JPH05443A - High stretch blow molded container and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Objective] To provide a high-strength container having a uniform film thickness and a thin film. [Structure] Substantially unconstrained and highly stretched, the film thickness of the device membrane other than the mouth and neck is sufficiently stretched to form a thin film, and the device membrane other than the mouth and neck is oriented and crystallized to form the thickest part and the most film. The ratio of the difference in the thin portion was set to 50% or less to make the film thickness uniform. [Effect] Except for the mouth and neck, it is oriented and crystallized and has a high yield value and high strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly stretch blow-molded container which is thin and has no uneven thickness and whitening, and a method for producing the same.

[0002]

2. Description of the Related Art A container obtained by biaxially stretch-blow molding a molded preform by an apparatus using a stretching rod for forcibly stretching in the height direction is well known before the present application. However, it has been unknown at all to manufacture a biaxially stretch-blow-molded container and a container in this way using only a pressurized fluid, which is substantially unconstrained.

[0003]

The constrained biaxially-stretched container using the above-mentioned stretched rod has the drawback of having a low stretching ratio and a large uneven thickness, and its strength is uneven and small, so that it must be a thick-walled container. It was not satisfactory, and whitening was likely to occur, which was not satisfactory.

[0004]

The present inventor has solved the above problems by elucidating that such a defect occurs because the resin layer of the container wall of the molded container is not sufficiently and uniformly stretched, The present invention has been completed by successfully providing a thin and lightweight container having uniform strength without uneven thickness and whitening.

According to the present invention, "1. The film thickness of the stretch-formed container wall other than the mouth and neck is almost uniform, and the film thickness of the thickest part and the thinnest part is the thickest part of the film. A high stretch blow-molded container having a difference of 50% or less and in which the vessel wall excluding the mouth and neck is oriented and crystallized 2. The shoulder and the bottom are hemispherical shell-shaped, and the body is cylindrical. The high stretch blow-molded container according to claim 1. 3. The yield value in the circumferential direction of the body resin layer constituting the container wall is 1800 kg / cm ² or more, and the yield value in the height direction. Is 800 kg / cm ² or more,
The high stretch blow-molded container described in any one of 1. 4. The high stretch blow-molded container according to any one of claims 1 to 3, wherein the ratio of the amount of resin to the inner volume in the stretched portion of the container is 0.025 or less and there is no whitening. 5. The high stretch blow-molded container according to any one of claims 1 to 4, which has a thin wall thickness of 0.2 mm to 0.3 mm and is free from uneven thickness and whitening as measured on the body. 6. The thickness of the vessel wall blow-molded and stretch-molded using a pressurized fluid without restraining the parts other than the mouth and neck of the container is made almost uniform, and the difference in the thickness of the thinnest part from the thickest part A method for producing an unconstrained high-stretch blow-molded container, characterized in that the proportion is 50% or less, and the vessel wall excluding the mouth and neck is oriented and crystallized. 7. The stretched blow molding of 90% or more of at least one direction of the maximum stretched portion in the body radial direction and the stretched portion in the height direction of the molded container is carried out without restraint by high stretch blow molding. High stretch blow-molded container manufacturing method. 8. The stretching of the preform is finally carried out with a stretching ratio in the radial direction of 4.5 to 5.5 and a stretching ratio in the radial direction of 1.5 to 1.8 of the stretching ratio in the height direction. A method for producing an unconstrained high stretch blow-molded container according to any one of claims 6 to 7. Regarding

The high stretch blow molded container referred to in the present invention is
The film thickness of the stretch-formed container wall other than the mouth and neck is almost uniform, and the ratio of the film thickness difference between the thickest part and the thinnest part to the thickest part is 50% or less. ,
In addition, it is a high stretch blow-molded container in which the vessel wall excluding the mouth and neck is oriented and crystallized. In such a container of the present invention, 90% or more of the maximum stretched portion in the radial direction of the body portion of the container formed by the pressurized fluid without restraining the preform other than the mouth and neck portion is unconstrained and high stretch blow molding is performed. It can be manufactured by Further, the performance of the container is further improved by unconstrained high stretch blow molding of 90% or more of the stretching in the height direction.

