JP3432139B2 - Laminated foam and foam molded article using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a tray,
The present invention relates to a laminated foam used for food containers such as bowls and cups, and a foamed molded product using the foam, which is suitable for the food containers.

[0002]

2. Description of the Related Art For example, as a food container to be sold in a state of containing food at a supermarket store, a single-layer foam sheet made of a styrene homopolymer (polystyrene) has been conventionally formed by a method such as vacuum forming. Thermoforming was the mainstream.

However, with the recent spread of microwave ovens in general households and the increase in convenience stores, for example, foods cooked up to the stage before heating are cooked in a microwave oven together with their containers. The opportunities are increasing, and food containers are required to have heat resistance.

[0004]

In order to meet the above-mentioned requirements, a non-foamed polypropylene container was first examined, but this one does not have sufficient heat insulating property and, for example, food is transferred to tableware made of ceramics. As with the case of cooking with heat instead, the heat of the cooked food also raises the temperature of the container itself, causing a problem that it cannot be taken out of the microwave with bare hands. It was not suitable for the food containers of the type mentioned above.

Then, styrene, (meth) acrylic acid, and (meth) acrylic acid ester, which are excellent in heat resistance against cooking by a microwave oven and have excellent heat insulating properties, are added. A foamed sheet mainly composed of a copolymer with maleic anhydride or the like has been proposed (for example, JP-A-3-109441, Japanese Patent Publication No.
55586, etc.).

However, these foamed sheets have insufficient oil resistance, and there is a possibility that the inner surface of the container may be attacked by high temperature oil when heated and cooked especially in the state of containing oily food.

Then, next, an oil resistant film such as an olefin resin or polyethylene terephthalate is laminated on the surface of the foamed sheet requiring oil resistance (mainly the inner surface of the container) to improve the oil resistance of the container. Improved laminated sheets have been proposed.

However, in such a laminated sheet, the styrene resin forming the foamed sheet and the resin forming the film such as olefin resin and polyethylene terephthalate do not have good compatibility and adhesiveness with each other. In addition, for example, when the manufactured laminated sheet is wound in a roll shape, or when it is unwound from the roll and subjected to thermoforming, peeling between layers is likely to occur, resulting in poor handleability. .

Therefore, it has been studied to laminate and adhere both layers by using an adhesive, but for that purpose, a special adhesive which exhibits good adhesiveness to any resin is required, There is a problem that the cost is too high to be used as a material for food containers having high versatility.

There is also a problem that it is difficult to recycle a molded product such as a food container formed of a laminate having a complicated resin structure as described above.

Then, (A) a propylene-based resin showing a molecular weight distribution with an overhang of the curve showing that a branched polymer is contained in the high molecular region of the molecular weight distribution curve by gel permeation chromatography, B) A foamed sheet prepared by foaming a mixture of propylene-based copolymer resin obtained by copolymerizing propylene and α-olefin has been proposed (JP-A-6-192460).

However, the above foamed sheet has a lower strength per weight than the foamed sheet of styrene resin due to the characteristics of the propylene resin itself, so that a container having a strength suitable for practical use is obtained. Then, since the weight is considerably large, that is, the amount of resin used per container must be increased, the fact that the resins of (A) and (B) above are both special resins makes it a highly versatile food product. There is a problem that the cost is too high to use as a material for a container or the like.

An object of the present invention is to provide a novel laminated foam capable of producing a food container excellent in heat resistance, heat insulation and oil resistance at a lower cost, and the above food product formed from such laminated foam. It is an object to provide a foamed molded product that is suitable as a container and is easy to recycle.

[0014]

Means for Solving the Problems To solve the above problems, a laminated foam of the present invention comprises (i) at least one side of a foam layer of a styrene resin, (ii) an olefin resin and a styrene resin. Consisting of a series
Includes a single continuous phase of styrene resin in the phase
Of a single occlusion type in which a rubber-like polymer
It has a particle shape and is
From the group consisting of Japanese carboxylic acid esters and vinyl acetate
Contains a copolymer of at least one selected and ethylene
At least one intermediate layer made of a mixture with the rubber-modified styrene resin and (iii) an olefin resin layer are laminated in this order.

The foamed molded article of the present invention is obtained by thermoforming the above laminated foamed article.

According to the present invention, the heat insulating property is excellent.
The heat resistance and oil resistance were improved by mixing the styrene resin with an olefin resin on the surface (inner surface or both inner and outer surfaces) of the foam layer of the styrene resin of (i) that requires heat resistance and oil resistance. Since the layer of the olefin resin (iii), which has excellent oil resistance, is laminated through the intermediate layer (ii), it has excellent heat resistance, heat insulation, and oil resistance especially when used for cooking. It becomes possible to manufacture food containers and the like.

According to the present invention, by mixing the styrene resin with the olefin resin as described above, the intermediate layer of (ii) is a foamed layer of styrene resin of (i), and (iii) )) Has good compatibility and adhesiveness with both olefin resin layers, so each layer of (i) to (iii) is directly heat-bonded without using a special adhesive or the like. By doing so, it is possible to produce a laminated foam that is free from delamination and has excellent handleability, and the entire laminated foam is mainly composed of a styrene resin and an olefin resin as described above. Is made of general-purpose inexpensive resin, and the strength of styrene-based resin is high per weight, and the amount of resin used per container is small. Foam molded body It is possible to manufacture at low cost.

