JP2023173425A - Laminate sheet, and food packaging container - Google Patents

Abstract

To provide an inorganic substance-containing laminate sheet which has good heat resistance and moldability.SOLUTION: A laminate sheet includes an inner layer and outer layers stacked on both surfaces of the inner layer, wherein the inner layer contains a polyethylene-based resin, a polypropylene-based resin, inorganic substance powder, and lauric acid diethanolamide, in the inner layer, a 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 mass% or more and 1.0 mass% or less with respect to the whole inner layer, the outer layer contains a polyethylene-based resin and a polypropylene-based resin, and in the outer layer, a mass ratio of the polyethylene-based resin to the polypropylene-based resin is 20:80 to 50:50.SELECTED DRAWING: None

Description

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

In recent years, attempts have been made to reduce the content of resin components in various resin products from the viewpoint of environmental protection.
One such attempt is to increase the amount of inorganic substances (calcium carbonate, etc.) contained in resin products (for example, Patent Documents 1 and 2).

Patent No. 6857428 JP 2021-112862 Publication

Here, it is known that when the blending amount of an inorganic substance is increased with respect to a resin composition, molding processability may be reduced.

Further, resin products are required to have specific properties (such as heat resistance) depending on the purpose and the like.

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

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

(1) A laminated sheet comprising an inner layer and an outer layer laminated on both sides of the inner layer,
The inner layer contains a polyethylene resin, a polypropylene resin, an inorganic powder, and lauric acid diethanolamide,
In the inner layer, the mass ratio of the total amount of the polyethylene resin and the polypropylene 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 based on the entire inner layer,
The outer layer includes a polyethylene resin and a polypropylene resin,
In the outer layer, the mass ratio of the polyethylene resin and the polypropylene resin is 20:80 to 50:50.
Laminated sheet.

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

(3) The laminate 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 substance powder is heavy calcium carbonate particles.

(5) The laminated sheet according to (4), wherein the heavy calcium carbonate particles have an average particle diameter 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 ratio of the thickness of the outer layer 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), wherein the laminated sheet 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 laminate sheet having good heat resistance and moldability is provided.

Hereinafter, embodiments of the present invention will be described, 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 an outer layer laminated on both sides of the inner layer) and satisfies all of the following requirements.
(Requirement 1) The inner layer contains a polyethylene resin, a polypropylene resin, an inorganic powder, and lauric acid diethanolamide.
(Requirement 2) In the inner layer, the mass ratio of the total amount of polyethylene resin and polypropylene 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 based on the entire inner layer.
(Requirement 4) The outer layer contains a polyethylene resin and a polypropylene resin, and the mass ratio of the polyethylene resin to the polypropylene resin in the outer layer is 20:80 to 50:50.

The main technical feature of the laminated sheet of the present invention is the composition of its inner layer.
The inner layer in the present invention contains a predetermined resin (a polyethylene resin and a polypropylene resin) and an inorganic powder, and the blending amounts of the resin and the inorganic powder are approximately the same (requirements 1 and 2). Such resin compositions with a high proportion of inorganic substance powder usually tend to have poor moldability.
However, the present inventors have found that by blending a predetermined amount of lauric acid diethanolamide in the inner layer that satisfies Requirement 2 (requirements 1 and 3), the heat resistance is improved without impairing the moldability of the resin composition. I discovered a surprising finding:
Such an effect was not impaired even when an outer layer containing a predetermined ratio of polyethylene resin and polypropylene resin was disposed 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 S 2029.
In the present invention, "the heat resistance of the laminated sheet is good" means that when the laminated sheet is subjected to a heat resistance test according to JIS S 2029, the overall surface condition is good (no unevenness, deformation, etc.). (not to do so), etc.

The heat resistance of the laminated sheet can be evaluated by the method shown in the 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 there is no distortion etc. in the obtained molded product. Includes things that are completely unacceptable.

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

Hereinafter, the structure of the laminated sheet of the present invention will be explained in detail.

(1) Inner layer The inner layer contains a polyethylene resin, a polypropylene resin, an inorganic powder, and lauric acid diethanolamide.

(Type of polyethylene resin blended into the inner layer)
As the polyethylene resin, a resin containing ethylene component units as a main component can be used. One type of polyethylene resin can be used alone or two or more types can be used in combination.

