JPH0144581B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a three-dimensional packaging container that can be easily heated, and more specifically, a packaging container that can easily undergo heating operations such as heat sterilization of the contents or warming the contents before meals. The present invention relates to a three-dimensional container. Prior Art and Technical Problems of the Invention Metal cans have been used for many years as packaging containers that have almost perfect sealing properties, gas barrier properties, and excellent shape retention, but in recent years metal cans have become difficult to dispose of. This has led to the problem of so-called can pollution. As an alternative to metal cans, various three-dimensional packaging containers made of plastic have come into wide use in recent years. However, the biggest disadvantage of three-dimensional plastic containers is that plastic has low thermal conductivity, and as a result, the container walls act as a heat transfer barrier, and it takes an extremely long time to sterilize the contents or heat the contents for eating. It means that it is necessary. For example, in Japanese Patent Publication No. 58-35458 and No. 59-18263, a plastic container with excellent shape retention and gas barrier properties is proposed by wrapping a metal foil laminate around the outer circumferential surface of a plastic body with openings at both ends. However, it has been proposed that a lid body is engaged with the openings at both ends and sealed by heat sealing. Although this composite container has an excellent combination of shape retention due to the plastic body and gas barrier properties due to the metal foil laminate, the thickness of the plastic body that provides shape retention to the container does not allow it to move in the cross-sectional direction of the container. The heat conduction of the container becomes extremely poor, and it becomes necessary to take an extremely long time for the above-mentioned heat sterilization (retort sterilization) and for heating the contents during consumption. OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide a three-dimensional packaging container made of plastic that overcomes the above-mentioned drawbacks of conventional plastic containers. Another object of the present invention is to have excellent thermal conductivity;
To provide a three-dimensional packaging container made of plastic that can be easily heated. Still another object of the present invention is to provide a three-dimensional plastic packaging container that is easily heated and is formed from a thermoplastic resin containing metal fiber staples and in which the metal fiber staples are protected from corrosion. Structure of the Invention According to the present invention, the aspect ratio (l/d) is 2.
There is provided a three-dimensional packaging container that is easy to heat and is characterized by comprising at least one layer of thermoplastic resin containing the metal fiber staples described above. According to the invention, the aspect ratio (l/d)
Provided is a three-dimensional packaging container that is easy to heat and is characterized by comprising a base layer made of a thermoplastic resin containing two or more metal fiber staples, and a protective resin layer located at least on the inner surface of the base layer. . Characteristics and Effects of the Invention The present invention is characterized in that the aspect ratio is within a certain range, that is, 2.
The knowledge that high thermal conductivity can be obtained with a relatively small blending ratio when metal fibers within the above range are blended into a thermoplastic resin is applied to plastic three-dimensional containers. Since the thermal conductivity of metal is extremely high (2 to 3 orders of magnitude) compared to resin, the thermal conductivity of a resin composition containing metal as a filler is also greatly improved. The thermal conductivity of this blended composition is greatly influenced by the metal filling rate (mixing ratio) as well as the aspect ratio (ratio of length (l) to diameter (d)) of the metal filler. Expressed as a formula, it is as shown below. k=k ₁ (1+ABφ ₂ )/(1−BΨφ ₂ ) A=f|l/d| B=(k ₂ /k ₁ −1)/(k ₂ /k ₁ +A) Ψ=1+[(1− φm)/φ ² m〕φ ₂ However, k: Thermal conductivity of thermoplastic resin filled with metal filler k ₁ : Thermal conductivity of thermoplastic resin k ₂ : Thermal conductivity of metal filler l/d: Aspect of metal filler Ratio φ ₂ : Filling rate of metal filler φm : Closest packing rate of metal filler Also, the value of A=f|l/d| is as shown in Table 1, and φm is for non-oriented fibrous filler.
It is 0.52.

