JP4991345B2 - Laminated sheet for thermoforming and packaging container - Google Patents

Description

  The present invention relates to a thermoplastic resin sheet having heat insulation, heat resistance, oil resistance, heat resistance capable of heating in a microwave oven, improved rigidity and surface smoothness, and a packaging container obtained by molding the sheet. About. The packaging container of the present invention is suitably used as a packaging container for packaging foods such as cooked foods and prepared vegetables.

  In thermoplastic resin sheets, which are materials for packaging containers used for packaging foods and the like, polyolefin resin foams, especially polypropylene resin foams, are often used as materials and containers aimed at heat and oil resistance. Polypropylene resin foam has heat resistance that can be heated in a microwave oven, but is less rigid than polystyrene resin foam, and its weight can be increased by holding one of the containers by hand when the contents are heated. There is a risk that the contents may spill due to bending. If the container is thickened to increase rigidity or the expansion ratio is kept low, there is a problem that the container becomes heavy and the material cost increases.

Conventionally, for example, techniques disclosed in Patent Documents 1 and 2 have been proposed for thermoforming laminated sheets and packaging containers using polypropylene-based resins.
Patent Document 1 discloses a laminated sheet in which a non-foamed layer having a specific melt tension containing a polypropylene resin and a filler is laminated on at least one side of a polypropylene resin foam layer in order to increase the rigidity of the polypropylene resin foam. A thermoformed packaging container is disclosed.
In Patent Document 2, a sheet obtained by laminating a filler-containing polypropylene foam layer as an intermediate layer and a filler-containing or non-containing thermoplastic resin layer as a surface layer is molded with a temperature difference on one side of male and female, and the thickness distribution or A container molding method that results in uniform foaming is disclosed.

On the other hand, polystyrene resin foam, which is the main material for packaging containers, has poor oil resistance and low heat resistance, and therefore cannot be used for microwave oven heating. Patent Document 3 proposes a packaging container composed of a sheet in which a polyolefin film is laminated on both surfaces of a foamed layer composed of a mixed resin of a polyolefin resin and a polystyrene resin and an inorganic filler, in order to improve the point. Yes.
JP 2003-225978 A JP 7-186292 A Japanese Patent Publication No. 5-23589

However, the above-described conventional technique has the following problems.
Since the container disclosed in Patent Document 1 contains a large amount of filler in the non-foamed layer, there is a problem that the container becomes heavy and the surface smoothness is impaired.
Since the container disclosed in Patent Document 2 is molded with a double-sided mold, there is a problem that the cost is increased and the molding speed is also slow.
The container disclosed in Patent Document 3 has a problem that the compatibility between the polypropylene and the styrene resin of the foam layer is insufficient, and the heat resistance and rigidity are not sufficient.

  The present invention has been made in view of the above circumstances, has heat insulation, heat resistance, oil resistance, heat resistance that can be heated in a microwave oven, and has improved rigidity and surface smoothness. An object of the present invention is to provide a packaging container.

In order to achieve the above object, the present invention provides a foamed layer (A) comprising a composition containing 0.5 to 33 parts by mass of an inorganic filler with respect to 100 parts by mass of a polyolefin resin, and a polyolefin resin on one or both sides thereof. A non-foamed reinforcing layer (B) comprising a composition containing 3 to 70 parts by mass of an inorganic filler with respect to 100 parts by mass, and a non-foamed surface layer comprising a composition mainly comprising a polyolefin resin on the outermost surface ( C) and laminated sheets,
The foam layer (A) has a thickness in the range of 0.1 mm to 2.0 mm, an open cell ratio of 30% or less,
The reinforcing layer (B) has a thickness in the range of 0.05 mm to 2.0 mm,
The surface layer (C) has a surface roughness Rz of 15 μm or less,
The laminated sheet provides a laminated sheet for thermoforming characterized by having a thickness in the range of 0.2 mm to 2.5 mm and a density in the range of 0.15 to 1 g / cm ³ .

The present invention mainly comprises a foamed layer (A), a non-foamed reinforcing layer (B) made of a composition containing a polyolefin resin and an inorganic filler on one or both sides, and a polyolefin resin on the outermost surface. A sheet laminated with a non-foamed surface layer (C) comprising a composition,
The resin of the foam layer (A) is from a composition containing (a1) 50 to 96 parts by mass of a polyolefin resin, (a2) 3 to 40 parts by mass of a polystyrene resin, and (a3) 0.5 to 10 parts by mass of a rubber resin. The inorganic filler in the foam layer (A) is in the range of 0.2 to 33 parts by mass with respect to 100 parts by mass of the resin, and the foam layer (A) is in the range of 0.2 to 2.0 mm in thickness. Yes, the open cell rate is 30% or less,
The reinforcing layer (B) includes 3 to 70 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin, and has a thickness of 0.05 to 2.0 mm.
The surface layer (C) has a thickness in the range of 0.003 to 0.3 mm, a surface roughness Rz of 15 μm or less,
The laminated sheet provides a laminated sheet for thermoforming characterized by having a thickness in the range of 0.3 to 2.5 mm and a density in the range of 0.15 to 1 g / cm ³ .

  In the laminated sheet for thermoforming of the present invention, the surface layer (C) is preferably made of a polypropylene resin.

  In the thermoformed laminated sheet of the present invention, the surface layer (C) is preferably made of a resin composition containing 0.5 to 17 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin.

  The laminated sheet for thermoforming of the present invention is preferably formed by laminating a film or a printed film (D) on one side or both sides of the laminated sheet.

