JP2023044122A - Resin laminated sheet for thermoforming, and molded article - Google Patents

Abstract

To provide a resin laminated sheet for thermoforming which has a large content of an inorganic substance, is excellent in moldability, and is less likely to generate odor in heating, and a molded article obtained by molding the sheet.SOLUTION: A resin laminated sheet for thermoforming of the present invention has an inner layer containing an inorganic substance and a thermoplastic resin, a first polyolefin-based resin layer provided on one surface of the inner layer, and a second polyolefin-based resin layer provided on the other surface of the inner layer, wherein the first polyolefin-based resin layer and the second polyolefin-based resin layer do not contain an antistatic agent, the mass ratio of the inorganic substance to the thermoplastic resin is 80:20 to 50:50, and the total of thicknesses of the first polyolefin-based resin layer and the second polyolefin-based resin layer is 10-30% based on the whole thickness of the resin laminated sheet.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a thermoforming resin laminate sheet that has a high content of inorganic substances, is excellent in moldability, and generates little odor when heated, and a molded article obtained by molding the sheet.

Conventionally, synthetic resin sheets made of polyolefin polymers and inorganic fillers are known to be excellent in rigidity, heat resistance, oil resistance and the like. Sheet-like synthetic resin sheets are secondary processed by methods such as vacuum and pressure molding, and are used for thermoformed products such as cups and trays.

A resin sheet containing an inorganic filler may generate an odor when heated. Generation of such odor causes various problems. For example, if an odor is generated due to heating of the resin sheet during secondary processing, the working environment deteriorates. In addition, when the food container is heated in a microwave oven, an odor may be generated, and the odor may migrate to the food. This makes it difficult to use synthetic resin sheets made of inorganic fillers for food containers.

Known methods for reducing the odor of a resin sheet containing an inorganic filler during heating include a method of improving components in the sheet and a method of improving the layer structure. As the former, Patent Document 1 discloses that the generation of odor is prevented by adding phosphites and fatty acid amides to a resin composition comprising a polypropylene resin and a filler. Patent Document 2 discloses the use of polypropylene with a relatively narrow molecular weight distribution on the low molecular weight side using a metallocene catalyst to reduce crystalline low molecular weight PP, which is the main cause of odor. . As the latter, Patent Document 3 discloses suppressing odor by coating a synthetic resin layer containing an inorganic filler with a surface layer containing a specific antistatic agent.

Japanese Patent No. 4495386 Japanese Patent No. 4847667 Japanese Patent No. 3081342

In a synthetic resin sheet containing an inorganic filler, as the amount of the inorganic filler in the resin increases, the surface conditions of the sheet and the molded article deteriorate, and there is a risk that moldability will deteriorate. Therefore, in some cases, a method of forming an outer layer or laminating a film for covering is adopted. In addition, if the amount of the inorganic filler is increased, further improvement is required to suppress the generation of odor during secondary processing of the sheet or during heating such as heating of the food container in a microwave oven.

An object of the present invention is to provide a resin laminated sheet for thermoforming which contains a large amount of inorganic substances, is excellent in moldability, and generates little odor when heated, and a molded article obtained by molding the sheet.

The thermoforming resin laminated sheet of the present invention comprises an inner layer containing an inorganic substance and a thermoplastic resin, a first polyolefin resin layer (hereinafter referred to as "first PO layer") provided on one surface of the inner layer, A second polyolefin-based resin layer (hereinafter referred to as a "second PO layer") is provided on the other surface of the inner layer, and the first polyolefin-based resin layer and the second polyolefin-based resin layer contain an antistatic agent and the mass ratio of the inorganic substance and the thermoplastic resin is 80:20 to 50:50, and the total thickness of the first polyolefin resin layer and the second polyolefin resin layer is the resin It is characterized by being 10 to 30% of the total thickness of the laminated sheet.

