JPS6357312B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a biaxially oriented bottle molded from a thermoplastic polyester containing ethylene terephthalate as the main repeating unit, and more specifically, it has excellent mechanical properties, gas barrier properties, chemical resistance, etc. The present invention relates to a biaxially oriented bottle that has excellent protection against objects and has excellent thermal stability with less deformation, shrinkage, etc. 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. Blow molding technology can also be used for hollow containers such as bottles and cans.
In particular, recent improvements in biaxial stretch blow molding technology have been particularly remarkable. 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) is generally made of amorphous material by injection molding or extrusion molding. temperature range in which the parison can be formed and then oriented, e.g. glass transition temperature (Tg)
The product is heated to a temperature range below the melting point (T _n ) and stretched in the axial direction by an extrusion rod connected to a spindle and in the circumferential direction by blowing compressed gas in a blow mold having the desired volumetric structure of the container. is being stretched. 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 distortions generated during the stretching process. For example, when a polyester bottle after molding is stored in a hot and humid atmosphere such as in the summer, the bottle may gradually shrink and its internal volume may fluctuate, or the content may be at a temperature close to the glass transition temperature of polyester, such as 60°C or higher. When filling the bottle, it has the fatal disadvantage that shrinkage occurs during or after filling, making it impossible to fill the contents accurately, and the bottle deforms, making it impossible to maintain its original shape. Currently, the range of applications is severely restricted, as this greatly reduces the commercial value of the bottle. Generally, polyethylene terephthalate molded products such as threads with a one-dimensional structure or films with a two-dimensional structure are subjected to a heat treatment called heat setting 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 a similar idea, a method of heat-fixing stretch-oriented bottles in order to improve their heat resistance has been proposed in Japanese Patent Publication No. 49-3073 and Japanese Patent Application Laid-open No. 52-52.
It is disclosed in Publication No. 126376, etc. However, no matter what shape a stretch-oriented bottle is molded using the normal blow molding method, it is impossible to achieve a uniform stretch ratio over the entire bottle, and the bottle is not stretched at all. It is an integral molded product consisting of a stopper, a neck to shoulder part and bottom part with a low stretching ratio, and a body part with a high stretching ratio. Although thermal fixation at .degree. C. shows a tendency to reduce thermal shrinkage, not only is it not possible to obtain a sufficient effect, but the low-stretched portions are prone to whitening due to thermal crystallization, resulting in a fatal drawback of impairing the aesthetic appearance of the bottle. 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.
In other words, the attempt was made to prevent the whitening phenomenon by heat-setting the low-stretched areas at a low temperature and the high-stretched areas at a high temperature, but especially in the stretching orientation where the draw ratio changes continuously from the unstretched area to the stretched area. It is nearly impossible to create a temperature gradient that corresponds to the stretching ratio for a plastic bottle, and even if it were possible to create a certain temperature distribution, the cycle time required for heating and cooling the mold would be Not only does it take a long time to process, which significantly reduces productivity, but it also consumes a large amount of thermal energy, and if you try to increase the density enough to provide sufficient heat resistance, it will result in whitening. If an attempt is made to avoid this, the density cannot be increased enough to provide sufficient heat resistance, and in any case, a satisfactory biaxially oriented bottle cannot be obtained, making this method difficult to commercialize in practice. In view of these circumstances, the present inventors analyzed the heat shrinkage behavior of biaxially oriented bottles obtained under various conditions, and found that they had excellent heat resistance through a stretch-forming process without any particular heat-setting treatment. As