The polyethylene resin in the present invention includes a resin in which the ethylene component unit is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, most preferably 80% by mass or more.

Polyethylene 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 copolymer Examples include copolymers.

Note that "high-density polyethylene (HDPE)" is polyethylene having a density of 0.942 g/cm ³ or more.
“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)" refers to a density of 0.911 g/ ^cm3 or more and less than 0.940 g/cm3 (preferably a density of 0.912 g/ ^{cm3 or} more and less than 0.928 g/ ^cm3 ) It is a polyethylene with

As the polyethylene resin, resins containing high-density polyethylene and linear low-density polyethylene are preferable from the viewpoint of easily increasing heat resistance and moldability, 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) of 5 g/10 minutes or more and 15 g/10 minutes or less according to JIS K 6922-1 (ISO1133) from the viewpoint of easily improving heat resistance and moldability. It is preferably 6 g/10 minutes or more and 14 g/10 minutes or less.

Linear low-density polyethylene has a MFR (190°C, 2.16 kg) of 0.5 g/10 minutes or more 1. It is preferably 5 g/10 minutes or less, and more preferably 0.6 g/10 minutes or more and 1.4 g/10 minutes or less.

In resins containing high-density polyethylene and linear low-density polyethylene, the mass ratio of both (high-density polyethylene: linear low-density polyethylene) is preferably 90, from the viewpoint of particularly easy to increase 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 resin includes high density polyethylene and linear low density polyethylene,
The MFR (190°C, 21.6 kg) of high-density polyethylene according to JIS K 6922-1 (ISO1133) is 5 g/10 minutes or more and 15 g/10 minutes or less,
The MFR (190°C, 2.16 kg) of linear low density polyethylene according to JIS K 6922-1 (ISO1133) 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 into the inner layer)
As the polypropylene resin, a resin containing propylene component units as a main component can be used. One type of polypropylene resin can be used alone or two or more types can be used in combination.

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

Examples of the polypropylene resin include polypropylene homopolymers (propylene homopolymers), copolymers of propylene and other α-olefins (those copolymerizable with propylene), and the like.
Examples of "other α-olefins" include 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.).

The propylene homopolymer includes linear or branched polypropylene exhibiting various stereoregularities (isotactic, syndiotactic, atactic, hemiisotactic, etc.).

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

As the polypropylene resin, a resin containing one or more of a polypropylene homopolymer and a polypropylene block polymer is preferable from the viewpoint of easily increasing heat resistance and moldability, and a resin containing only one or more of a polypropylene homopolymer and a polypropylene block polymer is preferable. Resins are more preferred.

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

Examples of the inorganic substance powder 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, etc.

Examples of inorganic 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, Examples include 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, and graphite.

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

In order to improve the dispersibility and reactivity of the inorganic powder, the inorganic powder may be surface-treated.
Examples of surface treatment methods include physical methods (such as plasma treatment) and chemical methods (methods using coupling agents and surfactants).

The shape of the inorganic substance powder is not particularly limited, and may be any of particles (spherical, irregularly shaped, etc.), flakes, granules, fibers, and the like.

The average particle diameter 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.

Preferred embodiments of the present invention include embodiments in which the inner layer does not substantially contain inorganic powder having a particle size of more than 50.0 μm, from the viewpoint of easily suppressing uneven distribution of inorganic powder.
Preferred embodiments of the present invention include embodiments in which the inner layer does not substantially contain inorganic substance powder with 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" refers to an embodiment in which the content of the component is less than 0.1% by mass relative to the inner layer, more preferably 0.01% by mass or less. It includes certain embodiments, and more preferably embodiments that do not contain it at all.

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

As the inorganic powder, calcium carbonate particles are preferred. When the blending amount of calcium carbonate particles is increased in a resin composition, molding processability may particularly decrease. However, according to the present invention, heat resistance can be improved without impairing molding processability due to the action of lauric acid diethanolamide, etc. It can also increase

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

The inner layer has a larger number of contact interfaces with the thermoplastic resin (polypropylene resin, polyethylene resin), which makes it easier to achieve the effects of the present invention and to improve the mechanical properties of the laminated sheet. preferably includes heavy calcium carbonate particles.
Moreover, the calcium carbonate particles contained in the inner layer are preferably made of heavy calcium carbonate particles, and it is more preferable that the inorganic substance powder contained in the inner layer is made of 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 (chemical precipitation reaction, etc.).
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 diameter 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 easy to achieve. .0 μm or less.