  Moreover, this invention provides the packaging container formed by thermoforming the laminated sheet for thermoforming which concerns on this invention mentioned above in a container shape or a container shape with a lid | cover.

Moreover, this invention is inorganic with respect to 100 mass parts of polyolefin-type resin on the foam layer (A) which consists of a composition which contains 0.5-33 mass parts of inorganic fillers with respect to 100 mass parts of polyolefin-type resin, and the single side | surface or both surfaces. A non-foamed reinforcing layer (B) made of a composition containing 3 to 70 parts by mass of a filler and a non-foamed surface layer (C) made of a composition mainly comprising a polyolefin resin were laminated on the outermost surface. A packaging container formed by thermoforming a sheet,
The density of the entire container is in the range of 0.15 to 1 g / cm ³ ;
The thickness of the bottom of the container is in the range of 0.1 to 2.5 mm;
The open cell ratio of the curved portion at the boundary between the bottom and the side wall is 55% or less,
The packaging container is characterized in that the surface roughness Rz of the flat part on the inner surface side of the container at the bottom is 20 μm or less.

In the present invention, the foamed layer (A), the reinforcing layer (B) containing the filler-containing polyolefin resin layer on one or both sides, and the surface layer (C) containing the polyolefin resin on the outermost surface are laminated. A packaging container in which a sheet is formed,
The resin of the foam layer (A) is from a composition containing (a1) 50 to 96 parts by mass of a polyolefin resin, (a2) 3 to 40 parts by mass of a polystyrene resin, and (a3) 0.5 to 10 parts by mass of a rubber resin. And the inorganic filler in the foam layer (A) is in the range of 0.2 to 33 parts by mass with respect to 100 parts by mass of the resin,
The reinforcing layer (B) includes 3 to 40 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin,
The density of the entire container is in the range of 0.15 to 1 g / cm ³ ;
The thickness of the bottom of the container is in the range of 0.1 to 2.5 mm;
The open cell ratio of the curved portion at the boundary between the bottom and the side wall is 55% or less,
Provided is a packaging container characterized in that the surface roughness Rz of the flat part on the inner surface side of the bottom part is 20 μm or less.

  In the packaging container of the present invention, it is preferable that a back-printed film layer (D) is formed on at least the inner surface side of the container. This film (D) can contain, for example, titanium oxide (white) and other colorants.

  According to the present invention, the laminated sheet for thermoforming having heat insulation, heat resistance, oil resistance, heat resistance that can be heated in a microwave oven, improved rigidity and surface smoothness, and obtained by molding the sheet. A packaging container can be provided.

  FIG. 1 is a cross-sectional view showing an embodiment of a laminated sheet for thermoforming according to the present invention. The laminated sheet 1 for thermoforming according to this embodiment includes a foam layer 2 (A layer) made of a composition containing 0.5 to 33 parts by mass of an inorganic filler with respect to 100 parts by mass of a polyolefin resin, and a polyolefin group on both surfaces thereof. Non-foamed reinforcing layer 3 (B layer) made of a composition containing 3 to 70 parts by weight of an inorganic filler with respect to 100 parts by weight of the resin, and a non-foamed surface made of a composition mainly comprising a polyolefin resin on the outermost surface The layer 4 (C layer) is laminated.

Note that the layer configuration shown in FIG. 1 is merely an example of the present invention, and the present invention is not limited only to this illustration. For example, the reinforcing layer 3 (B layer) may be laminated only on one side of the foam layer 2 (A layer), or the surface layer 4 (C layer) may be formed by placing the B layer on one side of the A layer. In the case of laminating only the B layer, it may be laminated only on the outside of the B layer, or the C layer may be provided on both the outside of the B layer and the outside of the A layer on the side where the B layer is not provided.
Below, the detail of the material used in the laminated sheet for thermoforming of this invention is described.

(Polyolefin resin)
Examples of the polyolefin resin used in the laminated sheet for thermoforming of the present invention include low density polyethylene, high density polyethylene, linear low density polyethylene, isotactic polypropylene, syndiotactic polypropylene, attack polypropylene, and other polypropylene, ethylene- Propylene random polymer, ethylene-propylene block copolymer, ethylene-propylene butene copolymer, propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymer (for example, Ethylene-methyl methacrylate copolymer), ethylene-unsaturated carboxylic acid metal salt copolymer (for example, ethylene-magnesium acrylate (or zinc) copolymer), propylene-butene copolymer, propylene-none Maleic acid copolymer, propylene-olefin copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer), modified product of unsaturated carboxylic acid (eg maleic anhydride) of polyethylene or polypropylene, and the like The mixture of 2 or more types is mentioned. Polypropylene such as a propylene homopolymer or a polypropylene copolymer containing 50 mol% or more of propylene units is particularly preferred.

(Polystyrene resin)
As the polystyrene resin used in the laminated sheet for thermoforming according to the present invention, monomers such as styrene, methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, paramethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene, and the like are used. A resin obtained by homopolymerization or a resin obtained by copolymerizing two or more of these monomers can be used. Particularly preferred is homopolystyrene (PS). Multi-branched polystyrene (manufactured by Dainippon Ink & Chemicals, trade name “HP550P”) can also be used. When heat resistance is required, for example, a heat-resistant polypolystyrene resin comprising a styrene copolymer containing 3 to 15% by mass of the monomer and acrylic acid, methacrylic acid, acrylonitrile, and maleic anhydride is used. May be.