【table】

[Table] From the above equation, it is clear that when metal fibers with a large aspect ratio are blended into the resin, the thermal conductivity can be significantly improved with a relatively small amount blended. According to the present invention, by using the resin composition blended with the metal fiber staples described above as the wall-constituting material of the three-dimensional container, the thermal conductivity of the container wall is increased, and, for example, heat sterilization or heating before consuming the contents is facilitated. The advantage is achieved that the process can be carried out within a relatively short period of time. However, since the metal fiber staple blended into the resin is of course a good conductor of electricity, it has the advantage that the above-mentioned heating can be easily and efficiently performed by high-frequency heating. Furthermore, the metal fibers blended into the resin have the advantage of increasing the rigidity of the blended composition to the limit required for three-dimensional containers, increasing the heat distortion temperature of the container, and improving the heat resistance of the container. In a preferred embodiment of the present invention, a resin layer containing metal fibers is used as a base layer, and a protective resin layer containing no metal fibers is provided on at least the inner surface, preferably both surfaces, of this base layer. Although metal fibers have the above-mentioned advantages, they have the disadvantage of being inferior in corrosion resistance compared to resins, but according to this preferred embodiment of the present invention, a protective resin is added on the metal fiber-containing resin base layer. By providing the layer, it is possible to prevent the occurrence of corrosion such as rust on the metal fibers and the tendency of metals to be leached into the contents, and also to significantly improve the appearance characteristics of the container wall. The present invention will be described in detail below with respect to its embodiments. Embodiments of the Invention In the present invention, as the metal fiber, a metal fiber obtained by any method known per se such as a melt spinning method, a stretching method, an extrusion method, a cutting method, a chatter vibration cutting method, etc. is used. The types of metals that make up the fibers are
It can be of any material such as steel, cast iron, stainless steel, brass, copper, aluminum, etc., with the formula l/d
(In the formula, l is the length of the metal fiber, and d is the diameter of the metal fiber.)
It is important for the purpose of the present invention that the aspect ratio defined by . In other words, when the amount of metal fibers blended is set to a constant value in a relatively low range and the aspect ratio of the metal fibers is changed, the thermal conductivity of the blended resin composition will sharply increase when the aspect ratio exceeds a certain standard. It shows a tendency to increase. This is thought to be because when the aspect ratio of the filled metal fibers exceeds a certain standard value, they come into almost uniform contact within the matrix, forming a stable heat conduction path. The preferred metal fiber has a diameter of 1 to 1000μ.
m, especially from 5 to 100 μm, and the staple length is from 0.1 to 1000 mm, especially from 0.5 to 100 mm. Any thermoplastic resin that can be thermoformed can be used as the resin for blending the metal fibers, such as low-, medium-, or high-density polyethylene, crystalline polypropylene, crystalline ethylene, etc.
Olefin resins such as propylene copolymers, propylene-butene copolymers, and ionically crosslinked olefin copolymers; styrene resins such as polystyrene, styrene-butadiene copolymers, and styrene-butadiene-acrylonitrile copolymers; polycarbonates; Polyester; polyamide; acrylic resin; polyacetal resin, etc. are used. Among these, in terms of economy and ease of manufacture,
Olefin resins are preferred, and polypropylene is most preferred in terms of retort sterilization. The amount of metal fiber added to the thermoplastic resin varies depending on the aspect ratio and diameter of the metal fiber, but it is preferably in the range of 1 to 60 volume%, especially 5 to 40 volume% based on the resin. desirable. That is, if it falls below this range, no significant improvement in thermal conductivity can be expected, while if it exceeds the above range, the thermoformability into containers will deteriorate and the mechanical properties of the containers will also deteriorate. . The resin and the metal fibers are easily mixed by dry blending the two and, if necessary, kneading this mixture under conditions in which the resin is melted. The kneading operation may be performed using, for example, a roll, a kneader, a pelletizer, etc., or may be performed within a cylinder of an extruder, injection machine, etc. The three-dimensional packaging container according to the present invention can be manufactured by means known per se, except for using the metal fiber-containing resin described above. In addition, the structure of the container itself is
