JP7152089B1 - LAMINATED SHEET AND FOOD PACKAGING CONTAINER - Google Patents

Abstract

An object of the present invention is to provide an inorganic substance-containing laminated sheet having good heat resistance and moldability. The present invention provides a laminated sheet comprising an inner layer and outer layers laminated on both sides of the inner layer, wherein the inner layer is made of polyethylene resin, polypropylene resin, inorganic powder, and diethanolamine laurate. In the inner layer, the mass ratio of the total amount of the polyethylene-based resin and the polypropylene-based resin to the inorganic substance powder is 50:50 to 60:40, and the content of the lauric acid diethanolamide is , 0.1% by mass or more and 1.0% by mass or less with respect to the entire inner layer, and the outer layer is composed only of a polypropylene-based resin. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a laminated sheet and a food packaging container.

In recent years, from the viewpoint of environmental protection, attempts have been made to reduce the content of resin components in various resin products.
Examples of such attempts include increasing the blending amount of inorganic substances (eg, calcium carbonate) in resin products (for example, Patent Documents 1 and 2).

Japanese Patent No. 6857428 Japanese Patent Application Laid-Open No. 2021-112862

Here, it is known that if the amount of the inorganic substance compounded with respect to the resin composition is increased, the moldability may be lowered.

In addition, resin products are required to have specific properties (heat resistance, etc.) according to their uses.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inorganic substance-containing laminated sheet having good heat resistance and moldability.

The present inventors have found that the above problems can be solved by blending a predetermined amount of lauric acid diethanolamide together with a predetermined thermoplastic resin and inorganic powder in the inner layer of the laminated sheet, and have completed the present invention. reached. More specifically, the present invention provides:

(1) A laminated sheet comprising an inner layer and outer layers laminated on both sides of the inner layer,
The inner layer contains a polyethylene-based resin, a polypropylene-based resin, an inorganic substance powder, and lauric acid diethanolamide,
In the inner layer, the mass ratio of the total amount of the polyethylene-based resin and the polypropylene-based resin to the inorganic substance powder is 50:50 to 60:40,
The content of the lauric acid diethanolamide is 0.1% by mass or more and 1.0% by mass or less with respect to the entire inner layer,
wherein the outer layer is made of only polypropylene-based resin,
Laminated sheet.

(2) the polyethylene-based resin in the inner layer includes high-density polyethylene and linear low-density polyethylene;
MFR (190° C., 21.6 kg) according to JIS K 6922-1 (ISO1133) of the high-density polyethylene is 5 g/10 min or more and 15 g/10 min or less,
MFR (190° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the linear low-density polyethylene is 0.5 g/10 min or more and 1.5 g/10 min or less,
The laminated sheet according to (1), wherein the mass ratio of the high-density polyethylene and the linear low-density polyethylene is 90:10 to 50:50.

(3) The laminated sheet according to (1), wherein the polypropylene resin in the inner layer and/or the outer layer is a polypropylene homopolymer and/or a polypropylene block polymer.

(4) The laminated sheet according to (1), wherein the inorganic powder is ground calcium carbonate particles.

(5) The laminated sheet according to (4), wherein the heavy calcium carbonate particles have an average particle size of 0.7 μm or more and 6.0 μm or less based on an air permeation method according to JIS M-8511.

(6) The laminated sheet according to (1), wherein the thickness ratio of each of the outer layers is 2.0% or more and 10.0% or less with respect to the total thickness of the laminated sheet.

(7) The laminated sheet according to any one of (1) to (6), which is a laminated sheet for vacuum forming.

(8) A food packaging container formed from the laminated sheet according to any one of (1) to (6).

According to the present invention, an inorganic substance-containing laminated sheet having good heat resistance and moldability is provided.

Embodiments of the present invention will be described below, but the present invention is not limited thereto.

<Laminated sheet>
The laminated sheet of the present invention has a three-layer structure (that is, an inner layer and outer layers laminated on both sides of the inner layer) and satisfies all of the following requirements.
(Requirement 1) The inner layer contains polyethylene-based resin, polypropylene-based resin, inorganic powder, and lauric acid diethanolamide.
(Requirement 2) In the inner layer, the mass ratio of the total amount of polyethylene-based resin and polypropylene-based resin to the inorganic substance powder is 50:50 to 60:40.
(Requirement 3) The content of lauric acid diethanolamide is 0.1% by mass or more and 1.0% by mass or less with respect to the entire inner layer.
(Requirement 4) The outer layer consists of polypropylene resin only.