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

The present inventors have improved the compatibility of polypropylene resin, polyethylene resin, and inorganic powder by blending lauric acid diethanolamide among various additives into the inner layer, and as a result, the resulting laminated sheet We have discovered an unexpected finding that the moldability and heat resistance of the material can be improved.

(Other ingredients blended into the inner layer)
The inner layer may or may not contain other components other than polypropylene resin, polyethylene resin, inorganic powder, and lauric acid diethanolamide within a range that does not impede the effects of the present invention.

As other components, any component that can be normally blended into the resin sheet can be used.
Examples of such components include thermoplastic resins (other than polyethylene resins and polypropylene resins), lubricants, dispersants, antistatic agents, antioxidants, thermal stabilizers, ultraviolet absorbers, and the like.
The types and amounts of these components can be appropriately set depending on the desired effect.

Thermoplastic resins other than polyethylene resins and polypropylene resins include ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, and the like.

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

(Ratio of ingredients mixed in the inner layer)
In the inner layer, the mass ratio of the total amount of polyethylene resin and polypropylene resin to the inorganic substance powder is 50:50 to 60:40, and the content of lauric acid diethanolamide is in the range of 50:50 to 60:40 with respect to the entire inner layer. It is 0.1% by mass or more and 1.0% by mass or less.

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

In the inner layer, the effect of the present invention tends to be more easily achieved as the mass ratio of polypropylene resin to polyethylene resin increases.
In the inner layer, the mass ratio of polypropylene resin to polyethylene resin (polypropylene resin: polyethylene 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% by mass, based on the entire inner layer, from the viewpoint of easily increasing 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% by mass, based on the entire inner layer, from the viewpoint of not impairing heat resistance and moldability. .8% by mass or less.

The lower limit of the content of the polyethylene 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 easily improving moldability.

The upper limit of the content of the polyethylene resin is preferably 45% by mass or less, more preferably 43% by mass or less, based on the entire inner layer, from the viewpoint of easily increasing heat resistance.

The lower limit of the content of the polypropylene 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 easily improving moldability.

The upper limit of the content of the polypropylene resin is preferably 20% by mass or less, more preferably 13% by mass or less, based on the entire inner layer, from the viewpoint of easily increasing 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 fully meeting the needs of environmental protection.

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, based on the entire inner layer, from the viewpoint of not impairing moldability.

(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 structures (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 each contain a polyethylene resin and a polypropylene resin, and in each outer layer, the mass ratio of the polyethylene resin to the polypropylene resin is from 20:80 to It is 50:50.

A preferred embodiment of the present invention includes an embodiment in which the first outer layer and the second outer layer have the same configuration (thickness, shape, etc.).

(Polyethylene resin blended into the outer layer)
As the polyethylene resin blended in the outer layer, the same resins as those listed above (types of polyethylene resin blended in the inner layer) can be employed.

The polyethylene resin blended in the outer layer may be the same as or different from the polyethylene resin blended in the inner layer.
From the viewpoint of easily achieving the effects of the present invention, it is preferable that the polyethylene resin blended in the outer layer is the same as the polyethylene resin blended in the inner layer.

As the polyethylene resin, resins containing high-density polyethylene and linear low-density polyethylene are preferable from the viewpoint of easily increasing heat resistance and moldability, 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) of 5 g/10 minutes or more and 15 g/10 minutes or less according to JIS K 6922-1 (ISO1133) from the viewpoint of easily improving heat resistance and moldability. It is preferably 6 g/10 minutes or more and 14 g/10 minutes or less.

Linear low-density polyethylene has a MFR (190°C, 2.16 kg) of 0.5 g/10 minutes or more 1. It is preferably 5 g/10 minutes or less, and more preferably 0.6 g/10 minutes or more and 1.4 g/10 minutes or less.

In resins containing high-density polyethylene and linear low-density polyethylene, the mass ratio of both (high-density polyethylene: linear low-density polyethylene) is preferably 90, from the viewpoint of particularly easy to increase 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 resin includes high density polyethylene and linear low density polyethylene,
The MFR (190°C, 21.6 kg) of high-density polyethylene according to JIS K 6922-1 (ISO1133) is 5 g/10 minutes or more and 15 g/10 minutes or less,
The MFR (190°C, 2.16 kg) of linear low density polyethylene according to JIS K 6922-1 (ISO1133) 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.