The container may be a single-layer container made of a resin composition containing metal fibers, or may be a laminated container comprising a layer of a resin composition containing metal fibers, another resin layer, a metal foil layer, or any one of the layers. For example, the container can be formed by melt-extruding the composition into a parison shape and then blow-molding it into a bottle shape, or by directly injecting it into a mold with a container-shaped cavity. It can also be done by Further, by preparing a sheet of the above composition and subjecting this sheet to vacuum forming, pressure forming, plug assist forming, stretch forming, etc., a cup-shaped bottomed container can be obtained. In addition, by once forming a pipe or a bottomed preform by extrusion or injection, and subjecting this pipe or bottomed preform to axial tension stretching and circumferential expansion stretching at the resin stretching temperature, It is also possible to obtain a container in which the resin matrix has biaxial molecular orientation. Furthermore, melt extruding the composition into a pipe shape,
This can be cut to a predetermined size to form a container body with both open ends sealed. An example of the container of the present invention is shown in FIGS. 1 and 2, which comprises a seamless body 1 and lids 4a and 4b attached to both open ends 2 and 3 of the body. The body 1 is formed from the resin composition described above, and as shown in the enlarged cross-sectional view of FIG. There is. A lining of a metal foil-containing laminate generally indicated by 7 is formed on the inner surface of the body 1 made of metal fiber-containing resin. Laminate layer 7 applied to the inner surface of this cylindrical body 1
As is clear from the cross-sectional view of FIG. 2, it consists of a laminate of a metal foil 8, a heat-sealable resin layer 9 inside the metal foil, and a resin layer 10 outside the metal foil. The laminate layer 7 is applied to the inner surface of the cylindrical body 1 in the form of a sheet having a dimension slightly larger in the lateral direction than the unfolded dimension of the body 1, and the seam 7 is formed by overlapping both ends of the sheet. ' is formed. The lids 4a, 4b are fixed to the open ends 2, 3 of the container body by means known per se, such as heat sealing, seaming, gluing, or the like. The thickness of the body portion 1 is desirably within a range of about 0.2 to 2 mm so as to obtain sufficient shape retention. In FIG. 3 showing another laminate suitable for forming the container of the present invention, this laminate 11 has a base layer 12 made of a metal fiber-containing resin composition, and metal fibers applied to both surfaces of the base layer 12. It consists of unblended protective resin layers 13 and 14. Protective resin layers 13 and 1
Preferably, 4 is a resin that has thermal adhesion to the resin layer constituting the base layer 12, and most preferably is the same type of resin as the resin layer constituting the base layer 12. The protective resin layers 13 and 14 have a thickness of 1/100 to 1/5 of the thickness of the base layer 12, and have a thickness of 3 in the final container shape.
A thickness of 400 μm to 400 μm, particularly 5 to 100 μm is desirable in order to prevent metal corrosion and metal elution without impairing excellent thermal conductivity. This type of laminate can be easily formed by coextruding a metal fiber-containing resin composition and a resin without metal fibers through a multilayer die, and by using this laminate, the cross section shown in FIG. A hollow-molded container such as a bottle, a pipe-shaped container body, and a cup-shaped container with a bottom are obtained. Alternatively, a laminated sheet for use in vacuum forming or the like can be easily obtained by extruding a resin melt containing metal fibers between resin films containing no metal fibers, and by so-called Sand-German lamination. In this laminated structure container of the present invention, the exposure of metal fibers to the outer surface is effectively prevented, and significant advantages are achieved in terms of appearance characteristics and corrosion prevention, as well as surface smoothness, heat sealability, and hygiene. physical characteristics etc. are also improved. In particular, as the protective resin layers 13 and 14, titanium dioxide, iron oxide, zinc oxide, barium sulfate,
