JP2014111339A - Laminated foamed sheet and foamed molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated foamed sheet or a foamed molded product excellent in flexural strength or impact strength by improving the strength of the foam layer of a laminated foamed sheet having a foam layer composed mainly of a styrene-(meth)acrylic acid copolymer resin.SOLUTION: There is provided a laminated foamed sheet having two or more layers, the sheet being prepared by co-extrusion of a first polystyrene-based resin composition composed mainly of a polystyrene resin or a high impact polystyrene resin and a second polystyrene-based resin composition composed mainly of a styrene-(meth)acrylic acid copolymer resin and containing a first foam layer 1b composed of the first composition and a second foam layer 1c composed of the second composition. A polyethylene resin (B) is contained in the second composition so that the ratio of the styrene-(meth)acrylic acid copolymer resin together with the polyethylene resin (B) to the total (A+B) is 3 mass% or more and 20 mass% or less.

Description

  The present invention relates to a laminated foamed sheet and a foamed molded article, and more specifically, a laminated foamed sheet having two foamed layers obtained by coextruding two kinds of polystyrene resin compositions, and the laminated foamed sheet Relates to a foam-molded product obtained by thermoforming.

Conventionally, a polystyrene resin foam sheet mainly composed of polystyrene resin (GPPS) is not only used as a sheet-like buffer material but also a raw material (raw sheet) for producing various foam molded products by thermoforming. Is also widely used.
In particular, the foam sheet containing GPPS as a main component is widely used as a raw sheet for producing food containers such as tray containers, basket containers, and cup containers as the foam molded article.

In recent years, food containers such as those described above are required to have improved heat resistance so that they can be directly heated in a microwave oven without transferring the food stored inside to another container. It has become like this.
However, since GPPS normally has a glass transition temperature of about 100 ° C., it is difficult to use a foamed container containing GPPS as a main component for heating in a microwave oven as described above.

For this reason, the use of a foamed sheet mainly composed of a styrene- (meth) acrylic acid copolymer resin having a glass transition temperature higher than that of GPPS has been conventionally studied.
However, it is difficult to say that styrene- (meth) acrylic acid copolymer resins have excellent strength against bending and impact, and it is difficult to give sufficient strength to foamed molded products such as containers. Have.

In addition to these problems, styrene- (meth) acrylic acid copolymer resins are more expensive than polystyrene resins (GPPS), high-impact polystyrene resins (HIPS), etc., so that foam molded products are expensive. There is a risk that it will be.
That is, if a foam sheet used as a raw material for a foam molded product is formed solely from a styrene- (meth) acrylic acid copolymer resin, the resulting foam molded product has a problem in terms of cost and brittleness. There is a risk of it.

  From this, as shown in the following Patent Document 1, the first foam layer mainly composed of a general-purpose polystyrene resin such as polystyrene resin and the styrene- (meth) acrylic acid copolymer resin are mainly used. It has been studied to use a laminated foam sheet having a second foam layer as a component as a raw material of a foam molded article.

JP 2001-277442 A

In the laminated foam sheet as described above, the first foamed layer having relatively high toughness is laminated on the second foamed layer using the styrene- (meth) acrylic acid copolymer resin. It is possible to suppress the occurrence of cracking due to bending or impact as compared with the foam sheet consisting only of the second foam layer.
In recent years, in such a laminated foam sheet and a foam-molded product obtained by thermoforming the laminated foam sheet, it has been demanded to further improve the bending strength and impact strength.

In the above-mentioned laminated foamed sheet, if the second foamed layer formed of the styrene- (meth) acrylic acid copolymer resin is once cracked by bending stress or impact force, it is originally like this There is a risk that the cracking of the second foamed layer may spread to the first foamed layer, which does not cause cracking with a small bending stress or impact force, and so-called “co-cracking”.
Therefore, it is considered effective to improve the bending strength and impact strength of the second foam layer itself in satisfying the above demand.

