JP5915108B2 - Blow molding container - Google Patents

Description

  The present invention relates to a blow-molded container, and more particularly, to a blow-molded container that is used after the container wall is bent after molding.

Plastic containers are widely used in various applications because they are easy to mold and can be manufactured at low cost. In particular, a container whose inner wall is formed of an olefin resin such as polyethylene is highly flexible. For example, it is known to be used as a bottle that can be used by compactly folding a used container. (For example, refer to Patent Documents 1 and 2).
In addition, a type of polyethylene container that is folded and used after molding has also been proposed (Patent Document 3).

JP 2003-2314 A JP 2003-54529 A JP 2005-14999 A

  By the way, since the well-known folding containers as proposed in Patent Documents 1 and 2 are folded at the time of disposal, there is no problem with the characteristics of the folds formed by folding. In a container that is folded and stored in such a form, the property of the folded portion becomes a problem. For example, when the wall surface of the container is folded or inverted inward to reduce the internal volume of the container, microcracks are likely to enter the crease, so that the container may be damaged during a drop impact or the ESC (environment There is also a problem that damage is likely to occur due to stress cracks.

  In order to increase the ESC resistance or to improve the drop impact strength, it is only necessary to increase the thickness of the container wall. However, the increase in the thickness naturally increases the cost significantly. It is also possible to use linear low density polyethylene (L-LDPE) with excellent ESC resistance for the inner layer of the container (blending to the inner layer or forming an L-LDPE layer). There is a problem that decreases. Furthermore, the use of metallocene-based high-density polyethylene with excellent ESC resistance and drop impact strength is also conceivable. However, such high-density polyethylene has a narrow molecular weight distribution, so that melt fracture tends to occur and drawdown increases. There is a problem that it is easy and the moldability is extremely poor.

Due to the problems as described above, it is difficult to maintain the shape of a container that is used in a form in which the container wall is bent after molding, as described in Patent Document 3, for example. The body of the container is formed of a flexible polyethylene, and a plurality of support bands (outer cylinders) for maintaining the form are wound around the outer surface of the body part and fixed. When the band is peeled off, the band is wound. A means has been proposed in which only the trunk portion of the portion that has been placed is folded inward to reduce the volume. That is, according to such means, the container body is formed of polyethylene so flexible that it is difficult to maintain the shape of the container alone, so that there is no problem of ESC, and the shape of the container is the outer surface of the trunk. Since it is held by a support band wound around, there is no problem of drop strength.
However, in such a type of container, the support band is peeled off every time the volume of the container is folded to reduce the volume, causing problems such as generation and scattering of dust. There is also a problem that the construction of the container becomes complicated and the manufacturing cost increases.

  Accordingly, an object of the present invention is to provide a folded portion of a blow molded container that is used after the container wall is folded after molding without problems such as an increase in cost, a decrease in compressive strength, a molding processability and a decrease in appearance. It is an object of the present invention to provide a blow molded container that is less prone to micro cracks and has excellent drop impact resistance.

According to the present invention, a fold line composed of a ridge line part and a valley line part is formed in the body part, and a blow molded container to be used in a state where the wall part is folded after molding,
The wall portion has a layer structure including at least two layers of an outer layer and an inner layer,
Said inner layer, density is formed at a 0.940 g / cm ³ or more metallocene high density polyethylene, the outer layer, the density is formed by 0.940 g / cm ³ or more nonmetallocene high density polyethylene,
A blow molded container is provided in which the thickness ratio of the inner layer to the outer layer (inner layer / outer layer) is in the range of 5/95 to 60/40 .

In the present invention, the folding is performed by reversing, folding, or folding the body at the folding line .

  In the blow molded container of the present invention, since the metallocene high-density polyethylene having excellent ESC resistance and impact strength is used for the inner layer, it is difficult for microcracks to enter the wall part (folded part) of the container folded after molding. Accordingly, the drop impact strength is also increased, and damage is effectively suppressed by the drop impact.

  In addition, the outer layer uses non-metallocene high-density polyethylene (that is, high-density polyethylene using a Ziegler catalyst or Philip catalyst) with a wide molecular weight distribution and good moldability, so that melt fracture is unlikely to occur and Inconvenience due to deterioration of moldability such as deterioration is effectively avoided.