Blending a pigment such as calcium carbonate has the advantage that the metal fiber blended layer is hidden and the appearance characteristics are further improved. The invention is illustrated by the following example. Examples 1 to 4 Thermoplastic resins and metal fibers shown in Table 2 were mixed using a two-roll calendar roll mill at the filling rates also shown in Table 2 to obtain composite materials in which metal fibers were uniformly dispersed. . Next, a pipe with an inner diameter of 52.3 mm and a wall thickness of 0.6 mm was extruded using the metal fiber-filled composite material and cut into a length of 135 mm. Furthermore, a modified polypropylene resin powder (melting point: 160°C), which has been graft-polymerized, was coated on aluminum foil with a thickness of 15 μm (average film 7 μm thick) to form a laminate. Furthermore, after laminating polyethylene terephthalate with a thickness of 12 μm on the aluminum foil surface of the laminate using a urethane adhesive, a copolyester resin is applied thereon with a thickness of 30 μm by extrusion coating,
A laminate for inner surface coating was prepared. Next, the laminate is slit to have a length of 135 mm and a width of 175 mm, one end of which is bent 5 mm in the width direction so that the polypropylene layer is on the inside to form a folded part, and the laminate sheet is folded back. The polypropylene pipe is wound on a mandrel so that the folded end faces outward, and the folded end and the other end are overlapped to form a cylindrical laminate, and the polypropylene pipe is placed on the outside of this cylindrical laminate. It was fitted on the outside of the cylindrical laminate. Next, the diameter of the mandrel is expanded outward, and while the cylindrical body is pressed against the inner surface of the pipe, the joints of the laminate are simultaneously heated and bonded using a high-frequency heating coil provided on the outer periphery of the mandrel. A composite can was made. One open end of the plastic/metal foil composite can thus obtained has a liquid pot-type score and tab made of a laminate of 5 μm epoxy phenol resin/100 μm aluminum foil/12 μm polyethylene terephthalate/20 μm copolyester. The lid and body were thermally fused by high-frequency induction heating of the lid material. The plastic can with this lid attached was filled with 250 ml of coffee, and a lid having the same structure as the lid was heat-bonded to the opening in the same manner. The sealed can thus obtained was heat sterilized in a hot water retort at 125°C for 20 minutes. F ₀ in the center of coffee for Example 1
When the value (heating time [minutes] required to kill a certain concentration of bacteria or spores at a certain temperature) was measured, it was 11.7, indicating that the sterilization conditions were sufficient. Moreover, when the top lids of Examples 1 to 4 were opened and the coffee was sampled, the flavor was very good, and no off-taste or odor was observed at all. Examples 5 and 6 In Example 1, the composite materials shown in Table 2 were used as pipe materials, and nylon 6 was used instead of maleic anhydride-modified polypropylene in the inner coating laminate.
Example 1 except that (melting point 215°C, density 1.14 g/cm ³ , relative viscosity 2.3) was laminated by extrusion coating method.
A plastic/metal foil composite can was fabricated in the same manner as above. The plastic/metal foil composite can thus obtained was filled with coffee in the same manner as in Example 1.
Heat sterilization was performed in a hot water retort at 125°C for 20 minutes. F ₀ in the center of coffee for Example 6
When the value was measured, it was 13.2, indicating that the sterilization conditions were sufficient. Furthermore, when the top lids of the coffees of Examples 5 and 6 were opened and the coffee was sampled, the flavor was very good and no unusual odor was observed. Comparative Example 1 The pipe in which only polypropylene as a matrix resin was used as the pipe material in Example 1 was filled with coffee and subjected to hot water retort heat sterilization at 125°C for 20 minutes. When the F ₀ value of the center of the coffee was measured, it was 7.8, indicating that the sterilization conditions were insufficient for coffee.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a perspective view of a container using the thermoplastic resin containing metal fiber staples of the present invention, and FIG. 2 is a cross-sectional perspective view showing an enlarged cross-section of the cylinder shown in FIG. FIG. 3 is a cross-sectional perspective view of a laminate used for a container that is another specific example of the present invention. Reference code 1 is a seamless body, 2 and 3 are both open ends, 4a and 4b are lids, 5 is a matrix resin, 6 is a metal fiber staple, 7 is a metal foil-containing laminate, 8 is a metal foil, and 9 is a heat-sealable resin layer,
10 is a metal foil outer resin layer, 11 is a laminate, 12 is a resin composition containing metal fibers, and 13 and 14 are protective resin layers.

Claims (1)

[Scope of Claims] A three-dimensional packaging container that is easy to heat and is characterized by comprising at least one layer of thermoplastic resin blended with metal fiber staples having an aspect ratio (l/d) of 1 or more. 2. An easily heated material comprising a base layer made of a thermoplastic resin blended with metal fiber staples having an aspect ratio (l/d) of 2 or more, and a protective resin layer located at least on the inner surface of the base layer. Three-dimensional packaging container.