However, a specific method for improving the strength of the foamed layer mainly composed of a styrene- (meth) acrylic acid copolymer resin has not been found, and it has been difficult to satisfy the above-mentioned demand conventionally. Have a problem.
The present invention aims to solve such problems, and improves the strength of the foamed layer of a laminated foamed sheet having a foamed layer mainly composed of a styrene- (meth) acrylic acid copolymer resin. Accordingly, it is an object of the present invention to provide a laminated foamed sheet or a foamed molded article that is superior in bending strength and impact strength.

  As a result of intensive studies by the present inventor to solve the above problems, the toughness of the foamed layer mainly composed of a styrene- (meth) acrylic acid copolymer resin is improved by containing a polyethylene resin in a predetermined ratio. As a result, the present invention has been completed.

  That is, the present invention relating to a laminated foam sheet includes a first polystyrene-based resin composition containing a polystyrene resin or a high-impact polystyrene resin as a main component and a styrene- (meth) acrylic acid copolymer resin as a main component. Two polystyrene resin compositions are coextruded and include a first foam layer made of the first polystyrene resin composition and a second foam layer made of the second polystyrene resin composition. A laminated foam sheet having a laminate structure of at least layers, wherein the second polystyrene-based resin composition further contains a polyethylene resin (B) together with the styrene- (meth) acrylic acid copolymer resin (A). And the proportion of the total (A + B) with the styrene- (meth) acrylic acid copolymer resin is 3% by mass or more and 20% by mass or less. Serial polyethylene resin (B) is characterized in that it is contained.

  The present invention also provides a foam-molded article, wherein the above-mentioned laminated foam sheet is thermoformed.

  According to the present invention, the strength of a foamed foam sheet having a foamed layer mainly composed of a styrene- (meth) acrylic acid copolymer resin and a foamed molded product obtained by thermoforming the laminated foamed sheet is improved. sell.

Schematic which shows the apparatus structure used for manufacture of a laminated foam sheet. The schematic sectional drawing which shows the structure of the confluence | merging metal mold | die of FIG. The schematic sectional drawing which shows the structure of the laminated foam sheet which concerns on one Embodiment.

Embodiments of the present invention will be described below.
The laminated foam sheet of this embodiment has a laminated structure of two or more layers including a first foamed layer and a second foamed layer.
In the present embodiment, the first foam layer and the second foam layer are directly laminated by performing extrusion foaming by coextrusion using a polystyrene resin composition for forming each of the first foam layer and the second foam layer.
In the present embodiment, the first foamed layer is formed by forming a first polystyrene-based resin composition containing polystyrene resin or high-impact polystyrene resin as a main component (hereinafter also referred to as “first resin composition”). In the formation of the second foam layer, a second polystyrene resin composition (hereinafter referred to as “second resin composition”) mainly composed of a styrene- (meth) acrylic acid copolymer resin is used. Is used).

  As said 1st resin composition, the thing similar to the formation material of the general polystyrene-type resin foam sheet called polystyrene paper (PSP) etc. can be employ | adopted, for example, the main component of the said 1st resin composition And a resin containing a component for making the resin into a predetermined foamed state can be employed.

As the resin as the main component of the first resin composition, polystyrene resin (GPPS) made of styrene homopolymer; block copolymer of conjugated diene such as butadiene and styrene monomer, rubber component is grafted to styrene polymer High impact polystyrene resin (HIPS) containing a rubber component such as a graft copolymer or a hydrogenated product thereof, or a mixed resin of these (GPPS and HIPS) can be used.
The first resin composition contains a resin other than polystyrene resin and high-impact polystyrene resin as long as the proportion of the total resin contained in the first resin composition is 10% by mass or less. For example, a resin that functions as an antistatic agent or the like may be contained.

As a component for making the said 1st foaming layer into a predetermined foaming state, a foaming agent, a bubble regulator, etc. are mentioned, for example.
As the foaming agent, a physical foaming agent having a boiling point below the resin temperature at the time of extrusion foaming and a chemical foaming agent having a decomposition temperature below the resin temperature can be employed. Nitrogen, carbon dioxide, propane, normal butane, isobutane, tert-butane, normal pentane, isopentane, cyclopentane, normal hexane, isohexane, cyclohexane, normal heptane, isoheptane, cycloheptane, benzene, toluene, dimethyl ether, water, etc. .
These physical foaming agents may be used alone or in combination of two or more.
Of these blowing agents, normal butane and isobutane are particularly preferred.
The amount of such physical foaming agent added during extrusion foaming is usually about 0.25 parts by mass to 5.0 parts by mass with respect to a total of 100 parts by mass of the resin contained in the first resin composition. .