The laminated sheet of the present invention has a main technical feature in the composition of its inner layer.
The inner layer in the present invention contains predetermined resins (polyethylene-based resin and polypropylene-based resin) and inorganic powder, and the blending amounts of the resin and inorganic powder are approximately the same (requirements 1 and 2). Such a resin composition containing a high proportion of inorganic substance powder usually tends to be poor in moldability.
However, the present inventors found that by blending a predetermined amount of lauric acid diethanolamide in the inner layer satisfying requirement 2 (requirements 1 and 3), the heat resistance was improved without impairing the moldability of the resin composition. I found an unexpected finding that I can do it.
Such an effect was not impaired even when an outer layer made of a polypropylene-based resin was placed on the surface of the inner layer (requirement 4).

In the present invention, "heat resistance" includes heat resistance evaluated based on a heat resistance test according to JIS S2029.
In the present invention, "the laminated sheet has good heat resistance" means that when the laminated sheet is subjected to a heat resistance test according to JIS S 2029, the overall surface condition is good (unevenness, deformation, etc. not to do), etc.

The heat resistance of the laminated sheet can be evaluated by the method shown in Examples.

In the present invention, "moldability" includes ease of molding (for example, vacuum molding).
In the present invention, "the laminated sheet has good molding processability" means that when the laminated sheet is molded, it can be molded to the desired dimensions, and the resulting molded product does not show distortion or the like. Including the totally unacceptable.

The moldability of the laminated sheet can be evaluated by the method shown in Examples.

The configuration of the laminated sheet of the present invention will be described in detail below.

(1) Inner Layer The inner layer contains polyethylene-based resin, polypropylene-based resin, inorganic powder, and lauric acid diethanolamide.

(Type of polyethylene resin blended in the inner layer)
As the polyethylene-based resin, a resin having ethylene component units as a main component can be used. Polyethylene-based resins can be used singly or in combination of two or more.

The polyethylene-based resin in the present invention includes resins having an ethylene component unit of preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and most preferably 80% by mass or more.

Examples of polyethylene-based resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), ultra-low-density polyethylene (ULDPE), linear low-density polyethylene (LLDPE), and ethylene-vinyl acetate. Polymer, ethylene-propylene copolymer, ethylene-propylene-butene 1 copolymer, ethylene-butene 1 copolymer, ethylene-hexene 1 copolymer, ethylene-4-methylpentene 1 copolymer, ethylene-octene 1 A copolymer etc. are mentioned.

“High density polyethylene (HDPE)” is polyethylene having a density of 0.942 g/cm ³ or higher.
"Medium Density Polyethylene (MDPE)" is polyethylene having a density of 0.930 g/cm ^{3 or more and less than 0.942 g/cm 3 .}
"Low density polyethylene (LDPE)" is polyethylene having a density of 0.910 g/cm ³ or more and less than 0.930 g/cm ³ .
"Ultra low density polyethylene (ULDPE)" is polyethylene having a density of less than 0.910 g/ ^cm3 .
“Linear low-density polyethylene (LLDPE)” means a density of 0.911 g/cm ³ or more and less than 0.940 g/cm ³ (preferably a density of 0.912 g/cm ³ or more and less than 0.928 g/cm ³ ). is a polyethylene having

As polyethylene-based resins, resins containing high-density polyethylene and linear low-density polyethylene are preferable from the viewpoint of easily improving heat resistance and molding processability, and resins consisting only of high-density polyethylene and linear low-density polyethylene are preferable. more preferred.

High-density polyethylene has an MFR (190°C, 21.6 kg) according to JIS K 6922-1 (ISO1133) of 5 g/10 minutes or more and 15 g/10 minutes or less, from the viewpoint that heat resistance and moldability are easily improved. and more preferably 6 g/10 minutes or more and 14 g/10 minutes or less.

Linear low-density polyethylene has an MFR (190° C., 2.16 kg) according to JIS K 6922-1 (ISO 1133) of 0.5 g/10 minutes or more, from the viewpoint that it is easy to improve heat resistance and moldability. It is preferably 5 g/10 minutes or less, more preferably 0.6 g/10 minutes or more and 1.4 g/10 minutes or less.

