JP2008207843A - Packaging container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive packaging container which has heat-resistance, oil-resistance and hard-to-leak property. <P>SOLUTION: This packaging container consists of: a container main body; and a lid which is internally fitted or internally/externally fitted on the container main body. The container main body is obtained by thermally molding a sheet for thermal molding wherein both surfaces of a base material layer (A) consisting of a composition containing a filler and a polypropylene-based resin, and overlaid with external layers (B) consisting of a polyolefin based resin. The thickness of the polyolefin-based resin layer (B1) on the closely jointed side of a section which closely joints to the fitted section between the container main body and the lid is at least 13 μm, and the surface roughness Ry of the internal surfaces of the container main body is 10 μm or lower. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a packaging container manufactured by thermoforming a polyolefin-based resin sheet, and more particularly, to an inexpensive packaging container having heat resistance / oil resistance and resistance to liquid leakage. The packaging container of the present invention is suitably used as a packaging container for packaging foods such as cooked foods and prepared vegetables.

  2. Description of the Related Art Conventionally, there is a need for a packaging container that does not easily leak when the lid is closed so that the juice of the built-in food or moisture that has evaporated from the food and adhered to the lid does not leak outside the container. As a packaging container having heat resistance and oil resistance, a packaging container obtained by thermoforming a polypropylene resin sheet has been used so far. However, an inexpensive packaging container having both heat resistance / oil resistance and resistance to liquid leakage has not yet been provided.

An inner fitting structure and an inner / outer fitting are known as a structure that hardly leaks liquid from the fitting portion of the lid and the container main body (see, for example, Patent Documents 1 and 2).
Patent Document 1 discloses an inner fitting structure in which a hanging portion formed on a lid is fitted and closely adhered to an upright portion of the middle container in a packaging container including a lower container, a middle container, and a lid. .
Patent Document 2 discloses an internal / external fitting structure having a sealing property in which peripheral walls 15 and 25 and 16 and 26 are fitted in close contact with each other in FIG.
The polypropylene resin container contains a filler such as talc in the polypropylene resin in order to increase rigidity. When a filler-containing polypropylene such as talc is extruded alone to form a sheet, the surface of the sheet tends to become rough due to adhesion of the eyes to the mold, so the filler-containing polypropylene is sandwiched between the polypropylene-based resins that do not contain the filler. Extrusion is performed.

Furthermore, a polypropylene resin sheet for thermoforming in which a biaxially stretched film is laminated is known (for example, see Patent Document 3).
In Example 2 of Patent Document 3, an ethylene-propylene block copolymer containing 30% by mass of talc is extruded to form a sheet having a thickness of 600 μm, and a biaxially stretched polypropylene film having a thickness of 200 μm is thermally laminated to form a laminated sheet. Is disclosed. Similarly, Example 3 discloses that a laminated sheet is manufactured by thermally laminating a biaxially stretched polypropylene film having a thickness of 50 μm, and a cup container is vacuum-formed. In Patent Document 3, a high MFR resin is used to improve rigidity, and the product thickness is reduced to reduce costs.
Utility Model Registration No.3051376 Japanese Utility Model Publication No. 58-21546 Japanese Patent Laid-Open No. 62-169642

However, the above-described conventional technique has the following problems.
As disclosed in Patent Documents 1 and 2, the container of the inner fitting structure and the inner and outer fitting structure formed with a sheet containing a filler such as talc in polypropylene is due to the unevenness of the container surface by the filler, The contact state of the fitting surface to be brought into contact was insufficient, and the liquid could not be prevented from exuding.
A container having an internal fitting structure, for example, using a sheet in which a polyolefin resin layer such as polypropylene having a thickness of 5 to 15 μm is coextruded with a polypropylene resin layer having a thickness of 150 to 1200 mm containing a filler such as talc. When a lid for fitting to the main body is molded, the thickness of the polyolefin resin layer on the fitting surface to be fitted inside is stretched in the process of sheet molding and becomes as thin as about 3.5 to 11 μm. Since the polypropylene resin layer containing talc has large surface irregularities (roughness), the polyolefin resin layer with such a thinness does not sufficiently eliminate the irregularities on the surface of the sheet, and the container formed with this sheet Can not solve the leakage.

