Synthetic resin container and inspection method

Abstract

To inspect a sealed state of a seal part further easily in a synthetic resin container which is sealed by heat-sealing after filling a content therein.SOLUTION: In a range which includes at least one side of seal parts which overlap with each other when being heated-seal, a foamed region is formed which includes air bubbles inside in an unheated-sealed state. By detecting an increase degree of light transmissivity of a heated-seal part 8 formed after heated-sealing the seal parts, compared with the light transmissivity of the foamed region which remains unheated-sealing, quality of a sealed state of the seal parts is determined.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a synthetic resin container that is sealed by heat sealing after being filled with contents, and a method for inspecting the sealed state of the sealing portion thereof.

Background Art

[0002] Conventionally, a synthetic resin container that is sealed by heat sealing after being filled with contents has been known (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In products offered to the market using such containers, usually, after inspecting the sealed state of the sealing portion, they are shipped. Therefore, it is required to be able to more simply inspect the sealed state of the sealing portion.

[0005] Therefore, the inventors of the present invention have intensively studied to enable easier inspection of the sealed state of the sealing portion in a synthetic resin container that is sealed by heat sealing after being filled with contents, and as a result, have completed the present invention.

Means for Solving the Problems

[0006] The synthetic resin container according to the present invention is a synthetic resin container that is sealed by heat sealing after being filled with contents, and has a foamed region containing air bubbles inside in an unheat-sealed state in a range including a sealing portion sealed by heat sealing. The foamed region The said sealing portion overlapping their inner selvesIn the heat-sealed portion formed after heat sealing, the inner surfaces of the sealing portions that overlap each other during heat sealing are fused together, and the light transmittance of the heat-sealed portion remains the same as in the unheat-sealed state. Adjacent to the heat seal portion The configuration is such that the light transmittance is 10% or more higher compared to the light transmittance of the remaining foamed region.

[0007] Furthermore, the inspection method according to the present invention is a method for inspecting the sealing state of a synthetic resin container that is sealed by heat sealing after being filled with contents, wherein the sealing parts that overlap each other when heat sealing are inspected. of Within the included area, a foamed region containing air bubbles is formed inside in the unheated state. The foamed region The sealing portion overlapping their inner selves The degree of increase in light transmittance of the heat-sealed area formed after heat sealing. Compared with the light transmittance of the foamed region remaining adjacent to the heat-sealed portion in an unheat-sealed state. This method determines the quality of the seal in the sealing area by detecting certain factors. [Effects of the Invention]

[0008] According to the present invention, in a synthetic resin container that is sealed by heat sealing after being filled with contents, the sealing condition of the sealed portion can be inspected more easily. [Brief explanation of the drawing]

[0009] [Figure 1] This is an explanatory diagram showing an example of a synthetic resin container according to an embodiment of the present invention. [Figure 2] This is a photograph showing the state of the heat-sealed portion after the container shown in Figure 1 has been actually manufactured and the sealing portion has been heat-sealed. [Figure 3] This photograph shows a comparison of the appearance of the heat-sealed portion in Example 1 and the appearance of the heat-sealed portion in Comparative Example 2. [Figure 4] This graph shows the relationship between the bubble percentage and light transmittance of the foamed sample prepared in Example 1. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described below with reference to the drawings.

[0011] Figure 1 is an explanatory diagram showing an example of a synthetic resin container according to this embodiment. The container 1 shown in Figure 1 is integrally molded with a cylindrical neck portion 3 with an opening 2 at its upper end and a body portion 4 that widens in diameter relative to the neck portion 3 and has a bottom portion 5 formed at its lower end. After filling the contents through the opening 2, the opening 2 can be sealed by heat sealing to seal the contents. The container can be opened by pinching up the tab 7 that is formed to protrude from the side of the neck portion 3 and tearing the opening portion 6 which is grooved along the circumference. However, the specific form of the container 1, such as its shape, is not limited to this. It is sufficient that the container can be sealed by heat sealing after filling the contents, and it can be appropriately applied to various forms of synthetic resin containers, such as pouch-type containers in which the film material is fused and sealed by heat sealing after filling the contents through the opening of the bag-shaped film material, or cup-type containers in which a film-like lid material is fused to the periphery of the opening by heat sealing to seal it.

[0012] Furthermore, the container 1 shown in Figure 1 is an example of a so-called foamed direct blow bottle, in which a foamed resin material impregnated with a foaming agent and a non-foamed resin material without a foaming agent are combined in a die head, and a parison extruded from the die head to form a three-layer structure with a foamed layer in the middle and skin layers on the inner and outer layers is sandwiched between a pair of split molds, and blow air is blown into the parison to blow-molde it.

[0013] Any thermoplastic resin that is translucent in a non-foamed state and heat-sealable can be used as the resin material for molding container 1. More specifically, polyolefin resins such as polypropylene, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-polypropylene copolymer, or mixtures thereof are preferably used.