(Rubber resin (1): High impact polystyrene resin)
One of the rubber-based resins used in the laminated sheet for thermoforming according to the present invention is a high-impact polystyrene-based resin (hereinafter referred to as HIPS). This HIPS is a rubber-modified polystyrene in which a rubber polymer such as polybutadiene or a styrene-butadiene block copolymer is dissolved in a styrene monomer, and then graft-polymerized with styrene on the butadiene rubber-like polymer. A rubber-modified polystyrene resin in which the rubber content in the salami and a portion of the polystyrene outside the salami are bonded, or a styrene monomer is polymerized by a bulk polymerization method or a suspension polymerization method. This refers to a rubber-modified polystyrene resin obtained by heating and kneading polystyrene and a styrene-butadiene block copolymer rubber using a general kneader such as a uniaxial or multi-screw extruder or a Banbury mixer. As the styrenic monomer used here, styrene is generally used, but α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and the like can also be used. The amount of styrene contained in HIPS is preferably 91 to 97% by mass.

(Rubber resin (2): Styrene-conjugated diolefin thermoplastic elastomer)
Another example of the rubber-based resin used in the laminated sheet for thermoforming of the present invention is a styrene-conjugated diolefin-based thermoplastic elastomer (hereinafter referred to as SBS). This SBS is a thermoplastic elastomer composed of a styrene polymer block and a conjugated diolefin polymer block, and has a conjugated double bond in the main chain as represented by a styrene-butadiene thermoplastic elastomer. Have. Examples of the monomer constituting the styrenic polymer block include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, vinylnaphthalene, vinylanthracene and the like, and particularly styrene. These can be used alone or as a mixture of two or more according to the purpose. The monomer constituting the conjugated diolefin polymer block is a diolefin having a conjugated double bond, such as 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, and the like. It is done. These can be used alone or as a mixture of two or more according to the purpose. Of these block copolymers, styrene-butadiene block copolymers are particularly preferred. The amount of styrene contained in SBS is preferably 10 to 70% by mass.

(Rubber resin (3): styrene-butadiene-butylene-styrene thermoplastic elastomer)
Still another example of the rubber-based resin used in the laminated sheet for thermoforming according to the present invention is styrene-butadiene-butylene-styrene thermoplastic elastomer (hereinafter referred to as SBBS). SBBS is a copolymer composed of three or more monomers typified by a polymer in which a specific portion of a double bond of a styrene-butadiene block polymer is selectively hydrogenated, and has a double bond in a part of the molecule. It is a copolymer. A preferred SBBS in the present invention comprises a styrene polymer block at both ends which is a hard segment and an olefin polymer (butadiene / butylene) block which is a soft segment in the middle, and is a styrene-butadiene-styrene block copolymer. It is obtained by partially adding hydrogen to an elastomeric butadiene block. Examples of styrenic polymers used here are styrene, α-methylstyrene, p-methylstyrene, and mixtures thereof. The amount of styrene contained in SBBS is preferably 30 to 70% by mass.

(Rubber resin (4): Styrene-ethylene-butylene-styrene thermoplastic elastomer)
Still another example of the rubber-based resin used in the laminated sheet for thermoforming of the present invention includes styrene-ethylene-butylene-styrene thermoplastic elastomer (hereinafter referred to as SEBS). This SEBS is composed of a styrene polymer block at both ends, which is a hard segment, and an olefin polymer (ethylene / butylene) block, which is a soft segment in the middle, and butadiene of a styrene-butadiene-styrene block copolymer elastomer. Obtained by complete hydrogenation of the block. Examples of styrenic polymers used here are styrene, α-methylstyrene, p-methylstyrene, and mixtures thereof. The amount of styrene contained in SEBS is preferably 10 to 70% by mass.

(Inorganic filler)
Examples of the inorganic filler used in the thermoformed laminated sheet of the present invention include silica, alumina, calcium carbonate, talc, clay, mica, glass balloon, glass beads, calcium silicate, glass fiber, and carbon fiber. Among these, talc having an average particle diameter of 1 to 30 μm is particularly preferable. These inorganic fillers can be used alone or in combination of two or more. As the inorganic filler used for the foam layer (A layer), foam cells are likely to be uniform, and those having a small average particle size are suitable. Talc having an average particle size of 0.6 to 12 μm is preferred. Since the filler used for the B layer (reinforcing layer) is likely to have rigidity, a relatively large one having an average particle size of about 5 μm is suitable. Talc having an average particle size of 2 to 8 μm is preferred.

(Foaming agent, bubble regulator)
Examples of the foaming agent used for producing the foam layer (A layer) include a volatile foaming agent and a chemical foaming agent.
Examples of the volatile blowing agent include gases such as carbon dioxide, nitrogen, and air; volatile hydrocarbons such as propane, butane, and pentane; halogenated hydrocarbons such as methyl chloride.
Chemical foaming agents include sodium bicarbonate, anhydrous monosodium citrate, ammonium carbonate, azodicarbonamide, 4,4'-oxybisbenzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide, N, N'-dinitrosopentamethylenetetramine Etc. are exemplified.
As a compounding quantity of a foaming agent, the inside of the range of 0.1-6 mass parts is preferable with respect to 100 mass parts of resin for foaming layers. The type and amount of the foaming agent are appropriately selected depending on the foaming ratio and sheet extrusion conditions.
In the present invention, in order to foam the foamed layer (A layer) well, a cell regulator may be added to the resin composition of the foamed layer. Examples of the foam regulator include inorganic organic composite foam regulators such as sodium bicarbonate-citric acid compound; talc, silicon oxide, titanium oxide, magnesium oxide, aluminum oxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, carbonate Inorganic foam regulators such as potassium, calcium carbonate, tribasic lead sulfate, dibasic lead phosphite and boric acid; cellulose powder, wood flour, higher fatty acid metal salts such as calcium stearate, magnesium stearate and zinc stearate And organic bubble regulators such as organic tin compounds such as urea and dibutyltin dimaleate.