As described above, in the conventional biaxial stretch blow molding, not only the pressurized fluid but also the stretch rod is used in the height direction to perform the stretch molding. That is, the stretch forming in the height direction is a stretch forming constrained by a stretch rod, and not a substantially unconstrained stretch blow forming by a pressurized fluid. The restraint in the height direction also affects the stretching in the circumferential direction, so that sufficient free stretching cannot be performed. In this conventional stretch-blow molding, the circumferential direction of the container is also constrained by a mold for molding. Since it is required for the container to have a good outer shape, there is a tendency to make efforts only to improve the outer shape, and the strength of the container tends to depend on the thickness of the vessel wall. Therefore, the circumferential stretching of the container was not sufficient.

On the other hand, in the high stretch blow molding of the present invention, the stretch of the preform is stretched and blow molded with a pressurized fluid in a radial direction, that is, substantially without restraint in the circumferential direction and the height direction to form a container. is there.

[0009]

The constrained stretch blow molding which has been conventionally performed is a molding which prevents the free stretching of the vessel wall as described above. Because the force is applied to a part of the vessel wall without stretching freely and the whole is stretched, the force applied to the vessel wall differs depending on the portion of the vessel wall,
A portion to which a large amount of force is applied becomes thin, and a portion to which a small amount of force is applied becomes thick, and uniform stretching cannot be performed.

When stretched with a pressurized fluid without restraint, the same force acts on the entire vessel wall, and the stretch is performed similarly. The thicker film, in other words, the more resin, is further stretched so that the film thickness becomes uniform. As described above, the stretching mechanism is completely different between constrained stretching and unconstrained stretching. Theoretically, due to the internal pressure of the container, the cylindrical body is 2 in the circumferential direction with respect to 1 in the height direction.
Receive the stress of. That is, the body of the container is 2
Double stress is applied in the circumferential direction. Further, as can be understood from the fact that the shoulders and the bottom have a substantially spherical shape, they are subjected to a small stress which is almost the same as in the height direction. Therefore, in order to increase the strength of the container, it is absolutely necessary to increase the pressure resistance in the circumferential direction of the body, and if the pressure resistance in the radial direction of the container body can be increased, the wall thickness of the container can be reduced. Therefore, the amount of resin can be reduced. In this case, what is important is that the film thickness is uniform, and if the film thickness is non-uniform, the pressure resistance is determined by the weakest portion, and the container cannot be made uniform and have high pressure resistance.

However, the conventional constrained biaxial stretch blow molding cannot satisfy this requirement. As described above, in conventional stretch-blow molding, a force is applied to a part of the vessel wall to stretch the entire vessel wall. The vessel wall is not uniform, there are partial differences, uniform stretching is not possible, and the film thickness is non-uniform, so that a uniform and large pressure resistant container cannot be obtained.

In the high stretch blow molding of the present invention, at least 90% or more of the maximum stretched portion in the radial direction needs to be blow molded with a pressurized fluid, particularly a high pressure fluid, in an unconstrained state. It is optimal to perform unconstrained biaxial stretching blow molding for 90% or more of the stretching in the height direction, excluding the neck and neck portion of the unstretched portion. That is, it is most preferable that 90% or more of the entire molding process is performed in the unconstrained state by the time of the finishing process of contacting the blow mold and forming the shape of the container. Molding temperature 90 ℃ ~ 130
Most preferably, stretch blow molding is performed using a fluid at a temperature of 3 to 40 kg / cm ² .