[0014] In addition, as the foaming agent to be impregnated into the resin material, an inert gas such as carbon dioxide or nitrogen may be used as a physical foaming agent, or a carbonic acid compound, an azo compound, etc. that can generate these inert gases may be used as a chemical foaming agent.

[0015] In the present embodiment, the container 1 only needs to have a foamed region containing bubbles inside in a range including the sealing portion sealed by heat sealing (in the illustrated example, a range covering the entire circumference in the circumferential direction) in the non-heat-sealed state. Such a foamed region exhibits an opaque appearance due to the bubbles contained inside and has light-shielding properties and heat insulation properties. Therefore, in the container 1 shown in FIG. 1, by forming a foamed region over the entire container, it can be suitably used for contents whose quality may deteriorate due to light without providing a light-shielding layer or performing printing. Furthermore, when the contents are ice confections or the like, the cold feeling transmitted to the hand can also be reduced when gripping and eating the container 1.

[0016] In addition, when blow molding the container 1 as described above, the timing of merging the foaming resin material and the non-foaming resin material not containing a foaming agent in the die head may be adjusted so that a foamed region is selectively formed in the range including the sealing portion.

[0017] Further, after filling the contents into the container 1 from the opening 2 in the container 1 shown in FIG. 1, the portion surrounded by the broken line in the figure is used as a sealing portion, and by heat-sealing such a sealing portion, the opening 2 is sealed and the filled contents can be sealed. To heat-seal the sealing portion, for example, the sealing portion is sandwiched between a pair of heat-sealing bars, and in a state where the inner surfaces of the overlapping sealing portions are pressure-bonded, the heat emitted from the heating element provided in the heat-sealing bar is transmitted from the surface side to the inner surface side of the sealing portion, so that the inner surfaces of the sealing portion (more specifically, the surface layer portion on the inner surface side of the sealing portion) are fused together.

[0018] When heat-sealing the sealing portion in this way, in order for the inner surfaces of the sealing portion to be well fused, heat must be sufficiently transmitted to the inner surface side of the sealing portion. In the process, as the resin material softens or melts, many of the bubbles contained in the foamed region formed in the sealing portion disappear (or are flattened and crushed), and the foamed region changes to a non-foamed or low-foamed state portion, presenting a translucent appearance. Therefore, in the heat-sealed portion 8 formed after heat-sealing the sealing portion, the foamed region that had an opaque appearance changes to a non-foamed or low-foamed state portion, so that it comes to present a translucent appearance (see Fig. 2), and the light transmittance of the heat-sealed portion 8 increases according to the degree of this change.

[0019] Incidentally, Fig. 2 is a photograph showing the state of the heat-sealed portion 8 formed after actually manufacturing the container 1 shown in Fig. 1 and heat-sealing the sealing portion, and it can be seen that the heat-sealed portion 8 presents a translucent appearance.

[0020] On the other hand, when heat is not sufficiently transmitted to the inner surface side of the sealing portion and heat-sealing is not performed well, many of the bubbles contained in the foamed region remain without disappearing. Therefore, the degree of change of the foamed region to a non-foamed or low-foamed state portion is small, and accordingly, the degree of increase in the light transmittance of the heat-sealed portion 8 also tends to be small.

[0021] Therefore, when the degree of increase in the light transmittance of the heat-sealed portion 8 formed after heat-sealing the sealing portion is small compared to the light transmittance of the foamed region remaining in the non-heat-sealed state, it is considered highly likely that heat has not been sufficiently transmitted to the inner surface side of the sealing portion, and as a result, due to poor fusion or the like, the sealing of the opening 2 has not been properly performed.

[0022] In this embodiment, based on such an idea, by detecting the degree of increase in the light transmittance of the heat-sealed portion 8 formed after heat-sealing the sealing portion compared to the light transmittance of the foamed region remaining in the non-heat-sealed state, it is possible to determine whether the sealing state of the sealing portion is good or bad.

[0023] In other words, in determining the quality of the seal of the sealing portion in this manner, the container 1 includes a foamed region containing air bubbles in the area including the sealing portion when it is not heat-sealed. This ensures that when the inner surfaces of the sealing portions that overlap during heat sealing fuse together in the heat-sealed portion 8 formed after the sealing portion is heat-sealed, the foamed region changes to a non-foamed or low-foamed state, exhibiting a translucent appearance. If the seal is good, the light transmittance of the heat-sealed portion 8 is 10% or more, preferably 30% or more, higher than the light transmittance of the foamed region that remains in the unheat-sealed state. This makes it possible to visually distinguish between the heat-sealed portion 8 and the unheat-sealed portion (the foamed region that remains in the unheat-sealed state), allowing for a simpler inspection of the sealing quality of the sealing portion. In addition, consumers can visually confirm the airtightness of the contents, which is expected to enhance their sense of security regarding the product. [Examples]

[0024] The present invention will be described in more detail below with reference to specific examples.