[Foamed layer (A layer)]
In the laminated sheet for thermoforming of the present invention, the foam layer is a foam layer of a composition containing 0.5 to 33 parts by mass of an inorganic filler with respect to 100 parts by mass of the polyolefin resin. This foamed layer is formed by extrusion foaming a composition containing a polyolefin, particularly a resin mainly composed of a polypropylene resin, an inorganic filler, and a foaming agent. This foam layer may be blended with polystyrene resin or rubber resin in order to increase rigidity.

  The amount of the inorganic filler in the resin composition constituting the foamed layer is in the range of 0.5 to 33 parts by mass of the inorganic filler with respect to 100 parts by mass of the resin. If the amount of the inorganic filler is less than 0.5 parts by mass, the bubbles cannot be formed uniformly, and if it exceeds 33 parts by mass, the formation of open cells progresses and the rigidity decreases, which is not preferable.

As the resin for the foam layer, a resin obtained by blending a polyolefin resin with a polystyrene resin may be used. When the content of the polystyrene resin is about 3 parts by mass or more, the cell structure is improved and the rigidity of the resulting foamed layer is increased. On the other hand, if it exceeds 40 parts by mass, the fusion between the foamed layer and the olefin layer with filler will deteriorate, and the layer may peel off during molding.
When adding 5 parts by mass or more of polystyrene resin, it is preferable to add 0.5 parts by mass or more of rubber resin. The rubber resin acts as a compatibilizer for the polyolefin resin and the polystyrene resin. When rubber-based resin is added, bubbles are fine and shape is improved, and bubble breakage is reduced. On the other hand, if the rubber-based resin content exceeds 10 parts by mass, the cell constituent film becomes too soft, and the rigidity is lowered due to the formation of open cells, which is not preferable.

  This foam layer has an open cell ratio of 30% or less. If the open cell ratio exceeds 30%, the open cell portion cannot be adjusted to 55% or less when the container is molded, and the rigidity of the container decreases. In this part, since the sheet is extended and bent at the time of thermoforming, the bubbles are displaced and deformed, and bubbles are easily broken.

In the thermoformed laminated sheet of the present invention, the thickness of the foamed layer is in the range of 0.1 to 2.0 mm. When the thickness of the foamed layer is less than 0.1 mm, the sheet density is excessively increased and the effect of reducing the weight is not achieved. If the thickness exceeds 2.0 mm, it is difficult to determine the conditions during sheet extrusion, and the foam bubbles tend to become continuous bubbles when laminated with other layers. Moreover, the thickness of the whole sheet becomes thick, and the container shape is not determined at the time of molding.
The expansion ratio is not limited, but is preferably 1.3 to 10 times.

[Reinforcing layer (B layer)]
In the laminated sheet for thermoforming of the present invention, the reinforcing layer is a non-foamed resin layer made of a composition containing 3 to 70 parts by mass of an inorganic filler with respect to 100 parts by mass of the polyolefin resin. The resin to be used may be the same as or different from the foam layer, and a polypropylene resin is particularly preferable. The inorganic filler added to the reinforcing layer may be the same as or different from the inorganic filler used in the foam layer, and talc having an average particle diameter of 2 to 8 μm is particularly preferable.
When the amount of the inorganic filler in the reinforcing layer is less than 3 parts by mass, rigidity does not appear. On the other hand, if it exceeds 70 parts by mass, the surface becomes rough, and the surface layer (C layer) laminated on the outside must be thickened, resulting in a heavy weight. Moreover, elongation at the time of shaping | molding worsens and there exists a possibility that perforation may generate | occur | produce in the B layer part of a container.

  The thickness of the reinforcing layer is in the range of 0.05 mm to 2.0 mm. If this thickness is less than 0.05 mm, the thickness of the layer after molding becomes thin and rigidity does not appear. On the other hand, if it exceeds 2.0 mm, the shape of the container is poor when forming the container.

[Surface layer (C layer)]
In the laminated sheet for thermoforming of the present invention, the surface layer is a layer made of a non-foamed polyolefin resin for smoothing the surface of the container. The surface layer (C layer) has a surface roughness Rz of 15 μm or less. When the surface roughness exceeds 15 μm, bubbles are generated on the surface of the molded product when the film (plain color, printing) is laminated and then molded, and the attached film is broken. Moreover, the gloss of the film surface also deteriorates.

  The thickness of the surface layer is in the range of 0.003 to 0.3 mm. If the thickness is less than 0.003 mm, it is difficult to obtain surface smoothness, and the film may be cut during molding. Further, the surface roughness of the laminated sheet cannot be improved. On the other hand, if it exceeds 0.3 mm, the foamed layer has a large number of open cells and the molding is not stable.

  When the laminated sheet needs rigidity, an inorganic filler can be added to the surface layer. In this case, the amount of the inorganic filler is preferably in the range of 0.5 to 17 parts by mass with respect to 100 parts by mass of the resin of the surface layer. If the amount of the inorganic filler is less than 0.5 parts by mass, the effect of improving rigidity cannot be obtained. If the amount exceeds 17 parts by mass, the surface of the surface layer becomes rough, and the film (plain color, printing) is formed after lamination. Then, there is a possibility that bubbles (bubbles) are generated on the surface of the obtained molded product.