Further, in the foamed molded article of the present invention, the resin component is composed of two kinds of styrene resin and olefin resin as described above, and the recovered product after use is the laminated foam of the present invention. Since it can be used as a raw material for the intermediate layer in (ii), it also has an advantage of excellent recyclability.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below.

As described above, the laminated foam of the present invention comprises (i) a foamed layer of a styrene resin, and (ii) an olefin resin and a styrene resin.
Includes a single continuous phase made of styrene resin in the continuous phase
Of a single occlusion type in which the rubbery polymer
It has a dispersed particle shape and is
A group consisting of saturated carboxylic acid esters and vinyl acetate
It contains a copolymer of at least one selected from ethylene and ethylene.
It is characterized in that at least one intermediate layer made of a mixture with the rubber-modified styrenic resin contained therein and (iii) an olefin resin layer are laminated in this order.

Of the above, the intermediate layer of (ii) may be a single layer, but in particular (ii-1) the olefin resin (O) and the styrene resin (S) are mixed in a weight ratio (O) / (S). Expressed as (O) / (S) = 5/9
The first intermediate layer, which is contained in a ratio of 5 to 45/55, is in contact with the foamed layer of the styrene resin of (i), and (ii-2) the above two resins in a weight ratio (O) / (S). Expressed as (O) / (S) = 55 / 45-9
It is preferable to have a two-layer structure of the second intermediate layer in contact with the olefin resin layer (iii) contained at a ratio of 5/5.

The intermediate layer of such a two-layer structure is (ii-
Since the first intermediate layer of 1) has a styrene-rich composition as described above, it has excellent compatibility and adhesiveness with the foamed layer of the styrene resin of (i), and (ii-2 ) Second
The intermediate layer of olefin-rich composition has
It has excellent compatibility and adhesiveness with the olefin resin layer of ii), and since both intermediate layers of (ii-1) and (ii-2) have similar compositions, they are mutually compatible. Excellent in solubility and adhesion.

Therefore, in the laminated foam provided with the intermediate layer having the above-mentioned two-layer structure, each layer is more firmly adhered,
Further, it is excellent in handleability and the like without causing peeling between layers.

Among the above two-layered intermediate layers (ii-1)
In the first intermediate layer, the preferable value of the weight ratio (O) / (S) of the olefin resin (O) and the styrene resin (S) is in the range of 5/95 to 45/55 as described above. The inside is
The reason is as follows.

That is, the styrene resin is more than this range.
When the amount of (S) is small, the composition of the first intermediate layer becomes almost styrene-rich, and the compatibility and adhesiveness with the foamed layer of the styrene resin of (i) deteriorates, and both layers are If the olefin resin (O) is less than this range, the oil resistance and heat resistance of the laminated foam may deteriorate.

The weight ratio (O) / (S) of the two resins in the first intermediate layer is 10/90 to 40/6 even within the above range, considering the balance of the above characteristics.
It is preferably about 0, and more preferably about 20/80 to 30/70.

Among the two-layered intermediate layer (ii-2)
In the second intermediate layer, the preferable value of the weight ratio (O) / (S) of the olefin resin (O) and the styrene resin (S) is in the range of 55/45 to 95/5 as described above. The inside is
The reason is as follows.

That is, when the amount of the olefin resin (O) is less than this range, the composition of the second intermediate layer becomes almost olefin-rich, and the compatibility with the layer of the olefin resin (iii), If the styrene-based resin (S) is less than this range, the two intermediate layers (ii) There is a possibility that the compatibility and adhesiveness with the first intermediate layer of -1) will be reduced, and both layers will be easily separated from each other.

The weight ratio (O) / (S) of both resins in the second intermediate layer is 45/55 to 90/1 even within the above range in consideration of the balance of the above characteristics.
It is preferably about 0, more preferably about 35/65 to 80/20.

In the intermediate layer of the above-mentioned two-layer structure, at least one layer of them is further improved in heat resistance and heat insulation of the laminated foam, and by extension in the foamed molded product, for example, when the temperature of the contents is (i). In order to prevent the container from deforming even when it becomes higher than the heat deformation temperature of the foam layer of styrene resin,
It may be foamed.

The thickness of the intermediate layer of the two-layer structure is not particularly limited, but in the case of non-foaming, the thickness of each of the first and second intermediate layers is about 10 to 40 μm, especially 15 to 30.
The thickness of the intermediate layers is preferably about 20 to 80 μm, and more preferably about 30 to 60 μm.

In the case of foaming one or both of the intermediate layers, the density of the intermediate layer, considering the above-mentioned effect of further improving the heat resistance and heat insulating property of the laminated foam,
It is preferably about 0.1 to 0.77 g / cm ³ .
It is more preferably about 0.2 to 0.5 g / cm ³ .

Further, in consideration of the above effects, the thickness of the intermediate layer in this case is either one of the first and second intermediate layers, or both of them. Regardless, the total of both middle layers is 0.3
It is preferably about 2 mm, particularly about 0.5 mm.

The intermediate layer may be a single layer as described above, and the intermediate layer may be foamed in order to further improve the heat resistance and heat insulating properties of the laminated foam, and hence the foamed molded product.

The thickness of the intermediate layer having such a single-layer structure is preferably about 10 to 50 μm in the case of non-foaming, and 20
More preferably, it is about 40 μm.

When the intermediate layer having a single-layer structure is foamed, its density is 0.1 to 0.
About 77 g / cm ³ , especially 0.25 to 0.5 g / cm
^The thickness is preferably about ³ , and the thickness is preferably about 0.3 to 2 mm, particularly preferably about 0.5 to 1 mm.