  In the prior art disclosed in Patent Document 3, since the molecular orientation by biaxial stretching is affected at the time of vacuum forming and it is difficult to obtain accurate mold transferability, the dimensional accuracy of the portion mated with the lid is insufficient and the liquid leaks. A difficult container cannot be obtained stably.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inexpensive packaging container having heat resistance / oil resistance and resistance to liquid leakage.

  In order to achieve the above object, the present invention heats a thermoforming sheet in which an outer layer (B) made of a polyolefin resin is laminated on both surfaces of a base material layer (A) made of a composition containing a filler and a polypropylene resin. The container body obtained by molding, and a lid that fits inside or outside the container body, and the thickness of the outer layer (B1) on the side in close contact with the fitting portion of the lid of the container body is at least Provided is a packaging container having a surface roughness Ry of 13 μm or more and an inner surface of the container body of 10 μm or less.

  Further, the present invention provides a surface that is the inside of a container of a sheet in which an outer layer (B) made of a polyolefin resin having a thickness of 5 μm or more is laminated on both surfaces of a base material layer (A) made of a composition containing a filler and a polypropylene resin. A container body obtained by thermoforming a sheet for thermoforming laminated with a film (C) having a thickness of 10 μm or more, and a lid that fits inside or outside the container body, and an outer layer (B1 inside the container) ) And the film (C) has a total thickness of 13 μm or more, and a surface roughness Ry of the inner surface of the container body is 10 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the cheap packaging container which has the heat-resistant / oil-resistant property and the characteristic which is hard to leak can be provided.

  FIG. 1 is a cross-sectional view showing a layer structure of a thermoforming sheet (hereinafter referred to as a laminated sheet) constituting the packaging container of the present invention. This laminated sheet 1 has a two-type three-layer structure in which an outer layer (B) 3 made of a polyolefin resin is laminated on both surfaces of a base material layer (A) 2 made of a composition containing a filler and a polypropylene resin. .

  The packaging container of the present invention comprises a container body obtained by thermoforming the laminated sheet, and a lid that fits inside or outside the container body, and a portion that is in close contact with the fitting portion of the lid of the container body The thickness of the polyolefin resin layer (B1) on the close side is at least 13 μm or more, and the surface roughness Ry of the inner surface of the container body is 10 μm or less.

  The manufacturing method of this lamination sheet is not specifically limited. A co-extrusion method, a heat laminating method, a dry laminating method, an adhesive laminating method and the like conventionally used for producing a laminated sheet can be used, but a co-extrusion method requiring no intervening layer such as an adhesive layer or a thermal laminating method is preferable.

  Polypropylene resins used for the base material layer (A) include polypropylene such as isotactic polypropylene, syndiotactic polypropylene, and attack polypropylene, ethylene-propylene random polymer, ethylene-propylene block copolymer, ethylene-propylene block. Ten-copolymer, propylene-butene-1 copolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer, propylene-olefin copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer) Polymer), a modified product of unsaturated carboxylic acid (for example, maleic anhydride) of polyethylene or polypropylene, and a mixture of two or more of these. Polypropylene such as a propylene homopolymer or a polypropylene copolymer containing 50 mol% or more of propylene units is particularly preferred.

  Although it does not specifically limit as a filler used for a base material layer (A), An inorganic substance is preferable. For example, there are silica, alumina, calcium carbonate, talc, clay, mica, glass balloon, glass beads, calcium silicate, glass fiber, carbon fiber, etc. Among them, flaky and spherical talc is particularly preferable. These fillers can be used alone or in combination of two or more. Since the talc particle size tends to be rigid, a relatively large particle having an average particle size of 5 μm or more is suitable. However, if the particle size is too large, the unevenness of the layer increases. The average particle size is preferably 1 to 20 μm. Although content of a filler is not limited, 5-100 mass parts is preferable with respect to 100 mass parts of resin.

  The base material layer (A) should be provided with various additives, for example, an antioxidant, a colorant, an ultraviolet absorber, an antistatic agent, a plasticizer, a lubricant, and the like as necessary. It can be contained within a range that does not impair rigidity and other characteristics.