In the resin containing high-density polyethylene and linear low-density polyethylene, the mass ratio of the two (high-density polyethylene: linear low-density polyethylene) is preferably 90 from the viewpoint of particularly easily improving heat resistance and moldability. :10 to 50:50, more preferably 85:15 to 55:45, still more preferably 80:20 to 60:40.

In a preferred embodiment of the present invention, the polyethylene-based resin includes high-density polyethylene and linear low-density polyethylene,
MFR (190° C., 21.6 kg) according to JIS K 6922-1 (ISO1133) in high-density polyethylene is 5 g/10 minutes or more and 15 g/10 minutes or less,
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in linear low density polyethylene is 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less,
The mass ratio of high density polyethylene to linear low density polyethylene is 90:10 to 50:50.

(Type of polypropylene resin blended in the inner layer)
As the polypropylene-based resin, a resin containing propylene component units as a main component can be used. Polypropylene-based resins can be used singly or in combination of two or more.

The polypropylene resin in the present invention includes a resin having a propylene component unit of preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and most preferably 80% by mass or more.

Polypropylene resins include polypropylene homopolymers (propylene homopolymers), copolymers of propylene and other α-olefins (those copolymerizable with propylene), and the like.
"Other α-olefins" include, for example, α-olefins having 4 to 10 carbon atoms (ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4- dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, etc.).

Propylene homopolymers include linear or branched polypropylenes showing various stereoregularities (isotactic, syndiotactic, atactic, hemiisotactic, etc.).

The copolymer of propylene may be any of polypropylene random copolymer (random copolymer), polypropylene block copolymer (block copolymer), binary copolymer, terpolymer and the like. Specific examples include ethylene-propylene random copolymers, butene-1-propylene random copolymers, ethylene-butene-1-propylene random terpolymers, ethylene-propylene block copolymers, and the like.

The polypropylene-based resin is preferably a resin containing one or more of polypropylene homopolymer and polypropylene block polymer from the viewpoint of facilitating the improvement of heat resistance and molding processability, and consists of only one or more of polypropylene homopolymer and polypropylene block polymer. Resin is more preferred.

(Kinds of inorganic substance powder blended in the inner layer)
The inorganic powder is not particularly limited, and those contained in ordinary resin products can be used. The inorganic substance powder can be used singly or in combination of two or more.

Examples of inorganic substance powders include the following.
Carbonates, sulfates, silicates, phosphates, or borates of metals (calcium, magnesium, aluminum, titanium, iron, zinc, etc.);
oxides of metals (calcium, magnesium, aluminum, titanium, iron, zinc, etc.);
hydrates of the above salts or oxides;

Examples of inorganic substance powders include calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, graphite and the like.

The inorganic substance powder may be synthetic or derived from natural minerals.

From the viewpoint of enhancing the dispersibility and reactivity of the inorganic powder, the inorganic powder may be surface-treated.
Examples of surface treatment methods include physical methods (plasma treatment, etc.), chemical methods (methods using a coupling agent or surfactant), and the like.

The shape of the inorganic powder is not particularly limited, and may be particulate (spherical, irregular, etc.), flakes, granules, fibers, or the like.

The average particle size of the inorganic substance powder is not particularly limited, and is preferably 0.1 μm or more and 50.0 μm or less, more preferably 0.5 μm or more and 13.5 μm or less.

A preferred embodiment of the present invention includes an embodiment in which the inner layer does not substantially contain inorganic substance powder having a particle size of more than 50.0 μm, from the viewpoint of easily suppressing uneven distribution of inorganic substance powder.
A preferred embodiment of the present invention includes an embodiment in which the inner layer does not substantially contain inorganic substance powder having a particle size of less than 0.1 μm, from the viewpoint of easily suppressing an increase in viscosity during molding.
In the present invention, "the inner layer does not substantially contain a component" means that the content of the component in the inner layer is less than 0.1% by mass, more preferably 0.01% by mass or less. It includes some embodiments, more preferably none at all.

In the present invention, the "average particle size" of the inorganic powder means a value calculated from the results of measuring the specific surface area by the air permeation method according to JIS M-8511. As a measuring device, for example, a specific surface area measuring device SS-100 manufactured by Shimadzu Corporation can be preferably used.

Calcium carbonate particles are preferred as the inorganic powder. If the amount of calcium carbonate particles added to the resin composition is increased, the moldability may be particularly reduced. can also increase

The calcium carbonate particles may be either heavy calcium carbonate particles or light calcium carbonate particles.

From the viewpoint of having more contact interfaces with thermoplastic resins (polypropylene-based resins, polyethylene-based resins), the effect of the present invention is easily exhibited, and the mechanical properties of the laminated sheet are easily improved, the inner layer has preferably contains ground calcium carbonate particles.
The calcium carbonate particles contained in the inner layer are preferably heavy calcium carbonate particles, and the inorganic powder contained in the inner layer is more preferably heavy calcium carbonate particles.

“Heavy calcium carbonate” is calcium carbonate obtained by mechanically pulverizing (dry method, wet method, etc.) natural raw materials (limestone, etc.) containing CaCO ₃ as a main component.
"Light calcium carbonate" is calcium carbonate prepared by a synthetic method (such as a chemical precipitation reaction).
Therefore, heavy calcium carbonate and light calcium carbonate are clearly distinguished from each other.

When the inner layer contains heavy calcium carbonate particles, the average particle size thereof based on the air permeation method according to JIS M-8511 is preferably 0.7 μm or more from the viewpoint that the effects of the present invention are particularly likely to be exhibited. 0 μm or less.

(Lauric acid diethanolamide blended in the inner layer)
Lauric acid diethanolamide (CAS number: 120-40-1) is also called N,N-bis(2-hydroxyethyl)dodecanamide and the like, and is a component known as a surfactant or the like.

Among various additives, the present inventors have found that by blending lauric acid diethanolamide in the inner layer, the compatibility of polypropylene resin, polyethylene resin, and inorganic substance powder is improved, and as a result, the resulting laminated sheet We have found an unexpected finding that the molding processability and heat resistance of can be improved.

(Other ingredients blended in the inner layer)
The inner layer may or may not contain components other than polypropylene-based resin, polyethylene-based resin, inorganic substance powder, and lauric acid diethanolamide as long as the effects of the present invention are not impaired.

As the other components, any component that can be usually blended in the resin sheet can be employed.
Examples of such components include thermoplastic resins (other than polyethylene-based resins and polypropylene-based resins), lubricants, dispersants, antistatic agents, antioxidants, heat stabilizers, and ultraviolet absorbers.
The types and amounts of these components can be appropriately set according to the effects to be obtained.

Examples of thermoplastic resins other than polyethylene-based resins and polypropylene-based resins include ethylene-vinyl acetate copolymers and ethylene-propylene copolymers.

A preferred embodiment of the present invention includes a laminated sheet in which the inner layer is composed of only polyethylene-based resin, polypropylene-based resin, inorganic powder, and lauric acid diethanolamide.

(Proportion of ingredients blended in the inner layer)
In the inner layer, the mass ratio of the total amount of polyethylene-based resin and polypropylene-based resin to the inorganic substance powder is 50:50 to 60:40, and the content of lauric acid diethanolamide is It is 0.1 mass % or more and 1.0 mass % or less.

In the inner layer, the mass ratio of the total amount of polyethylene-based resin and polypropylene-based resin to the inorganic substance powder (total amount of polyethylene-based resin and polypropylene-based resin: inorganic substance powder) is 50:50 to 60:40, preferably 51: 49-59:41.

In the inner layer, the mass ratio of the polypropylene-based resin and the polyethylene-based resin tends to exhibit the effects of the present invention more easily as the ratio of the polyethylene-based resin increases.
In the inner layer, the mass ratio of polypropylene-based resin to polyethylene-based resin (polypropylene-based resin:polyethylene-based resin) is preferably 40:60 to 10:90, more preferably 30:70 to 10:90.

The lower limit of the content of lauric acid diethanolamide is 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0, based on the entire inner layer, from the viewpoint of easily improving heat resistance and moldability. .3% by mass or more.

The upper limit of the content of lauric acid diethanolamide is 1.0% by mass or less, preferably 0.9% by mass or less, more preferably 0% with respect to the entire inner layer, from the viewpoint of hardly impairing heat resistance and moldability. .8% by mass or less.

The lower limit of the content of the polyethylene-based resin is preferably 30% by mass or more, more preferably 32% by mass or more, based on the entire inner layer, from the viewpoint of facilitating molding processability.

The upper limit of the content of the polyethylene-based resin is preferably 45% by mass or less, more preferably 43% by mass or less, relative to the entire inner layer, from the viewpoint of facilitating an increase in heat resistance.

The lower limit of the content of the polypropylene-based resin is preferably 5% by mass or more, more preferably 7% by mass or more, based on the entire inner layer, from the viewpoint of facilitating molding processability.

The upper limit of the content of the polypropylene-based resin is preferably 20% by mass or less, more preferably 18% by mass or less, relative to the entire inner layer, from the viewpoint of facilitating an increase in heat resistance.

The lower limit of the content of the inorganic substance powder is preferably 40% by mass or more, more preferably 41% by mass or more, based on the entire inner layer, from the viewpoint of sufficiently meeting environmental protection needs.

The upper limit of the content of the inorganic substance powder is preferably 50% by mass or less, more preferably 49% by mass or less, relative to the entire inner layer, from the viewpoint that molding processability is not likely to be impaired.

(2) Outer layer The outer layer is a pair of layers laminated on the two surfaces of the inner layer (that is, in the laminated sheet of the present invention, two outer layers are formed so as to sandwich the inner layer).
In the present invention, the pair of layers are referred to as a first outer layer and a second outer layer.

The configurations (thickness, shape, etc.) of the first outer layer and the second outer layer may be the same or different. However, the first outer layer and the second outer layer are each made of polypropylene-based resin only.

In the present invention, "the outer layer consists of only a polypropylene-based resin" means that the outer layer does not substantially contain components other than the polypropylene-based resin.
In the present invention, "the outer layer does not substantially contain a component" means that the content of the component is less than 0.1% by mass with respect to the entire outer layer (the first outer layer and the second outer layer). , more preferably 0.01% by mass or less, and still more preferably not containing it at all.

Preferred embodiments of the present invention include embodiments in which the configurations (thickness, shape, etc.) of the first outer layer and the second outer layer are all the same.

(Polypropylene resin blended in the outer layer)
As the polypropylene-based resin to be blended in the outer layer, the same resins as listed above (kinds of polypropylene-based resin to be blended in the inner layer) can be employed.

The polypropylene resin blended in the outer layer may be the same as or different from the polypropylene resin blended in the inner layer.
From the viewpoint that the effect of the present invention is easily exhibited, it is preferable that the polypropylene-based resin blended in the outer layer is the same as the polypropylene-based resin blended in the inner layer.

The polypropylene-based resin is preferably a resin containing one or more of polypropylene homopolymer and polypropylene block polymer from the viewpoint of facilitating the improvement of heat resistance and molding processability, and consists of only one or more of polypropylene homopolymer and polypropylene block polymer. Resin is more preferred.

(3) Thickness of each layer of the laminated sheet The thickness of each layer in the laminated sheet of the present invention is not particularly limited, but by making the thickness of the outer layer thinner than the thickness of the inner layer, a good appearance can be obtained. The excellent properties exhibited by the inner layer can be expressed while exhibiting the properties.

The thickness ratio of the first outer layer and the second outer layer is preferably 2.0% or more, relative to the total thickness of the laminated sheet, from the viewpoint of easily exhibiting excellent mechanical properties10. 0% or less. In this aspect, the total thickness of the outer layers (the total thickness of the first outer layer and the second outer layer) is 4.0% or more and 20.0% or less with respect to the total thickness of the laminated sheet. be.

The lower limit of the ratio of the thicknesses of the first outer layer and the second outer layer is preferably 2.0% or more, more preferably 2.0% or more, relative to the total thickness of the laminated sheet, from the viewpoint that the appearance tends to be good. It is 3.0% or more, more preferably 4.0% or more.

The upper limit of the ratio of the thicknesses of the first outer layer and the second outer layer is preferably 10.0% or less, or more than It is preferably 9.0% or less, more preferably 8.0% or less.

In the laminate sheet of the present invention, the thickness ratio of the inner layer is adjusted according to the thickness of the outer layer, and is, for example, 80.0% or more and 96.0% or less of the total thickness of the laminate sheet.

The lower limits of the thicknesses of the first outer layer and the second outer layer are preferably 5 μm or more, more preferably 8 μm or more, from the viewpoint of easily obtaining a good appearance.

The upper limits of the thicknesses of the first outer layer and the second outer layer are preferably 100 μm or less, more preferably 90 μm or less, respectively, from the viewpoint of formability and the like.

The lower limit of the thickness of the inner layer is preferably 50 µm or more, more preferably 80 µm or more, from the viewpoint of easily obtaining good mechanical properties.

The upper limit of the thickness of the inner layer is preferably 900 μm or less, more preferably 850 μm or less, from the viewpoint of moldability.

The lower limit of the total thickness of the laminated sheet is adjusted according to the thickness of the outer layer and the inner layer, preferably 80 μm or more, more preferably 100 μm or more.

The upper limit of the total thickness of the laminated sheet is adjusted according to the thickness of the outer layer and the inner layer, preferably 950 μm or less, more preferably 900 μm or less.

The density of the laminated sheet is not particularly limited.

(4) Method for producing laminated sheet The method for producing the laminated sheet of the present invention is not particularly limited, and conventionally known methods for producing multilayer sheets and laminates can be employed.

Examples of the method for producing the laminated sheet include the following methods.
・Method of laminating the inner layer and outer layer formed into a sheet with a calender roll ・Method of co-extrusion of the inner layer and the outer layer A method in which co-extrusion molding is performed in the same process A method by extrusion inflation method using multiple annular dies

The laminated sheet may be stretched as necessary.

(5) Uses of laminated sheet The laminated sheet of the present invention can be subjected to any molding method. In addition, the laminated sheet of the present invention can be used for any application of ordinary resin sheets.

The method for forming the laminated sheet of the present invention is not particularly limited, and includes vacuum forming, air pressure forming, match mold forming and the like.
Among these, vacuum forming is preferable from the viewpoint of forming efficiency. Therefore, the laminate sheet of the present invention includes an embodiment that is a laminate sheet for vacuum forming.

Suitable applications of the laminated sheet of the present invention include materials for packaging containers.
Therefore, the present invention includes packaging containers, particularly food packaging containers, formed from the laminated sheet of the present invention.

Food packaging containers include arbitrary containers such as trays, cups, various containers, and bags.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

<Preparation and Evaluation of Laminated Sheet>
A laminated sheet was produced by the following method and evaluated.

(1) Preparation of materials Materials for each layer were prepared as follows.

(polyethylene resin)
Polyethylene resin (PE): a blend of HDPE and LLDPE (HDPE:LLDPE (mass ratio) = 70:30)
The MFR (190° C., 21.6 kg) according to JIS K 6922-1 (ISO1133) of the HDPE is 10 g/10 minutes.
The MFR (190° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the above LLDPE is 1.0 g/10 minutes.

(polypropylene resin)
Polypropylene resin-1 (PP-1): polypropylene homopolymer (polypropylene homopolymer, melting point 160° C.)
Polypropylene resin-2 (PP-2): polypropylene block copolymer (melting point 160° C.)

(inorganic substance powder)
Calcium carbonate particles-1 (Ca-1): heavy calcium carbonate particles (average particle size 0.3 μm, no surface treatment)
Calcium carbonate particles-2 (Ca-2): heavy calcium carbonate particles (average particle size 2.0 μm, no surface treatment)
Calcium carbonate particles-3 (Ca-3): heavy calcium carbonate particles (average particle size 10.0 μm, no surface treatment)
Calcium carbonate particles-4 (Ca-4): light calcium carbonate particles (average particle size 2.0 μm, no surface treatment)

The average particle diameter of the calcium carbonate particle group is a value specified based on the air permeation method according to JIS M-8511.

(Additive)
Lauric acid diethanolamide (LDEA)

(2) Preparation of Laminated Sheet Using the materials shown in the table, a three-layered laminated sheet was prepared by the multi-layer T-die method.
The total thickness of the laminated sheet was set at 400 μm.
The thickness of the inner layer was set to 360 μm (90% of the total thickness of the laminated sheet).
An outer layer was provided on both sides of the inner layer, and the thickness of each outer layer was set to 20 μm (5% of the total thickness of the laminated sheet).