As described above, by substantially unconstrained high stretch blow molding, the stretch is sufficiently stretched which cannot be predicted by the conventional stretch blow, so that the thickness of the vessel wall excluding the neck portion of the non-stretched portion becomes substantially uniform. The ratio of the film thickness difference between the thickest part and the thinnest part to the thickest part is 50% or less, and the performance of the vessel wall is dramatically improved. If the difference in film thickness between the thick part and the thin part exceeds 50%, the container wall cannot be said to be sufficiently uniform and the performance will be poor. Further, since it is sufficiently stretched to almost a saturated state by unconstrained high stretch blow molding, the yield value in the circumferential direction of the body resin layer of the thermoplastic polyester is 1800 kg / cm.
² or more, and the yield value in the height direction is 800 kg / cm ²
The above highly stretched highly stretched container is formed. Therefore, it is preferable to design the shape of the preform in advance so that 90% or more of the maximum stretched portion in the radial direction is blow-molded in an unconstrained state when it comes into close contact with the blow mold in the finishing step.

It is desirable that high-stretch blow molding is performed without any constraint in the radial direction and the height direction of the body of the container, where the highest pressure is applied. On the other hand, if the shoulder needs to have a specific shape, it may be formed by touching a blow mold. As described above, the shoulder portion is different from the body portion in that the applied internal pressure is small, so that the container is not affected even if the degree of stretching is low and the yield value is small by performing the molding with some restraint. Such a container of a container wall of a resin layer having a uniform thickness and being sufficiently stretched and highly oriented and crystallized except for the mouth and neck is a novel container that is not known at all before this application, and the yield value of the conventional container is It can be understood that the container of the present invention is a container having a vessel wall of a special resin layer having an extremely high yield value, because it is about 500 Kg / cm ² at best.

The yield value as referred to in the present invention is the stress at the point where the permanent deformation starts to increase sharply with a slight increase in the stress as the stress gradually increases in the process of deforming the container wall by applying stress. The value is the value of, and using a Tensilon UTM-III-100 manufactured by Toyo Baldwin Co., Ltd. as a tester, a test piece was punched with a punching blade having a shape conforming to JIS K7113 or ASTM D638, and the height direction and circumference from the body of the container were measured. The test piece punched in the direction was tested at a speed of 10 mm / min to obtain the yield value. Therefore, a high yield value means that the stress that causes permanent deformation is large and that the mechanical strength is large. This indicates that the container is unlikely to be deformed due to expansion due to internal pressure during storage.

The first feature of the present invention is that the film thickness of the sufficiently stretched container wall except the mouth and neck is substantially uniform. The second feature of the present invention is that the ratio of the difference in film thickness between the thinnest portion and the thickest portion of the vessel wall other than the mouth and neck is 50.
% Or less. If the difference in film thickness exceeds 50%, the pressure resistance becomes uneven and the container becomes distorted. The third feature of the present invention is that the vessel walls other than the mouth and neck are all oriented and crystallized. Due to these characteristics, the container is formed of thin container walls oriented with a uniform film thickness, is light and has high strength, and it has excellent pressure resistance, which is very convenient for handling the contents filling stage and distribution stage. The effect is played. The fourth feature of the present invention is that the yield value of the wall is very high. Due to this feature, mechanical strength is large, and there is an effect that deformation is less likely to occur during handling or filling and storage of contents. The fifth feature of the present invention is that the ratio of the amount of resin (g) in the stretched portion to the internal volume (cc) of the container is 0.025 or less, and particularly in the range of 0.005 to 0.025. The container weight is 20 to 50% less than that of the container No. 1 and the strength is equal to or more than the conventional one. The sixth feature of the present invention is that the gas barrier property of the vessel wall is excellent, and in particular, the oxygen permeation is small.
Although this point will be described in detail in the section of Examples in comparison with Comparative Examples, the present inventors have found that the gas barrier property is improved as described above because oriented crystallization progresses as the molecular orientation increases and crystallization progresses. I think this is because the degree increases.
Due to this feature, there is no danger of the contents being altered by oxygen, and the gas of the contents does not escape.

Most preferably, the container is completely unconstrained. When unconstrained blow molding is performed, the container is molded in a shape close to the preform shape, but since each container has the required outer shape, it is possible to arrange the outer shape by constraining it with a mold at the final finishing stage. In the present invention, it is necessary that the stretch forming in the unconstrained state of the vessel wall is at least 90% or more of the maximum stretched portion in the radial direction of the body of the molded container. It is highly preferable that 90% or more of the stretching in the height direction is unconstrained, that is, 90% or more of the entire stretch forming step is performed unconstrained. It is stretched without restraint to this extent and then finished.