  Polyolefin resins used for the outer layer (B) include low density polyethylene, high density polyethylene, linear low density polyethylene, isotactic polypropylene, syndiotactic polypropylene, attack polypropylene, and other polypropylene, ethylene-propylene random polymers, Ethylene-propylene block copolymer, ethylene-propylene butene copolymer, propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymer (for example, ethylene-methyl methacrylate) Copolymer), ethylene-unsaturated carboxylic acid metal salt copolymer (for example, ethylene-magnesium acrylate (or zinc) copolymer), propylene-butene copolymer, propylene-maleic anhydride copolymer, Lopylene-olefin copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer), modified product of unsaturated carboxylic acid (for example, maleic anhydride) of polyethylene or polypropylene, and a mixture of two or more of these Is mentioned. Among these, polypropylene such as a propylene homopolymer or a polypropylene copolymer containing 50 mol% or more of propylene units is particularly preferable. The resin material of the outer layer (B) may be the same as the polypropylene resin used for the base material layer (A).

  In the outer layer (B), various additives such as an antioxidant, a colorant, an ultraviolet absorber, an antistatic agent, a plasticizer, a lubricant, etc., as necessary, are provided on the outer layer (B), such as surface smoothness, etc. In the range which does not inhibit the characteristic of this, it can contain.

In the packaging container of the present invention, in order to suppress leakage from the fitting portion of the container body, the surface roughness Ry of the container body inner surface is 10 μm or less, more preferably 6 μm or less, and even more preferably 4 μm or less. When the surface roughness Ry exceeds 10 μm, the container body is filled with contents such as food containing liquid, or the contents to which water adheres due to condensation during storage, and the container body is covered with a lid and closed. When the package is tilted after being covered, the liquid inside leaks through the gap of the fitting portion.
The present inventor has made the inner fitting or inner / outer fitting container formed by molding the sheet having the layer structure of the present invention by setting the roughness of the surface of the inner fitting portion within such a range as a result of previous research. Other resin configurations such as, but not limited to, an amorphous polyester resin sheet, a stretched PS resin sheet, a sheet made of a mixture of a polystyrene resin and an acrylic resin, or a sheet made of a composition in which an inorganic filler such as talc is mixed. It has been found that an effect of preventing liquid leakage can be obtained even in a container having an inner fitting or inner / outer fitting structure formed by molding the non-foamed sheet.

  Further, the present invention is based on a laminated sheet (B1 / A / B2) having a two-layer / three-layer structure in which an outer layer (B) made of a polyolefin resin is laminated on both surfaces of the base material layer (A). It is obtained by thermoforming using a three-layer / four-layer laminated sheet (C / B1 / A / B2) in which a film (C) having a thickness of 10 μm or more is laminated on the outer surface of the outer layer (B1) which is the inner side of the sheet container. Provided is a packaging container comprising a container main body and a lid that fits inside or outside the container main body. This packaging container is characterized in that the total thickness of the outer layer (B1) and the film (C) inside the container is 13 μm or more, and the surface roughness Ry of the inner surface of the container body is 10 μm or less.

  The method for laminating the film (C) is not limited. General thermal laminating methods, adhesive laminating, dry laminating, etc. can be used. The material of the film is not limited. Back printed films and barrier films can be used. Uniaxial or biaxially stretched films can also be used.

  The packaging container of the present invention is a container body obtained by thermoforming using the above-mentioned laminated sheet (B1 / A / B2) or laminated sheet (C / B1 / A / B2), and the container body and the inner It consists of a lid that fits inside or outside. In the present invention, the shape of the packaging container is not limited, and the shape in plan view may be a polygon such as a rectangle or a hexagon, a circle, an ellipse, or a corner or a side may be rounded.

  The material of the lid combined with the container body is not limited. In general, polyolefins such as OPS, A-PET, and polypropylene (PP) having transparency are mainly used. PP is suitable for use in microwave heating. The packaging container of the present invention is not limited to a packaging container in which the container body and the lid are separate bodies, and may be a folded lid system in which the lid and the container body are continuous.

  The packaging container of the present invention is applied to a packaging container having a structure in which a fitting portion provided on a container body and a fitting portion provided on a lid are fitted inside or outside.