The molded article of the present invention is characterized by being obtained by thermoforming the thermoforming resin laminated sheet of the present invention.

The resin laminated sheet for thermoforming and the molded product of the present invention are excellent in moldability and can suppress the generation of odor during heating in spite of the high content of inorganic substances. Therefore, deterioration of the working environment during secondary processing can be suppressed, and it can be suitably used for food applications.

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

(1) Thermoforming resin laminated sheet The thermoforming resin laminated sheet according to the present embodiment (hereinafter referred to as "this sheet") includes an inner layer containing an inorganic substance and a thermoplastic resin, and one surface side of the inner layer. It has a first PO layer provided and a second PO layer provided on the other surface side of the inner layer. The first and second PO layers may be laminated directly on the surface of the inner layer, or may be laminated on the surface side of the inner layer via another layer such as an adhesive layer, as described later.

There are no particular limitations on the type, component, and shape of the inorganic material contained in the inner layer. Specific examples of the inorganic substance include inorganic fillers for the purpose of improving physical properties (for example, impact strength or heat resistance) of the laminated resin sheet. The inorganic substance may be used singly or in combination of two or more. Specific examples of the inorganic filler include talc, calcium carbonate, silica, diatomaceous earth, alumina, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, calcium silicate, glass beads, bentonite, glass flakes, and glass fiber. , carbon fiber, aluminum powder, molybdenum sulfide, boron fiber, potassium titanate, calcium titanate, hydrotalcite, carbon fiber, pumice powder, mica, calcium phosphate, and aluminum phosphate. Calcium carbonate as the inorganic substance is abundant in limestone as a raw material, so it is inexpensive and easily available, and it is known that surface-untreated calcium carbonate in particular has the same odor intensity as surface-treated talc. It is preferable because it does not require surface treatment. Further, when calcium carbonate is subjected to surface treatment, it is conceivable that an odor may be generated when the surface treatment agent is melted with the thermoplastic resin.

The structure and properties of the thermoplastic resin contained in the inner layer are not particularly limited. The thermoplastic resin is preferably a polypropylene-based resin and/or a polyethylene-based resin. The structures and properties of the polypropylene-based resin and the polyethylene-based resin are not particularly limited. The polypropylene-based resin and the polyethylene-based resin may be homopolymers or copolymers with other monomers. Moreover, the said polypropylene-type resin may be single 1 type, and may use 2 or more types. The polyethylene-based resin may also be used alone or in combination of two or more. Furthermore, as the polypropylene-based resin and the polyethylene-based resin, for example, a polypropylene-based resin and/or polyethylene-based resin having an MFR value of 0.2 to 2.0 g/10 min, or 0.3 to 1.0 g/10 min Resin can be used. In this document, the MFR value is based on the method of JIS K7210, and the polypropylene resin is measured at a temperature of 230 ° C and a load of 2.16 kg, and the polyethylene resin is measured at a temperature of 190 ° C and a load of 2.16 kg. It is a measured value.

Specific examples of the polypropylene-based resin include homopolypropylene (propylene homopolymer), or propylene and α-olefin (e.g., ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1- octene, 1-nonene or 1-decene). Specific examples of the polyethylene resin include homopolyethylene (ethylene homopolymer; low density polyethylene, high density polyethylene, etc.), or ethylene and α-olefin (eg, propylene, 1-butene, 1-pentene, 1 -hexene, 1-heptene, 1-octene, 1-nonene or 1-decene) (however, the polypropylene resin and the polyethylene resin are different resins).

There is no particular limitation on the mixing ratio of the polypropylene-based resin and the polyethylene-based resin in the thermoplastic resin. The polypropylene-based resin and the polyethylene-based resin can each be 5 to 40% by mass, preferably 10 to 30% by mass, based on 100% by mass of the thermoplastic resin. Further, when the polypropylene resin and the polyethylene resin are included, the total ratio of the polypropylene resin and the polyethylene resin is usually 50 to 100% by mass in 100% by mass of the thermoplastic resin. The lower limit of the ratio can be 55, 60, 65, or 70% by weight. Moreover, the upper limit of the ratio can be 95, 90, 85, or 80% by mass. Furthermore, the mass ratio of the polypropylene-based resin and the polyethylene-based resin is not particularly limited. The mass ratio can be usually (0.5-3):1, preferably (0.5-2):1.