  Furthermore, the laminated sheet for thermoforming of the present invention can be laminated with a film or a printed film (D layer) on one side or both sides. As the film or printed film (D layer), a polyolefin resin film that can be laminated to the surface layer (C layer), for example, a polypropylene resin film, is suitable, but the C layer-D layer is bonded via a binder resin. When doing so, other resin, for example, a polyester-type resin film and a polystyrene-type resin film, can also be used.

The laminated sheet for thermoforming according to the present invention is a material resin for a foam layer (A layer), a reinforcing layer (B layer) and a surface layer (C layer) in a plurality of extruders (a foaming agent in an extruder for forming an A layer). Can be produced by melting and co-extrusion foaming from a die for co-extrusion.
Not limited to the co-extrusion foaming method, after each layer is produced separately, the layers are stacked and integrated by thermal lamination, or the B layer and the C layer are laminated in advance, and the layers are produced separately. A method may be used in which the layer A is laminated and integrated by thermal lamination.

The laminated sheet for thermoforming of the present invention has a total thickness in the range of 0.2 mm to 2.5 mm and a density in the range of 0.15 to 1 g / cm ³ . If the total thickness is less than 0.2 mm, the molding cannot be controlled uniformly. If it exceeds 2.5 mm, the container shape cannot be produced during molding. If the density is less than 0.15 g / cm ³ , the rigidity will be insufficient. The density exceeding 1 g / cm ³ occurs when the foaming ratio of the foamed layer is low, the thickness is thin, the filler content is large, the blending amount of polystyrene resin is large, or when these are combined, There is a possibility that the foamed cells become uneven, the container becomes too heavy, and the heat insulation is lowered.

  The laminated sheet for thermoforming of the present invention is preferably used for producing a packaging container having a desired shape by a thermoforming method. This thermoforming method can be performed by using the same method and apparatus as those used for manufacturing various containers using a thermoplastic resin foam sheet.

  The packaging container according to the present invention manufactured using the laminated sheet for thermoforming is not particularly limited with respect to shape and size, and has various shapes such as a quadrilateral, a circle, an ellipse, and a polygon in plan view. Also, the three-dimensional shape can be various shapes such as a box shape (particularly a lunch box shape), a tray shape, and a bowl shape. Further, the packaging container according to the present invention may be a container type with a lid in which the lid and the container main body are separated from each other, and the lid and the container main body are connected via a part of the side wall serving as a hinge portion. .

In the packaging container of the present invention, the density of the entire container is in the range of 0.15 to 1 g / cm ³ , and the thickness of the bottom of the container is in the range of 0.1 to 2.5 mm. If the density is less than 0.15 g / cm ³ , the rigidity becomes insufficient. The density exceeding 1 g / cm ³ occurs when the foaming ratio of the foamed layer is low, the thickness is thin, the filler content is large, the blending amount of polystyrene resin is large, or when these are combined, There is a possibility that the foamed cells become uneven, the container becomes too heavy, and the heat insulation is lowered. Further, if the thickness of the bottom is less than 0.1 mm, the rigidity of the container is insufficient, and if the container containing the contents is held by hand, the container shape tends to be crushed. If the thickness exceeds 2.5 mm, the amount of resin used increases, the material cost increases, and the container cost increases.

  In the packaging container of the present invention, the open cell ratio of the portion curved at the boundary between the bottom and the side wall (the rising portion indicated by reference numeral 11 in the packaging container 10 in FIG. 2) is 55% or less. If the open cell ratio in this part exceeds 55%, the rigidity of the container is lowered, and the bubbles in the A layer are broken by the molding, resulting in unevenness, which deteriorates the appearance.

  In the packaging container of the present invention, the surface roughness Rz of the flat part on the container inner surface side at the bottom is 20 μm or less. When the surface roughness Rz exceeds 20 μm, the smoothness is deteriorated and the appearance is deteriorated.

<Method for producing laminated sheet>
Each composition used for a foam layer (A), a reinforcement layer (B), and a surface layer (C) was each pelletized with an extruder.
Each composition used for a surface layer (C) which supplies the pellet for the said foaming layer (A) to a 90 mm extruder, supplies the pellet which consists of a composition for the said reinforcement layer (B) to a 65 mm extruder. The pellet made of the product is supplied to a 40 mm extruder and co-extruded and foamed from a T-die, whereby the reinforcing layer (B) is laminated on one side or both sides of the foamed layer (A), and further the surface layer (C) A laminated sheet having a 4 to 5 layer structure was manufactured.

<Manufacturing method of container>
The obtained laminated sheet was molded under the manufacturing conditions of an upper heater of 220 ° C., a lower heater of 210 ° C., and a cycle time of 12 seconds, having a partition, an opening size of 125 mm × 178 mm, a bottom size of 125 mm × 75 mm, a depth A rectangular food packaging container having a length of 30 mm was produced.

<Foaming ratio of the foam layer in the laminated sheet>
A small sample is cut from the laminated sheet, the cross section is observed with a microscope, and the thicknesses of the reinforcing layer (B) and the surface layer (C) are measured at three points of the sample, respectively, and the average value is obtained as the reinforcing layer (B). The thickness of the surface layer (C). Cut a square sample of 2 cm × 2 cm from the laminated sheet, after measuring the thickness t ₀ and weight, by water displacement method to measure the apparent density of the laminated sheet, calculated expansion ratio of the foam layer in the laminated sheet of the following formula did.
f = [ρ _A × t _A ] / [ρ ₀ × t ₀ − (ρ _B × t _B + ρ _C × t _C )]
Where f is the expansion ratio of the foam layer, ρ _A is the specific gravity of the solid component of the foam layer (A), t _A is the thickness (mm) of the foam layer (A), ρ ₀ is the apparent specific gravity of the laminated sheet, and t ₀ is The thickness of the laminated sheet, ρ _B is the specific gravity of the reinforcing layer (B), t _B is the thickness (mm) of the reinforcing layer (B), ρ _C is the specific gravity of the surface layer (C), and t _C is the surface layer (C). Represents thickness (mm). The foam layer thickness t _A is calculated from the formula t _A = t ₀ − (t _B + t _C ).

<Open cell ratio>
Five samples of 2 cm × 2 cm are randomly cut from the laminated sheet, and the weight is measured. This sample was immersed in water, allowed to stand for 5 minutes under a vacuum of 0.09 MPa or less, then taken out, thoroughly wiped off the moisture adhering to the surface and cross section, measured for weight after immersion in water under vacuum, and the open cell ratio was calculated from the following formula. .
F = (V ₂ / V) × 100 = {(M−m) / [m × (f−1) / S ₀ ]} × 100
Where F is the open cell percentage, V ₂ is the open cell volume (cm ³ ), V is the actual bubble volume (cm ³ ) of the foam, M is the sample mass (g) after evacuation, and m is before water immersion. Sample mass (g), f is the expansion ratio (times), and S ₀ is the specific gravity of the laminate solid component. In addition, the open cell rate of the molded container was set to the open cell rate of the container in the same manner as described above by randomly cutting five 2 cm × 2 cm samples from each part of the container.

<Drawdown during molding>
In the production of the container, the laminated sheet is heated by the upper and lower heaters, held for the molding cycle time without applying vacuum and pressure air, and then taken out as it is, and the slack in the central part is measured.

<Bending strength of laminated sheet>
Using Autograph AG-1 (manufactured by Shimadzu Corporation), a test piece width of 25 mm × length 50 mm was set to 20 mm between fulcrums, and the center of the test piece was pressed at a speed of 100 mm / min with a jig. In MD, the longitudinal direction of the test piece was the longitudinal direction of the laminated sheet, and TD was the direction orthogonal to MD.

<Measurement of density of laminated sheet>
Samples having a diameter of 10 mm are cut out from five positions in the width direction of the sheet, the mass and thickness are measured, the density is calculated, and the average value is taken as the sheet density.

<Height and strength>
A container molded on Autograph AG-1 (manufactured by Shimadzu Corporation) was placed face down, an acrylic plate was placed on the entire bottom surface of the container, and the strength at which the container was buckled was measured by compressing the center at a speed of 100 mm / min.

<Thickness structure by sheet layer>
-The sheet was cut in the thickness direction at right angles to the extrusion direction, and the thickness of each layer was measured at 10 points equally in the width direction of the sheet using a digital microscope (VH8000 manufactured by Keyence Corporation), and the average value was expressed. .

<Surface roughness of laminated sheet 10-point average roughness Rz>
Based on JISB0601-1994, Rz was measured at a measurement length of 4 mm in the sheet flow direction and transverse direction at 5 points in the sheet width direction using SJ-400 manufactured by Mitutoyo, and the average value was obtained. .
A value obtained by adding the height Pi from the average line to the highest peak and the depth Vi from the deepest valley bottom to Rz was calculated as a roughness value Rz = (Z1 + Z2 + Z3 + Z4 + Z5) / 5.

<Tensile test in thermostatic chamber>
Take a test piece in the direction of sample flow (MD), use Autograph UA-X-TN (manufactured by Shimadzu Corporation with high-temperature bath), and perform a tensile test at each temperature of 100 ° C and 110 ° C. Test force, tensile strength, and elastic modulus were determined.
Tensile speed: 100 [mm / min].
Number of implementations: n = 5
Time in the thermostatic chamber: 50 seconds

<Molded container>
The molded container was a rectangular tray having an opening of 125 mm × 178 mm, a bottom of 75 mm × 125 mm, and a height of 30 mm.

<Compressive strength of container>
Using Autograph AG-1 (manufactured by Shimadzu Corporation), the maximum load was measured when the container was compressed 10 mm in the vertical direction with the short side of the container in the vertical direction.

<Open cell ratio of rising part of container>
A 25 mm × 30 mm sample is cut out from the curved surface portion where the side wall portion rises from the bottom portion of the container, and the following is performed in the same manner as the open cell ratio in the laminated sheet. The number of samples is n = 5 unless otherwise specified.
If the open cell ratio of this part exceeds 55%, when pressure is applied to the side surface of the container, this part will buckle and easily break.

[Examples 1-4, Comparative Examples 1-3]
The materials used were as follows.
Polypropylene: A resin manufactured by Nippon Polypro Co., Ltd., Novatec EX-9A for layer A (foamed layer), Novatec EA-7A for layer B (reinforcing layer), and FY-6C for layer C (surface layer).
Filler (talc): A product manufactured by Matsumura Sangyo Co., Ltd., for the A layer, a high filler average particle size 6.5 μm product, and for the B layer, a crown talc average particle size 15 μm product, each with talc 60 wt% + PP Used as a master batch with 40% resin by weight.
Foaming agent (bicarbonate / citric acid): EE-405D (manufactured by Eiwa Kasei Co., Ltd.).
The composition of each layer is shown in Table 1.

Using the materials shown in Table 1, a laminate sheet of three types and five layers composed of C / B / A / B ′ / C ′ was produced.
Using the obtained laminated sheet, a food packaging container (molded product) was produced by a thermoforming method.
The laminated sheets and molded products of Examples 1 to 4 and Comparative Examples 1 to 3 described in Table 2 were prepared, and the thickness of each layer, the thickness of the laminated sheet, the density and the surface roughness, and the molded product were evaluated. Compared. The results are summarized in Table 2.

As described in Table 2, the molded products produced using the laminated sheets of Examples 1 to 4 according to the present invention had no problems in appearance, strength, and the like.
In Comparative Example 1, since the thickness of the foamed layer (A) was 0.05 mm, which was less than the lower limit (0.1 mm) of the present invention, foaming could not be controlled, and there was variation in bubble breakage and foamed cell size. It was big.
In Comparative Example 2, since the thickness of the reinforcing layers B and B ′ was 0.03 mm, which was less than the lower limit (0.05 mm) of the present invention, the resulting molded product was insufficient in strength.
In Comparative Example 3, since the thicknesses of the surface layers C and C ′ were 0.002 mm, which was less than the specified lower limit (0.003 mm) of the present invention, film tearing and film peeling occurred during molding. In addition, since the surface roughness of this laminated sheet was 19 μm, exceeding the specified value (15 μm or less) of the present invention, partial film peeling (bubbles) occurred when a laminated sheet was laminated with a printed film or the like. did.

[Examples 5-6, Comparative Examples 4-5]
In the layer configurations of Examples 1 to 4 described above, the inorganic filler (talc) content of the reinforcing layers B and B ′ was increased or decreased. Table 3 shows the composition of each layer.

  As shown in Table 4, the laminated sheets and molded articles of Examples 5 to 6 and Comparative Examples 4 to 5 in which the amount of talc in the B and B ′ layers was increased or decreased were prepared. Thickness, density, surface roughness, and molded products were evaluated and compared. The results are summarized in Table 4.

From the results of Table 4, the molded products produced using the laminated sheets of Examples 5 to 6 according to the present invention had no problems in appearance, strength, and the like.
In Comparative Example 4, since the talc of the B and B ′ layers was 2 parts by mass and less than the specified value lower limit (3 parts by mass) of the present invention, the rigidity of the obtained molded product was insufficient.
In Comparative Example 5, since the talc of the B and B ′ layers exceeded 100 parts by mass and the specified upper limit (70 parts by mass) of the present invention, the foamed layer was perforated during molding.

[Example 7, Comparative Example 6]
In the layer configuration of Example 6, the thickness of each layer was changed to produce each laminated sheet and molded product of Example 7 and Comparative Example 6, and the thickness of each layer, the thickness, density and surface roughness of the laminated sheet, The molded products were evaluated and compared. The results are summarized in Table 5.

  From the results shown in Table 5, when the foam layer (A) was thinned, the reinforcing layers (B, B ') were thinned, and the surface layers (C, C') were thickened, the tendency of bubbles to communicate increased.

[Examples 8 to 9, Comparative Examples 7 to 9]
In the layer configuration of Example 1, the thickness of each layer of the foam layer (A) and the reinforcing layer (B, B ′) was increased or decreased to confirm the limit situation. The results are summarized in Table 6.

From the results in Table 6, the molded products produced using the laminated sheets of Examples 8 to 9 according to the present invention had no problems in appearance, strength, and the like.
In Comparative Examples 7 to 9, the thickness of any layer was outside the specified value range of the present invention, and the strength and appearance of the obtained molded products were deteriorated.

[Examples 11-15, Comparative Examples 10-11]
An attempt was made to add a polystyrene resin to the foamed layer (A).
The amount of the inorganic filler in the reinforcing layers B and B ′ was 25 parts by mass. A sheet obtained by laminating 20 μm of the back-printed film on the side that becomes the inner surface of the container after forming the laminated sheet was formed and evaluated. The resin used is as follows.
Polypropylene; A layer: Novatec EX-9A, EA9 (manufactured by Nippon Polypro), B layer: Novatec EA-7A (manufactured by Nippon Polypro), C layer: Novatec FY-6C (manufactured by Nippon Polypro).
Polystyrene (PS); Dick styrene EX710 (manufactured by Dainippon Ink & Chemicals, Inc.).
Rubber-based resin (SBBS); Tuftec P-2000 (manufactured by Asahi Kasei Chemicals).
Inorganic filler (talc): A commercial product manufactured by Matsumura Sangyo Co., Ltd. For the A layer, a high filler average particle size of 6.5 μm, and for the B layer, 15 μm of crown talc, 60% by mass of talc and polypropylene, respectively. Used as a master batch with 40% by mass of resin.
Foaming agent (bicarbonate / citric acid): EE-405D (manufactured by Eiwa Kasei Co., Ltd.) was added while adjusting 2 to 5 parts by mass with respect to 100 parts by mass of the resin.
Each layer was formed using these materials with the composition described in Table 7, and laminated sheets of Examples 11 to 15 and Comparative Examples 10 to 11 were produced.

  The laminated sheets and molded products of Examples 11 to 15 and Comparative Examples 10 to 11 were prepared, and the thickness of each layer, the thickness of the laminated sheet, the density and surface roughness, and the molded products were evaluated and compared. The results are summarized in Table 8.

  By mixing the polystyrene resin with the A layer, the bubbles were fine, the bubbles were shaped, the open cells were reduced, the bending strength and the compressive strength were increased, the surface roughness was improved, and the film peeling was also reduced.