[0025] [Example 1] A foamed resin material, which is made by adding talc as a foaming nucleating agent to low-density polyethylene and impregnating it with nitrogen gas as a physical foaming agent, and a non-foamed resin material using low-density polyethylene alone, were combined in a die head. The parison extruded from the die head was blow-molded to form a three-layer structure with a foamed intermediate layer and inner and outer skin layers, creating a foamed direct-blow bottle with a cylindrical body with a diameter of 40 mm. Two sample pieces measuring 40 mm in height and 30 mm in width (hereinafter also referred to as "foamed sample pieces") were cut from the molded bottle body with the center line as the center line, and these were heat-sealed. Figure 3 shows a photograph of the heat-sealed portion in this embodiment. The area enclosed by the dashed line in the figure is the heat-sealed portion, and the rest is the unheat-sealed portion.

[0026] [Sealing conditions] For heat sealing, we used the "Impulse Sealer V-301" manufactured by Fuji Impulse Co., Ltd. This sealing machine is a single-sided heating type impulse sealer, and the sealing conditions allow the pressing force to be adjusted by tightening a screw, and the heating time can be adjusted in 10 steps by turning a knob with markings from 1 to 10. The pressing force is controlled by the number of rotations the screw makes in the direction that decreases the pressing force, with the screw fully turned in the tightening direction that maximizes the pressing force being used as a reference. In this embodiment, the number of rotations is set to "0" to maximize the pressing force. Furthermore, the heating time increases with larger numbers on the scale, and in this embodiment, the scale was set to "Scale: 10" to maximize the heating time.

[0027] [evaluation] The condition of the heat-sealed portion formed after heat-sealing the sample piece was evaluated based on five items: sealability, appearance of the seal, bubble rate, light transmittance, and difference in light transmittance. (1) Whether or not a sticker is acceptable The heat-sealed sample pieces were pulled by hand to check the sealing condition, and cross-sectional images taken with the TXS90-ACTIS X-ray CT scanner manufactured by Tesco Corporation were used to check for the presence or absence of voids at the fusion interface. The degree of heat sealing was evaluated as "○ (good)" or "× (poor)". The results are shown in Table 1. (2) Appearance of the seal The difference between the heat-sealed and unheat-sealed areas was evaluated as "○ (distinguishable)" or "× (not distinguishable or difficult to distinguish)" based on visual inspection. The results are shown in Table 1. (3) Bubble percentage The specific gravity was measured using the "MDS-300" electronic hydrometer manufactured by Alpha Mirage Co., Ltd., and calculated using the following formula (1). The results are shown in Table 1. Bubble ratio = (1 - (Specific gravity in foamed state / Specific gravity in non-foamed state)) × 100 ... (1) (4) Light transmittance and difference in light transmittance The light transmittance of the heat-sealed portion and the light transmittance of the unheat-sealed portion were measured by dispersion transmitted light measurement at 500 nm using the UV-3600iPlus ultraviolet-visible-near-infrared spectrophotometer manufactured by Shimadzu Corporation. Table 1 shows the light transmittance of the heat-sealed portion and the difference in light transmittance between the heat-sealed portion and the unheat-sealed portion.

[0028] [Table 1]

[0029] [Example 2] The condition of the heat-sealed portion was evaluated in the same manner as in Example 1, except that the heating time was shortened by two scale divisions by setting it to "scale: 8". The results are shown in Table 1.

[0030] [Example 3] The condition of the heat-sealed portion was evaluated in the same manner as in Example 1, except that the heating time was shortened by 4 divisions by setting the scale to "6". The results are shown in Table 1.

[0031] [Comparative Example 1] The condition of the heat-sealed portion was evaluated in the same manner as in Example 1, except that the heating time was shortened by 6 divisions using the "scale: 4" setting. The results are shown in Table 1. Furthermore, the bubble rate could not be measured because the seal was insufficient and the sample pieces separated.

[0032] [Comparative Example 2] The condition of the heat-sealed portion was evaluated in the same manner as in Example 1, except that the pressing force was reduced by setting the pressing force to "rotation speed: 2". The results are shown in Table 1. Figure 3 shows a photograph of the heat-sealed portion in this comparative example, compared to a photograph of the heat-sealed portion in Example 1.

[0033] [Comparative Example 3] The condition of the heat-sealed portion was evaluated in the same manner as in Example 2, except that the pressing force was reduced by setting the pressing force to "rotation speed: 2". The results are shown in Table 1. Although the heat-sealed area appears to be sealed at first glance, X-ray CT images revealed that there were areas that were not properly fused.