When high stretch blow molding is performed with unconstrained pressurized fluid, the preform is first stretched in the radial direction regardless of temperature, pressure and wall thickness. The stretching ratio in the radial direction is 4.5 to 5.
It is 5. In the conventional biaxial stretch molding, the stretching ratio in the radial direction was at most 4.2, as compared with the substantially unconstrained high-stretch blow molding of the present invention using only the pressurized fluid, because the stretching effect was extremely good. It is understood that there is. When the stretching ratio is within this range, whitening of the container and uneven thickness can be prevented. When the radial stretching reaches the above range,
Stretching in the height direction is promoted, but stretching in this direction is also unconstrained and is stretch blow molding with a pressurized fluid. The draw ratio in the radial direction is 1.5 to 1.8 of the draw ratio in the height direction.
When the stretching ratio in the height direction is within this range, whitening of the container and uneven thickness can be prevented. When the stretching in the height direction reaches approximately the above range, the container hits a predesigned mold, and the finishing process is performed to adjust the outer shape.

When it is desired to keep the center position of the bottom of the obtained container constant, for example, the center of the bottom of the container is blown with the fixture installed inside the container that is preformed in the final finishing step. Although the final blow molding can be carried out by fixing it in contact with, it is not necessary to perform such a centering step if it is not necessary to keep the precise center position of the bottom constant.

As described above, it is apparent that the stretch blow molding is substantially unconstrained and the blow ratio is very different from that of the conventional biaxial stretch molding using a stretch rod. For easy description, the area stretching ratio, which is the product of the stretching ratio in the radial direction and the stretching ratio in the height direction, will be described. In the conventional biaxially stretch-molded container, the surface stretching ratio is at most about 10, but the high stretching ratio of the present invention is high. The molded container has a high drawability of 12 to 20 and 20 to 100%. For this reason, the oriented crystallinity is high, the yield value is high, and the strength of the container is very large. According to the conventional method, a container having a container weight of 50 g and an inner volume of 1500 ml and the container weight 36 of the present invention are used.
Comparing containers of the same shape using g of polyester, the container of the present invention exhibits the same or higher mechanical strength with a resin content of only 72%.

The high-stretching container of the present invention has a highly oriented crystallinity of the vessel wall, a uniform film thickness, a yield value in the circumferential direction of the body resin layer of the vessel wall of 1800 kg / cm ² or more, and a height direction. It is a novel high-strength, highly-stretched container having a yield value of 800 kg / cm ² or more, and has a particularly outstanding effect that cannot be predicted with conventional containers.

The yield value in the circumferential direction of the body of the high stretch molded container of the present invention is 1800 kg / cm ² or more, but 1900 k.
g / cm ² or more is preferable, and 2000 kg / cm ² or more is most preferable. When the preform is heated from both the outside and the inside in the case of substantially stretch-free high stretch molding, the heating becomes uniform, which is extremely suitable and effective for high stretch blow molding. This increases the draw ratio to increase the strength of the container, but because of this the wall thickness of the preform becomes large, and the internal temperature becomes low only by heating from the outside by ordinary heating, It is because there is a tendency that a good container cannot be obtained due to uneven stretching or whitening.

Since the container of the present invention has extremely excellent resistance to internal pressure, it is suitable as a container for gas-containing beverages.