The content ratio of the olefin resin and the styrene resin in the intermediate layer of the above single layer structure is not particularly limited either, but this is also represented by the weight ratio (O) / (S) of 5/95 to 95.
It is preferably / 5.

When the amount of the styrene resin (S) is less than this range, the compatibility and the adhesiveness of the intermediate layer having a single layer structure with the foam layer of the styrene resin (i) are lowered, and The layers may be easily separated from each other, and in the case of foaming the intermediate layer as described above, the foamability thereof is lowered, and the effect of improving the heat resistance and heat insulating property of the laminated foam is unsatisfactory. There is a possibility that it will be enough.

On the contrary, when the amount of the olefin resin (O) is less than the above range, (iii) of the intermediate layer having a single layer structure,
The compatibility and adhesiveness with the layer of the olefin resin may deteriorate, and both layers may be easily separated between the layers, and the oil resistance and heat resistance of the laminated foam may decrease.

The content ratio (S) / (O) of both resins is preferably about 20/80 to 80/20, even within the above range, in consideration of the balance of the above characteristics. More preferably, it is about 30/70 to 70/30.

As the styrene resin (S) forming the intermediate layer (ii) of the above single layer structure or the above two layer structure ,
In this invention, recently, one of high impact polystyrene
Species but more shock resistant than ever
And has high impact resistance comparable to ABS,
Expected to be able to compete well with ABS in terms of strike
Styrene-based resin in a continuous phase consisting of styrene-based resin
A rubber-like polymer containing a single continuous phase of resin
Scattered, single occlusion (occlusion on)
It has an encapsulation type dispersed particle shape and is
From acids, unsaturated carboxylic esters and vinyl acetate
Copolymer of ethylene with at least one selected from the group consisting of
Rubber modified styrenic resin containing coalesced is used
It

Such a rubber-modified styrenic resin is not only excellent in each of the above-mentioned characteristics, but also excellent in compatibility with an olefin resin, so that it does not require a compatibilizing agent and is uniform and There is an advantage that a good intermediate layer can be formed, which can contribute to further cost reduction of food containers and the like.

Examples of the styrene-based resin that is the basis of the rubber-modified styrene-based resin include styrene homopolymers,
Copolymers of styrene and other vinyl monomers can also be used.
Can be used. Other vinyl monomers copolymerizable with styrene
As, for example, α-methylstyrene, acrylonite
Ril, methacrylonitrile, acrylic acid, methacryl
Acid, acrylic acid ester, methacrylic acid ester, anhydrous
Examples include maleic acid. These styrenic resins
Are used alone or in combination of two or more.
I can do it.

As the rubbery polymer dispersed in the styrene resin, a diene rubber is particularly preferable in consideration of the effect of imparting impact resistance to the laminated foam, and the diene rubber is preferable. Examples thereof include polybutadiene, styrene-butadiene copolymer, ethylene-propylene-non-conjugated diene terpolymer, and the like.
As the polybutadiene, various polybutadienes from high cis polybutadiene having a high cis bond content to low cis polybutadiene having a low cis bond content can be used as the polybutadiene.

These rubbers may be used alone or in combination of two or more.

The rubber-like polymer is dispersed in a continuous phase composed of a styrene resin so as to have a single occlusion type dispersed particle shape.

The single occlusion type dispersed particle shape means that a large number of particles of the rubber-like polymer dispersed in the continuous phase of the styrene resin are inside the particles having the rubber-like polymer as an outer shell. It refers to one having a so-called core-shell structure in which a single continuous phase made of a styrene resin is included.

Such a single occlusion type dispersed particle shape is used in many ordinary rubber-modified styrenic resins.
Shown by the particles of the rubber-like polymer dispersed in the continuous phase of the styrene-based resin, inside the particles having the rubber-like polymer as an outer shell, the so-called salami structure in which many small particles of the styrene-based resin are included Clearly different.

The above-mentioned rubber-modified styrenic resin having a single-occlusion type dispersed particle shape has an advantage that the appearance such as gloss is improved as compared with a rubber-modified styrene resin having a salami structure.

The rubber-modified styrenic resin having a single occlusion type dispersed particle shape is obtained by polymerizing styrene in the presence of a block copolymer of styrene and a rubber component (such as a styrene-butadiene block copolymer). It is manufactured by

The dispersed particle size of the rubber-like polymer particles in the continuous phase of the styrene resin in the single occlusion type dispersed particle shape is preferably about 0.1 to 0.5 μm.

If the dispersed particle diameter of the rubber-like polymer particles is less than the above range, the impact resistance of the laminated foam may be reduced. On the other hand, when the dispersed particle size exceeds the above range, the rubber-modified styrene-based resin may have poor uniformity, which may also reduce the impact resistance of the laminated foam, and may also cause glossiness. The appearance of may deteriorate.

The dispersed particle size of the rubber-like polymer particles is more preferably about 0.2 to 0.4 μm even within the above range.

The dispersed particle shape and dispersed particle size of the rubber-like polymer particles are observed as follows.

That is, an ultrathin section of rubber-modified styrene resin was prepared using an ultramicrotome, etc., and was immersed in an osmium tetrachloride solution for about one day for staining, and then a transmission electron micrograph thereof was taken. , While confirming the dispersed particle shape of the particles of the rubber-like polymer in the photograph,
The dispersed particle size of the rubber-like polymer particles is measured.

The copolymer of at least one selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic acid esters and vinyl acetate, which is contained in the rubber-modified styrene resin, with ethylene is, for example, ethylene- Acrylic acid copolymer, ethylene-methacrylic acid copolymer,
Examples thereof include ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and ethylene-vinyl acetate copolymer.
These copolymers may be used alone or in combination of two or more.

The copolymer is preferably contained in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the rubber-modified styrene resin.

When the content of the copolymer is less than the above range,
There is a possibility that the compatibility with the olefin resin is reduced and the oil resistance of the laminated foam is reduced. On the other hand, if the content of the copolymer exceeds the above range, the heat resistance of the laminated foam may decrease.

In the above range, the content of the copolymer is preferably about 1 to 5 parts by weight per 100 parts by weight of the rubber-modified styrene resin.

Examples of the rubber-modified styrene-based resin include various resins disclosed in JP-A-8-151500. Specific examples thereof include, but are not limited to, Sumitomo Chemical Co., Ltd.'s trade name Sumibrite DJ series, and among them, product numbers DJ8000 and DJ9000 are particularly preferable because they are particularly excellent in oil resistance. used.

The olefin resin (O) forming the intermediate layer of (ii) together with the styrene resin (S) such as the rubber-modified styrene resin is, for example, high density polyethylene,
In addition to ethylene homopolymers such as low-density polyethylene and linear low-density polyethylene, and propylene homopolymers (polypropylene), random or block copolymers of propylene and ethylene can also be used. These olefin resins are also used alone,
Two or more kinds can be used in combination. However, considering the heat resistance and strength of the container, among the above, the olefin resin is preferably a propylene resin, and particularly polypropylene and ethylene-propylene block copolymers are preferably used.

[0062] (ii) The middle layer, the (S) (O) of the addition to the two resins, foaming agents for foaming the field layer even
And, or various additives such as cell regulators for adjusting the size of the bubbles during the foaming, may be added as necessary.

As the foaming agent, depending on the foaming method of the layer,
Any of various conventionally known foaming agents such as gaseous, volatile and decomposable types can be used.

Among the above, examples of the gaseous foaming agent include gases such as carbon dioxide, air and nitrogen.
Examples of volatile foaming agents include propane and n-
Examples thereof include aliphatic hydrocarbons such as butane, i-butane and pentane, cycloaliphatic hydrocarbons such as cyclopentane, halogenated hydrocarbons such as trichlorofluoromethane, dichlorofluoromethane and methyl chloride. Further, as the decomposing type foaming agent, an organic foaming agent such as azodicarbonamide or dinitrosopentamethylenetetramine, or an inorganic type combination of a weak acid and an inorganic salt which generates carbon dioxide by the reaction with the weak acid. And a foaming agent. Examples of the inorganic salt include alkali metal or alkaline earth metal carbonates or bicarbonates (such as sodium bicarbonate) and ammonium carbonate. Examples of the weak acid include oxalic acid, malonic acid, maleic acid, fumaric acid, succinic acid,
Itaconic acid, citraconic acid, adipic acid, formic acid, acetic acid,
Propionic acid, butyric acid, stearic acid, oleic acid, caprylic acid, enanthic acid, caproic acid, valeric acid, lactic acid, tartaric acid, citric acid, phthalic acid, benzoic acid, benzenesulfonic acid, toluenesulfonic acid, chloroacetic acid, diglycolic acid Examples thereof include organic acids, such as boric acid, inorganic acids such as boric acid, and acidic acids such as acidic calcium tartrate. Of these, citric acid is particularly preferably used.

These foaming agents may be used alone or in combination of two or more.

In particular, when the intermediate layer of (ii) is manufactured by the extrusion molding method described later, a weak acid and an inorganic salt which reacts with the weak acid to generate carbon dioxide by heat during molding are combined. Inorganic decomposition type foaming agents are preferably used.

The above-mentioned weak acid and inorganic salt may be added to the resin composition separately, or both may be added by coating with a wax or a thermoplastic resin or in the form of a masterbatch. Good.

Such an inorganic decomposing type foaming agent which is a combination of a weak acid and an inorganic salt also has the function of a foam control agent itself, and has finer and more uniform bubbles than other foaming agents. (Ii) has the advantage of improving the heat insulating properties of the intermediate layer and improving the appearance of the foam such as gloss. This effect is also obtained when the weak acid and the inorganic salt are used in combination with another foaming agent such as a gaseous or volatile foaming agent.

The weak acid and the inorganic salt as the inorganic decomposing type foaming agent are based on 100 parts by weight of the total amount of both the (S) and (O) resins.
It is preferably added in a total amount of 0.01 to 5 parts by weight.

Examples of the bubble control agent include inorganic powders such as talc and silica, acidic salts such as polyvalent carboxylic acids,
Examples thereof include a reaction mixture of a polycarboxylic acid and sodium carbonate or sodium bicarbonate. These air bubble regulators may be used alone or in combination of two or more.

The addition amount of the bubble control agent is preferably about 0.01 to 2 parts by weight based on 100 parts by weight of the total amount of both the (S) and (O) resins.

Examples of the additives other than the bubble control agent include colorants, flame retardants, lubricants (hydrocarbons, fatty acids,
Examples thereof include fatty acid amide-based, ester-based, alcohol-based waxes, metallic soaps, silicone oil, low-molecular-weight polyethylene, etc.), spreading agents (liquid paraffin, polyethylene glycol, polybutene, etc.), and dispersants. These other additives do not interfere with the production of the intermediate layer of (ii), and the characteristics of the produced intermediate layer, and thus the foaming of the styrene-based resin of (i) to the intermediate layer of (ii). The layer is added in an amount that does not affect the properties of the layer and the laminated foam formed by laminating the layer of the olefin resin (iii), or the foamed molded article produced from the laminated foam.

The intermediate layer of (ii) above and (iii) described later
The foam layer (i) constituting the laminated foam of the present invention together with the olefin resin layer (1) is formed of a styrene resin as described above. That is, any of the above-exemplified styrene homopolymers, copolymers of styrene and other vinyl monomers, and various rubber-modified styrene resins can be used.

According to the present invention, however, the heat resistance and the heat insulating property as a whole are increased by the action of the intermediate layer of (ii) and the layer of the olefin resin of (iii) laminated via the intermediate layer. In addition, since oil resistance is ensured, as the styrene-based resin for forming the foamed layer (i), in consideration of production cost, thermoformability, and the like, normal and general-purpose polystyrene is preferably used.

As in the case of the intermediate layer of (ii) above, the styrenic resin forming the foamed layer of (i) includes a foaming agent for foaming the layer, a size of bubbles at the time of foaming, etc. Various additives such as a bubble control agent for adjusting the above are appropriately added.

The kind of each additive may be the same as in the case of the intermediate layer (ii). Further, the addition amount of each additive is such that the numerical range of the addition amount with respect to 100 parts by weight of the styrene-based resin forming the foamed layer of (i) is (S) (O) of both resins in the intermediate layer of (ii) It may be set so as to be in the same range as the numerical value range for 100 parts by weight in total.

The foamed layer (i) is for imparting heat insulating property and strength to the container. Considering such characteristics, the density is not limited to this, but the density is 0.05 to
It is preferably about 0.35 g / cm ³ , and 0.07
More preferably, it is about 0.2 g / cm ³ .

The olefin resin layer (iii) constituting the laminated foam of the present invention together with the foam layer (i) and the intermediate layer (ii) has various properties which can impart oil resistance to the laminated foam. It is made of olefin resin. As the olefin-based resin, any of various olefin-based resins exemplified in the intermediate layer (ii) can be used.

The olefin resin layer (iii) may be non-foamed or may be foamed in order to further improve the heat resistance and heat insulation of the laminated foam, and thus the foamed molded product, as in the case of (ii) above. Good.

Of these, the thickness of the non-foamed olefin resin layer is preferably about 20 to 80 μm, considering the effect of imparting sufficient oil resistance to the container, and is preferably 35 to 6
More preferably, it is about 0 μm.

When the layer of the olefin resin is foamed, the density thereof is not more than 0, considering the effect of the oil resistance and the effect of further improving the heat resistance and heat insulating property of the foamed molded article. 1~0.77g / cm ³ or so, and even preferable particularly 0.25~0.5g / cm ³ or so, the thickness of about 0.3 to 2 mm, in particular 0.5 to 1.5
It is preferably about mm.

As in the case of the layers (i) and (ii), the olefin resin forming the layer (iii) contains a foaming agent for foaming the layer, and the size of bubbles during foaming. Various additives such as a bubble control agent for adjusting the above may be appropriately added.

The type of each additive is (i) (ii)
The same as in the case of both layers. Further, the addition amount of each additive is (iii) when the numerical range of the addition amount relative to 100 parts by weight of the olefin resin forming the layer of the olefin resin is (i
It may be set so as to be in the same range as the numerical value range for 100 parts by weight of the total amount of both resins (S) and (O) in the intermediate layer i).

Further, as the layer of the olefin resin of (iii) above, a biaxially oriented polypropylene film or sheet,
Non-stretched polypropylene cast film or sheet,
A commercially available olefin resin sheet or film such as a polypropylene sheet containing a large amount of an inorganic substance such as talc, or an olefin resin sheet or film having a printed surface may be used.

The laminated foam of the present invention comprising the layers (i) to (iii) described above is specifically, for example, one side of the foam layer of the styrene resin of (i) (particularly the inner surface of the container). Side surface)
Through (ii) the intermediate layer (single layer structure or double layer structure)
3 layers or 4 in which layers of the olefin resin of (iii) are laminated
5-7 in which a layer structure or a layer of the olefin resin of (iii) is laminated on both surfaces of the foam layer of (i) through the intermediate layer of (ii) (single layer structure or two layer structure) Includes layered structures. Whether the intermediate layer of (ii) and the layer of the olefin resin of (iii) are laminated on one side of the foamed layer of (i) or on both sides is determined by foam molding produced from the laminated foam. It can be appropriately changed depending on the use of the body.

Although various methods can be considered for producing such a laminated foam, a mixture obtained by previously dry blending a resin and an additive is melted and kneaded by using an extrusion molding machine, and then the tip of the extrusion molding machine. From the viewpoint of production cost, it is preferable to continuously manufacture by a so-called extrusion molding method, in which the material is extruded into the atmosphere through a die (die) connected to and foamed and molded into a sheet. That is, the following manufacturing methods (a) to (c) utilizing the extrusion molding method are preferably adopted. (A) Using an extrusion molding machine, each layer of (i) to (iii) is separately extruded into a sheet, and then directly heat-bonded by, for example, a heat laminating method to produce a laminated foam. To do. (B) The melt of resin for each layer melted and extruded from the tip of the extrusion molding machine prepared for the number of layers at approximately the same time in the confluent die or in the feed block connected to the single layer die. A laminated foam is manufactured by a so-called coextrusion method in which the particles are joined together and laminated, and then extruded into the air to foam. (C) By combining the above two methods, a part of each layer of (i) to (iii) is laminated by a coextrusion method, and a part of the layers is laminated by thermal bonding to produce a laminated foam.

The thermal laminating method referred to here is as follows.
Depending on the type of two layers to be heat-bonded, the following two types of bonding methods can be mentioned.

Thermal Laminating Method (I) When at least one of the two layers to be heat-bonded is a non-foamed film, that is, when both layers to be heat-bonded are both non-foamed films, one is non-foamed. A method of adhering when a film is the other and a foam sheet, one of which is about 180 to 2
A pair of pressure rolls heated to about 20 ° C. and having an interval narrower than the total thickness of both layers are used.

Then, the two layers to be heat-bonded are laminated between the pair of pressure rolls in such a state that the film of the two layers is laminated so as to be in contact with the heated roll (heating roll) of the pair of pressure rolls. . Then, the film in contact with the heating roll is heated from behind by the heating roll, and is pressed by the pair of pressure rolls with the layer (non-foamed film or foamed sheet) on the other side to be heat-bonded, thereby forming both layers. Are heat-bonded.

Thermal laminating method (II) This is an adhering method when the two layers to be thermally adhered are both foam sheets.

Specifically, the two heat-bonding surfaces to be heat-bonded are blown with hot air heated to about 350 ° C. to soften them, and then a space between the pair of pressure rolls having a distance smaller than the total thickness of both layers. Both layers are heat-bonded by passing through.

In each of the above production methods, a solid foaming agent such as a masterbatch of the aforementioned inorganic decomposing foaming agent and a weak acid is used to form the foaming layer (i). In the case of foaming the first layers, these may be added in the dry blending step or the subsequent melting and kneading steps.

When a gaseous or volatile foaming agent is used, it may be pressed into the molten and kneaded resin composition. Specifically, for example, a gaseous or volatile foaming agent may be pressed into the resin composition melted and kneaded in the screw cylinder of the extruder through a nozzle provided in the screw cylinder of the extruder.

In the present invention, a non-foamed resin layer may be further laminated on the outermost surface of one side or both sides of the food container in order to improve its appearance and strength.

In particular, the layers (ii) and (iii) are laminated only on one side of the foamed layer of the styrene resin of (i), and the foamed layer of the styrene resin of (i) above is the uppermost layer of the laminated foam. When exposed to the surface layer, or when the layer of the olefin resin of (iii) located in the outermost layer of the laminated foam as described above is foamed, on the foamed layer, the above non-foamed resin It is preferable to stack the layers.

Examples of the resin constituting the non-foamed resin layer include polystyrene and copolymers of styrene and other vinyl monomers such as (meth) acrylic acid, (meth) acrylic acid ester, and maleic anhydride. Styrene resin, rubber-modified styrene resin obtained by modifying such styrene resin with rubber such as diene rubber, polypropylene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, high-density polyethylene,
Examples thereof include olefin resins such as low density polyethylene, polyethylene terephthalate, ethylene-butene copolymer, ethylene-octene copolymer, ethylene-propylene copolymer rubber and the like. These resins may be used alone or in combination of two or more. In particular, considering the recycling aspect, ease of stacking, and the balance of physical properties with the foam, as the resin that constitutes the non-foamed resin layer, it is preferable to use a resin that has a component similar to that of the underlying layer. To be done. Further, a commercially available printing film or the like can also be used.

The non-foamed resin layer may contain an inorganic filler. As such an inorganic filler,
Examples thereof include talc, clay, calcium carbonate, silica and magnesium hydroxide.

To laminate the non-foamed resin layer on both sides or one side of the laminated foam, (I) non-foamed on the laminated foam produced by the above-mentioned production methods (a) to (c). A layer of resin is laminated by the thermal lamination method or the like, (II) In the manufacturing method of (a), when a foamed layer is laminated by the thermal lamination method or the like, a non-foamed resin layer is also laminated at the same time, Alternatively, (III) In the production method of (ii) above, a method of simultaneously extruding while laminating a layer of non-foamed resin may be considered.

Next, the foamed molded product of the present invention will be described.

The foamed molded article of the present invention is manufactured by thermoforming by a method such as vacuum molding or pressure molding using the above-mentioned laminated foamed material as a raw material.

Since the above-mentioned foamed molded article has the laminated foam as a raw material which is excellent in heat resistance, heat insulation and oil resistance as described above, and can be manufactured at low cost, it itself has the above-mentioned characteristics. In addition, it is an inexpensive and highly versatile food container.

[0102]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples.

The specific constitution of each component used in the following Examples and Comparative Examples is as follows. (a) Styrene resin A1: polystyrene [trade name H manufactured by Denki Kagaku Kogyo Co., Ltd.
RM-2] A2: Styrene-methacrylic acid copolymer resin [trade name TF-2-311 manufactured by Denki Kagaku Kogyo Co., Ltd., styrene-based heat-resistant resin] A3: A styrene-butadiene block in a continuous phase composed of polystyrene The particles of the copolymer are dispersed so as to have a single occlusion type dispersed particle shape, and a rubber-modified styrene resin containing an ethylene-acrylic acid ester copolymer [Sumitomo Chemical ( (Trade name: Sumibright DJ9000 manufactured by K.K.) (b) Olefin resin B1: ethylene-propylene block copolymer [trade name: SK311 manufactured by Nippon Polyolefin Co., Ltd.] (c) Foaming agent Citric acid and sodium bicarbonate Masterbatch solid decomposition type inorganic foaming agent [trade name HK-70 manufactured by Boehringer Ingelheim Chemicals] Examination of configuration of intermediate layer >> A mixture obtained by dry-blending the components shown in Table 1 below was extruded to have a thickness of 6
Five kinds of films having a thickness of 0 μm were prepared.

[0104]

[Table 1] In addition, as another film, a film having the same thickness of 60 μm as A-
A PET film was prepared.

Then, two films of the above-mentioned six kinds were laminated with the combinations shown in Table 2 below, and heat-bonded under the following conditions using a heat-sealing machine, and the adhesive strength was measured. did.

<Heat Adhesion Conditions> Sealing temperature: 160 ° C. Sealing time: 2 seconds Sealing pressure: 3 kg / cm ² Sealing width: 10 mm The results are shown in Table 2.

[0107]

[Table 2] From the table, it was first found that the film made of a mixture of polypropylene and polystyrene as a model of the intermediate layer (ii) cannot be heat-bonded to the polyethylene terephthalate film.

Also, PP / PS = 30/70, PP / PS = 50/50 and PP, which consist of a mixture of the above polypropylene and polystyrene.
All of the three types of films with / PS = 70/30 are well heat-bonded regardless of the difference in the content ratio of polypropylene and polystyrene, but they are models of the foam layer (i) of styrene resin PS = 100 film, polystyrene-rich PP / PS = 30/70 film is the best heat-bonded film, and on the contrary, it is a model of olefin resin layer (iii) model PP = 100 film. On the other hand, it was also confirmed that the polypropylene rich PP / PS = 70/30 film had the best thermal adhesion.

From these facts, when the intermediate layer (ii) for thermally bonding the foamed layer (i) of the styrene resin and the layer (iii) of the olefin resin has a two-layer structure, styrene is used. It has been found that it is preferable to make the intermediate layer on the side in contact with the foamed layer (i) of the resin based on styrene rich, and the intermediate layer on the side in contact with the layer (iii) of the olefin resin based on olefin rich composition such as polypropylene. .

Example 1 <Production of Foamed Layer (i) of Styrene Resin> The resin A1 as a styrene resin was fed to a hopper of a tandem type extruder having two screw cylinders, and While melting and kneading in a first screw cylinder having a screw diameter of 90 mm, butane as a volatile foaming agent was press-fitted from a nozzle provided in this first screw cylinder.

Next, the above-mentioned melted and kneaded product was added to the second
After being supplied to a screw cylinder having a screw diameter of φ115 mm and uniformly cooled in the screw cylinder, a discharge rate of 100 kg / hour was obtained from a cylindrical die having a diameter of 170 mm attached to the tip of the second screw cylinder. It was extruded into the air into a cylinder and foamed.

Then, the obtained cylindrical resin foam was continuously cooled by a cooling mandrel, and then continuously cut into a sheet shape by a cutter at two points on the circumference to obtain a thickness of 2.
A styrene resin foam layer (i) having a diameter of 15 mm and a density of 0.09 g / cm ³ was prepared.

<Preparation of First Intermediate Layer (ii-1)> 70 parts by weight of the A3 resin as a styrene resin,
A mixture obtained by dry blending 30 parts by weight of the above-mentioned B1 resin as an olefin resin is extrusion-molded to obtain a thickness of 25
Non-foaming first intermediate layer (ii-1) containing olefin resin (O) and styrene resin (S) in a weight ratio of (O) / (S) = 30/70 μm Was produced.

<Preparation of Second Intermediate Layer (ii-2)> 30 parts by weight of the above A3 resin as a styrene resin,
A mixture obtained by dry blending 70 parts by weight of the above-mentioned B1 resin as an olefin resin is extruded to obtain a thickness of 25.
Non-foaming second intermediate layer (ii-2) containing μm of olefin resin (O) and styrene resin (S) in a weight ratio (O) / (S) = 70/30 Was produced.

<Production of Laminated Foam> The three layers of the styrene resin foam layer (i), the first intermediate layer (ii-1) and the second intermediate layer (ii-2) produced above are All of them were sequentially heat-bonded by the thermal lamination method (I). Then, on the surface of the second intermediate layer (ii-2) of this laminate, a commercially available unstretched polypropylene cast film (thickness 30
μm) were superposed and heat-bonded again by the thermal laminating method (I) to produce a laminated foam.

The thickness of each layer constituting the above laminated foam is
The measurement was performed using a micrometer before the heat bonding. The density of the foam layer was calculated from the thickness and basis weight of the foam layer by the following formula.

[0117]

[Equation 1] Example 2 A foam layer (i) of styrene resin having a thickness of 1.50 mm and a density of 0.15 g / cm ³ was prepared in the same manner as in Example 1 except that the resin of A2 was used as the styrene resin. did.

Then, the foamed layer (i) of this styrene resin
The same non-foaming first and second intermediate layers (ii-1) and (ii-2) as those used in Example 1 were sequentially bonded in this order by the thermal laminating method (I). After that, on the surface of the second intermediate layer (ii-2) of such a laminated body, this was also obtained in Example 1.
The same as that used in 1., a commercially available unstretched polypropylene cast film (thickness 30 μm) as an olefinic resin layer (iii) is overlaid, and heat-bonded again by the thermal laminating method (I) to be laminated. A foam was produced.

Example 3 Foaming of a styrenic resin consisting of A1 resin was carried out in the same manner as in Example 1 except that the extrusion conditions were changed to a thickness of 0.70 mm and a density of 0.21 g / cm ^3. Layer (i)
Was produced.

Then, the foamed layer (i) of this styrene resin
Was prepared in Preparation II of the first intermediate layer (ii-1) below, having a thickness of 600 μm (= 0.6 mm) and a density of 0.35 g / cm ^3.
Of the foamed first intermediate layer (ii-1) and the non-foamed second intermediate layer (ii-) heat-bonded by the heat lamination method (II), and then the same as used in Example 1. 2) and this time by thermal bonding by the thermal laminating method (I), and on the surface of the second intermediate layer (ii-2) of the laminate, the same olefin as used in Example 1 was used. A commercially available unstretched polypropylene cast film (thickness 30 μm) is overlaid as the resin layer (iii), and the thermal lamination method is performed again.
The laminated foam was produced by heat bonding according to (I). <Preparation of First Intermediate Layer (ii-1) II> 70 parts by weight of the resin A3 as a styrene resin,
A tandem type extrusion molding of a mixture obtained by dry blending 30 parts by weight of the resin B1 as an olefin resin and 0.5 parts by weight of the foaming agent (c) described above with two screw cylinders as described above. Supply to the machine hopper, 1
While melting and kneading in a first screw cylinder having a screw diameter of 90 mm, butane as a volatile foaming agent was press-fitted from a nozzle provided in this first screw cylinder.

Next, the above-mentioned melted and kneaded product was added to the second
After being supplied to a screw cylinder having a screw diameter of φ115 mm and uniformly cooled in the screw cylinder, a discharge rate of 100 kg / hour was obtained from a cylindrical die having a diameter of 170 mm attached to the tip of the second screw cylinder. It was extruded into the air into a cylinder and foamed.

Then, the obtained cylindrical resin foam was continuously cooled by a cooling mandrel, and then continuously cut into a sheet shape by a cutter at two points on the circumference, and the thickness was 600 μm as described above. (= 0.6mm), density 0.35g
A foamed first intermediate layer (ii-1) of / cm ³ was prepared.

Comparative Example 1 Comparative Example 1 was prepared by using only the foam layer (i) of the styrene resin of Example 1 alone.

Heat and oil resistance test The laminated foam of each example and the single layer foam of the comparative example were
The laminated foam has a length of 156 mm, a width of 126 mm, and a styrene foam sheet molding machine (vacuum molding machine) so that the layer of the olefin resin (iii) is on the inner surface side of the container.
It was thermoformed into a 30 mm deep baking dish.

Then, when the above-mentioned baking dish containing 150 cc of salad oil was placed in a microwave oven and heated, the presence or absence of deformation of the entire container and the state of the inner surface of the container were observed. Salad oil temperature (℃)
Was recorded. In addition, it is observed whether or not the inner surface of the container is pierced to cause perforation when the container is continuously heated from the deformed temperature to a temperature higher by 20 ° C., and the salad oil in which the perforation is generated is also observed. The temperature (° C) was recorded.

The above results are shown in Table 3.

[0127]

[Table 3] From the table, it was found that all of the foam containers formed of the laminated foams of Examples 1 to 3 having the constitution of the present invention were superior in heat resistance and oil resistance to the styrene resin single layer foam. In particular, any of the foam containers formed from the laminated foam of each of the above-mentioned examples does not cause perforation even when heated to a temperature 20 ° C. higher than the deformation temperature as described above, and the inner surface thereof is completely It was not corroded, and no phenomenon such as delamination or swelling due to poor adhesion was observed.

[0128]

As described above in detail, according to the present invention,
Heat-resistant, heat-insulating and oil-resistant food containers and the like, a novel laminated foam that can be produced at a lower cost, and formed from such laminated foam, suitable as the food container and the like, and recyclable The peculiar function and effect that an easily foam-molded article can be provided is exhibited.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Asada 35-7-105 Saikiji-cho, Nara City, Nara Prefecture (72) Inventor Shizuka Horino 5-7-6 Shinko, Nara City, Nara Prefecture (56) References 2-148913 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 9/00-9/42

Claims (5)

(57) [Claims] 1. A continuous layer comprising (i) an olefin resin and a styrene resin on at least one surface of a foam layer of the styrene resin (i).
Includes a single continuous phase of styrene resin in the phase
Of a single occlusion type in which a rubber-like polymer
It has a particle shape and is
From the group consisting of Japanese carboxylic acid esters and vinyl acetate
Contains a copolymer of at least one selected and ethylene
At least one intermediate layer made of a mixture with the rubber-modified styrene resin, and (iii) an olefin resin layer are laminated in this order. 2. The laminated foam according to claim 1 , wherein at least one of the intermediate layer (ii) and the olefin resin layer (iii) is foamed. 3. The intermediate layer of (ii), wherein (ii-1) the olefin resin (O) and the styrene resin (S) are represented by a weight ratio (O) / (S) of (O). / (S) = 5/95 to 45/55, the first intermediate layer in contact with the foam layer of the styrene resin of (i), and (ii-2) the above two resins in the weight ratio ( O) / (S)
(O) / (S) = 55/45 to 95/5, the content of (i
The laminated foam according to claim 1, which has a two-layer structure of ii) a second intermediate layer that is in contact with the olefin resin layer. 4. The first intermediate layer of (ii-1) above and the second intermediate layer of (ii-2) above.
The laminated foam according to claim 3 , wherein at least one layer of the intermediate layer of (3) and the layer of the olefin resin (iii) is foamed. 5. A foamed molded article, which is obtained by thermoforming the laminated foamed body according to any one of claims 1 to 4 .