  As the chemical foaming agent, conventionally known ones can be employed, for example, inorganic chemical foaming such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide, sodium borohydride and the like. Agents, azo compounds such as azodicarbonamide, azobissulfuramide, azobisisobutyronitrile and diazoaminobenzene, N, N'-dinitrosopentanemethylenetetramine and N, N'-dimethyl-N, N'-di Nitroso compounds such as nitrosoterephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide and p, p'-oxybisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide trihydrazinotriazine, barium azodi Rubokishireto, and citric acid.

Examples of the air conditioner for adjusting the foaming state of the first foam layer together with the foaming agent include talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, and hydroxide. Inorganic compounds such as aluminum, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, and glass beads, and organic compounds such as polytetrafluoroethylene can be employed.
The amount of the air bubble regulator added is usually about 0.01 parts by mass to 6.0 parts by mass with respect to 100 parts by mass of the resin contained in the first resin composition.

  In addition, the first resin composition includes various stabilizers such as weathering agents and anti-aging agents, processing aids such as lubricants, functional agents such as slip agents, antifogging agents, and low molecular antistatic agents, pigments, fragrances, and the like. Such various additives as described above can be contained.

In the second resin composition for forming the second foam layer, styrene- (meth) acrylic acid copolymer is used for imparting toughness to the second foam layer to improve the strength of the laminated foam sheet and the foam molded product. It is important to contain the polyethylene resin (B) together with the coalesced resin (A), and the proportion of the total (A + B) with the styrene- (meth) acrylic acid copolymer resin is 5% by mass or more and 20% by mass. It is important to contain the polyethylene resin (B) so as to be the following.
The second resin composition in this embodiment contains a cyclic polyolefin resin (C) and a styrene thermoplastic elastomer (D) as optional components.

(A) Styrene- (meth) acrylic acid copolymer resin The styrene- (meth) acrylic acid copolymer resin is not particularly limited, and styrene and (meth) acrylic acid are the main components. As long as it contains, you may contain a 3rd component.
That is, as long as the main component is a styrene monomer and an acrylic acid monomer and / or a methacrylic acid monomer, a resin obtained by polymerizing other monomers together with these monomers is also a styrene- (meth) acrylic acid copolymer of this embodiment. It can be used as a polymer resin.

  In making the laminated foam sheet of the present embodiment capable of producing a foam molded article having excellent heat resistance, the styrene- (meth) acrylic acid copolymer resin has a glass transition temperature of 110 ° C. or higher. What is shown is preferred.

In addition, about the glass transition temperature of this styrene- (meth) acrylic acid copolymer resin, a differential scanning calorimeter (DSC) is based on the method described in JIS K7121: 1987 "Method for measuring transition temperature of plastic". Can be measured.
More specifically, for example, a model name “DSC6220 type” manufactured by SII Nanotechnology Co., Ltd. is used, and a sample is placed on the DSC sample side so that there is as little gap as possible at the bottom of the aluminum measurement container. Place a 6 mg filled sample, place an aluminum measuring vessel containing alumina on the reference side, raise the temperature from 30 ° C. to 220 ° C. at a rate of 20 ° C./min under a nitrogen gas flow rate of 30 ml / min, After being held for 10 minutes, it is quickly removed, allowed to cool in an environment of 25 ± 10 ° C., and then re-heated to 220 ° C. at a temperature increase rate of 20 ° C./min. Can be calculated to obtain the glass transition temperature of the styrene- (meth) acrylic acid copolymer resin.
The midpoint glass transition temperature can be determined according to “9.3 Determination of Glass Transition Temperature” of the same standard.

In addition, as a styrene- (meth) acrylic acid copolymer resin of this embodiment, the ratio of the styrene monomer to all the structural units is 85 mass% or more and 95 mass% or less, and the remainder is an acrylic acid monomer and A binary copolymer or a ternary copolymer composed of methacrylic acid monomers is preferred.
Among these, as the styrene- (meth) acrylic acid copolymer resin employed as the main component of the second resin composition in the present embodiment, 85% by mass or more and 95% by mass or less of styrene monomer and 5% by mass or more and 15% by mass or more. The following binary copolymers with methacrylic acid monomers are preferred.

The styrene- (meth) acrylic acid copolymer resin preferably has a mass average molecular weight (Mw) of 150,000 to 300,000, and the styrene- (meth) acrylic acid copolymer resin has a mass of The average molecular weight is more preferably 200,000 to 250,000.
Further, the styrene- (meth) acrylic acid copolymer resin has a melt mass flow rate (MFR) of 0.5 g / 10 min or more measured under conditions of a temperature of 200 ° C. and a load of 5 kgf in accordance with JIS K7210. 0 g / 10 min or less is preferable, and 1.0 g / 10 min or more and 2.0 g / 10 min or less is more preferable.

  In addition, it is not necessary to contain only one styrene- (meth) acrylic acid copolymer resin in the second foamed layer, and if necessary, two or more styrene- (meth) acrylic acid co-polymers can be used. It is good also considering the resin mixture which combined coalescence resin as a main component of a 2nd resin composition.

(B) Polyethylene resin Although it does not specifically limit as said polyethylene resin, For example, a density is 0.942 g / cm < ³ > or more by superposing | polymerizing ethylene under medium and low pressure using a Ziegler Natta catalyst and a metallocene catalyst. High-density polyethylene resin ((B1) HDPE) polymerized to a high density, and α-olefin such as 1-butene, 1-hexene and 1-octene are polymerized together with ethylene in the same manner as the high-density polyethylene resin (HDPE). The linear low density polyethylene resin ((B2) LLDPE) polymerized so as to have a lower density than the high density polyethylene resin (HDPE), or shorter chain branching than the linear low density polyethylene resin. The density is 0.880 g / cm ³ or more and less than 0.910 g / cm ³ An ultra-low density polyethylene resin ((B3) VLDPE) polymerized so as to be in an ultra-low density state can be employed.

Further, as the polyethylene resin, a low density polyethylene resin ((B4) LDPE) in which long chain branching is formed in the molecule by polymerizing ethylene under high pressure can be employed.
Among them, as the polyethylene resin to be contained in the second foamed layer together with the styrene- (meth) acrylic acid copolymer resin, a high density polyethylene resin having a density of 0.942 g / cm ³ or more and 0.970 g / cm ³ or less. (B1) or a density of 0.910 g / cm ³ or more 0.942 g / cm ³ less than the linear low density polyethylene resin (B2) or a density of 0.880 g / cm ³ or more 0.910 g / cm less than ³ It is preferable that any of the ultra-low density polyethylene resin (B3).

The high-density polyethylene resin (B1), the linear low-density polyethylene resin (B2), and the ultra-low-density polyethylene resin (B3) have a temperature of 190 ° C. and a load of 2 in accordance with JIS K6922-2. It is preferable that the melt mass flow rate (MFR) measured under the condition of .16 kgf is 0.1 g / 10 min or more and 1.5 g / 10 min or less.
It is preferable that the MFR of the polyethylene resin is in the above range. By adopting the polyethylene resin exhibiting this preferable MFR, the effect of improving the strength of the second foamed layer becomes more prominent, and the laminated foamed sheet or foam molding This is because the effect of improving the strength of the product is more prominently exhibited.
In order to exert the strength improvement effect of the laminated foam sheet more remarkably, it is more preferable that the MFR of the polyethylene resin is 0.2 g / 10 min or more and 0.8 g / 10 min or less.
In the second foam layer of this embodiment, it is not necessary to contain this polyethylene resin alone, and if necessary, two or more polyethylene resins are combined and contained in the second resin composition. Also good.

(C) Cyclic polyolefin resin In addition, in this embodiment, cyclic polyolefin resin (C) which is an arbitrary component can be further contained in a laminated foam sheet.
The cyclic polyolefin resin is an effective component for imparting excellent strength to the second foamed layer in the same manner as the polyethylene resin, and the cyclic polyolefin resin is not particularly limited. For example, a cyclic olefin is metathesis-opened. A homopolymer (COP) obtained by ring polymerization or a copolymer (COC) of a cyclic olefin and an α-olefin can be employed.
Especially, in this embodiment, as cyclic polyolefin resin, the copolymer (COC) which copolymerized norbornene and ethylene by the metallocene catalyst is preferable.

  When the second foamed layer is formed using the cyclic polyolefin resin (C), if necessary, using the styrene- (meth) acrylic acid copolymer resin (A) and the polyethylene resin (B). Decreases the heat resistance (heat resistance deformation property) of the laminated foam sheet as the content of the styrene- (meth) acrylic acid copolymer resin in the second foam layer is lowered, while the polyethylene resin and the cyclic polyolefin. If the content of the resin is lowered and the styrene- (meth) acrylic acid copolymer resin is excessively contained, the strength improving effect by the polyethylene resin or the cyclic polyolefin resin may not be sufficiently exhibited.

Therefore, in making the laminated foam sheet of this embodiment excellent in heat resistance and strength, the styrene- (meth) acrylic acid copolymer resin (A) and the polyethylene resin (B) are in a mass ratio (A : B) is important to be contained in the second resin composition so as to be 80:20 to 97: 3.
For the same reason, when the cyclic polyolefin resin (C) is contained in the second resin composition, the total content (B + C) of the polyethylene resin (B) and the cyclic polyolefin resin (C) is: The total (A + B + C) in which the styrene- (meth) acrylic acid copolymer resin is further added is preferably 20% by mass or less.
In this case as well, the polyethylene resin (B) is preferably contained in an amount of 3% by mass or more, more preferably 5% by mass or more in order to make the laminated foam sheet excellent in strength.
That is, when the cyclic polyolefin resin (C) is contained in the second resin composition, the proportion of the total (A + B + C) of the styrene- (meth) acrylic acid copolymer resin and the polyethylene resin exceeds 0% by mass. The total content (B + C) of the polyethylene resin (B) and the cyclic polyolefin resin (C) is preferably greater than 3% by mass with respect to the total (A + B + C). It is preferable to adjust so that it may become 20 mass% or less.

(D) Styrenic thermoplastic elastomer In this embodiment, in addition to the styrene- (meth) acrylic acid copolymer resin (A), the polyethylene resin (B), and the cyclic polyolefin resin (C). The second resin composition contains a styrenic thermoplastic elastomer as an optional component.
Examples of the styrenic thermoplastic elastomer include styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene block copolymer (SIPS), styrene-butadiene-butylene-styrene copolymer (SBBS), and styrene- Examples include ethylene-butylene-styrene block copolymer (SEBS) and styrene-ethylene-propylene-styrene block copolymer (SEPS).
When the styrene-based thermoplastic elastomer is contained in the second resin composition, it is not necessary to contain the styrenic thermoplastic elastomer alone, and two or more kinds may be used in combination.

  The styrene-based thermoplastic elastomer (D) is an effective component for imparting toughness of the second foamed layer, but is generally an expensive material. Therefore, the styrene- (meth) acrylic acid copolymer resin (A), When the total of the polyethylene resin (B) and the cyclic polyolefin resin (C) is 100 parts by mass, the total amount is preferably 1 to 15 parts by mass. The content is more preferably from 10 parts by mass to 10 parts by mass, and particularly preferably from 3 parts by mass to 5 parts by mass.

(E) Other resins In the second resin composition, if the ratio of the total resin contained in the first resin composition is 10% by mass or less, the other resin (E) is an optional component. For example, a resin that functions as a polystyrene resin (GPPS), a high-impact polystyrene resin (HIPS), a butadiene rubber, an antistatic agent, or the like may be included.

In addition, the second resin composition can contain a foaming agent and a bubble regulator to adjust the second foamed layer to a predetermined foamed state in the same manner as the first resin composition, and various additives. It can be included.
In addition, content of the foaming agent and bubble regulator in said 2nd resin composition can be made into the same thing as content in 1st resin composition.