The preform used in the present invention is preferably made of a thermoplastic polyester such as polyethylene terephthalate, but in addition to this, a polyester as a main material, for example, saponified ethylene-vinyl acetate copolymer, polyvinylidene chloride Resins, copolymers containing acrylonitrile or methacrylonitrile as a main component, barrier nylons such as aromatic nylon, nylon 6, nylon 66, nylon 11 and barrier copolymerized polyesters such as polyethylene terephthalate / ethylene isophthalate A preform prepared by blending or laminating a gas barrier substance, or a polyester as a main material, with a small amount of a resin such as ethylene glycol, isophthalic acid, benzoic acid, naphthalene 1.4 dicarboxylic acid, or naphthalene 2.6 dicarboxylic acid. Preform formed by the agglomeration or blend also included.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows the relationship between the draw ratio in the radial direction and the draw ratio in the radial direction with respect to the height direction in the blow molding process. Explaining with the reference numerals attached to the curves, in this figure, the wall thickness becomes non-uniform in the regions 4 to 5 where the radial stretching ratio is low, and in the regions shown by the dotted lines 7 or more, over stretching causes whitening. Occurs. According to the present invention, unconstrained stretching is performed, so that the container is formed in the region of 6 to 7, the wall thickness is uniform, and whitening does not occur. Next, the effects of the present invention will be described with reference to specific examples.

Example 1 Thickness of 4.50 m molded from polyethylene terephthalate
m, thick resin preform of 36.0 g, uniformly heated to 120 ° C. from both inside and outside, and virtually unconstrained under the conditions shown in Table 1 by high stretch blow molding to have an internal capacity of 1500 ml. A filled container was manufactured.

Example 2 Thickness of 4.55 m molded from polyethylene terephthalate
m, a thick preform having a resin amount of 36.2 g was uniformly heated from both the inner side and the outer side to 110 ° C., and a container having an inner volume of 1500 ml was manufactured by high stretch blow molding under the conditions shown in Table 1. .

Comparative Example 1 Thickness of 4.20 m molded from polyethylene terephthalate
A container having an inner volume of 1500 ml was manufactured by biaxial stretching using a stretching rod under the conditions shown in Table 1 using a thin preform having m and a resin amount of 50.0 g.

Comparative Example 2 Thickness 4.20 m molded from polyethylene terephthalate
Using a thin preform having m and a resin amount of 50.0 g, a container having an internal capacity of 1500 ml was manufactured under the conditions shown in Table 1.

Comparative Example 3 Thickness of 4.20 m molded from polyethylene terephthalate
Using a thin-walled preform having m and a resin amount of 36.0 g, a container having an inner volume of 1500 ml was manufactured under the conditions shown in Table 1. However, the body part was whitened and did not function as a product. This comparative example is not a conventional example, but an example in which only the amount of resin is the same as that of the example for the purpose of comparison.

Table 2 shows the performance of the containers of Examples 1 and 2 and Comparative Examples 1, 2 and Comparative Example 3.

[0033]

[Table 1]

* 1: Polyester resin manufactured by Mitsui Petrochemical Co., Ltd. * 2: Polyester resin manufactured by Eastman Kodak * 3: Calculated by subtracting 7 g of the weight of the mouth and neck. * 4: Average of the values measured at 4 locations in the circumferential direction on the body of 10 containers each.

[0035]

[Table 2]

* 5: Toyo Baldwin Tensilon UTM-III-100 was used as a tester, and a test piece was punched out in a height and circumferential direction from the body of the container by a punching blade having a shape conforming to JIS K7113 or ASTM D638 standards. The test piece punched out was tested at a speed of 10 mm / min to determine the yield value.

[0037]

[Equation 1]

Σ ... Yield value F ... Load A ... Original average cross-sectional area of parallel part of test piece * 6: n-heptane-carbon tetrachloride-based density gradient tube (Ikeda Rika Co., Ltd.) The density of the sample was obtained under the conditions, and the crystallinity was calculated according to the following formula.