  The inner fitting refers to a fitting method in which the peripheral edge of the lid is fitted inside the opening edge of the container body when the lid is closed. FIG. 2 is a cross-sectional view of an essential part showing an example of an internally fitted packaging container. In FIG. 2, reference numeral 10 denotes an internally fitted packaging container, 11 denotes a container body, 12 denotes a lid, 13 denotes a fitting portion of the container body, and 14 denotes a fitting portion of the lid. The fitting part 13 of the container body is formed in a reverse taper shape in which the inner surface of the opening edge of the container body 11 is inclined upward in the container inner direction. 13 is formed in a reverse taper shape that is inclined upward in the container inner direction at substantially the same angle as 13. When the lid is closed, the lower end portion of the fitting portion 14 of the lid is fitted over the upper end portion of the fitting portion 13 of the container body, and the fitting portion 14 of the lid and the fitting portion 13 of the container body are in contact with each other. The lid 12 is fixed detachably. In the case of the packaging container 10 for the purpose of preventing liquid leakage, the fitting part 14 of the lid and the fitting part 13 of the container main body are in close contact with each other over the entire circumference of the container opening to block the inside and outside of the container.

  Further, in addition to the inner fitting structure, the inner / outer fitting is a convex strip having an inverted U-shaped section by extending the fitting portion (which becomes an inner fitting portion) of the lid and the container body outward and downward. The fitting structure has an inner and outer fitting portion with the outer surface of the ridge as the outer fitting portion. FIG. 3 is a cross-sectional view of an essential part showing an example of a packaging container fitted inside and outside. In FIG. 3, reference numeral 20 denotes a packaging container that fits inside and outside, 21 a container body, 22 a lid, 23 a fitting part of the container body, 24 a fitting part of the lid, 25 a ridge on the container body side, Reference numeral 26 denotes a protrusion on the lid side. When the lid 20 is closed, the ridge 26 of the lid 22 is fitted so that the ridges 25 of the container body 21 are sandwiched between the ridges 25 of the container body 21. The inner fitting and the outer fitting come into contact with each other to fix the lid 22 so as to be removable. Usually, the lid 22 can be firmly fixed as compared with the internal fitting, but requires a force for attachment and detachment. In the case of the packaging container 20 for the purpose of preventing liquid leakage, the inner fitting parts of the lid 22 and the container main body 21 or the inner fitting parts and the outer fitting parts extend over the entire circumference of the container opening. Close the inside and outside of the container closely.

[Examples 1-4, Comparative Examples 1-2]
<Manufacture of laminated sheets>
Each composition (refer Table 1) used for a base material layer (A) and an outer layer (B) was each pelletized with the extruder.
The substrate layer (A) pellets are supplied to a 900 mm extruder, the pellets made of the outer layer (B) composition are supplied to a 65 mm extruder, and coextruded from a T die. A laminated sheet having a two-layer / three-layer structure in which outer layers (B1, B2) are laminated on both surfaces of (A) was produced.

<Molded product>
The laminated sheet is vacuum-compressed and has a fitting portion at the opening, and is fitted into the substantially quadrilateral container main body of length 151 mm × width 109 mm × height 17 mm, and the fitting portion of the container main body. A substantially quadrangular lid having a fitting portion and having a length of 151 mm × width of 109 mm × height of 17 mm was manufactured.

<Fitting part structure and size>
A stepped portion provided on the upper portion of the side wall of the container main body was inclined to the inner side of the container and raised by 7 mm to form a fitting portion of the container main body, and the tip thereof was extended horizontally to form a flange portion. The lid is composed of a top surface and a side wall portion inclined to the outside at the periphery of the top surface. The lower portion of the side wall is extended substantially horizontally, and the tip is raised to form a fitting portion of the lid. The flange was extended horizontally.
The width at which the container fitting portion and the lid fitting portion are in close contact with each other when the lid is closed is 5 mm.

<Measurement of thickness>
The cross section of the container body was measured using an optical microscope (VH-8000, manufactured by Keyence Corporation).

<Measurement of surface roughness>
The surface roughness Ry (Rmax) was measured according to JIS B-0601-1994. The maximum value Rmax of the difference between the height to the highest peak and the depth to the deepest valley in the reference length L = 4 mm was measured using SJ-400 manufactured by Mitutoyo Corporation.
In the measurement of the laminated sheet, five points were measured for each of the sheet flow direction and the transverse direction, and the average value was calculated.
In the measurement of the container, 10 points at equal intervals were selected from the circumference of the fitting part of the container body, the inner surface of the fitting part was measured, and the average value was calculated.