[0034] [Comparative Example 4] In Example 1, two foamed sample pieces were stacked without heat sealing, and their light transmittance was measured, resulting in a value of 19.8%. For reference, this value is listed in the "Light Transmittance" column of the evaluation items in Table 1. In Examples 1-3 and Comparative Examples 1-3, this value was used as the light transmittance of the unheat-sealed portion, and the difference in light transmittance between the heat-sealed and unheat-sealed portions was calculated. For reference, the bubble rate of the foamed sample pieces is also listed in the "Bubble Rate" column of the evaluation items in Table 1.

[0035] [Comparative Example 5] A direct blow bottle with a cylindrical body of 40 mm in diameter was formed by blow molding a parison extruded from a die head using low-density polyethylene alone. Two sample pieces measuring 40 mm in height and 30 mm in width (hereinafter also referred to as "non-foamed sample pieces") were cut from the formed bottle body with the center line as the centerline. Without heat sealing, the two pieces were stacked and their light transmittance was measured, which was 80.1%. For reference, this value is listed in the "Light Transmittance" column of the evaluation items in Table 1.

[0036] In Examples 1 to 3 and Comparative Example 1 described above, the sealing conditions were changed so that the heating time decreased in that order. It was confirmed that as the heating time decreased, the difference in light transmittance between the heat-sealed portion and the unheat-sealed portion decreased. Among the examples evaluated as having good sealing, the difference in light transmittance in Example 3, which had the shortest heating time, was 12.1%, while the difference in light transmittance in Comparative Example 1, which was evaluated as having poor sealing, was 5.5%.

[0037] Furthermore, in each of the following cases, Example 1 and Comparative Example 2, and Example 2 and Comparative Example 3, the sealing conditions were changed so that the pressing force was different while the heating time was the same. However, from these comparisons, it can be confirmed that the difference in light transmittance between the heat-sealed and unheat-sealed areas also decreases when the pressing force is reduced. In Comparative Example 2, where the difference in light transmittance was 4.6%, although the evaluation of whether the seal was successful was deemed good, as shown in Figure 3, it was difficult to visually distinguish between the heat-sealed and unheat-sealed areas. Moreover, in Comparative Example 3, where the difference in light transmittance was 2.3%, as mentioned above, although it appeared to be sealed at first glance, X-ray CT images revealed that there were unfused areas in places, so the evaluation of whether the seal was successful was deemed poor.

[0038] Based on these results, we concluded that in order to easily determine the quality of the seal by visually inspecting the appearance of the sealed portion, it is necessary for the difference in light transmittance between the heat-sealed portion and the unheat-sealed portion to be 10% or more. Considering the evaluation results of Examples 1 and 2, we concluded that, more preferably, if the difference in light transmittance is 30% or more, it is possible to more easily determine the quality of the seal.

[0039] Furthermore, Figure 4 shows a graph illustrating the relationship between the bubble percentage and light transmittance of the foamed sample prepared in Example 1. From this graph, it can be seen that in the region with a low bubble percentage of about 10%, the change in light transmittance is steep, while at higher bubble percentages, the change in light transmittance becomes smoother. Therefore, in order to increase the difference in light transmittance between the heat-sealed and unheat-sealed areas and to more clearly determine the quality of the seal, it is preferable to set the bubble percentage of the foamed area in the unheat-sealed state to 10% or more.

[0051] Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention. [Explanation of Symbols]

[0052] 1 container 8 Heat seal section

Claims

1. A synthetic resin container that is sealed by heat sealing after being filled with contents, In a heat-sealed portion, the area including the sealing portion to be sealed by heat sealing is provided with a foamed region containing air bubbles inside in the unheat-sealed state, and in the heat-sealed portion formed after overlapping and heat-sealing the inner surfaces of the sealing portions containing the foamed region, the inner surfaces of the sealing portions that overlap each other during heat sealing are fused together. A synthetic resin container characterized in that the light transmittance of the heat-sealed portion is 10% or more higher than the light transmittance of the foamed region that remains adjacent to the heat-sealed portion in an unheat-sealed state.

2. The synthetic resin container according to claim 1, wherein the light transmittance of the heat-sealed portion is 30% or more higher than the light transmittance of the foamed region that remains in an unheat-sealed state.

3. A synthetic resin container according to claim 1 or 2, wherein the bubble rate of the foamed region in the unheated state is 10% or more.

4. A method for inspecting the sealing condition of a synthetic resin container that is sealed by heat sealing after being filled with contents, When heat sealing, a foamed region containing air bubbles is formed inside the area including the overlapping sealing parts in the unheated state. An inspection method characterized by determining the quality of the sealing state of a sealing portion by detecting the degree of increase in the light transmittance of the heat-sealed portion formed after overlapping and heat-sealing the inner surfaces of the sealing portions having the foamed region, by comparing it with the light transmittance of the foamed region remaining adjacent to the heat-sealed portion in an unheated state.

Images