[0039]

[Equation 2]

D: Density of sample (g / cm ³ ) da: 1.335 (g / cm ³ ) dc: 1.455 (g / cm ³ )

* 7: Voids are generated and the product is not satisfactory. * 8: The container wall is cut out and the Modern Cont
roll company (Oxytran-100) at 25 ° C., 1
The oxygen permeability QO ₂ (c
c / m ² · day · atm) was measured. * 9: Oxygen permeability coefficient PO of the thickness of the container body wall per unit
₂ (cc · cm / cm ² · sec · cmHg) was calculated from the oxygen permeability. * 10: Use an empty container 24 hours or more after molding,
Carbonated water is filled up to the line of sight, sealed with a cap, and left at room temperature for 24 hours. Therefore, after measuring the height of the container and the diameter of the body, the same portion after storing at 38 ° C. for 24 hours was measured and the pressure resistance was evaluated from the rate of change.

[Evaluation] As described above, 90% or more of the maximum radial stretched portion of the body portion of the vessel membrane that constitutes the vessel wall of the present invention is unconstrained and 90% of the heightwise stretched portion. The high stretch blow-molded container, which has been stretched without restraint as described above, has very good strength, so that the amount of resin used can be reduced by 20 to 50%. If PO ₂ is small, the amount of oxygen permeation can be almost the same as or smaller than that of the conventional container even if the wall thickness is made thin. From this point as well, the amount of resin can be reduced in the container of the present invention. To be understood. The preform is stretched at a final radial stretch ratio of 4.5 to 5.
5. The draw ratio in the radial direction is 1.5 to the draw ratio in the height direction.
By setting 1.8, 90% or more of the maximum stretched portion in the radial direction of the body part of the vessel wall was stretched without restraint, and 90% or more of the stretch was stretched without restraint. It is understood that a high stretch blow-molded container having a difference in film thickness of 50% or less is produced, and if the stretch ratio deviates from the above range, uneven thickness and whitening occur.

[0043]

As described above, the present invention provides a container having a uniform film thickness, a high draw ratio, a high strength, and an excellent gas barrier property without whitening, by substantially unconstrained stretch blow molding. It is a thing. Further, the container of the present invention is very excellent in pressure resistance of the body part to which the most internal pressure is applied, and particularly excellent in pressure resistance at high temperature, that is, heat pressure stability, and therefore is very suitable for a gas-containing beverage.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a radial stretch ratio in a blow molding process and a radial stretch ratio with respect to a height direction.

[Equation 3]

Claims (8)

[Claims] 1. The film thickness of a stretch-formed container wall other than the mouth and neck is substantially uniform, and the ratio of the difference in film thickness between the thickest part and the thinnest part to the thickest part is Fifty
%, And a highly stretch blow-molded container in which the vessel wall excluding the neck and neck is oriented and crystallized. 2. The high stretch blow-molded container according to claim 1, wherein the shoulder portion and the bottom portion have a hemispherical shell shape, and the body portion has a cylindrical shape. 3. The yield value in the circumferential direction of the body resin layer constituting the container wall is 1800 kg / cm ² or more, and the yield value in the height direction is 800 kg / cm ² or more.
A high stretch blow-molded container according to any one of items 1 to 2. 4. The high-stretch blow-molded container according to claim 1, wherein the ratio of the amount of resin to the internal volume in the stretched portion of the container is 0.025 or less and there is no whitening. 5. A wall thickness of 0.2 mm to 0.
5. A thin wall having a thickness of 3 mm and free from uneven thickness and whitening.
A high stretch blow-molded container described in any one of 1. 6. A container wall formed by blow molding using a pressurized fluid without constraining parts other than the mouth and neck of the container to make the film thickness of the container almost uniform, and to make the thinnest part of the film thicker than the thickest part. A method for producing an unconstrained high-stretch blow-molded container, wherein the ratio of the difference in film thickness is 50% or less, and the container wall excluding the mouth and neck is oriented and crystallized. 7. The stretch-blow molding is performed without restraining 90% or more of at least one of the maximum stretched portion in the body radial direction and the stretched portion in the height direction of the molded container. 6. The method for producing a high stretch blow-molded container described in 6. 8. The preform is finally stretched to a radial stretch ratio of 4.5 to 5.5 and a radial stretch ratio of 1.5 to 1.8 as a height stretch ratio. The method for producing an unconstrained high stretch blow-molded container according to any one of claims 6 to 7, characterized in that: