JP2012224342A - Packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging container capable of reliably preventing deterioration of freshness, flavor, and appearance of food by sufficiently absorbing water, blood or the like coming from the food in the packaging container without any risk that the child or a pet may eat a water-absorbing mat by mistake.SOLUTION: This packaging container 1 includes a substrate 50 of a container body and a porous olefin based water absorption resin film 60 adhered over the entire surface of the substrate 50. The olefin based water absorption resin film 60 is obtained by laminating a water absorbing layer 61 and a waterproof layer 62, wherein a surface at the side of the waterproof layer 62 is adhered to the substrate 50, and a surface at the side of the water absorbing layer 61 is disposed at the side of an article to be housed of the container. The water absorbing layer 61 includes 25 to 55 wt.% of olefin based resin and 45 to 75 wt.% of inorganic fine powder having a surface treated with a hydrophilization agent. At least uniaxial stretching is applied thereto.

Description

  The present invention relates to a packaging container in which food such as meat, seafood, and fried foods is stored.

In general, meat, seafood, fried foods, etc. are stored in packaging containers such as expanded polystyrene, and are sold over-the-counter with a wrapping film on them if necessary. In some cases, moisture or blood oozes from the inside into the packaging container. The moisture and blood reduce the freshness and taste of foods such as meat and seafood, and reduce the appearance at the store, so it is necessary to remove them quickly. Also in the case of fried foods, the food comes into contact with the oil that comes from the inside of the food and the condensed water droplets that are generated by cooling, and there is a problem that the freshness, taste, and appearance of the food are also lowered. .

  For this reason, a water absorbing mat is laid as a rug on the bottom of the packaging container, and countermeasures are taken to absorb moisture, blood, etc. from food with the water absorbing mat. As an example of such a water-absorbing mat, a foamed polyurethane-based sheet is generally used. In Patent Document 1, a polyolefin sheet having a large number of minute holes and a thickness of 0.1 to 1 mm is laminated with a water-absorbent sheet made of an airlaid nonwoven fabric mainly composed of a heat-adhesive conjugate fiber and pulp. A water-absorbing mat is disclosed in which the pore diameter of the surface of the polyolefin-based sheet that is in contact with the food is smaller than the diameter of the surface of the polyolefin-based sheet that is in contact with the water-absorbing sheet. There are Patent Documents 2 and 3 as other prior art documents.

JP 2008-44653 A JP-A-10-212367 JP-A-7-300568

  However, these water-absorbing mats are simply placed as a rug in the packaging container, so that children and pets may accidentally eat. In addition, since the water-absorbing mat is only laid on the bottom of the packaging container, the absorption of moisture, blood, etc. that ooze laterally in the packaging container is insufficient, and the freshness, taste, and appearance of the food There is also a problem that the decrease cannot be sufficiently prevented.

  The present invention has been found in view of the above problems, and there is no risk that a child or pet accidentally eats the water-absorbing mat, and sufficiently absorbs moisture, blood, etc. from the food in the packaging container, It is an object of the present invention to provide a packaging container that can reliably prevent deterioration of freshness, taste and appearance of food.

The packaging container of the present invention is a packaging container comprising a base material of a container main body and a porous olefin-based water-absorbing resin film adhered to the entire surface of the base material, wherein the olefin-based water-absorbing resin film is A water-absorbing layer and a waterproof layer are laminated, the surface on the waterproof layer side is bonded to the substrate, the surface on the water-absorbing layer side is disposed on the container side of the container, and the water-absorbing layer is an olefin-based layer It contains 25 to 55% by weight of resin and 45 to 75% by weight of inorganic fine powder whose surface is treated with a hydrophilizing agent, and is stretched at least in a uniaxial direction.
According to this configuration, since the water-absorbing resin film is bonded and integrated to the container body, it is possible to reliably eliminate the risk that children and pets accidentally eat the water-absorbing mat, and the entire inner surface of the container body is covered. By adhering the water-absorbing resin film, it is possible to sufficiently absorb moisture, blood, etc. from the food in the bottom and sides in the packaging container, and reliably prevent deterioration of food freshness, taste and appearance. . In addition, the water absorption layer located on the container side of the container can sufficiently absorb moisture, blood, etc. from the food, and the moisture layer retained by the water absorption layer on the base material side of the container. It is possible to suppress the influence on an adhesive layer or the like made of an adhesive or an olefin-based resin, which will be described later, and conversely, prevent components from the adhesive or the like from flowing out to the container side of the container. Furthermore, the water absorption layer contains 25 to 55% by weight of an olefin resin and 45 to 75% by weight of an inorganic fine powder whose surface is treated with a hydrophilizing agent, and is configured to be stretched at least in a uniaxial direction. It is possible to improve moldability, water absorption, and detachability of the wrapping film, and to reliably control the flow and storage of moisture and blood from food.

In the packaging container of the present invention, the water absorption layer preferably has a porosity of 28 to 80%.
According to this configuration, it is possible to more reliably control the flow and storage of moisture, blood, etc. from the food.

In the packaging container of the present invention, the waterproof layer contains an olefin resin, or contains an olefin resin and an inorganic fine powder, and is stretched at least in a uniaxial direction. It is preferably 25% and smaller than the porosity of the water absorption layer.
According to this structure, the waterproof layer excellent in film forming property and waterproofness can be obtained. In addition, the waterproof layer can be configured to contain or not contain inorganic fine powder, but when the waterproof layer is a microporous resin film containing inorganic fine powder and stretched at least in a uniaxial direction. Moreover, the cost reduction of an olefin type water absorption resin film can be aimed at. In this case, in order to maintain the waterproof property so as not to permeate the water, it is preferable that the porosity is in the range of 0 to 25% and is smaller than the porosity of the water absorption layer.

In the packaging container of the present invention, it is preferable that the water absorbing layer has a multilayer structure in which a first water absorbing layer on the container side and a second water absorbing layer on the waterproof layer side are laminated. Furthermore, it is preferable that the liquid absorption coefficient (water absorption speed) of the second water absorption layer is larger than the liquid absorption coefficient (water absorption speed) of the first water absorption layer.
According to this configuration, the difference in liquid absorption coefficient due to the capillary phenomenon of each of the first water absorption layer and the second water absorption layer can be used, and moisture, blood, etc. from food can be absorbed smoothly. It is possible to prevent water, blood, and the like stored in the second water absorption layer from flowing back to the food side.

  The water absorption layer is a multilayer structure in which the first water absorption layer and the second water absorption layer are laminated, and as a specific method for differentiating the respective liquid absorption coefficients, for example, the porosity of the first water absorption layer and It can be mentioned that the porosity of the second water-absorbing layer is different. In this case, the porosity of the first water-absorbing layer is preferably 31 to 51%, and the porosity of the second water-absorbing layer is preferably The rate may be 40 to 62%, and the porosity of the second water absorption layer may be larger than the porosity of the first water absorption layer.

Moreover, it is preferable that the packaging container of the present invention has a configuration in which the surface of the base material and the waterproof layer side of the olefin-based water-absorbing resin film are bonded via an adhesive.
According to this structure, a base material and an olefin type water absorbing resin film can be adhere | attached firmly.

In the packaging container of the present invention, the olefin-based water-absorbing resin film is formed by laminating a water-absorbing layer, a waterproof layer, and an adhesive layer made of an olefin-based resin in this order, and the base material and the olefin-based water-absorbing resin film. However, it is preferable that the adhesive layer be bonded by heat fusion.
According to this configuration, the base material and the olefin-based water-absorbing resin film can be firmly bonded, the number of steps for producing the packaging container can be reduced, and further, from the adhesive usually used for dry lamination. Thus, it is possible to provide a more hygienic packaging container without worrying about the influence of the solvent component and the unreacted component.

In the packaging container of the present invention, the inorganic fine powder in the water absorption layer is preferably calcium carbonate.
According to this configuration, when a wrapping film is applied to the packaging container, the frictional resistance between the water-absorbing resin film and the wrapping film can be reduced to improve the slipperiness, and the wrapping film can be attached and detached smoothly.

In the packaging container of the present invention, the base material is at least one resin selected from the group consisting of polyethylene resin, polypropylene resin, polystyrene resin, polyamide resin, and polyester resin, or these resins and inorganic fillers. It is preferable to include a composite material.
According to this structure, it is easy to shape | mold in a tray shape as a packaging container, and a thing with a suitable external appearance can be obtained as a packaging container.

More preferably, in order to sufficiently absorb liquids such as water and blood generated from foods such as meats, seafood, and fried foods, Japan TAPPI No. In accordance with 51: 2000 (Bristow method), the transfer amount (water absorption amount) of distilled water measured on the surface of the olefin-based water-absorbing resin film on the water absorption layer side is preferably 6 to 310 ml / m ² . More preferably, when a wrapping film is applied to a packaging container, JIS K7125 is used in order to improve the slipperiness by reducing the frictional resistance between the water-absorbing resin film and the wrapping film, and to smoothly attach and detach the wrapping film. : A wrapping film of a predetermined material such as a polyolefin film such as a polyvinyl chloride film, a polyvinylidene chloride film, or a polyethylene film, in accordance with 1999, with the surface on the water absorption layer side of the olefin-based water-absorbing resin film as the first test piece. It is preferable that the static friction coefficient measured as the second test piece (counter member) is 0.3 to 0.5.

  According to the packaging container of the present invention, by adhering the water absorbent resin film to the container body, it is possible to surely eliminate the risk of accidental eating of the water absorbent mat by children and pets, and the bottom portion in the packaging container. Moisture, blood, etc. from the food can be sufficiently absorbed to the side, and the deterioration of the freshness, taste and appearance of the food can be surely prevented. In addition, it is possible to eliminate the manual work process of installing a water-absorbing mat that has been used in the packaging container, to reduce the risk of contamination and to improve the hygiene safety. In addition, it is possible to eliminate the manual work involved in inventory management, unpacking, and packing of conventionally used water-absorbing mats, and to improve the efficiency of the manufacturing process. Furthermore, it is possible to contribute to the reduction of carbon dioxide emission by eliminating the transport and carry-in of the water-absorbing mat, which is a separate material from the packaging container.

  In addition, the water absorption layer located on the container side of the container can sufficiently absorb moisture, blood, etc. from the food, and the moisture layer retained by the water absorption layer on the base material side of the container. It is possible to suppress the influence on an adhesive layer or the like made of an adhesive or an olefin-based resin, which will be described later, and conversely, prevent components from the adhesive or the like from flowing out to the container side of the container. Furthermore, the water absorption layer contains 25 to 55% by weight of an olefin resin and 45 to 75% by weight of an inorganic fine powder whose surface is treated with a hydrophilizing agent, and is configured to be stretched at least in a uniaxial direction. It is possible to improve moldability, water absorption, and detachability of the wrapping film, and to reliably control the flow and storage of moisture and blood from food.

(A) is a top view of the packaging container of embodiment by this invention, (b) is the longitudinal cross-sectional view. It is an expanded sectional view of the A section of FIG.1 (b). It is an expanded sectional view of the site | part corresponded to the A section of the packaging container of embodiment by this invention. It is the schematic which shows the adhesion process of a base material and an olefin type water absorption resin film.

[Packaging Container of Embodiment]
As shown in FIGS. 1 and 2, the packaging container 1 according to the present embodiment has a tray shape with an open top surface, a bottom portion 2, and a side wall 3 that rises in a tapered shape so as to spread outward from the peripheral end of the bottom portion 2. , And an edge 4 having an arcuate cross-section projecting outward from the upper end of the side wall 3. And each of the bottom part 2, the side wall 3, and the edge part 4 is a porous olefin-based water-absorbing resin film bonded over the entire surface of the base material 50 of the container body and the inner surface side (contained material side) of the base material 50. 60. As an example of the embodiment, the base material 50 of the container main body formed of foamed polystyrene or the like, and the porous material bonded to the entire inner surface side of the base material 50 through the adhesive layer 63 made of ethylene resin or the like. The packaging container 1 comprised from the property olefin type water absorbing resin film 60 can be mentioned.

  Hereinafter, the olefin water-absorbing resin film 60 constituting the packaging container 1 of the embodiment according to the present invention and the base material 50 of the container body will be specifically described.

[Configuration of Olefin-based Water Absorbing Resin Film 60]
The olefin-based water-absorbing resin film 60 includes a laminate formed by laminating a water-absorbing layer 61 made of an olefin-based resin and a waterproof layer 62. Further, the olefin-based water-absorbing resin film 60 is a waterproof layer 62 of this laminate. It is good also as a structure which laminated | stacked the contact bonding layer 63 which consists of an olefin resin on the side. The example of FIG. 2 is an olefin-based water-absorbing resin film 60 in which a water-absorbing layer 61, a waterproof layer 62, and an adhesive layer 63 are laminated. Alternatively, a structure in which a large number of laminated bodies including the water absorbing layer 61 and the waterproof layer 62 are laminated, and the adhesive layer 63 may be laminated on the surface of the laminated body on the substrate 50 side as necessary.

[Water absorption layer 61]
The water absorption layer 61 in the olefin water-absorbing resin film 60 imparts liquid absorption characteristics to the olefin water-absorbing resin film 60. Here, “liquid” refers to moisture, water vapor, blood, body fluid, cooking fluid, oil, condensed water droplets, and the like that come out of the contents in the packaging container 1.

  The water absorption layer 61 contains an olefin resin. In the present invention, the olefin resin contributes to the film-forming property of the film as a matrix resin. Examples of the olefin resin used for the water absorbing layer 61 include high density polyethylene, medium density polyethylene, low density polyethylene, ethylene / α-olefin copolymer, ethylene / cyclic olefin copolymer and other ethylene resins, propylene resin, Examples thereof include olefinic resins such as polymethyl-1-pentene. These may be used in combination of two or more. These olefin resins show crystallinity, and those having a crystallinity of 20% or more by X-ray diffraction method are preferable, and those having a crystallinity of 35 to 75% are more preferable. Those that do not exhibit crystallinity do not have sufficient pores (openings) formed on the film surface due to stretching described below.

  Among the olefin resins, propylene resins are preferably used from the viewpoint of stretch moldability. As the propylene-based resin, it is preferable to use an isotactic polymer or a syndiotactic polymer obtained by homopolymerizing propylene. Copolymers mainly composed of propylene having various stereoregularities obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene and 4-methyl-1-pentene. Polymers can also be used. The copolymer may be a binary system or a ternary or higher multi-element system, and may be a random copolymer or a block copolymer.

  The olefin resin used for the water absorption layer 61 is added in a proportion of 25 to 55% by weight. This ratio is preferably 30 to 50% by weight. If the olefin-based resin is less than 25% by weight, the stretch moldability and the tear strength of the stretched film are lowered, which is not preferable. Conversely, if the olefin-based resin exceeds 55% by weight, the number of vacancies formed is not preferable. If it is within the same range, when casting the cast resin from the die to the cast roll by lateral drawing, the dripping phenomenon of the molten resin sheet is suppressed, and in the case of vertical drawing, the drawdown is suppressed, and the cast sheet The moldability can be improved, and the stretch moldability is not impaired and the sheet can be prevented from cracking.

  Moreover, the water absorption layer 61 contains the inorganic fine powder by which the surface was hydrophilized with the hydrophilizing agent. In the present invention, the inorganic fine powder is added to make the film porous and to impart water absorption characteristics. In addition, the friction resistance between the olefin-based water-absorbing resin film 60 and the wrapping film is reduced to improve the slipperiness, and the packaging container and the wrapping film can be smoothly attached and detached.

  Inorganic fine powders that can be used include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, titanium oxide, barium sulfate, zinc oxide, magnesium oxide, diatomaceous earth, silicon oxide, and other inorganic fine powders. Examples thereof include a composite inorganic fine powder having a surrounding aluminum oxide or hydroxide, and hollow glass beads. Among these, heavy calcium carbonate, calcined clay, and diatomaceous earth are preferable because they are inexpensive and can form many pores during stretching, and the porosity can be easily adjusted. Heavy calcium carbonate and light calcium carbonate are preferable because the average particle size and particle size distribution can be easily obtained.

  These inorganic fine powders have their surfaces hydrophilized with a hydrophilizing agent. By using the inorganic fine powder subjected to the hydrophilization treatment, it is possible to improve the wetting of the film surface and the pores and to easily introduce the liquid into the water absorption layer 61. The hydrophilizing agent for treating the surface of the inorganic fine powder for hydrophilizing the inorganic fine powder is an anionic or cationic one that is water-soluble and has an average molecular weight in the range of 1,000 to 150,000. Examples include ionic polymer surfactants. Examples of these polymer surfactants include those described in Patent Document 2.

  Hydrophilic treatment of inorganic fine powder with a hydrophilizing agent is, for example, when an inorganic particle is wet pulverized, an anionic or cationic or nonionic system that is water-soluble and has an average molecular weight in the range of 1,000 to 150,000. It is possible to carry out the surface treatment by introducing a high molecular surfactant such as a sulfonate, diallylamine salt, alkyldiallylamine salt, or hydrophilic vinyl polymer into the vessel and grinding it. These treatments may be performed twice or more individually using different surface treatment agents. Preferable examples of the inorganic fine powder subjected to the hydrophilization treatment include those described in Patent Document 3, and specific examples thereof include “AFF-Z” manufactured by Phematech.

  The inorganic fine powder used for the water absorption layer 61 is added at a ratio of 45 to 75% by weight. This ratio is preferably 50 to 70% by weight. If the inorganic fine powder is less than 45% by weight, formation of communication holes (communication holes) becomes difficult, which is not preferable from the viewpoint of water absorption. On the other hand, if the inorganic fine powder exceeds 75% by weight, it is not preferable because the film is difficult to stretch. In addition to the inorganic fine powder, different kinds of inorganic fine powder and organic fine powder may be combined and blended.

  Further, the water absorption layer 61 may include a dispersant of inorganic fine powder. The dispersant is added to improve the dispersibility of the inorganic fine powder in the water absorption layer 61 and to impart characteristics such as improvement in the uniformity of pores in the water absorption layer 61 and improvement in water absorption performance. Further, the inorganic fine powder can be fixed in the water absorption layer 61 by the dispersant. As the dispersant that can be used, known ones can be used, but acid-modified polyolefin resins are particularly preferable. Specific examples thereof include “Yumex 1001” manufactured by Sanyo Chemical Industries. When using a dispersing agent for the water absorption layer 61, it is preferable to add in the ratio of 0.01 to 10 weight%. If the dispersant is less than 0.01% by weight, the original function of the dispersant cannot be fully exerted, which is not preferable. On the contrary, if the dispersant exceeds 10% by weight, the inorganic fine powder may be aggregated, which is not preferable. Moreover, you may mix | blend well-known additives, such as a heat stabilizer, a ultraviolet stabilizer, antioxidant, an antiblocking agent, a nucleating agent, a lubricant, and a coloring agent, in the water absorption layer 61 as needed. These additives are preferably blended in a proportion of 0.01 to 3% by weight.

  Moreover, it is preferable that the water absorption layer 61 is extended | stretched at least by the uniaxial direction. A thin and uniform film can be obtained by stretch molding, and at the same time, a large number of pores and openings with inorganic fine powder as the core are formed in the inside and surface of the layer, and these holes and mouths communicate with each other. Water absorption performance can be expressed. Various known methods can be employed for the stretch molding. For example, as a specific method of uniaxial stretching, stretching between rolls (hereinafter referred to as “longitudinal stretching” in the present invention) that stretches by utilizing the peripheral speed difference of a group of rolls in the transport direction (production line direction) of the resin film, resin Examples thereof include clip stretching (hereinafter, referred to as lateral stretching in the present invention), rolling, and the like that are stretched using a tenter oven in a direction (width direction) perpendicular to the film transport direction.

  According to the longitudinal stretching method, it is easy to obtain the water absorbing layer 61 having any porosity, rigidity, opacity, smoothness, and glossiness by arbitrarily adjusting the stretching ratio. In particular, the longitudinal stretching method is preferable because it is easy to obtain the water absorption layer 61 having an arbitrary water absorption amount (distilled water transfer amount) by arbitrarily adjusting the porosity. Therefore, the draw ratio is not particularly limited, and is determined in consideration of the physical properties desired for the olefin water-absorbing resin film 60 and the properties of the thermoplastic resin used. The draw ratio in the longitudinal stretching method is usually in the range of 3 to 11 times, preferably 4 to 10 times, and more preferably 5 to 7 times. If it is in the same range, the water absorption layer 61 which has a desired physical property can be manufactured stably.

  According to the lateral stretching method, although there is no degree of freedom of stretching ratio as long as the longitudinal stretching method due to equipment limitations, it is easy to adjust the film width to be obtained. If the film width can be increased, the application will be expanded and the product yield will be improved easily. The draw ratio of the transverse drawing method is usually 4 to 11 times, more preferably 4 to 10 times, and particularly preferably 5 to 9 times. By setting the stretching ratio to 4 times or more, communication holes are formed, and it becomes easy to prevent stretching unevenness and manufacture the water absorbing layer 61 having a more uniform film thickness. Moreover, by making it 11 times or less, it becomes easy to prevent a stretch cut and a rough perforation more effectively.

  On the other hand, as a specific method of biaxial stretching, sequential biaxial stretching using both inter-roll stretching (longitudinal stretching) using the peripheral speed difference of the roll group and clip stretching (lateral stretching) using a tenter oven is used. Can be mentioned. According to the sequential biaxial stretching method, it is easy to arbitrarily adjust the magnification by longitudinal stretching, and the sheet width can be adjusted by lateral stretching. Therefore, it is easy to obtain the water absorption layer 61 having any porosity, rigidity, opacity, smoothness, glossiness, and sheet width. Another specific method of biaxial stretching includes simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are simultaneously performed. More specifically, a combination of a tenter oven and a pantograph, a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor, and the like can be mentioned. Moreover, the simultaneous biaxial stretching method by the tubular method which is a stretching method of an inflation film can be mentioned.

  According to the simultaneous biaxial stretching method using a tenter oven, the ratio of longitudinal stretching and lateral stretching can be adjusted at the same time, so that it is easy to produce the water absorption layer 61 that is isotropic and suppresses shrinkage caused by stress relaxation as much as possible. It is. In addition, since there are fewer parts that rely on rolls for stretching and transport of resin films, and the ratio of transport by clips increases, the surface of the resin film is less susceptible to rubbing due to contact with equipment such as rolls, resulting in more stable quality. A resin film can be manufactured. According to the biaxial stretching method, it is easy and preferable to adjust the porosity arbitrarily to obtain the water absorption layer 61 having an arbitrary water absorption. The draw ratio is not particularly limited, and is determined in consideration of physical properties desired for the olefin-based water-absorbent resin film 60 and characteristics of raw materials to be used. Since the water-absorbent resin film 60 uses an olefin-based resin as a raw material, the area stretch ratio is usually preferably 10 to 90 times, and more preferably 15 to 60 times. If it is in the same range, the water absorption layer 61 which has a desired physical property can be manufactured stably.

  Whether it is uniaxial stretching or biaxial stretching, the stretching is performed at a temperature 5 ° C. or more lower than the melting point of the matrix resin, more preferably 5 ° C. or more lower than the melting point of the crystal part of the olefin resin. The temperature is preferably higher than the softening temperature of the amorphous part of the resin. The pores of the water absorbing layer 61 obtained as a result of the stretch molding preferably have a porosity of 28 to 80%. When the porosity of the water absorption layer 61 is 28% or more, there is a tendency that pores communicating with the inside of the film are generated and desired water absorption performance is easily exhibited. Further, if the porosity is 80% or less, stretch cracks are unlikely to occur during film production, and thus there is a tendency that more stable production is facilitated. When the water absorbing layer 61 is a uniaxially stretched film, the porosity is preferably 28 to 64%, more preferably 33 to 57%, and particularly preferably 36 to 54%. When the water absorption layer 61 is a biaxially stretched film, it is preferably 30 to 80%, more preferably 35 to 79%, still more preferably 38 to 78%, and 40 to 75%. It is particularly preferred. The porosity of the uniaxial or biaxially stretched resin film can be controlled by adjusting the content of the olefin resin or the inorganic fine powder in the water absorption layer 61 and the stretch ratio.

  The presence of pores inside the layer can be confirmed by observing the cross section with an electron microscope. The porosity is obtained by taking an electron micrograph of the layer cross section and determining the area ratio (%) of the occupancy in the cross-sectional area taken in the photograph. Specifically, after embedding the olefin-based water-absorbing resin film 60 with an epoxy resin and solidifying it, using a microtome, for example, a cut surface parallel to the thickness direction of the film (that is, perpendicular to the surface direction) is produced. Then, after metallizing the cut surface, the photograph was magnified to an arbitrary magnification (for example, 500 times to 2000 times) that can be easily observed with a scanning electron microscope, and the holes were traced and painted on the tracing film. The figure is subjected to image processing with an image analysis device, and the area ratio (%) of the holes occupying the measurement range can be obtained and used as the porosity (%). When the olefin water-absorbing resin film 60 has a multilayer structure, the porosity (%) can be obtained for each layer by the above method.

[Waterproof layer 62]
The olefin water-absorbing resin film 60 has a waterproof layer 62. The waterproof layer 62 preferably includes an olefin resin. In this case, the olefinic resin contributes to the film-forming property of the film, and at the same time contributes to waterproofing due to the inherent hydrophobicity of the olefinic resin. Here, “waterproof” not only absorbs and does not permeate moisture, water vapor, blood, body fluid, cooking fluid, oil, condensed water droplets, etc. coming out of the contents in the packaging container, but also the base material 50 and olefin of the container body. When an adhesive is used for adhesion to the water-absorbing resin film 60, this means that harmful substances (organic solvent and unreacted low molecular weight substances) from the adhesive are prevented from permeating to the container.

  In addition, when a film-like product is formed by stretching a laminate of the water-absorbing layer 61 of the olefin-based water-absorbing resin film 60 to form a film-like product, the waterproof layer 62 ensures uniform stretch moldability, and the inorganic fine powder It becomes possible to prevent effectively the crack of the film of the water absorption layer 61 with much content of. As the olefin resin used for the waterproof layer 62, the same resin as that described in the water absorption layer 61 can be used. The olefin resin used for the waterproof layer 62 is preferably added in a proportion of 60 to 100% by weight, more preferably in the range of 70 to 100% by weight. Within the same range, a waterproof effect can be obtained, cast sheet molding is possible, and stretch moldability is not impaired, and cracking of the film can be prevented.

Moreover, the waterproof layer 62 may contain inorganic fine powder and organic fine powder, and does not need to contain it. If these fine powders are contained, the cost of the olefin water-absorbing resin film 60 can be reduced. If not contained, a higher waterproof effect can be expected. When inorganic fine powder is used for the waterproof layer 62, it is preferably added in a proportion of 0 to 40% by weight, more preferably in the range of 0 to 30% by weight. Within the same range, a waterproof effect can be obtained, cast sheet molding is possible, and stretch moldability is not impaired, and cracking of the film can be prevented. As the inorganic fine powder that can be used for the waterproof layer 62, the same inorganic fine powder as that described for the water-absorbing layer 61 can be used. However, from the viewpoint of waterproofing, the surface is hydrophilized with a hydrophilizing agent. Use is not preferred. Furthermore, a dispersant or a known additive can be used for the waterproof layer 62 in the same manner as the water absorption layer 61.

  Lamination of the water absorption layer 61 and the waterproof layer 62 can be achieved by co-extrusion of the water absorption layer 61 and the waterproof layer 62 or a method of forming the waterproof layer 62 as a base film and then extruding the water absorption layer 61 thereto. The waterproof layer 62 is also preferably extended at least in the uniaxial direction. A thin and uniform film can be obtained by stretching. In the stretch molding, various known methods and stretch ratios can be employed in the same manner as the water absorbing layer 61 described above. The pores of the waterproof layer 62 obtained as a result of the stretch molding have a porosity that is smaller than that of the water absorption layer 61, and the porosity is preferably 0 to 25%, preferably 0 to 20%. More preferably. If the porosity of the waterproof layer 62 is 25% or less, since there are almost no pores communicating with the layers, water absorption does not occur and the waterproof property tends to be easily achieved.

[Adhesive layer 63]
The olefin water-absorbing resin film constituting the present invention can be adhered to the base material 50 via an adhesive on the surface of the waterproof layer 62, but has an adhesive layer 63 made of an olefin resin. This is preferable. The adhesive layer 63 includes an olefin resin. In this case, the olefin-based resin is used to bond the base material 50 of the container body and the olefin-based water-absorbing resin film 60 by heat-sealing the adhesive layer 63. The adhesive layer 63 is preferably laminated and bonded to the olefin water-absorbing resin film 60 (preferably on the waterproof layer 62 side) in advance. By using such an adhesive layer 63, the bonding process can be further simplified, and a stronger bond between the base material 50 and the olefin-based water-absorbing resin film 60 can be achieved, and at the same time, an adhesive usually used for dry lamination can be used. The sanitary packaging container 1 can be provided without worrying about the influence of the solvent components and unreacted components.

As the olefin resin used for the adhesive layer 63, the melting point is preferably 5 ° C. or more lower than the melting point of the main olefin resin used for the waterproof layer 62 by 10 to 120 ° C. Specifically low density or medium density high-pressure polyethylene of 0.900~0.935g / cm ³ density, the density of 0.860~0.970g / cm ³ straight chain linear polyethylene, ethylene-propylene copolymerization Copolymers, ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / α-olefin copolymers such as ethylene / octene copolymers, ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers, alkyl groups Ethylene / acrylic acid alkyl ester copolymer having 1 to 8 carbon atoms, ethylene / methacrylic acid alkyl ester copolymer having 1 to 8 carbon atoms in the alkyl group, Zn / Al of ethylene / methacrylic acid copolymer, Instead of a metal salt such as Li, K, Na, etc., an ethylene resin having a melting point of 50 to 140 ° C. or a propylene / α-olefin copolymer. Melting point ninety to one hundred fifty-five ° C. propylene resin to be, can be used ADMER (registered trademark) modified polyolefin or the like imparted with adhesiveness, or the like. These may be used alone or in combination of two or more. The lamination of the adhesive layer 63 to the olefin-based water-absorbing resin film 60 is performed by co-extrusion with the water-absorbing layer 61 and the waterproof layer 62 constituting the olefin-based water-absorbing resin film 60, or by forming the waterproof layer 62 as a base film and then extruding it. Can be achieved by lamination or coating methods.

[Multi-layered water absorption layer 61]
In the olefin-based water-absorbing resin film 60, the water-absorbing layer 61 is suitable as a water-absorbing layer 61 having a multilayer structure for functionalization in addition to the single-layer structure shown in FIG. When the water absorption layer 61 has a multilayer structure, as shown in FIG. 3, the liquid absorption coefficient is larger than the liquid absorption coefficient of the first water absorption layer 611 on the container side and the water absorption layer 62 side on the waterproof layer 62 side. It is preferable to have a multilayer structure in which the second water absorption layer 612 having a coefficient is stacked. In the present invention, the liquid absorption coefficient serving as an index of the water absorption rate of the water absorption layer 61 is JAPAN TAPPI No. The liquid absorptivity test method (Bristow method) of 51: 2000 is used. In order to obtain the liquid absorption coefficient of the first water absorption layer 611 and the liquid absorption coefficient of the second water absorption layer 612 individually, the resin composition and the forming conditions constituting the respective layers are used. The two-layered olefin-based water-absorbing resin film 60 provided on the surface of the water-absorbing layer 61 may be separately prepared to obtain the liquid absorption coefficient of the water-absorbing layer 61. Usually, the liquid absorption coefficient of the first water absorption layer 611 is in the range of 10 to ²⁰⁰ ml / m ² · ms ^1/2 , and the liquid absorption coefficient of the second water absorption layer 612 is 20 to 200 ml / m ² · ms ^{1. / 2} , preferably the first water absorption layer 611 has a liquid absorption coefficient of 15 to 150 ml / m ² · ms ^1/2 , and the second water absorption layer 612 has a liquid absorption coefficient of 30. Within the range of ~ 150 ml / m ² · ms ^1/2 .

  Thus, as a method for differentiating the liquid absorption coefficients of the respective water absorption layers 611 and 612, first, the porosity of the respective water absorption layers 611 and 612 is differentiated, and the pores of the first water absorption layer 611 are thereby determined. The porosity is set to 31 to 51%, the porosity of the second water absorption layer 612 is set to 40 to 62%, and the porosity of the second water absorption layer 612 is larger than the porosity of the first water absorption layer 611. To do. In order to make such a configuration, the area stretch ratio in the first water absorption layer 611 is made smaller than the area stretch ratio in the second water absorption layer 612 (for example, the first water absorption layer 611 is a uniaxially stretched film, The second water-absorbing layer 612 is a biaxially stretched film or the like, and the number of stretching axes is different), the content of the inorganic fine powder in the first water-absorbing layer 611 is the content of the inorganic fine powder in the second water-absorbing layer 612 It can be considered to be smaller than the amount. Another method is to make a difference in the pore diameter of each layer. Specifically, it is conceivable that the average particle diameter of the inorganic fine powder in the first water absorption layer 611 is made larger than the average particle diameter of the inorganic fine powder in the second water absorption layer 612. If the area draw ratio in both layers is the same, the pore diameter obtained by stretching is proportional to the average particle diameter of the inorganic fine powder used, so the difference in pore diameter is used to change the liquid absorption coefficient by capillary force. Can make a difference. Further, as another method, there can be mentioned a method of making a difference in the wettability of each layer. Specifically, the liquid absorption coefficient can be made different by making the surface treatment amount of the inorganic fine powder in the first water absorption layer 611 smaller than the surface treatment amount of the inorganic fine powder in the second water absorption layer 612. it can.

  In the olefin-based water-absorbing resin film 60 constituting the packaging container 1, the water-absorbing layer 61 preferably has a layer thickness of 24-240 μm, more preferably a layer thickness of 40-200 μm. When the water absorption layer 61 has a two-layer structure, the layer thickness of the first water absorption layer 611 is 6 to 60 μm, more preferably 10 to 50 μm, and the layer thickness of the second water absorption layer 612 is 18 to 180 μm, and more preferably. The layer thickness is preferably 30 to 150 μm. The waterproof layer 62 is preferably 6 to 60 μm thick, more preferably 10 to 50 μm thick, and the adhesive layer 63 is 1 to 20 μm thick, more preferably 3 to 10 μm thick. preferable.

[Transition amount of distilled water]
In the packaging container 1, in order to sufficiently absorb moisture, blood, and the like generated from food such as meat, seafood, and deep-fried food, Japan TAPPI No. 51: conforms to 2000, it is preferable that the transfer amount of distilled water was measured in terms of water-absorbing layer 61 side of the olefinic water resin film 60 is 6~310ml / ^{m 2,} a 12~260ml / ^{m 2} Is more preferable. If the transfer amount of distilled water is less than 6 ml / m ² , moisture, blood, etc. generated from these contents cannot be sufficiently absorbed. On the contrary, if it exceeds 310 ml / m ² , it is sufficient as an assumed water absorption amount, but there is a tendency to become an excessive specification in the same application, which causes an increase in cost.

[Static friction coefficient]
When applying a wrapping film to the packaging container 1, in order to improve the slipperiness by reducing the frictional resistance between the water-absorbing resin film 60 and the wrapping film and to smoothly attach and detach the wrapping film, conform to JIS K7125: 1999. Then, using a friction measuring device (device name: TR-2, manufactured by Toyo Seiki Co., Ltd.), the surface of the olefin-based water-absorbing resin film 60 on the water-absorbing layer 61 side is the first test piece, and a polyvinyl chloride film (for example, a trade name) : Diawrap (registered trademark), manufactured by Mitsubishi Plastics, Inc., polyvinylidene chloride film (for example, trade name: Saran Wrap (registered trademark), manufactured by Asahi Kasei Chemicals), or polyethylene film (for example, trade name: Dialup (registered trademark)) ) Rappin of specified materials such as polyolefin films such as Super, manufactured by Mitsubishi Plastics Co., Ltd. The static friction coefficient measured using the film as the second test piece (the counterpart material) is preferably 0.3 to 0.5, and more preferably 0.3 to 0.45. If the coefficient of static friction is less than 0.3, the wrapping film is slippery. Conversely, if it exceeds 0.5, the wrapping film tends to stick to the packaging container 1, and the wrapping film tends to be difficult to attach and detach.

[printing]
In order to improve the designability, the packaging container 1 of the present invention may be printed on the surface of the substrate 50, but may be printed on the surface of the water absorbing layer 61 on the container side. According to such printing, not only the appearance of the packaging container 1 is simply modified, but also the one in which the water absorption layer 61 absorbs blood or the like (drip mark) looks like a stain, the same color printing or pattern printing in advance. The effect of making it inconspicuous can be obtained. Such printing is preferably performed lightly so that the liquid absorption on the surface of the water absorbing layer 61 is not hindered by the formation of a film with ink or the filling of the pores of the water absorbing layer 61 with ink. As the printing method, offset printing, rotary offset printing, gravure printing, flexographic printing, letter press printing, inkjet printing, and the like can be used. In addition, since the printing is in direct contact with food, the printing may use ink that does not use raw materials as listed in the “Voluntary Regulations for Printing Inks for Food Packaging Materials” established by the Printing Ink Federation. Preferably, it is more preferable to use an edible ink composed of raw materials according to the Food Sanitation Law and the food additive usage standards.

[Configuration of base material 50 to be a container body]
[Substrate 50]
For the base material 50 serving as a container body constituting the packaging container 1, it is preferable to use a resin sheet made of a thermoplastic resin that can be plastically deformed by heat, for the purpose of later forming into a tray shape as the packaging container 1. . Examples of the thermoplastic resin constituting the substrate 50 include polyethylene resin, polypropylene resin, polystyrene resin, polyamide resin, polyester resin, vinyl chloride resin, and these may be used alone or in combination. Moreover, it may be used as a composite material of these resins and inorganic fillers. The thermoplastic resin constituting the substrate 50 may be, for example, a natural color or colored polypropylene, or may be a filler-filled polypropylene or a foamed polypropylene. Similarly to the olefin-based water-absorbing resin film 60, if the substrate 50 is also made of an olefin-based resin, the packaging container 1 can be easily recycled after use. The thermoplastic resin constituting the substrate 50 may be HIPS (impact polystyrene) or expanded polystyrene. Polystyrene resin is preferable because it easily follows deformation in vacuum forming, drawing, and the like and has good moldability. The layer thickness of the substrate 50 is preferably 250 to 4200 μm, and more preferably 350 to 3900 μm. If the layer thickness is less than 250 μm, the strength tends to be insufficient as a packaging container 1 for containing food or the like. Conversely, if it exceeds 4200 μm, it tends to be difficult to form into a container.

[Forming packaging containers]
In the manufacturing process of the packaging container 1 of the present embodiment, the adhesion between the base material 50 and the olefin-based water-absorbing resin film 60 is variously known as a laminating method such as dry lamination, extrusion lamination, hot melt lamination, and thermal lamination. The method can be adopted. For the adhesion between the resin sheet and the resin film, a dry laminate using an organic solvent-based adhesive may be employed. Here, an adhesion method using thermal lamination will be described with reference to FIG.

  As shown in FIG. 4, while feeding the resin sheet 501 from the base material supply roll 81 around which the resin sheet 501 to be the base material 50 is wound, the olefin-based water absorbent resin film is wound around which the olefin-based water absorbent resin film 60 is wound. The olefin water-absorbing resin film 60 is fed out from the roll 82. The fed-out resin sheet 501 is a resin sheet made of, for example, polystyrene, and the fed-out olefin-based water-absorbing resin film 60 is formed by laminating, for example, a water-absorbing layer 61, a waterproof layer 62, and an adhesive layer 63 containing an ethylene-based resin in this order. is there.

  The fed resin sheet 501 is moved to the dielectric heating roll 86 and the pressing roll 87 by the guide roll 83, and the fed olefin water-absorbing resin film 60 is fed to the dielectric heating roll 86 by the guide roll 84 and the expander roll 85. And moved to the holding roll 87. At this time, a preheating machine (not shown) such as an infrared heater may be installed on the expander roll 85 on the olefin water-absorbing resin film 60 side to preheat the adhesive layer 63 of the film. The olefin-based water-absorbing resin film 60 is drawn out so that the adhesive layer 63 is on the resin sheet 501 side serving as the base material 50.

  The resin sheet 501 heated and pressed by the dielectric heating roll 86 and the pressing roll 87 and the olefin water-absorbing resin film 60 are bonded via the adhesive layer 63 by the heating and pressing, and the base material 50, the adhesive layer 63, the waterproof layer 62, and the water absorption layer 61 are laminated in this order to form a laminated sheet. Next, the laminated sheet is fed to a heating unit and a molding unit (not shown) by a feeding roll 88, and the laminated sheet is heated by a heater or the like in the heating unit, and the laminated film heated by a mold in the molding unit is used as a packaging container 1. Mold to the shape of Conventionally known techniques such as vacuum molding and compression molding can be employed for molding. Thereafter, the packaging container 1 of the present invention can be obtained by trimming the packaging container 1 portion from the molded laminated sheet.

  The packaging container 1 of this embodiment can eliminate the risk of accidental eating of the water-absorbing mat by a kid or pet by adhering the olefin-based water-absorbing resin film 60 to the container body. By adhering the olefin-based water-absorbing resin film 60 over the entire inner surface of the material 50, the moisture and blood from the food are sufficiently absorbed in the bottom and sides in the packaging container 1, and the freshness and taste of the food Thus, it is possible to reliably prevent the appearance from being deteriorated. Further, the water absorption layer 61 located on the container 1 side of the container 1 can sufficiently absorb moisture, blood, etc. from the food, and the water absorption layer 61 is located on the waterproof layer 62 located on the substrate 50 side of the container. It is possible to suppress the influence on the adhesive layer 63 and the like due to moisture held by the container, and conversely prevent components from the adhesive and the like from flowing out to the container 1 side. Furthermore, it is possible to improve moldability, improve water absorption, and improve the detachability of the wrapping film, and can reliably control the flow and storage of moisture and blood from the food.

〔Example〕
Next, examples of the packaging container 1 according to the present embodiment will be described.

  As an example, the packaging container 1 of the embodiment is formed by laminating a waterproof layer 62 and a water absorbing layer 61 in this order on an expanded polystyrene base material 50 via an adhesive layer 63 containing an ethylene-based resin. The material 50 is formed by providing a laminated film of a water absorption layer 61, a waterproof layer 62, and an adhesive layer 63.

The base material 50 is a highly foamed polystyrene obtained by foaming polystyrene having a basis weight of 140 g / m ^{2 at} a foaming ratio of about 10 times with a resin sheet 501 having a layer thickness of 1900 μm (1.9 mm) before heat molding. At the time of the subsequent secondary foaming, the layer thickness of the base material 50 swells to 3800 μm (3.8 mm), which is about twice that maximum, and the foaming ratio is about 20 times.

The olefin water-absorbing resin film 60 was prepared according to the following procedure. First, the raw materials used in the production examples of the olefin-based water-absorbing resin film 60 are shown in Table 1, and the blending examples 1 to 11 of the olefin-based resin composition are shown in Table 2. These are prepared by melting and kneading a resin composition prepared by mixing raw materials described in Table 1 in the proportions described in Table 2 in a biaxial kneader set at 210 ° C., and then in an extruder set at 230 ° C. Extruded into a strand, cut with a strand cutter after cooling to prepare pellets of Formulation Examples 1 to 11, and used in subsequent production examples.

<Production Examples 1-8>
T-die set to 250 ° C. after melt-kneading the resin compositions shown in Table 3 from the resin compositions of Formulation Example 8 to Formulation Example 10 to be the waterproof layer 62 shown in Table 2 with an extruder set at 230 ° C. The sheet was further extruded into a sheet shape and cooled to 60 ° C. with a cooling device to obtain an unstretched sheet. After heating this resin sheet to 140 ° C., it is stretched at a magnification of 5 times in the transport direction (longitudinal direction) of the resin sheet using the peripheral speed difference of the roll group, then cooled at 60 ° C. and uniaxially stretched resin A sheet was obtained. Next, the resin composition of Formulation Example 1, Formulation Example 2, Formulation Examples 4 to 7 to be the water absorbing layer 61 described in Table 2, and the resin composition of Formulation Example 11 to be the adhesive layer 63 described in Table 2 Melted and kneaded with two extruders set at 230 ° C., extruded from a T-die set at 250 ° C. into a sheet shape, melt-laminated on the front and back surfaces of the uniaxially stretched resin sheet, and the water absorption layer 61 / A resin sheet having a laminated structure of waterproof layer 62 / adhesive layer 63 was obtained.

  Next, the resin sheet having this laminated structure is heated again to 155 ° C. using a tenter oven, and stretched at a magnification of 8 times in a direction (lateral direction) orthogonal to the resin sheet conveyance direction by a clip stretching method. Further, heat treatment was performed by heating to 160 ° C. in an oven. Next, it is cooled to 60 ° C., the ears are slit, and a laminated film in which the biaxially stretched waterproof layer 62 is laminated with the uniaxially stretched water absorbing layer 61 and the adhesive layer 63 is obtained. A water-absorbent resin film 60 was obtained. Table 4 shows the thickness, density, and porosity of each layer of the obtained olefin-based water-absorbing resin film 60. In addition, Table 5 summarizes the measurement results of the amount of transferred distilled water and the static friction coefficient measured from the obtained olefin-based water-absorbing resin film 60 by the above-described method.

  About the olefin type water absorbing resin film 60 of the manufacture example 1 and the manufacture example 6, the transfer amount of distilled water was inadequate and it was unsuitable as a water absorbing resin film. Moreover, about the olefin type water absorbing resin film 60 of the manufacture example 5, the rough tearing occurred frequently in the water absorbing layer 61 at the time of transverse stretching, and it was not possible to stably form the film, and the olefin type water absorbing resin film 60 was not obtained. . Therefore, no later evaluation was performed.

<Production Examples 9 and 10>
After melt-kneading the resin composition of Formulation Example 9 to be the waterproof layer 62 shown in Table 2 with an extruder set at 230 ° C., it was extruded into a sheet form from a T-die set at 250 ° C., and this was put into a cooling device. And cooled to 60 ° C. to obtain an unstretched sheet. After heating this resin sheet to 140 ° C., it is stretched at a magnification of 5 times in the transport direction (longitudinal direction) of the resin sheet using the peripheral speed difference of the roll group, then cooled at 60 ° C. and uniaxially stretched resin A sheet was obtained. Then, the resin composition of formulation example 2 which becomes the 1st water absorption layer 611 of Table 2, the resin composition of formulation example 3, and the resin composition of the formulation example 4 which becomes the 2nd water absorption layer 612 of Table 2, Each is melt-kneaded by two extruders set at 230 ° C., supplied to an extrusion die set at 250 ° C., laminated in the die, extruded into a sheet, and melted on the surface of a uniaxially stretched resin sheet. Laminated. Next, the resin composition of Formulation Example 11 to be the adhesive layer 63 shown in Table 2 was melt-kneaded with an extruder set at 230 ° C. and extruded into a sheet form from a T die set at 250 ° C., and uniaxially stretched resin A resin sheet having a laminated structure of the first water absorbing layer 611 / the second water absorbing layer 612 / the waterproof layer 62 / the adhesive layer 63 was obtained by melt lamination on the back surface of the sheet.

  Next, the resin sheet having this laminated structure is heated again to 155 ° C. using a tenter oven, and stretched at a magnification of 8 times in a direction (lateral direction) orthogonal to the resin sheet conveyance direction by a clip stretching method. Further, heat treatment was performed by heating to 160 ° C. in an oven. Next, it is cooled to 60 ° C., the ears are slit, and a laminated film in which the biaxially stretched waterproof layer 62 is laminated with the uniaxially stretched water absorbing layer 61 and the adhesive layer 63 is obtained. A water-absorbent resin film 60 was obtained. Table 4 shows the thickness, density, and porosity of each layer of the obtained olefin-based water-absorbing resin film 60. In addition, Table 5 summarizes the measurement results of the amount of transferred distilled water and the static friction coefficient measured from the obtained olefin-based water-absorbing resin film 60 by the above-described method.

<Production Examples 11 to 13>
In the two extruders set to 230 ° C., the resin composition of Formulation Example 9 to be the waterproof layer 62 described in Table 2 and the resin composition of Formulation Example 4 to be the water absorption layer 61 described in Table 2 After melt-kneading each, it is supplied to an extrusion die set at 250 ° C., laminated in the die and extruded into a sheet shape, cooled to 60 ° C. by a cooling device, and a laminated structure of the water absorption layer 61 / waterproof layer 62 is obtained. The non-stretched sheet was obtained and used as the olefin-based water-absorbing resin film 60 of Production Example 11. Next, this unstretched sheet was heated to 140 ° C., stretched 6 times in the machine direction (MD) using the peripheral speed difference of the roll group, cooled to 60 ° C., and both the water absorption layer 61 and the waterproof layer 62 were uniaxially stretched. A uniaxially stretched resin sheet was obtained and used as the olefin water-absorbing resin film 60 of Production Example 12. Next, this uniaxially stretched resin sheet was heated again to about 155 ° C. using a tenter oven and stretched 9 times in the transverse direction (TD), and then further heated to 160 ° C. for heat treatment. Subsequently, it cooled to 60 degreeC, the ear | edge part was slit, the laminated film which biaxially stretched both the water absorption layer 61 and the waterproof layer 62 was obtained, and this was made into the olefin type water absorption resin film 60 of manufacture example 13. Table 4 summarizes the thickness, density, and porosity of each layer of the obtained olefin-based water-absorbing resin film 60. In addition, Table 5 summarizes the measurement results of the amount of transferred distilled water and the static friction coefficient measured from the obtained olefin-based water-absorbing resin film 60 by the above-described method. The thickness of each layer is set by adjusting the discharge amount of each extruder.

  About the olefin type water absorption resin film 60 of the manufacture example 11, the transfer amount of distilled water was inadequate and it was unsuitable as a water absorption resin film.

<Production Example 14>
Two extrusions in which the resin composition of Formulation Example 9 to be the waterproof layer 62 described in Table 2 and the resin composition of Formulation Example 4 to be the second water absorption layer 612 described in Table 2 were set at 230 ° C. After melt-kneading each in a machine, it is supplied to an extrusion die set at 250 ° C., laminated in the die and extruded into a sheet shape, cooled to 60 ° C. by a cooling device, and the second water absorbing layer 612 / waterproof An unstretched sheet having a layered structure of layers 62 was obtained. After heating this resin sheet to 140 ° C., it is stretched at a magnification of 5 times in the transport direction (longitudinal direction) of the resin sheet using the peripheral speed difference of the roll group, then cooled at 60 ° C. and uniaxially stretched resin A sheet was obtained. Next, the resin composition of Formulation Example 4 to be the first water-absorbing layer 611 described in Table 2 and the resin composition of Formulation Example 11 to be the adhesive layer 63 described in Table 2 are set to individual 230 ° C. Were melt-kneaded by these two extruders, extruded into a sheet form from a T-die set at 250 ° C., melt-laminated on the front and back surfaces of the uniaxially stretched resin sheet, and the first water-absorbing layer 611 / second water-absorbing layer A resin sheet having a laminated structure of layer 612 / waterproof layer 62 / adhesive layer 63 was obtained.

  Next, the resin sheet having this laminated structure is heated again to 155 ° C. using a tenter oven, and stretched at a magnification of 8 times in a direction (lateral direction) orthogonal to the resin sheet conveyance direction by a clip stretching method. Further, heat treatment was performed by heating to 160 ° C. in an oven. Next, it is cooled to 60 ° C., the ear is slit, and the first water absorption layer 611 and the adhesive layer 63 that are uniaxially stretched are laminated on the surfaces of the second water absorption layer 612 and the waterproof layer 62 that are biaxially stretched, respectively. A laminated film was obtained, and this was designated as an olefin-based water-absorbing resin film 60. Table 4 shows the thickness, density, and porosity of each layer of the obtained olefin-based water-absorbing resin film 60. In addition, Table 5 summarizes the measurement results of the amount of transferred distilled water and the static friction coefficient measured from the obtained olefin-based water-absorbing resin film 60 by the above-described method.

<Manufacture of packaging containers using the olefin-based water-absorbing resin film of Production Example>
According to FIG. 4, while the resin sheet 501 before thermoforming is fed from the base material feed roll 81, the olefin-based water-absorbing resin film 60 obtained in Production Examples 2-4, 7-10, 12-14 is wound. The water absorbent resin film was fed from a roll 82. The sheet speed was 6 m / min. The fed resin sheet 501 is moved to the dielectric heating roll 86 and the pressing roll 87 by the guide roll 83, and the fed olefin water-absorbing resin film 60 is fed to the dielectric heating roll 86 and the pressing roll by the guide roll 84 and the expander roll 85. Moved to roll 87. The olefin water-absorbing resin film 60 obtained in Production Examples 2 to 4, 7 to 10 and 14 is formed of the adhesive layer 63 by an infrared heater (not shown) installed on the expander roll 85 on the olefin water-absorbing resin film 60 side. Preheating was performed. Moreover, about the olefin type water-absorbing resin film 60 obtained in Production Examples 12 and 13, a knife coater (not shown) provided immediately before the expander roll 85 is used to attach an adhesive (Toyo Morton Co., Ltd.) to the waterproof layer 62 side. Manufactured, trade name: TM-329 and trade name: CAT-18B mixed solution of equal amounts) were applied so that the solid content was 3 g / m ² . The resin sheet 501 and the olefin water-absorbing resin film 60 heated and pressed by the dielectric heating roll 86 and the pressing roll 87 set at a roll temperature of 110 ° C. and a pressure of 0.3 MPa are passed through the adhesive layer 63 or an adhesive. The laminated sheet was bonded and laminated in the order of the base material 50, the adhesive layer 63 or the adhesive, the waterproof layer 62, and the water absorption layer 61.

  Next, this laminated sheet was fed by a feeding roll 88 and moved to a small continuous indirect heating vacuum forming machine (not shown). The laminated sheet is the heating unit of the same device, the olefin water-absorbing resin film 60 side is 300 ° C., the resin sheet 501 side is a polystyrene foam resin sheet, 150 ° C., the polystyrene non-foam resin sheet is 300 ° C., the foamed polyolefin In the case of a resin sheet, a composite material sheet of 300 ° C., a polyolefin resin sheet, and an inorganic filler is heated for 12 seconds by a heater set at 400 ° C., and then the olefin water-absorbing resin film 60 is placed on the inner side (container side) The laminated sheet heated by vacuum forming was formed into a mold shape. Then, the packaging container 1 part was trimmed from the laminated sheet after shaping | molding, and the packaging container 1 of the Example was obtained.

  Further, each of the packaging container 1 of the example and the polystyrene foamed resin sheet base material 50 alone having a maximum layer thickness of 3800 μm with a water-absorbing mat placed on the bottom of the packaging container accommodates the fried chicken, and closes the lid. A water absorption test was performed to confirm the water absorption state after 3 hours. As a result, in the packaging container 1 of the embodiment, water droplets did not adhere to the bottom 2 or the side wall 3 visually, whereas in the case using the water absorbent mat, water droplets were formed on the side wall of the packaging container or the bottom around the water absorbent mat. It was confirmed that the packaging container 1 of the example exhibited high water absorption.

[Modifications of packaging containers]
In addition to the configurations of the respective inventions, embodiments, modifications thereof, and examples, the invention disclosed in the present specification is changed to other configurations disclosed in the present specification within the applicable range. Specified by adding other configurations disclosed in this specification to these configurations, or by deleting these partial configurations to the extent that partial effects can be obtained. Including the superordinate concept, the following modifications are also included.

  The packaging container of the present invention includes an appropriate structure for adhering a porous olefin-based water-absorbing resin film over the entire surface of the container. The olefin-based water-absorbing resin film 60 includes a water-absorbing layer 61 and a waterproof layer 62, but can have a laminated structure of three or more layers including other layers. For example, in addition to the laminated structure of the first water-absorbing layer 611 and the second water-absorbing layer 612 in which the water-absorbing layer 61 is multilayered, the laminated structure of the combination of the water-absorbing layer 61, the waterproof layer 62, and the adhesive layer 63, the waterproof layer 62 is multilayered. And the like, and those with other known functional layers (for example, a light shielding layer, a gas barrier layer (not shown)) added. Further, the water absorption layer 61 itself may be laminated in three or more layers for the purpose of adding higher liquid absorption capability. For example, the internal water absorption rate (liquid absorption coefficient) may be differentiated in two or more stages so that backflow can be prevented more effectively. For example, the internal layer reacts with moisture such as quicklime. The water absorption may be further increased by using inorganic fine powder, or for example, it may be designed so that oil and moisture can be sufficiently absorbed by laminating water absorption layers with different target liquids. In addition, when the olefin-based water-absorbing resin film 60 and the base material 50 can be bonded to each other without using the adhesive layer 63 and an adhesive, it is also possible to bond them by welding.

  Further, the base material 50 serving as the container body may be not only a single-layer resin sheet but also a multi-layered one. For example, an adhesive layer for enhancing adhesiveness may be provided on the surface in contact with the olefin-based water-absorbing resin film 60, or other known functional layers (for example, a light shielding layer, a gas barrier layer, etc.) may be added.

  The present invention can be used for packaging containers in which foods such as meats, seafood, and fried foods are stored.

DESCRIPTION OF SYMBOLS 1 ... Packaging container 2 ... Bottom part 3 ... Side wall 4 ... Edge part 50 ... Base material of container main body 501 ... Resin sheet 60 ... Olefin type water absorption resin film 61 ... Water absorption layer 611 ... First water absorption layer 612 ... Second water absorption Layer 62 ... Waterproof layer 63 ... Adhesive layer 81 ... Base material feed roll 82 ... Olefin-based water absorbent resin film feed roll 83, 84 ... Guide roll 85 ... Expander roll 86 ... Dielectric heating roll 87 ... Presser roll 88 ... Feed roll

Claims (9)

A packaging container comprising a base material of a container body and a porous olefin-based water-absorbing resin film adhered to the whole surface of the base material,
The olefin-based water-absorbing resin film is formed by laminating a water-absorbing layer and a waterproof layer,
The surface on the waterproof layer side is bonded to the base material, the surface on the water absorption layer side is disposed on the container side of the container,
The water-absorbing layer contains 25 to 55% by weight of an olefin resin and 45 to 75% by weight of inorganic fine powder whose surface is treated with a hydrophilizing agent, and is stretched at least in a uniaxial direction. container.   The packaging container according to claim 1, wherein the water absorption layer has a porosity of 28 to 80%.   The waterproof layer contains an olefin resin and an inorganic fine powder, is stretched at least in a uniaxial direction, and has a porosity of 0 to 25%, which is smaller than the porosity of the water absorption layer. The packaging container according to claim 1 or 2.   The water absorption layer has a multilayer structure in which a first water absorption layer on the container side and a second water absorption layer on the waterproof layer side are laminated, and the liquid absorption coefficient of the second water absorption layer is the first The packaging container according to any one of claims 1 to 3, which has a liquid absorption coefficient larger than that of the water absorption layer.   The porosity of the first water absorption layer is 31 to 51%, the porosity of the second water absorption layer is 40 to 62%, and the porosity of the second water absorption layer is the first porosity. The packaging container according to claim 4, wherein the packaging container has a larger porosity than the water absorption layer.   The packaging container according to any one of claims 1 to 5, wherein a surface of the base material and the waterproof layer side of the olefin-based water-absorbing resin film are bonded via an adhesive. The olefin-based water-absorbing resin film is formed by laminating a water-absorbing layer, a waterproof layer, and an adhesive layer made of an olefin-based resin in this order,
The packaging container according to any one of claims 1 to 5, wherein the base material and the olefin-based water-absorbing resin film are bonded by thermal fusion bonding of the adhesive layer.   The packaging container according to any one of claims 1 to 7, wherein the inorganic fine powder in the water absorption layer is calcium carbonate. The base material includes at least one resin selected from the group consisting of polyethylene resin, polypropylene resin, polystyrene resin, polyamide resin, and polyester resin, or a composite material of these resins and an inorganic filler. The packaging container according to any one of claims 1 to 8.

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