(Polypropylene resin blended into the outer layer)
As the polypropylene resin blended in the outer layer, the same resins as those listed above (types of polypropylene resin 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 of facilitating the effects of the present invention, the polypropylene resin blended in the outer layer is preferably the same as the polypropylene resin blended in the inner layer.

As the polypropylene resin, a resin containing one or more of a polypropylene homopolymer and a polypropylene block polymer is preferable from the viewpoint of easily increasing heat resistance and moldability, and a resin containing only one or more of a polypropylene homopolymer and a polypropylene block polymer is preferable. Resins are more preferred.

(Other ingredients added to the outer layer)
The outer layer may or may not contain other components other than the polyethylene resin and the polypropylene resin as long as the effects of the present invention are not impaired.

As other components, any component that can be normally blended into the resin sheet can be used.
Examples of such components include thermoplastic resins (other than polypropylene resins and polyethylene resins), lubricants, dispersants, antistatic agents, antioxidants, thermal stabilizers, ultraviolet absorbers, and the like.
The types and amounts of these components can be appropriately set depending on the desired effect.

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

A preferred embodiment of the present invention includes a laminated sheet in which the outer layer is made only of polypropylene resin and polyethylene resin.

(Ratio of ingredients mixed in the outer layer)
In each outer layer, the mass ratio of polyethylene resin to polypropylene resin is 20:80 to 50:50.

In each outer layer, the mass ratio of polyethylene resin to polypropylene resin (polyethylene resin: polypropylene resin) is 20:80 to 50:50, preferably 25:75 to 45:55.

The lower limit of the content of the polyethylene resin is preferably 20% by mass or more, more preferably 25% by mass or more, based on the outer layer (per layer), from the viewpoint of easily improving moldability.

The upper limit of the content of the polyethylene resin is preferably 50% by mass or less, more preferably 45% by mass or less based on the outer layer (per layer), from the viewpoint of easily increasing heat resistance.

The lower limit of the content of the polypropylene resin is preferably 50% by mass or more, more preferably 55% by mass or more, based on the outer layer (per layer), from the viewpoint of easily improving moldability.

The upper limit of the content of the polypropylene resin is preferably 80% by mass or less, more preferably 75% by mass or less, based on the outer layer (per layer), from the viewpoint of easily increasing heat resistance.

(3) Thickness of each layer of the laminated sheet, etc. The thickness of each layer in the laminated sheet of the present invention is not particularly limited, but a good appearance can be achieved by making the outer layer thinner than the inner layer. However, it is possible to express the excellent characteristics exhibited by the inner layer.

The ratio of the thickness of the first outer layer and the second outer layer is preferably 2.0% or more, respectively, based on the total thickness of the laminated sheet, from the viewpoint of easily exhibiting excellent mechanical properties. It is 0% or less. In this aspect, the total thickness of the outer layer (the sum of the thicknesses of the first outer layer and the second outer layer) is 4.0% or more and 20.0% or less of the total thickness of the laminated sheet. be.

The lower limit of the ratio of the thickness of the first outer layer and the second outer layer is preferably 2.0% or more, more preferably 2.0% or more of the total thickness of the laminated sheet, from the viewpoint of easy appearance It is 3.0% or more, more preferably 4.0% or more.

The upper limit of the ratio of the thickness of the first outer layer and the second outer layer is preferably 10.0% or less, and more preferably 10.0% or less of the total thickness of the laminated sheet, from the viewpoint that the effect of the inner layer is more likely to be exerted. Preferably it is 9.0% or less, more preferably 8.0% or less.

In the laminated sheet of the present invention, the ratio of the thickness 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 laminated sheet.

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

The upper limit of the thickness of the first outer layer and the second outer layer is preferably 100 μm or less, more preferably 90 μm or less, from the viewpoint of moldability 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 and the like.

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

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

The density of the laminated sheet is not particularly limited.

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

Examples of methods for manufacturing the laminated sheet include the following methods.
・Method of laminating the inner and outer layers formed into sheets using a calendar roll ・Method of coextruding the inner and outer layers Method of performing co-extrusion molding in the same process ・Extrusion inflation method using multiple annular dies

The laminated sheet may be stretched as necessary.

