 20℃,
A bottomed parison with an open top end was molded under molding conditions with injection and cooling cycle times of 15 seconds and 25 seconds.

The parison has the shape shown in Fig. 2, and has an outer diameter of 30rnn and an inner diameter of 26mm from the opening A to the lower end of the neck C.
mm, and the flange B protrudes between them. The outer diameter of the parison gradually becomes thinner from C to the bottom curved surface starting point E, and the outer diameter of E is 24 m thick. The total length of the parison is 140r1Lm, and the length from A to the lower end of flange B is 2
3r! The length of the neck from the lower end B of the Lml tsuba to C is 10
It is mm. This parison is fitted into an upward parison fitting part equipped with an autorotation drive unit with the parison opening end facing downward, and has a far-infrared heater and a heat reflection plate on 10 sides that can freely adjust the heating distribution. Heat the parison while rotating it in an oven until the temperature distribution of the parison reaches 1 at point C at the neck.
15℃, 100℃ at point D on the body, 115℃ at point F on the bottom.
When the temperature reached the temperature, it was removed from the heating oven and immediately transferred to a stretch blow molding machine.

When the split mold of the stretch blow molding machine is closed, the BC surface of the parison neck is set in advance to be in complete contact with the split mold, and after the mold is closed, the parison is stretched by a stretching rod and subsequent pressurized gas. I went to

The cavity structure of the blow mold is shaped like a beer bottle, and as shown in Figure 2, the total length is 265 mm and the outer diameter of the body is 80 mm.
The internal volume of mm1 is 1000 d.

In addition, the forming conditions for biaxial stretching blowing are stretching rod hydraulic pressure 80K.
f/(: 7n1 compressed gas pressure 20K'/d and mold temperature 20°C. After degassing: the bottle is removed from the neck part that was in contact with the mold from the beginning. From the outside, points of sudden wall thickness displacement, which were considered to be stretching fixation points, were observed near the boundary with the contacting part and the boundary between the contacting part and the non-contacting part of the bottom stretching rod.

In this bottle, the distance from the stretching start point of the unstretched part with density ρ6 = 1.342 to the position of the stretched part where the density ρ'' (=fove + 0.008) first exceeds is 0.46 cn near the neck.
L, also 0.3801n near the bottom, d/ρ1-
ρ are 58 and 48, respectively.

Next, after blow molding was performed under the same conditions, water flow was stopped, and without degassing, electricity was started to flow to the heater installed in the blow mold to heat the mold temperature to 140°C. The time required for heating is about 2 minutes, and when the mold temperature reaches 140°C, the power supply is automatically stopped, and then water starts flowing through the cooling pipe, cooling the mold temperature to 400°C in about 1 minute. After this, the bottle was degassed and taken out. There was no difference in appearance between the bottles thus obtained and the bottles taken without heat-setting.

Furthermore, this bottle was filled with boiling water, left to stand for 5 minutes, the hot water was removed, and the inner volume was filled with 20°C water.
The shrinkage rate due to boiling water light filling, determined from the internal volume ratio before and after boiling water light filling, was 0.87%, and no change in appearance was observed due to this treatment. On the other hand, when bottles that were not heat-set were filled with boiling water, significant deformation was observed, especially at the shoulders and bottoms. I asked for 17
．． It was as large as 4% and could not withstand filling with boiling water.

Examples 2 to 4 Using polyethylene terephthalate having an intrinsic viscosity of 0.8, 1.0, and 1.2, a bottomed parison with an opening at the upper end similar to that of Example 1 was molded under the injection molding conditions shown in Table 1. After that, the parison was heated in a parison heating oven to the temperature shown in Table 2, and biaxial stretch blow molding was performed.

The neck and bottom of the resulting bottle both satisfied formula (1). Therefore, this time, after stretch blow molding was performed under the same conditions as above, the bottle was subsequently heat-set using the method and conditions described in Example 1.
As shown in Table 2, the bottles that were heat-set were able to hold enough water to fill with boiling water, but the comparative examples that were not heat-set showed shrinkage with deformation at the shoulders and bottom. Ta. Tables 3 and 4 show the performance of bottles made of polyethylene terephthalate with an intrinsic viscosity of 1.0. In the bottle shown in Example 3, the entire bottle was densely packed except for the unstretched parts such as the neck and bottom, and the heat resistance was significantly improved compared to the bottle before heat setting.

Moreover, since the heat treatment was carried out under internal pressure, no decrease in the degree of orientation was observed, but rather an increase in the degree of crystallinity, resulting in an improvement in strength and physical properties. Regarding drop strength, the bottom corner has sufficient orientation effect, so
It maintains the same strength as the bottle before heat treatment. Therefore, these bottles were given remarkable heat resistance and excellent strength and physical properties by the heat setting treatment. Comparative example 1
~4 Intrinsic viscosities are 0.62, 0.8011.00 and 1, respectively
．． A bottomed parison was molded from polyethylene terephthalate No. 21 under the injection molding conditions shown in Table 1, and then each parison was heated in a heating oven to the parison temperature shown in Table 2, and biaxially stretched blow molded in the same manner as in Example 1. I went to

The properties of the obtained bottles are shown in Table 2, but none of them satisfied the above-mentioned (Kawa) formula. Therefore, this time, after stretch blow molding was performed under the same conditions as above, heat setting was performed using the method and conditions described in Example 1.
In each of the obtained bottles, a ring-shaped opaque (whitened) area appeared near the neck and bottom, and shrinkage was observed in the vicinity. Furthermore, fill this bottle with boiling water and
After standing for a minute, the internal volume was measured and the shrinkage rate due to filling with boiling water was determined, and as shown in Table 3'', about 5 to 7% shrinkage was observed.