  Furthermore, since high density polyethylene excellent in mechanical strength is used for both the inner layer and the outer layer, the compressive strength does not decrease.

  In addition, when polyethylene other than the specific high-density polyethylene described above, for example, linear low-density polyethylene (L-LDPE) is used as the polyethylene forming the inner layer or the outer layer, the compressive strength is reduced. The self-supporting property of the container is impaired due to a decrease in buckling strength.

The figure which shows the side cross section immediately after shaping | molding of the blow molding container of this invention. The figure which shows the state by which the container wall was bent after shaping | molding of the container of FIG. The figure which shows the layer structure of the container wall of FIG.

  In FIG. 1 showing a side cross-section immediately after molding of the blow molded container of the present invention, the container denoted as 1 as a whole is connected to the neck portion 3 in which a screw for engaging with a cap, a support ring and the like are formed, and the neck portion 3. It is formed from the trunk | drum 5 and the bottom part 7 which has closed the lower end of the trunk | drum 5. FIG.

  In such a container 1, a plurality of portions that are recessed inward in the entire circumferential direction are continuously arranged in the height direction on the body portion 5, whereby the ridge line portions 5 a and the valley line portions 5 b are alternately arranged. Is formed.

The container 1 is formed into the shape shown in FIG. 1, and then, as shown in FIG. 2, the inwardly recessed portion of the trunk portion 5 is folded (or folded) by compression from above and below. A) transformed into a form. That is, the trunk portion 5 of the container 1 in FIG. 1 is folded or folded into the shape of FIG. 2 with the ridge line portion 5a and the valley line portion 5b serving as the fold line 5c. That is, in FIG. 1, the portion indicated by A is a portion that is bent after molding.
In the container 1 having such a configuration, the inner volume is reduced by compressing the container 1 in the axial direction after the molding, and the portion A of the body portion 5 is bent to form the container 1. Can be made compact as shown in FIG.

Further, in the example of FIG. 1, a part (part A) of the body part 5 is indented inward, but this part A is a flat surface, and when desired after molding, the container 1 By compressing or pressing the portion A of the body portion 5 inward, a part of the body portion 5 may be pushed into a concave or folded shape.
In such a case, there is an advantage that printing or the like can be easily performed also on the portion A that is pushed into a concave surface or folded.

  Further, in the example of FIG. 1, a portion A that is bent after molding is recessed inwardly in the body portion 5, and a plurality of such recessed portions are continuously arranged in the height direction. However, on the contrary, in the portion A that is bent after molding, a plurality of portions in which the entire circumferential direction bulges outward can be continuously arranged in the height direction. Even in such a form, the internal volume is reduced by compressing the container 1 in the axial direction or pressing the body part 5 inward from the outside and inverting it, and the form of the container 1 is compact. It can be.

  Furthermore, in the example of FIG. 1, a portion A that is bent after molding is formed in the body portion 5, but such a portion A can also be formed in the bottom portion 7. For example, the center portion (or the whole) of the bottom portion 7 can be molded into a shape that bulges downward, and the bulge portion of the bottom portion 7 can be inverted upward after molding. Such inversion of the bottom 7 also has the advantage that the self-supporting property of the container 1 is improved.

  By the way, when bending is performed after molding as described above, there is no problem if it is immediately discarded, but when it is used in such a form, that is, the contents are accommodated. If the container 1 is held in a state of being broken, microcracks are easily formed in the fold line 5c (the ridge line portion 5a and the valley line portion 5b in the example of FIG. 1). There is a problem that it is easy to break, and that it is liable to be broken by an environmental stress crack (ESC).

  The present invention has succeeded in solving such a problem. Specifically, as shown in FIG. 3, the layer structure of the wall portion of the container 1 is at least two of the inner layer 10 and the outer layer 15. The resin described below is used as a resin having a multilayer structure having layers and forming the inner layer 10 and the outer layer 15.

First, as the resin forming the inner layer 10, a metallocene high-density polyethylene having a density of 0.940 g / cm ³ or more, preferably 0.950 to 0.965 g / cm ³ is used.
In general, a metallocene high-density polyethylene having a high density is excellent in environmental stress crack resistance (ESC resistance) and has high impact strength. For this reason, for example, as shown in FIG. 2, the container 1 in which a fold line 5c (corresponding to the ridge line part 5a and the valley line part 5b) is formed by being bent is filled with the contents, and in this state, Even when held, it is possible to effectively avoid the occurrence of microcracks at the folds.

The metallocene-based high-density polyethylene is obtained using metallocene as a polymerization catalyst, and has excellent ESC resistance and high impact strength, but has a narrow molecular weight distribution and poor moldability. There is a problem that melt fracture tends to occur during molding, and the drawdown is large. However, in the present invention, such a metallocene high-density polyethylene is used in the inner layer, so that the appearance failure of the container due to melt fracture or drawdown is effectively avoided.
Furthermore, since the density is high, the material strength is high, and the compressive strength is not lowered by the use of such polyethylene.

  The metallocene high-density polyethylene as described above is preferably one having an MFR (190 ° C.) in the range of 0.1 to 10.0 g / 10 min from the viewpoint of moldability.

In the present invention, as the resin forming the outer layer 15, nonmetallocene high-density polyethylene having a density of 0.940 g / cm ³ or more, preferably 0.950 to 0.965 g / cm ³ is used. Non-metallocene high-density polyethylene is a high-density polyethylene obtained by using a Ziegler catalyst or a Philip catalyst as a polymerization catalyst, and has a wide molecular weight distribution and good moldability, that is, melt fracture, drawdown, etc. The problem does not occur at all.
Further, like the inner layer 10, since such polyethylene has a high density and high material strength, the use of such polyethylene does not lower the compressive strength.

  Further, such non-metallocene high-density polyethylene is inferior to metallocene high-density polyethylene in terms of ESC resistance, but since such polyethylene is used for the outer layer 15, it does not come into contact with the contents. That is, the non-metallocene high-density polyethylene described above is used for the outer layer 15, and the inner layer 10 in contact with the contents is made of metallocene high-density polyethylene that has excellent ESC resistance and is difficult to enter microcracks. Damage to the container 1 due to the occurrence of cracks can be effectively suppressed.

  Further, the MFR (190 ° C.) of such a nonmetallocene high-density polyethylene is the same as that of the metallocene high-density polyethylene forming the inner layer 10 from the viewpoint of moldability, specifically 0.1 to 10. It should be in the range of 0 g / 10 min.

In the present invention, the above-described inner and outer layers 10 and 15 sufficiently exhibit the characteristics of the specific high-density polyethylene forming these layers, and the microcracks at the folds are not made thicker than necessary. The thickness ratio (inner layer / outer layer) is set in the range of 5/95 to 60/40 from the viewpoint of effectively preventing the drop impact property due to the occurrence of the damage and the damage of the container 1 . Further, it is preferable that the basis weight of the inner layer is in the range of 30 to 50% by weight of the total resin basis weight. For example, when the thickness of the inner layer 10 is excessively thick as compared with the outer layer 15, the occurrence of melt fracture and drawdown due to a decrease in molding processability is increased, and the appearance of the container 1 is easily damaged, Furthermore, when the thickness of the inner layer 10 is excessively thin compared to the outer layer 15, the characteristics of the metallocene high density polyethylene that suppresses the occurrence of microcracks, improves the resistance to ESC, and further improves the impact strength. In order to fully demonstrate, the thickness of the inner layer 10 must be increased more than necessary, and as a result, the entire thickness of the container wall becomes thick, which is unsatisfactory in terms of cost increase due to an increase in the basis weight. End up.

In the present invention, the above-described inner and outer layers 10 and 15, particularly the outer layer 15, specify the virgin for the regrind (scrap resin) generated at the time of molding the container within a range that does not impair the characteristics of the specific high-density polyethylene described above. It can also be used by mixing with high density polyethylene. In this case, from the viewpoint of reusing resources while maintaining moldability, the amount of regrind is 70 parts by weight or less per 100 parts by weight of virgin high-density polyethylene, or 60% by weight per container. The following weight per unit area is recommended.
In addition, various compounding agents such as pigments, ultraviolet absorbers, lubricants and the like can be blended in appropriate amounts in amounts that do not impair the properties required for the inner and outer layers 10 and 15.

In the container 1 of the present invention, in addition to the inner and outer layers 10 and 15 described above, a gas barrier resin layer may be provided as an intermediate layer between the inner and outer layers 10 and 15 in order to improve gas barrier properties.
Typical examples of such a gas barrier resin include an ethylene vinyl alcohol copolymer (saponified ethylene vinyl acetate copolymer) and an aromatic polyamide, and an ethylene vinyl alcohol copolymer is particularly preferably used. By forming such a gas barrier resin layer, the oxidative deterioration of the contents due to oxygen permeation can be effectively suppressed, and excellent contents preservation can be ensured.

  The ethylene vinyl alcohol copolymer as described above is generally an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, particularly 25 to 50 mol%, and a saponification degree of 96 mol% or more, In particular, a saponified copolymer obtained by saponification to be 99 mol% or more is preferred.

  When the gas barrier resin layer as described above is provided, the thickness is preferably in the range of about 10 to 100 μm. That is, if this thickness is too thin, sufficient gas barrier properties cannot be exhibited, and if it is provided thicker than necessary, the container becomes thicker than necessary, resulting in an increase in cost.

  Further, when the gas barrier resin layer as described above is used as an intermediate layer, the gas barrier resin layer is interposed through the adhesive resin layer in order to improve the adhesion with the inner and outer layers 10 and 15 and prevent delamination. Is preferably provided. Thereby, the gas barrier resin layer can be firmly fixed to the inner and outer layers 10 and 15. Adhesive resins used for forming such an adhesive resin layer are known per se. For example, a carbonyl group (> C═O) is 1 to 100 meq / 100 g resin in the main chain or side chain, particularly 10 to 100 meq / 100 g. Resin contained in the amount of resin, specifically, olefin resin graft-modified with carboxylic acid such as maleic acid, itaconic acid, fumaric acid or its anhydride, amide, ester, etc .; ethylene-acrylic acid copolymer; An ion-crosslinked olefin copolymer; an ethylene-vinyl acetate copolymer; and the like are used as the adhesive resin. The thickness of such an adhesive resin layer may be such that an appropriate adhesive force can be obtained, and is generally 0.5 to 20 μm, preferably about 1 to 8 μm.

  The container 1 of the present invention having the inner and outer layers 10 and 15 described above does not use a special member for forming a folding line or maintaining the shape of the container, but has a very simple structure. It can be molded by a blow molding method known per se, for example, by co-extrusion using a resin composition for forming each layer, the tubular parison having the layer structure described above is melt-extruded, and its end is After closing, blow molding can be performed to obtain a bottle-shaped container having the shape shown in FIG. 1 (so-called direct blow molding). Further, a test tube-shaped preform having the above-described layer structure is formed by coextrusion or co-injection, and the preform is subjected to per se known biaxial stretch blow molding, for example, in the shape shown in FIG. A bottle-shaped container can also be obtained.

  The container 1 of the present invention obtained in this way is molded, filled with the container contents, and then deformed by bending the container wall as shown in FIG. Is done. Of course, the container wall can be bent and deformed before filling the container contents, and the contents can be filled and used in this state. In addition, the container wall can be bent and deformed in accordance with the change in the container internal pressure after filling, and can be used in this state. In other words, the container was bent and deformed with the contents after being blow-molded. Any usage that contacts the container wall is acceptable.

Such a container of the present invention effectively prevents the occurrence of microcracks at the fold line 5c, is excellent in ESC resistance, has improved strength against dropping impact, and is effectively damaged by microcracks. It is prevented.
Further, it is not necessary to increase the thickness of the container wall more than necessary to prevent the occurrence of microcracks, etc., and an increase in cost due to an increase in the basis weight is avoided, and further, a reduction in compressive strength is not caused.
Further, no special member is required for maintaining the shape or bending, and therefore the structure of the container is not complicated, and the manufacturing cost is not increased.