The thermoplastic resin may be the polypropylene-based resin and /or the polyethylene-based resin alone, or may contain other thermoplastic resins.

The mass ratio of the inorganic material and the thermoplastic resin in the inner layer is 80:20 to 50:50. When the mass ratio is within the above range, the amount of resin can be reduced, and as a result, the amount of heat generated during combustion can be suppressed and the environmental load can be reduced, which is preferable.

There are no particular restrictions on the type and structure of the polyolefin-based resin that constitutes the first and second PO layers. The polyolefin resin may be a homopolymer, a copolymer of two or more olefins, or a copolymer of olefins and other monomers. Further, as the polyolefin resin, for example, a polyolefin resin having an MFR value of 1.0 to 3.0 g/10 minutes, or 1.5 to 3.0 g/10 minutes, particularly an MFR value within the above range Certain homo PP resins can be used.

The polyolefin-based resins constituting the first and second PO layers may be the same polyolefin-based resin, or may be polyolefin-based resins having different structures or properties. The same polyolefin resin is usually used.

When a polypropylene-based resin or a polyethylene-based resin is used as the polyolefin-based resin, it may be the same resin as the polypropylene-based resin or the polyethylene-based resin contained in the inner layer, or may be a resin with different properties, such as a resin with a different MFR. For example, as the polyolefin-based resin, a polypropylene-based resin or a polyethylene-based resin having a larger MFR than the polypropylene-based resin or the polyethylene-based resin contained in the inner layer can be used. More specifically, for example, a polypropylene-based resin or polyethylene-based resin having an MFR of 2.0 or more is used as the polyolefin-based resin, and a polypropylene-based resin or polyethylene-based resin contained in the inner layer has an MFR of 1.0. The following polypropylene-based resins or polyethylene-based resins can be used.

Specific examples of the polyolefin-based resin include polyethylene resins (e.g., high-density polyethylene and low-density polyethylene); polypropylene resins; polystyrene resins; copolymers of ethylene or propylene and other monomers (e.g., propylene - ethylene copolymer resins and ethylene-vinyl acetate copolymer resins). The polyolefin-based resin may be used alone or in combination of two or more.

The first and second PO layers may consist of only the polyolefin resin, or may contain other resins.

The total thickness of the first and second PO layers is 10-30%, preferably 10-25%, of the total thickness of the sheet. It is preferable that the total thickness of the first and second PO layers is within the above range, because odor during heating can be reduced. As long as the total thickness of the first and second PO layers is within the above range, the thickness of the first and second PO layers can be set as appropriate. Specifically, the total thickness of the first and second PO layers can be, for example, 0.04 to 0.12 mm, preferably 0.04 to 0.1 mm. The thicknesses of the first PO layer and the second PO layer may be the same or different.

In this sheet, the first and second PO layers do not contain an antistatic agent. In this sheet, even if the first and second PO layers do not contain an antistatic agent, generation of odor during heating can be suppressed, which is preferable. The type of the antistatic agent is not limited as long as it is a component that has the property of increasing the electrical conductivity of the resin. Specific examples of the antistatic agent include ionic compounds, particularly ionic compounds comprising at least one of metal salts and organic salts. In addition, "not containing" the antistatic agent includes not only the case where the antistatic agent is not contained at all, but also the case where the antistatic agent is contained in a very small amount to the extent that the antistatic effect cannot be exhibited (for example, polyolefin resin 0.01 parts by mass or less, or 0.005 parts by mass or less, or 0.001 parts by mass or less per 100 parts by mass).

The layer structure of this sheet is not particularly limited as long as it includes the inner layer, the first PO layer, and the second PO layer. The sheet may be composed only of the inner layer, the first PO layer, and the second PO layer, and may have other layers as necessary. Further, the other layer may be a single layer, or may be two or more layers having the same or different compositions or physical properties.

There is no particular limitation on the type of the other layer. Specific examples of the other layer include a laminate film layer with decorative printing on the surface layer, a gas barrier layer, and an adhesive layer for bonding between layers. Moreover, there is no particular limitation on the stacking positions of the other layers. The other layer may be provided between the inner layer and the first PO layer, between the inner layer and the second PO layer, or the outer surface of the first or second PO layer (laminated on the inner layer). on the surface opposite to the surface on which it is located).

The specific shape of this sheet is not particularly limited, and can be appropriately determined as necessary. Therefore, the term "sheet" also includes a film form. The thickness of this sheet can be, for example, 0.1 to 3 mm, or 0.3 to 2 mm.

The sheet may contain in-process losses such as selvedge loss and skeleton loss generated when obtaining the sheet or molded product, and other components as necessary, within a range that does not significantly impair the moldability. Specific examples of the other components include, for example, additives used in known resin sheets, such as flame retardants, ultraviolet absorbers, fluorescent whitening agents, antistatic agents (however, the first PO layer and the 2PO layers.), antifog agents, lubricants, antiblocking agents, flow improvers, plasticizers, dispersants, and antimicrobial agents. The other component may be contained in any one of the inner layer, the first PO layer, and the second PO layer, or may be contained in all of them.

(2) Molded article The molded article can be obtained by thermoforming the sheet. The molding usually includes thermoforming. The specific method of thermoforming is not particularly limited, and known thermoforming methods such as hot plate forming, vacuum forming, pressure forming, vacuum pressure forming, double-sided vacuum forming, plug forming, or press forming can be used. can. Also, the conditions for thermoforming are not particularly limited. Molding conditions can be appropriately determined as necessary.

There are no particular restrictions on the specific uses of the present molded article. Such uses include containers such as packaging containers, for example, food and beverage containers. As the container for food and drink, a container for food and drink which is heated and cooked together with the container, for example, a container for food for heating in a microwave oven is particularly preferable. When the present molded product is used as a container for food and drink, especially as a container for food and drink that is heated and cooked in its entirety, the generation of odor during heating can be reduced, thereby suppressing the transfer of odor to the food and drink. preferable.

The shape and dimensions of the molded product are not particularly limited and can be set as appropriate. When the molded article is a container, the shape of the container specifically has a body and a bottom formed at one end of the body, and has an opening at the other end of the body. container. The opening may further have a flange. In addition, the said "container" includes not only the whole container but a part of container. For example, the "container" includes not only the main body of the container but also the lid of the container. Therefore, the "container" may be only the main body of the container or only the lid of the container.

EXAMPLES The present invention will be specifically described below with reference to Examples. It should be noted that the present invention is not limited to the forms shown in the examples. The embodiment of the present invention can be variously changed within the scope of the present invention depending on the purpose, application, etc.

(1) Production of resin sheet The following components were used as raw materials.
(A) Calcium carbonate; heavy calcium carbonate (average particle size 1.5 μm)
(B) polypropylene resin <for first and second PO layers>
(B-1) Homopolypropylene: manufactured by Japan Polypropylene Corporation, grade name "FY6C" (MFR 2.4 g/10 minutes)
<For inner layer>
(B-2) Homopolypropylene: manufactured by Japan Polypropylene Corporation, grade name "EA9" (MFR 0.5 g/10 minutes)
(C) Polyethylene resin High-density polyethylene: Grade name “B5803” manufactured by Keiyo Polyethylene Co., Ltd. (MFR: 0.3 g / 10 minutes)

<Examples 1 and 2>
(A) Calcium carbonate, (B-2) homopolypropylene, and (C) high-density polyethylene were blended at a ratio of 60:20:20 to prepare an inner layer composition. (B-1) homopolypropylene used for the first and second PO layers and the inner layer composition are dry-blended in respective extruders, then supplied to a hopper, and the melt-blended resin is co-extruded. Thus, resin sheets of Examples 1 and 2 were obtained (thickness: 0.40 mm, layer structure: first PO layer/inner layer/second PO layer). Specifically, a twin-screw extruder is used for the inner layer, and a single-screw extruder is used for the first and second PO layers. First and second PO layers were formed and laminated. Table 1 shows the layer ratio of each layer (first PO layer/inner layer/second PO layer) in the resin sheets of Examples 1 and 2.

<Comparative Example 1>
A resin sheet of Comparative Example 1 was produced in the same manner as in Example, except that the layer ratio of the inner layer and the first and second PO layers was changed to 2/96/2.

<Comparative Example 2>
A resin sheet of Comparative Example 2 was produced in the same manner as in Example except that only the inner layer composition of Example was used (layer ratio: 0/100/0).

(2) Container manufacturing method Using a vacuum pressure forming apparatus (manufactured by Asano Laboratory), the resin sheets of Examples and Comparative Examples are thermoformed by a vacuum pressure forming method to form a bottom on one end side of the body. and a container with an opening at the other end was produced (long side 232 mm x short side 195 mm x depth 34 mm).

(3) Performance Evaluation The container moldability and odor of the resin sheets of Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 1 below.

(I) Container Moldability The container moldability of the laminated resin sheet was evaluated by visually observing the thermoformed container. In Table 1, "◯" indicates good (the molded product has no wrinkles), and "X" indicates the bad (the molded product has wrinkles).

(II) Odor Sensory Test A sample (35±1 g) obtained by cutting the laminated resin sheet into approximately 10 mm squares was placed in an Erlenmeyer flask and stoppered, and the Erlenmeyer flask and the stopper were fixed with a fixing clip. After that, using Espec's "Gear Oven GPH-100", it was heated at 80° C. for 2 hours, the Erlenmeyer flask was taken out, and a human sensory test was immediately conducted. The sensory evaluation level of the chalk-like odor generated during heating was evaluated in the following five stages, and 1 and 2 were defined as acceptable ranges.
1: Slightly felt 2: Slightly felt 3: Slightly strongly felt 4: Smell 5: Strong smell

Although the resin sheets of Examples contained a large amount of inorganic substances in the inner layer, the molded articles did not have wrinkles and were excellent in container moldability. Moreover, in both Examples 1 and 2, in which the total thickness of the first and second PO layers was within the scope of the present invention, the generation of odor during heating was reduced to the extent that there was no practical problem. On the other hand, Comparative Example 2, which does not have the first and second PO layers, and Comparative Example 1, in which the total thickness of the first and second PO layers is outside the scope of the present invention, generate more odor than the Examples. was

Claims (4)

A resin laminate having an inner layer containing an inorganic substance and a thermoplastic resin, a first polyolefin resin layer provided on one surface of the inner layer, and a second polyolefin resin layer provided on the other surface of the inner layer. a sheet,
The first polyolefin resin layer and the second polyolefin resin layer do not contain an antistatic agent,
The mass ratio of the inorganic substance and the thermoplastic resin is 80:20 to 50:50,
A resin laminate sheet for thermoforming, wherein the total thickness of the first polyolefin resin layer and the second polyolefin resin layer is 10 to 30% of the total thickness of the resin laminate sheet. 2. The resin laminate sheet for thermoforming according to claim 1, wherein the inorganic substance contains calcium carbonate. A molded article obtained by thermoforming the thermoforming resin laminated sheet according to claim 1 or 2. 4. The molded product according to claim 3, wherein the molded product is a container for food and drink that is microwaveable.