This shrinkage due to filling with boiling water is due to insufficient heat-setting effect, and it is desirable to strengthen heat-setting by extending treatment time or increasing treatment temperature. The opaque areas became more apparent, indicating that these bottles could not be heat-set without altering the appearance of the bottle. Bottles with such a ring-shaped whitened (opaque) part on the bottom have a significant drop in drop strength, as shown in Table 4.
It cannot withstand practical use. Example 5 After drying pellets with an intrinsic viscosity of 0.85 made of copolymerized polyethylene terephthalate/isophthalate containing 10 mol% of isophthalic acid as an acid component by a conventional method, the cylinder temperature was adjusted using an injection molding machine manufactured by Nippon Steel Corporation. The temperature was set to 240℃-2600C-270℃ from one side of the hopper, and the injection pressure was 50k9/6 in gauge pressure! i1 A parison having the same shape as in Example 1 was molded under the molding conditions of a mold temperature of 20° C. and injection and cooling cycle times of 15 seconds and 25 seconds.

This parison was heated in a heating oven to the temperature shown in Table 5, and then a biaxially oriented bottle was molded under the same stretch blowing conditions as in Example 1.

The obtained bottle had the characteristics shown in Table 5.
It can be seen that the continuously changing portions of the stretching ratio at the neck and bottom of the bottle satisfy equation (H).

Separately, stretch blow molding was performed under the same conditions as above, and then heat setting treatment was performed using the method and conditions described in Example 1.

The bottles subjected to this treatment showed no decrease in transparency due to crystallization, and no difference in appearance was observed from bottles that had not been heat-set. Furthermore, by filling the bottle with boiling water and measuring the volume after leaving it for 5 minutes,
The shrinkage rate due to filling with boiling water was calculated to be 1.05%, indicating that the bottle could sufficiently withstand filling with boiling water.

On the other hand, a bottle that has not been heat-set satisfies the equation () at the shoulder and bottom of the bottle, but when it is filled with boiling water, shrinkage with deformation is observed in the shoulder and bottom. It could not withstand the filling of water. Comparative Example 5 Using the same parison as used in Example 5, this parison was heated in a heating oven to the temperature shown in Table 5, and then stretch blow molding was performed.

The properties of the obtained bottle are shown in Table 5, and the part where the stretching ratio changes continuously at the neck and bottom of the bottle is (
) It can be seen that the formula is not satisfied. Next, stretch blow molding was performed under the same conditions as above, and then heat setting was performed using the method and conditions described in Example 1.

The bottles subjected to this treatment had ring-shaped opaque areas near the neck and bottom, and shrinkage was observed in the vicinity. Furthermore, when this bottle was filled with boiling water and left to stand for 5 minutes, the change in internal volume was measured, and a shrinkage of about 5.8% was observed. This shrinkage due to filling with boiling water is due to insufficient heat-setting effect, and it is desirable to strengthen the heat-setting conditions by extending the processing time or increasing the processing temperature, but if this is done, the ring-shaped opaque As the area became more obvious, this bottle showed that it was not possible to heat set the bottle without changing the appearance of the bottle.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view cut along the parting line of a blow mold for a bottle manufactured in an embodiment according to the present invention, and A, b, and c are drawings defined by the present invention. The approximate location corresponding to the division, and 1, 2, 3, etc.
..., 28 are numbered at intervals of 1c7n from just below the flange of the bottle, and are the numbers of the parts where the physical property values were measured. Further, FIG. 2 is a schematic diagram illustrating the relationship between the blow mold and the parison structure and the stretch blow split mold used in the present invention, which can be heat-set. FIG. 3 is a cross-sectional view of the mold shown in FIG. 2 taken along the line X-X5. Furthermore, FIG. 4 is an enlarged view of the opening, neck, and shoulder of the parison and split mold in FIG. 2. Furthermore, FIG. 5 is an enlarged view corresponding to FIG. 4 showing the relationship between the conventional parison structure and the blow split mold. a... thermally stable stretched portion, b.
...Thermally unstable stretched part (part where the stretching ratio changes continuously), c... Unstretched part, 29...
...Parison, 30...Fixed stand, 32,3
4...Insulation block, 31, 33, 35...
... Split mold, 36... Heater, 37, 38
......Cooling pipe, 39...Connecting pipe, 40.
...Stretching rod, 41...Parison fitting part, A...Parison opening, B...Brim part, C...Neck part, D... Center of the torso, E
...... Bottom curved surface start part, F... ... Bottom center.

Claims (1)

[Claims] 1 A bottomed parison made of a thermoplastic polyester whose main repeating unit is ethylene terephthalate is biaxially stretched and blow molded using a compressed gas and a stretching rod at the stretching temperature of the polyester to form an unstretched part, a stretched part, and an unstretched part. In a method for producing a polyester container, in which a container consisting of a part in which the stretching ratio changes continuously from the drawing part to the drawing part is formed and then heat-set, when the parison is brought to the drawing temperature, The temperature of the parison part corresponding to the shoulder and bottom part is 1 to 20 degrees higher than the temperature of the parison part corresponding to the body of the container.
After giving a temperature distribution such that the temperature is higher than the stretching temperature, biaxial stretch blow molding is performed using a mold, a stretching rod, and a compressed gas at a temperature lower than the stretching temperature. 1. A method for producing a transparent polyester container having a volume shrinkage rate of 2% or less when filled with boiling water, the method comprising heat-treating at a temperature range of 20° C. or more lower than that of a polyester container.