[Examples 16 to 18, Comparative Example 12]
Talc was added as an inorganic filler to the surface layer (C), and the other laminated sheets and molded articles of Examples 16 to 18 and Comparative Example 12 were prepared in the same manner as in Example 11 to obtain the surface roughness of the C layer. Then, the strength of the laminated sheet and the evaluation of the molded product were performed. The results are summarized in Table 9.

It was found that when the filler was added to the surface film C, the strength was improved. However, if the addition amount is large, the surface roughness is deteriorated and film peeling occurs.
It was found that the gloss of the film was lost when the surface roughness of the pasted molded product exceeded 20 μm.

It is sectional drawing which shows one Embodiment of the laminated sheet for thermoforming of this invention. It is the schematic which shows the standing part in the packaging container of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated sheet for thermoforming, 2 ... Foam layer (A layer), 3 ... Reinforcement layer (B layer), 4 ... Surface layer (C layer), 10 ... Container for packaging, 11 ... Stand-up part.

Claims (9)

A foam layer (A) comprising a composition containing 0.5 to 33 parts by mass of an inorganic filler with respect to 100 parts by mass of the polyolefin resin, and 3 to 70 inorganic fillers with respect to 100 parts by mass of the polyolefin resin on one or both sides thereof. A non-foamed reinforcing layer (B) made of a composition containing parts by mass, and a non-foamed surface layer (C) made of a composition mainly comprising a polyolefin resin on the outermost surface,
The foam layer (A) has a thickness in the range of 0.1 mm to 2.0 mm, an open cell ratio of 30% or less,
The reinforcing layer (B) has a thickness in the range of 0.05 mm to 2.0 mm,
The surface layer (C) has a surface roughness Rz of 15 μm or less,
The laminated sheet has a thickness in the range of 0.2 mm to 2.5 mm and a density in the range of 0.15 to 1 g / cm ³ . A foamed layer (A), a non-foamed reinforcing layer (B) made of a composition containing a polyolefin resin and an inorganic filler on one or both sides, and a non-foamed layer made of a composition mainly comprising a polyolefin resin on the outermost surface. A sheet laminated with a foamed surface layer (C),
The resin of the foam layer (A) is from a composition containing (a1) 50 to 96 parts by mass of a polyolefin resin, (a2) 3 to 40 parts by mass of a polystyrene resin, and (a3) 0.5 to 10 parts by mass of a rubber resin. The inorganic filler in the foam layer (A) is in the range of 0.2 to 33 parts by mass with respect to 100 parts by mass of the resin, and the foam layer (A) is in the range of 0.2 to 2.0 mm in thickness. Yes, the open cell rate is 30% or less,
The reinforcing layer (B) includes 3 to 70 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin, and has a thickness of 0.05 to 2.0 mm.
The surface layer (C) has a thickness in the range of 0.003 to 0.3 mm, a surface roughness Rz of 15 μm or less,
The laminated sheet has a thickness in the range of 0.3 to 2.5 mm and a density in the range of 0.15 to 1 g / cm ³ .   The laminated sheet for thermoforming according to claim 1 or 2, wherein the surface layer (C) is made of a polypropylene resin.   A surface layer (C) consists of a resin composition which contains 0.5-17 mass parts of inorganic fillers with respect to 100 mass parts of resin, The laminated sheet for thermoforming according to any one of claims 1 to 3 .   The laminated sheet for thermoforming according to any one of claims 1 to 4, wherein the laminated sheet is formed by laminating a film or a printed film (D) on one side or both sides of the laminated sheet.   A packaging container formed by thermoforming the laminated sheet for thermoforming according to any one of claims 1 to 5 into a container shape or a container shape with a lid. A foam layer (A) comprising a composition containing 0.5 to 33 parts by mass of an inorganic filler with respect to 100 parts by mass of the polyolefin resin, and 3 to 70 inorganic fillers with respect to 100 parts by mass of the polyolefin resin on one or both sides thereof. A sheet obtained by laminating a non-foamed reinforcing layer (B) made of a composition containing parts by mass and a non-foamed surface layer (C) made of a composition mainly composed of a polyolefin resin on the outermost surface was thermoformed. A packaging container comprising:
The density of the entire container is in the range of 0.15 to 1 g / cm ³ ;
The thickness of the bottom of the container is in the range of 0.1 to 2.5 mm;
The open cell ratio of the curved portion at the boundary between the bottom and the side wall is 55% or less,
The packaging container is characterized in that the surface roughness Rz of the flat part on the inner surface side of the container at the bottom is 20 μm or less. Packaging in which a sheet is formed by laminating a foam layer (A), a reinforcing layer (B) containing a filler-containing polyolefin resin layer on one or both sides, and a surface layer (C) containing a polyolefin resin on the outermost surface. A container for
The resin of the foam layer (A) is from a composition containing (a1) 50 to 96 parts by mass of a polyolefin resin, (a2) 3 to 40 parts by mass of a polystyrene resin, and (a3) 0.5 to 10 parts by mass of a rubber resin. And the inorganic filler in the foam layer (A) is in the range of 0.2 to 33 parts by mass with respect to 100 parts by mass of the resin,
The reinforcing layer (B) includes 3 to 40 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin,
The density of the entire container is in the range of 0.15 to 1 g / cm ³ ;
The thickness of the bottom of the container is in the range of 0.1 to 2.5 mm;
The open cell ratio of the curved portion at the boundary between the bottom and the side wall is 55% or less,
A packaging container, wherein the surface roughness Rz of the flat part on the inner surface side of the bottom part is 20 μm or less.   The packaging container according to claim 7 or 8, wherein a back-printed film layer (D) is formed on at least an inner surface side of the container.

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