In the table, the value shown in "outer layer" is the value for one outer layer. In this example, outer layers (a total of two layers) having the same composition and thickness were provided on both sides of the inner layer.

(3) Evaluation of laminated sheet The laminated sheet was evaluated for heat resistance and moldability by the following methods. The results are shown in the "evaluation" section of the table.

(Heat-resistant)
The heat resistance of the laminated sheet was evaluated by the following method.

[Heat resistance evaluation method]
A heat resistance test according to JIS S 2029 was conducted.
Specifically, the laminated sheet was placed in a constant temperature bath adjusted to 130° C., held for 1 hour, taken out, and allowed to cool at room temperature for 30 minutes.
After standing to cool, the appearance of the laminated sheet was visually observed and evaluated according to the following criteria.

[Evaluation criteria for heat resistance]
A: The overall surface condition is very good (no unevenness, deformation, etc. occurred at all).
B: The overall surface condition is good (a little unevenness, deformation, etc. occurred).
C: The overall surface condition is poor (unevenness, deformation, etc. clearly occurred).

(Moldability)
The moldability of the laminated sheet was evaluated by the following method.

[Method for evaluating moldability]
The laminated sheet was preheated with a far-infrared heater and then formed into a tray-shaped container having a bottom diameter of 50 mm, an opening diameter of 50 mm, a height of 30 mm and a flange width of 5 mm using a vacuum forming machine.
The moldability of the obtained container was evaluated according to the following criteria.

[Evaluation Criteria for Moldability]
Each container was visually observed and measured, and the ease of molding of each laminated sheet was evaluated according to the following criteria.
A: The shape of the container was molded to almost the desired dimensions, and no distortion of the shape of the container was observed.
B: Slight distortion of container shape was observed.
C: Distortion of container shape was clearly observed.

As shown in the table, the laminated sheet satisfying the requirements of the present invention was excellent in moldability and the heat resistance of the resulting molded article.

Although data are not shown, when various inorganic powders (such as talc) were used in place of the calcium carbonate particles, the same tendency as described above was obtained. However, heavy calcium carbonate particles were particularly preferred in terms of cost and effectiveness.

Although data are not shown, the same tendency as described above was obtained regardless of the mass ratio of the polypropylene-based resin and the polyethylene-based resin in the inner layer. However, when the ratio of the polyethylene-based resin to the polypropylene-based resin was high, there was a tendency for better results to be obtained.

Claims (7)

A laminated sheet comprising an inner layer and outer layers laminated on both sides of the inner layer,
The inner layer contains a polyethylene-based resin, a polypropylene-based resin, an inorganic substance powder, and lauric acid diethanolamide,
In the inner layer, the mass ratio of the total amount of the polyethylene-based resin and the polypropylene-based resin to the inorganic substance powder is 50:50 to 60:40,
The polyethylene-based resin in the inner layer contains high-density polyethylene and linear low-density polyethylene,
MFR (190° C., 21.6 kg) according to JIS K 6922-1 (ISO1133) of the high-density polyethylene is 5 g/10 minutes or more and 15 g/10 minutes or less,
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the linear low density polyethylene is 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less,
The mass ratio of the high-density polyethylene and the linear low-density polyethylene is 90:10 to 50:50,
The content of the lauric acid diethanolamide is 0.1% by mass or more and 1.0% by mass or less with respect to the entire inner layer,
wherein the outer layer is made of only polypropylene-based resin,
Laminated sheet. 2. The laminated sheet according to claim 1, wherein the polypropylene resin in the inner layer and/or the outer layer is a polypropylene homopolymer and/or a polypropylene block polymer. 2. The laminated sheet according to claim 1, wherein said inorganic powder is ground calcium carbonate particles. 4. The laminate sheet according to claim 3 , wherein the heavy calcium carbonate particles have an average particle size of 0.7 μm or more and 6.0 μm or less based on an air permeation method according to JIS M-8511. 2. The laminate sheet according to claim 1, wherein the thickness ratio of said outer layers is 2.0% or more and 10.0% or less with respect to the total thickness of said laminate sheet. The laminate sheet according to any one of claims 1 to 5 , wherein the laminate sheet is a laminate sheet for vacuum forming. A food packaging container molded from the laminated sheet according to any one of claims 1 to 5 .