<Leakage test>
About 10 packaging containers, put in water of about 30% of the volume of each container, close the lid, fix one corner part facing down, and the diagonal corner part facing up, 10 The time when water leakage was confirmed up to three of them was measured and taken as the leakage time. Judgment criteria were as follows.
A: 10 hours or more (passed).
○: 2 hours or more and less than 10 hours (pass).
□: 30 minutes or more and less than 2 hours (pass).
Δ: 3 minutes or more and less than 30 minutes (failed).
X: Less than 3 minutes (failed).

  For the laminated sheets of Examples 1 to 4 and Comparative Examples 1 and 2 having the layer constitution shown in Table 1 and the packaging container formed therewith, the thickness of each layer, the thickness of the laminated sheet, and the laminated sheet The surface roughness, the thickness of the B1 layer of the container, the surface roughness and the liquid leakage time were measured. The results are summarized in Table 1.

From the results in Table 1, the packaging containers manufactured in Examples 1 to 4 according to the present invention had a small surface roughness Ry of 10 μm or less, and the results of the leak test were good.
On the other hand, in Comparative Examples 1 and 2, since the thickness of the B1 layer was less than the specified value (13 μm or more) of the present invention and the surface roughness Ry exceeded the specified value (10 μm or less) of the present invention, the leakage test Was rejected.

[Examples 5 to 9, Comparative Example 3]
<Manufacture of laminated sheets>
Although it is the same as that of manufacture of the lamination sheet in Examples 1-4 mentioned above, each composition used for a base material layer (A) and an outer layer (B) shall be shown in Table 2, and lamination | stacking of B1 / A / B2 When the sheet was co-extruded, the laminate film C was added to the side that would be the inner side surface of the container and heat-laminated to produce a laminated sheet (C / B1 / A / B2) having a three-layer / four-layer structure. The material of the laminate film C is shown in Table 2.

  For the laminated sheets of Examples 5 to 9 and Comparative Example 3 shown in Table 2 and the packaging container formed therewith, the thickness of each layer, the thickness of the laminated sheet, and the surface roughness of the laminated sheet were as described above. The thickness, surface roughness, and liquid leakage time of the B1 + C layer of the container were measured. The results are summarized in Table 2.

From the results in Table 1, the packaging containers manufactured in Examples 1 to 4 according to the present invention had a small surface roughness Ry of 10 μm or less, and the results of the leak test were good.
On the other hand, in Comparative Example 3, the thickness of the B1 + C layer was less than the specified value (13 μm or more) of the present invention, and the surface roughness Ry exceeded the specified value (10 μm or less) of the present invention. It was a pass.

It is sectional drawing which shows the layer structure of the lamination sheet which comprises the container for packaging of this invention. It is principal part sectional drawing which shows an example of the packaging container of an internal fitting. It is principal part sectional drawing which shows an example of the packaging container of internal / external fitting.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated sheet, 2 ... Base material layer (A), 3 ... Outer layer (B), 10 ... Inner fitting packaging container, 11 ... Container main body, 12 ... Cover, 13 ... Fitting part of container main body, 14 DESCRIPTION OF SYMBOLS: Fitting part of lid | cover, 20 ... Packaging container of inner / outer fitting, 21 ... Container main body, 22 ... Lid, 23 ... Fitting part of container main body, 24 ... Fitting part of lid, 25 ... Convex of container main body side Ridge, 26 ... convex on the lid side.

Claims (2)

  A container body obtained by thermoforming a thermoforming sheet in which an outer layer (B) made of a polyolefin resin is laminated on both surfaces of a base material layer (A) made of a composition containing a filler and a polypropylene resin; and a container body And the inner layer or the inner / outer lid, and the outer layer (B1) on the close side of the portion close to the fitting portion of the lid of the container body has a thickness of at least 13 μm or more, and the surface roughness of the inner surface of the container body A packaging container having a thickness Ry of 10 μm or less.   Thickness is 10 μm or more on the inner surface of the sheet in which the outer layer (B) made of polyolefin resin having a thickness of 5 μm or more is laminated on both surfaces of the base material layer (A) made of a composition containing a filler and a polypropylene resin. A container body obtained by thermoforming a thermoforming sheet laminated with the film (C), and a lid that fits inside or outside the container body. The outer layer (B1) inside the container and the film (C )) And the surface roughness Ry of the inner surface of the container body is 10 μm or less.

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