  Such a container of the present invention is widely used as a container for storing a liquid such as a liquid detergent, shampoo or beverage.

The invention is illustrated in the following examples.
In the examples and comparative examples, the characteristics of the containers were evaluated by the following methods.

1. Compressive strength;
After filling with a specified amount (200 ml) of tap water and capping, push the top of the cap at a speed of 20 mm / min with a compression tester (trade name: Orientec UNIVERSAL TESTING INSTRUMENT RTG-1310). Measure the strength at.
At 4 mm strain, 250 N or more was judged as ◯, and the others were judged as ×.

2. Drop strength;
After filling with a specified amount (200 ml) of tap water and capping, it is stored at 5 ° C. and 23 ° C. for 24 hours. After that, it dropped 1.2 times at a height of 1.2 m, 10 times in a vertical posture with the bottom down, and 10 times in a horizontal posture in which it was laid down. The thing was determined as x.

3. ESC resistance;
The container is folded to the state shown in FIG. 2 and a weakly acidic detergent assuming the content liquid is filled at 10% (20 ml) of the specified amount at 23 ° C., and the nozzle surface is heat-sealed and then stored in an environment at 65 ° C. for 24 hours. .
Those that were not damaged during storage over time were passed, and those that were damaged even in part of the container were rated as x.
After the storage, the inner surface of the container was observed for those that passed, and the case where microcracks were seen was judged as Δ, and the case where there was no cracks was judged as ○.

4). appearance;
The case where there was no problem in the appearance of the container was judged as 若干, there was some shark skin and cloudiness, but the case within the limit sample was judged as ○, and the case where rough skin was generated on the outer surface was judged as ×.
A sample that exceeds the limit sample but does not affect the outer surface can be used if the outer layer is colored.

5. Comprehensive evaluation;
Out of the above four evaluation items, it was judged as unacceptable (x) if there was at least one x, and passed if not.
Further, if there was at least one evaluation item of Δ in the pass, it was determined as Δ, and in other cases, the appearance was ◎, and the others were judged as ◯.

<Examples 1-6, Comparative Examples 1-4>
The following polyethylene was prepared as a container forming material.
Metallocene high density polyethylene (metallocene HDPE);
Evolue SP6505 made by Prime Polymer
Density: 0.957 g / cm ³
MFR (190 ° C.): 0.45 g / 10 min
General-purpose non-metallocene (Ziegler catalyst) high-density polyethylene (general-purpose HDPE):
Hi-Zex 6008B made by Prime Polymer
Density: 0.956 g / cm ³
MFR (190 ° C.): 0.36 g / 10 min
Metallocene linear low density polyethylene (metallocene LLDPE, for comparative example);
Exelen GMH5001 manufactured by Sumitomo Chemical Co., Ltd.
Density: 0.920 g / cm ³
MFR (190 ° C.): 0.50 g / 10 min

Using the above-mentioned various polyethylenes, a container having a layer structure shown in Table 1 and having the shape shown in FIG. 1 (container weight 18 g, internal volume 200 ml, wall thickness 0.70 mm) is obtained by a direct blow molding method. Molded.
In Comparative Example 4, a container having a single-layer structure was formed using a 1: 1 weight ratio blend of general-purpose HDPE and metallocene LLDPE.
Table 1 shows the results of evaluating various characteristics of the obtained container.

1: Container (bottle)
3: Neck 5: Body 7: Bottom 10: Inner layer 15: Outer layer

Claims (2)

A fold line formed of a ridge line part and a valley line part is formed in the body part, and is a blow molded container used for use in a state where the wall part is folded after molding,
The wall portion has a layer structure including at least two layers of an outer layer and an inner layer,
Said inner layer, density is formed at a 0.940 g / cm ³ or more metallocene high density polyethylene, the outer layer, the density is formed by 0.940 g / cm ³ or more nonmetallocene high density polyethylene,
A blow molded container, wherein a thickness ratio of the inner layer to the outer layer (inner layer / outer layer) is in a range of 5/95 to 60/40 .   A blow-molded container in which the folding is performed by reversing, folding, or folding a body portion at the folding line.

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