a result of intensive research to provide a biaxially oriented bottle having the following characteristics, the present invention was achieved. That is, the present invention is made of a thermoplastic polyester having an intrinsic viscosity of at least 0.60 and having ethylene terephthalate as a main repeating unit, and has unstretched portions in the neck and bottom center portions, and stretched portions in the shoulder, body, and bottom corner portions. A biaxially oriented bottle having a portion in which the stretching ratio changes continuously from the unstretched portion to the stretched portion, from the neck to a portion of the shoulder, and from the center of the bottom to the corner, the unstretched portion being a biaxially oriented bottle. In the part where the stretching ratio continuously changes from ρ to the stretched part, the position of the stretched part where the density first exceeds ρ (g/cm ³ ) from the stretching start point of the unstretched part having density ρ ₀ (g/cm ³ ). Biaxial orientation characterized in that the ratio of the distance d (cm) to the density increase (ρ - ρ ₀ ) is expressed by the following formula [], and the density of the stretched portion exceeding d is at least greater than ρ. Shit bottle. d/ρ−ρ ₀ <80 [] (However, ρ≧ρ ₀ +0.026) The biaxially oriented bottle of the present invention is disclosed in Japanese Patent Publication No. 49-3073 and Japanese Patent Application Laid-Open No. 52-126376. It has excellent mechanical properties, gas barrier properties, chemical resistance, etc. without the need for special heat-setting treatment, and has excellent protection against contents, while also preventing deformation when filled with high-temperature contents. This bottle has excellent thermal stability with little shrinkage. Therefore, it has the characteristic of being able to withstand heat such as high-temperature filling and heat sterilization. Of course, another major feature is that it does not require heat fixation and has excellent transparency without problems such as whitening. To explain in more detail the structural and shape characteristics of the biaxially oriented bottle of the present invention, the biaxially oriented bottle has mostly a stretched portion a having a thermally stable structure, as shown in FIG. , there are very few thermally unstable stretched portions, ie, portions b where the stretching ratio changes continuously from unstretched portions to stretched portions, and other features include unstretched portions c. Taking as an example a cylindrical narrow-mouth bottle of the present invention obtained by stretch-blow molding using a substantially amorphous polyester bottomed parison with an open top end, the entire body of the bottle, The shoulder and bottom corner of the bottle are part a above, the neck and center of the bottom are part c above, and a small part from the neck to the shoulder and from the center of the bottom to the corner. There is only part b in a small part. The stretched part a, which has a thermally stable structure, is a part where crystallization is promoted more than molecular chain orientation during stretching, and there are crosslinking points (microcrystals) that are sufficient to suppress strain relaxation. This part has good heat resistance due to the presence of Taking polyethylene terephthalate as an example, the density ρ of this part is at least 0.026 or more greater than the density ρ ₀ =1.340 to 1.342 g/cm ³ of the unstretched part, that is, 1.366 to 1.368 g/cm ³ or more, preferably 1.368 or more. X-rays were incident on a specimen cut into 1 mm wide strips from the side wall of the bottle in the axial and circumferential directions from the thickness direction (edge and end view), and the orientation angle of the (100) crystal plane was measured. The obtained degree of orientation is between 80 and 90 in the main orientation direction.
Further, the thermally unstable stretched portion b refers to the following two portions in terms of molecular structure. One is a low-stretched area in which no microcrystals are observed due to stretching and the molecular chains are slightly oriented, and when heat is applied to this area, the stretched rubber contracts like relaxing. The other is a region where molecular chain orientation is promoted more than crystallization during stretching, and heat resistance is poor because there are no crosslinking points (microcrystals) sufficient to suppress strain relaxation.
This part has a density increase of less than 0.026 compared to the unstretched part, that is, 1.366 to 1.368 g/cm ³ or less, and the degree of orientation determined by the above method is 90 in the main orientation direction.
That's all. Furthermore, the unstretched part c is a substantially non-oriented part, and although it softens when treated for a short period of time at a temperature around 80°C, no structural changes such as whitening occur, and the softening is similar to that of the unstretched part. This can be solved by increasing the wall thickness, so the existence of this part does not pose any problem in terms of heat resistance at temperatures around 80°C. Therefore, the biaxially oriented bottle having excellent heat resistance as used in the present invention is one that has a structure in which most of the bottle consists of the above-mentioned part a, and there is very little part b, especially the low-stretched part. Another major feature is that the above-mentioned section b is fixed only in the areas that have the least effect on the volume of the bottle, that is, in extremely narrow areas near the top of the neck and the center of the bottom. In this case, it is more preferable that the bottom of the bottle be a self-supporting bottom with a concavely curved bottom at the center as shown in FIG. 1, since this facilitates the fixation of part b. On the other hand, for biaxially oriented bottles molded by normal molding methods, d/ρ−ρ ₀ exceeds 100,
Since there is a large amount of the above-mentioned portion b, even if the density of the body portion satisfies the value of ρ ₀ +0.026 or more according to the present invention, the bottle cannot be made to have excellent heat resistance with little heat shrinkage and thermal deformation. Note that d/ρ−ρ ₀ is particularly preferably
80 or less. The thermoplastic polyester having ethylene terephthalate as a main repeating unit as used 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, diphenyl ether 4,
4'-dicarboxylic acid, naphthalene 1,4- or 2,6-dicarboxylic acid, adipic acid, sebacic acid, decane 1,10-dicarboxylic acid, hexahydroterephthalic acid, and as other glycol components propylene glycol, 1,4 -butanediol,
Neopentyl glycol, diethylene glycol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-
bis(4-hydroxyethoxyphenyl)propane, or P-oxybenzoic acid as the oxyacid;
It means a polyester containing P-hydroethoxybenzoic acid or the like. In addition, polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol can also be used as copolymerization components if their molecular weight is about 3000 or less, but copolymerization in large amounts reduces heat resistance, so they are usually used as glycol components. It is preferable to limit the amount to 2 to 3 mol% or less. 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
It has an intrinsic viscosity of 0.6 or more, more preferably 0.7 to 1.4. Intrinsic viscosity is the intrinsic viscosity measured at 30°C of a solution of polyester dissolved in a phenol/tetrachloroethane mixed solvent (6/4 weight ratio). If the intrinsic viscosity is less than 0.55, it will be difficult to obtain a transparent amorphous molded product during parison molding, and the mechanical strength will also be insufficient. Although the influence of intrinsic viscosity on the thermal shrinkage of bottles has not been known until now, polyesters with high intrinsic viscosity shift the appropriate drawing temperature for parisons to higher temperatures than polyesters with low intrinsic viscosity, and parisons made of low-viscosity polyesters A biaxially oriented bottle can be formed even under temperature conditions where polyester does not become oriented due to the super draw phenomenon during stretching, and the higher the intrinsic viscosity of the polyester, the higher the heat resistance can be obtained. The biaxially oriented bottle of the present invention can be produced by stretch blow molding under specific conditions from a substantially non-oriented and amorphous bottomed parison with an open top end obtained by a commonly known method. can. That is, first, a substantially non-oriented and amorphous bottomed parison with an open top end is made of polyester by injection molding.
Alternatively, it is formed by cutting an extruded pipe and sealing one end by heating and pressurizing it. Next, the known method is to heat the parison in a heating device to a stretching temperature, for example, in a temperature range above the glass transition temperature (Tg) and below the melting point (Tm), and then press the parison with a stretching rod in a blow mold having a desired volumetric structure. Bottles are manufactured by stretch blow molding using gas. On the other hand, the most preferable manufacturing method for the biaxially oriented bottle of the present invention is, for example, in manufacturing by such a known method, when heating the parison to the stretching temperature, the neck part or neck to shoulder part of the desired bottle shape is After giving a temperature distribution such that the temperature of the parison portion corresponding to the top and bottom of the bottle is 1 to 20°C higher than the temperature of the parison portion corresponding to the body of the bottle, the parison structure and the blow-splitting mold structure are prepared in advance. When the parison is fitted into the parison fitting part and the split mold is closed, at least 3 mm or more of the parison part corresponding to the neck of the bottle will be in the corresponding part of the split mold before stretching blowing. The parison with the temperature distribution is biaxially stretched and blow-molded using a stretching rod and pressurized gas using a blow mold designed to be in close contact with the parison. 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 feature of this manufacturing method is that in order to improve the stretching effect of the shoulder and bottom parts of bottles where the stretching ratio is small, it is best to create a clear stretching start point between the unstretched part and the stretched part. As a result of further intensive research based on the knowledge of researchers and others, we have discovered a practical manufacturing method that makes this possible. It is known that when drawing yarn, which is a one-dimensional structure, a temperature gradient is easily created by local heating at the contact points of pins and rolls, and the drawing points are fixed. However, in the case of a parison, which is a three-dimensional structure, it is technically extremely difficult to do so, and there is no knowledge to date of fixing the stretching point on the parison before stretching. When actually heating a parison, since the heat transfer area is large, a sudden temperature change point cannot be obtained only by the temperature gradient that can be applied during heating. Even with molding, it is difficult to clearly fix the stretching points. However, as in the present invention, a parison in which the parison portion corresponding to the neck and bottom of the bottle is heated to a temperature of 1 to 20 degrees Celsius, preferably 1 to 15 degrees Celsius higher than the parison portion corresponding to the body, has a rapid temperature gradient change. Even if there is no dot, when the blow mold is closed, the parison portion corresponding to the neck of the bottle, at least 3 mm or more, preferably 5 mm or more, is brought into contact with the water-cooled neck of the blow mold, thereby forming a contact surface. It is possible to create a significant temperature gradient at the boundary with the non-contact surface, and since the area near the interface on the non-contact side is still at a higher temperature than the body, it is possible to clearly fix the stretching point of the neck. . Also, at the bottom of the parison, after the blow mold is closed, the stretching rod contacts the bottom of the parison and stretches in the axial direction, so the contact area between the tip of the stretching rod and the bottom of the parison is rapidly cooled, and the contact area is also non-contacted. A significant temperature gradient occurs at the interface between the parts,
The stretch point can be fixed in the same way as the neck. On the other hand, when a parison heated to a uniform temperature as in the conventional method is stretch-blow-molded using this method, the neck part that comes into contact when the blow mold is closed and the bottom part that comes into contact with the stretching rod during stretching will experience a temperature drop, and the non-contact areas will drop. The area near the side boundary also becomes lower in temperature than other non-contact areas, making it completely impossible to bring the stretching start point to the contact boundary surface. For this reason, it is necessary to heat the parison part, which corresponds to the neck part that comes into contact with the mold when the blow mold is closed and the bottom part that comes into contact with the stretching rod during stretching, to a higher temperature in advance than the non-contact parts. In this way, the biaxial stretch blow molded bottle has the same stretching effect as the body in the region from the neck to the shoulder where the stretching ratio is small and in the region from the center of the bottom to the curved portion. Therefore, it has the advantage that not only excellent heat resistance is obtained, but also mechanical strength, gas barrier properties, etc. are improved in the portion where the drawing ratio is small. In the present invention, the substantially amorphous bottomed parison with an open top end formed by injection molding or extrusion molding is heated to the drawing temperature using a heating oven equipped with a conventional heating element such as a block heater or an infrared heater. It takes place inside. Furthermore, various methods are used to provide a parison temperature distribution by heating. For example, a parison is loaded into a spindle that moves while rotating in a heating oven, and the parison moves 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 only that section can be heated to a higher temperature than other parts.
Alternatively, there are various methods such as adjusting the heating by installing a heat shielding plate or a heat reflecting plate in the oven section corresponding to the body of the parison, which has a relatively low temperature distribution, or using local high-frequency heating or dielectric heating. Although there are methods, there are no restrictions on the method of providing temperature distribution to the parison. Furthermore, the temperature distribution of the parison is given in the axial direction, and it is desirable that the temperature on the same circumference is uniform in the circumferential direction. It is preferable to heat it while rotating it by a drive device. The parison stretching temperature (approximately equal to the heating temperature when stretch blow molding is performed immediately after heating) 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 used. It varies depending on the intrinsic viscosity etc. Usually
80-170°C is preferred. However, in order to obtain a bottle with better heat resistance, it is not necessary to apply a uniform stretching temperature, but rather, depending on the intrinsic viscosity (V) of the polyester used, the stretching temperature (T )°C is more preferably applied. 60V+85≧T≧60V+45... [] In other words, the optimum temperature for stretching shifts to the higher temperature side as the intrinsic viscosity of polyester increases, and it is recommended to perform stretch blow molding as high as possible within the temperature range that allows oriented crystallization during stretching. preferable. Therefore, in the present invention, the parison portion corresponding to the neck, shoulder and bottom of the bottle is heated at a temperature of 1 to 20°C, preferably 1 to 15°C, higher than this stretching temperature (T).
It is stretch-blow molded at high temperatures. Next, the relationship between the parison structure and the stretch blow split mold used in the present invention will be described. FIG. 2 illustrates the relationship between the two using an example. FIG. 2 is an explanatory diagram showing the state when the split mold with the parison fitted into the parison fitting portion is closed. Furthermore, FIG. 3 is an enlarged view of the opening, neck, and shoulder of the parison and split mold in FIG. 2. As seen in the figure, the feature of the present invention is that at least 3 mm or more of the neck portion below the parison collar is already in complete contact with the closed mold before stretch blowing. On the other hand, FIGS. 4 and 5 show an example of the relationship between the parison structure and the split mold structure, which does not apply to the present invention, that is, the conventional method. In FIGS. 4 and 5, there is no contact between the neck and the closed split mold. Biaxial stretch blow molding machines have two directions for gripping the parison during the heating of the parison and the stretch blowing process in the blow mold. That is, one type has the parison fitting portion facing upward, and in this case, the parison is fitted with the opening facing downward. This is the so-called inverted type. The other type is a so-called suspension type fitting in which the parison fitting part faces downward and the parison opening faces upward. In order to satisfy the condition that when the blow split mold is closed, which is a component of the present invention, at least 3 mm or more of the parison portion corresponding to the bottle neck is in close contact with the blow split mold before starting stretching blowing. It is also important to appropriately select the settings of the parison and/or the blow splitting mold of the part to be brought into close contact, depending on the above-mentioned gripping direction of the parison. For example, in the case of a suspended type gripping direction, even if the outer diameter of the parison is designed to match the diameter of the neck of the split mold so that it will come into close contact with the blow split mold, the parison will have softened after being heated to the appropriate temperature for stretching. The larger the parison, the more it tends to sag downward due to its own weight, so when the heated parison is inserted into the blow mold and the mold is closed, the parts that should be in contact may no longer make contact. Normal. For this reason, in the case of suspension type fitting, it is preferable to take measures such as designing the outer diameter of the parison at the neck part to be contacted in advance to be larger than the corresponding part of the blow splitting mold. On the other hand, in the case of inverted fitting, the parison tends to become thicker due to its own weight during the heating stage, so even if the outside diameter of the neck of the parison that comes into contact with it and the diameter of the corresponding blow split mold neck are the same, good. 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 neck that is in contact with the mold by at least 3 mm is then rapidly cooled. Immediately thereafter, the parison is stretched in the axial direction by extrusion of a stretching rod connected to the parison fitting, preferably by a factor of at least 2 times, and subsequently or almost simultaneously, preferably by a factor of 5.
It is stretched in the circumferential direction preferably by a factor of 8 or more (circumferential ratio to the parison) using a pressurized gas of Kg/cm ² or more, especially 10 Kg/cm ² 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 The temperature of the non-contact area near the bottom that is in contact with the rod is the highest, and the temperature of the area 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 area and the non-contact area. 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 bottle and the mold not only creates a rapid 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. At this time, it is preferable for the bottom of the bottle to have a concave center at the bottom as shown in FIG. 1, since this makes it easier to fix the stretching point. In the biaxially oriented bottle thus obtained, the wall thickness suddenly becomes thinner immediately near the part that was in contact with the mold and the stretching rod, and the boundary between the stretched part and the unstretched part is clearly formed. . In addition, since the transition from the unstretched part to the highly stretched part is steep, the biaxial structure satisfies the conditions set forth in claim 1 without almost producing a low stretched part, which is most unstable against heat shrinkage. Oriented bottles can be obtained with good reproducibility and high productivity. The above describes particularly preferable stretch blow molding in which the neck and the split mold are brought into contact.
Even with the parison structure and split mold structure shown in Figures and Figure 5, a ring made of aluminum or the like is fitted in advance to the parison portion corresponding to the neck of the bottle, which provides a temperature gradient, and stretch blow molding is performed. By doing so, you can achieve your goals. The point is that the stretching points are clearly fixed at the neck and bottom, and the stretching is done in a state close to the netting phenomenon. Hereinafter, the present invention will be explained in detail with reference to Examples.
The methods for evaluating and measuring the characteristic values of the biaxially oriented bottles listed in the Examples and Comparative Examples are as follows. (i) Numbering Cut the bottle in the axial direction along the parting line of the blow mold attached to the bottle. Starting just below the flange of the cut bottle, number 1, 2, 3, etc. at 1 cm intervals along the shape of the bottle, as shown in Figure 1. 0 for the bottles manufactured in the examples
~8 is the neck to shoulder area, 9~23 is the torso,
23 to 27 are the bottom, and 28 is the center of the bottom. (ii) Wall thickness Measure the thickness at each location using a micrometer. (iii) Density The density at each position number on the bottle was measured using a calcium nitrate-water density gradient tube on test pieces cut from each position on the bottle and measuring 1 to 5 mm on each side. The measurement temperature is 30°C. (iv) Degree of orientation Width 1mm in the axial and circumferential directions from the side wall of the bottle
A tanzak-shaped specimen is cut out, and X-rays are incident on it from the thickness direction (edge and end view).
The degree of orientation was calculated from the measurement of the orientation angle of the (100) crystal plane in each direction. (v) Heat shrinkage rate Fill a bottle to the brim with 80°C hot water and leave it for 5 minutes. After 5 minutes, remove the hot water, fill with 20℃ water, measure the internal volume (V) after treatment, and compare it with the internal volume (V ₀ ) before treatment to determine the volumetric shrinkage rate Vs (%). is calculated using the following formula. Vs (%) = V ₀ - V / V ₀ × 100 (vi) Tensile properties JIS K-6301 from the cylindrical part of the maximum diameter of the bottle
Punch out a dumbbell size 3 test piece specified in
Tensile speed using “Tensilon” manufactured by Toyo Sokki Co., Ltd.
Measure the tension at yield and break at 10 mm/min and convert it to stress per unit cross-sectional area of the original sample. (vii) Drop test Fill a bottle with 1 water, close the cap, and drop the bottle repeatedly from a height of 1.2 m onto a concrete floor with the bottom facing down to determine the number of drops until it breaks. Example 1 Polyethylene terephthalate pellets with an intrinsic viscosity of 0.62 were dried at 130°C and under a reduced pressure of 0.1 mmHg for 16 hours to a moisture content of 0.01% or less, and then molded using an N-95 injection molding machine manufactured by Nippon Steel Corporation. The cylinder temperature is 250℃ - 270℃ - 280℃ from the hopper side, the injection pressure is 40Kg/cm ² in gauge pressure, the mold temperature is 20℃, and the injection and cooling cycle times are 15 seconds and 25 seconds. A parison with a bottom and an opening was molded. The parison has the shape shown in Figure 2, and the outer diameter from the opening A to the lower end C of the neck is 30 mm.
mm, and the inner diameter is 26 mm, with the flange B protruding between them. The outer diameter of the parison gradually decreases from C to the curved starting point E at the bottom, and the outer diameter of E is 24 mm. The total length of the parison is 140mm, from A to flange B.
The length to the lower end of the collar is 23 mm, and the length of the neck from the lower end of the collar B to C is 10 mm. This parison is fitted into an upward-facing parison fitting part equipped with an autorotation drive device, with the open end of the parison facing downward, and an oven equipped with a far-infrared heater and a heat reflection plate on 10 sides allows for freely adjusting the heating distribution. The parison is heated while rotating in the oven, and when the temperature distribution of the parison reaches 115℃ at point C at the neck, 100℃ at point D at the body, and 115℃ at point F at the bottom, it is removed from the heating oven and placed in a stretch blow molding machine. was immediately transferred to. 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. I went there. 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, the outer diameter of the body is 80 mm, and the internal volume is 1000 ml. The molding conditions for biaxial stretching blowing are a stretching rod oil pressure of 30 Kg/cm, a compressed gas pressure of 20 Kg/cm ² and a blow mold temperature of 20°C. The bottle obtained in this way appears to have stretching fixing points near the boundary between the neck part that originally contacted the blow mold and the non-contact part, and the bottom part near the boundary between the contact part and the non-contact part of the stretching rod. A sharp wall thickness displacement point was also observed from the outside. Further, the density ρ ₀ of the unstretched part is 1.342, and the density ρ ₀ of the unstretched part is ρ ₀ +0.026, that is, from the position having ρ 0 of the unstretched part.
The distance to the position of the stretched part having a density ρ of 1.368 is 1.5 cm from the neck unstretched part and 1.2 cm from the bottom unstretched part, so near the neck d/ρ− ρ ₀ =58 near the bottom d/ρ−ρ ₀ =46. This biaxially oriented bottle was filled with hot water at 80°C, and after being left for 5 minutes, the volumetric shrinkage rate was measured and found to be 1.35%. Examples 2 to 4 Using polyethylene terephthalate (PET) with intrinsic viscosities of 0.80, 1.00, and 1.21, a bottomed parison with an opening at the top end similar to that of Example 1 was molded under the injection molding conditions shown in Table 1. The temperature distribution shown in Table 2 was imparted to the parison in a parison heating oven. Thereafter, biaxial stretch blow molding was performed in the same manner as in Example 1. The characteristic values of the obtained bottles are as shown in Table 2, and the higher the viscosity of PET, the higher the temperature it can be stretched, and the smaller the shrinkage rate of the bottle. Also,
In each bottle, a sharp wall thickness change point was observed at a position considered to be the stretching start point near the boundary between the unstretched part and the stretched part. This can also be confirmed by the measurement results of wall thickness, density, and degree of orientation at each part of the bottle obtained in Example 3 shown in Table 3. The mechanical properties are shown in Table 4. Comparative Examples 1 to 4 Bottomed parisons were molded from polyethylene terephthalate having intrinsic viscosities of 0.62, 0.80, 1.00, and 1.21 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. Biaxial stretch blow molding was performed in the same manner as in Example 1 by heating. The characteristics of the obtained bottle are shown in Table 2. Comparative Examples 1 to 4 correspond to Examples 1 to 4, respectively, and show examples in which the temperature of the parison before stretch blowing is uniform. If the parison temperature distribution is uniform, the parison neck should be at least 3 mm from the mold surface.
Even though one of the requirements of the present invention of close contact was satisfied, small deformation occurred in the shoulder portion, and shrinkage was observed in the bottom portion as well. In addition, as is clear from Table 3, the wall thickness of these bottles changed gradually from the unstretched part to the stretched part, and no abrupt change point in the wall thickness was observed as in the bottles of the present invention. .

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[Table] Example 5 and Comparative Examples 5 to 8 Polyethylene terephthalate having an intrinsic viscosity of 1.0 was injection molded under the conditions shown in Table 1 to obtain five parisons having the same shape as in Example 1. As is, these parisons are set so that 10 mm of the neck part BC of the parisons is in contact with the mold in the mold closed state shown in FIGS. 2 and 3. Of these five parisons, one parison leaves 5mm below the flange B, another one leaves 3mm below the flange, and the other parison leaves 1mm below the flange, and has an outer diameter of 30mm. The part was cut in the outer circumferential direction using a lathe so that it was 29 mm. In addition, the remaining two are made by cutting the entire outer circumference of the neck BC and making the outer diameter
30mm was changed to 29mm. These parisons were used as the parisons of Example 5 and Comparative Examples 5 to 8, respectively. Next, these parisons were subjected to biaxial stretch blow molding under the same stretching conditions as in Example 1, except that they were heated to have the temperature distribution shown in Table 5. The characteristic values of the biaxially oriented bottle thus obtained are shown in Table 5, and the characteristic values of Example 3 are also listed again. As is clear from this result, bottles whose bottle characteristics fall outside the scope of claim 1 have a large shrinkage rate, and even if the manufacturing conditions simply provide a temperature distribution during parison heating, the mold does not change when the blow mold is closed. It can be seen that it is difficult to prevent small deformation and contraction of the shoulders unless the contact between the necks of the parison exceeds at least 3 mm.

[Table] Example 7 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. 240℃－260℃－270 from the hopper side
A parison having the same shape as in Example 1 was molded under the following molding conditions: the injection pressure was 50 Kg/cm ² gauge pressure, the mold temperature was 20° C., and the injection and cooling cycle times were 15 seconds and 25 seconds. This parison was heated in a heated oven and Table 6
After providing the temperature distribution shown in , a biaxially oriented bottle was molded under the same stretch blowing conditions as in Example 1. The characteristic values of the obtained bottles are shown in Table 6. Comparative Examples 8 to 10 In the same manner as in Example 7, three parisons of copolymerized polyethylene terephthalate/isophthalate were molded by injection molding. One of them was used as Comparative Example 8, and the remaining two parisons as Comparative Examples 9 and 10 were cut from 30 mm to 29 mm by cutting the outer diameter of the parison neck in the same way as Comparative Example 6.
It was set to mm. Next, these three parisons were heated to the parison temperature shown in Table 6, and then subjected to biaxial stretch blowing under the same stretch blowing conditions as in Example 1. The characteristic values of the obtained bottles are shown in Table 6. Even with copolymerized polyester, bottles that do not meet the requirements of the present invention have a large shrinkage rate, and bottles that do not have a parison temperature distribution during stretch blowing and those that do not have a parison neck contact area with the mold are accompanied by deformation, especially those that do not meet both requirements. Comparative examples that did not meet the requirements were significantly deformed.

【table】 [Brief explanation of drawings]

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 in the present invention. The approximate positions corresponding to the divisions and 1, 2, 3, . . . , 28 are numbered at 1 cm intervals from just below the flange of the bottle, and are the numbers of the parts where the physical property values were measured. Furthermore, FIG. 2 is a schematic diagram illustrating the relationship between the parison structure and the stretch-blow split mold used in the present invention, and is an explanation showing the state when the parison is fitted into the parison fitting part and the split mold is closed. It is a diagram. Furthermore, FIG. 3 is an enlarged view of the opening, neck, and shoulder of the parison and split mold in FIG. 2. Furthermore, FIG. 4 is a schematic diagram showing the relationship between the conventional parison structure and the stretch-blow split mold corresponding to FIG. 2, and FIG. 5 shows the openings of the parison and split mold in FIG. , is an enlarged view of the neck and shoulders. a: thermally stable stretched portion, b: thermally unstable stretched portion (portion where the stretching ratio changes continuously),
c: unstretched portion, 29: parison, 30: fixed base, 31, 32: split mold, 33: stretched rod, 3
4: Parison fitting part, A: Parison opening, B:
Flange, C: Neck, D: Center of body, E: Start of bottom curved surface, F: Center of bottom.

Claims (1)

[Scope of Claims] 1. Made of thermoplastic polyester containing ethylene terephthalate as a main repeating unit and having an intrinsic viscosity of at least 0.60, with an unstretched portion at the center of the neck and bottom, and an unstretched portion at the shoulder, body, and bottom corner portions. and a part of the shoulder from the neck,
A biaxially oriented bottle that has a part from the center of the bottom to the corner where the stretch ratio changes continuously from the unstretched part to the stretched part, and the stretch ratio changes continuously from the unstretched part to the stretched part. In the part to be stretched, the distance d (cm) from the stretching start point of the unstretched part with density ρ ₀ (g/cm ³ ) to the position of the stretched part that first exceeds density ρ (g/cm ³ ) and the density increase ( ρ−ρ ₀ )
A biaxially oriented bottle characterized in that the ratio of . d/ρ−ρ ₀ <80 [] (However, ρ≧ρ ₀ +0.026)