(5) Application of laminated sheet The laminated sheet of the present invention can be subjected to any molding method. Moreover, the laminated sheet of the present invention can be employed for any purpose of ordinary resin sheets.

The method for forming the laminated sheet of the present invention is not particularly limited, and examples thereof include vacuum forming, pressure forming, match molding, and the like.
Among these, vacuum forming is preferred 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 uses for 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 any containers, including trays, cups, various containers, bags, and the like.

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

<Preparation and evaluation of laminated sheet>
A laminated sheet was produced and evaluated using the following method.

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

(Polyethylene resin)
Polyethylene resin (PE): blend of HDPE and LLDPE (HDPE:LLDPE (mass ratio) = 70:30)
Note that the MFR (190° C., 21.6 kg) of the above HDPE according to JIS K 6922-1 (ISO1133) is 10 g/10 minutes.
The MFR (190° C., 2.16 kg) of the above LLDPE according to JIS K 6922-1 (ISO1133) 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 size 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 A three-layer laminated sheet was prepared using the materials shown in the table by the multilayer T-die method.
The total thickness of the laminated sheet was set to 400 μm.
The thickness of the inner layer was set to 360 μm (90% of the total thickness of the laminated sheet).
Outer layers were provided on both sides of the inner layer, and the thickness of each outer layer was set to 20 μm (each 5% of the total thickness of the laminated sheet).

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

(3) Evaluation of laminated sheet The heat resistance and moldability of the laminated sheet were evaluated 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 cooling, the appearance of the laminated sheet was visually observed and evaluated based on the following criteria.

[Heat resistance evaluation criteria]
A: The overall surface condition was very good (no unevenness, deformation, etc. occurred at all).
B: The overall surface condition is good (some 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.

[Evaluation method of moldability]
After preheating the laminated sheet with a far-infrared heater, it was formed into a tray-shaped container with 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 based on 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 based on the following criteria.
A: The container was molded to approximately the intended dimensions, and no distortion of the container shape was observed.
B: Slight distortion of the container shape was observed.
C: Distortion of the container shape was clearly observed.

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

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

Although data is not shown, the same tendency as described above was obtained regardless of the mass ratio of the polypropylene resin to the polyethylene resin in the inner layer. However, when the ratio of polyethylene resin to polypropylene resin was high, better results tended to be obtained.

Although data is not shown, the same tendency as described above was obtained even when "PP-2" was used instead of "PP-1" as the polypropylene resin in the outer layer.

Claims (8)

A laminated sheet comprising an inner layer and an outer layer laminated on both sides of the inner layer,
The inner layer contains a polyethylene resin, a polypropylene resin, an inorganic powder, and lauric acid diethanolamide,
In the inner layer, the mass ratio of the total amount of the polyethylene resin and the polypropylene 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 based on the entire inner layer,
The outer layer includes a polyethylene resin and a polypropylene resin,
In the outer layer, the mass ratio of the polyethylene resin and the polypropylene resin is 20:80 to 50:50.
Laminated sheet. The polyethylene resin in the inner layer and/or the outer layer includes high density polyethylene and linear low density polyethylene,
The MFR (190°C, 21.6 kg) of the high-density polyethylene according to JIS K 6922-1 (ISO1133) is 5 g/10 minutes or more and 15 g/10 minutes or less,
The linear low density polyethylene has an MFR (190°C, 2.16 kg) according to JIS K 6922-1 (ISO1133) of 0.5 g/10 minutes or more and 1.5 g/10 minutes or less,
The laminate sheet according to claim 1, wherein the mass ratio of the high-density polyethylene to the linear low-density polyethylene is 90:10 to 50:50. The laminate 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. The laminated sheet according to claim 1, wherein the inorganic substance powder is heavy calcium carbonate particles. The laminated sheet according to claim 4, wherein the average particle diameter of the heavy calcium carbonate particles is 0.7 μm or more and 6.0 μm or less based on an air permeation method according to JIS M-8511. The laminated sheet according to claim 1, wherein the ratio of the thickness of the outer layer is 2.0% or more and 10.0% or less with respect to the total thickness of the laminated sheet. The laminated sheet according to any one of claims 1 to 6, wherein the laminated sheet is a laminated sheet for vacuum forming. A food packaging container formed from the laminated sheet according to any one of claims 1 to 6.