The first foamed layer and the second foamed layer each have an apparent density of 0.05 g / cm ^{3 in} that the basis weight of the entire laminated foamed sheet is suppressed and economic merit is easily obtained. It is preferably formed so as to be in the range of 0.5 g / cm ³ or less.

Moreover, it can suppress that the open cell rate of a 1st foam layer or a 2nd foam layer becomes high because an apparent density shall be 0.05 g / cm < ³ > or more.
That is, by setting the apparent density of the first foam layer and the second foam layer to 0.05 g / cm ³ or more, it is possible to ensure good elongation of the laminated foam sheet during thermoforming, and crack the foam molded product. It can suppress that the problem that it produces | generates or the width | variety of a molding condition becomes narrow arises.

In addition, from the viewpoint of heat insulation and strength of the laminated foamed sheet or foam molded product, the first foamed layer and the second foamed layer have an apparent density (the apparent density of the first foamed layer and the first foamed layer). The average value with the apparent density of the second foamed layer (hereinafter, also referred to as “average apparent density”) is excessively small. If either of the first foamed layer and the second foamed layer, or both, the strength is insufficient. There is a risk of causing it.
On the other hand, when the average apparent density is excessive, the heat insulating properties of the laminated foamed sheet and the foamed molded product may be insufficient.
In addition, when the average apparent density is excessive, there is a risk of causing a cost problem in that a large amount of resin is required to secure the total thickness of the first foam layer and the second foam layer to a certain level or more. Have
Accordingly, in order to excellent in low cost and strength and heat insulating properties of the multilayer foamed sheet or foamed molded article is preferably the average apparent density is 0.05 g / cm ³ or more 0.35 g / cm ³ or less It is more preferably 0.07 g / cm ³ or more and 0.30 g / cm ³ or less, and particularly preferably 0.08 g / cm ³ or more and 0.25 g / cm ³ or less.

In addition, if the total thickness of the first foamed layer and the second foamed layer is excessively thin, the laminated foamed sheet or the foamed molded product may be insufficient in strength and heat insulating properties. There is a risk of making it unsuitable for thermoforming.
Therefore, when making the laminated foamed sheet easy to thermoform and making the laminated foamed sheet or foamed molded article excellent in strength and heat insulation, the total thickness should be 0.5 mm or more and 3 mm or less. Is preferable, 0.6 mm or more and 2.5 mm or less is more preferable, and 0.7 mm or more and 2.3 mm or less is particularly preferable.

In addition, said 2nd foam layer is important when exhibiting the heat resistance excellent in the laminated foam sheet and the foaming molded article.
However, if the ratio of the second foam layer to the total of the first foam layer is made excessive, the brittleness improvement effect and cost merit of the first foam layer are fully reflected in the laminated foam sheets and foam molded products. There is a risk of being lost.
From this, the second foamed layer occupies the total of the first foamed layer and the second foamed layer in making the laminated foamed sheet and the foamed molded article relatively inexpensive and excellent in heat resistance and toughness. The mass ratio is preferably 20% by mass or more and 80% by mass or less, and more preferably 30% by mass or more and 70% by mass or less.

In the laminated foam sheet of this embodiment, a first foam layer and a second foam layer are formed by extrusion foaming by coextrusion.
When the laminated resin sheet is prepared by co-extrusion of the first resin composition and the second resin composition, it is preferable that the viscosity of both resins in the confluence mold is close because extrusion foaming is easy.
Moreover, it is better that the density of the first foam layer and the second foam layer is not separated from the strength of the laminated foam sheet.
For this reason, it is preferable that ratio (X / Y) of the density (X) of a 2nd foam layer and the density (Y) of a 1st foam layer is 0.3-2.5, 0.4- More preferably, it is 2.0.
In particular, in consideration of the fact that the first foamed layer tends to be softened and secondarily foamed more easily than the second foamed layer during thermoforming, X <Y, that is, the ratio (X / Y) is 1. Those less than 0.0 are preferred.

For coextrusion for forming the laminated foam sheet according to the present embodiment, a method employed in a general extrusion foaming process can be employed.
As a specific example of the equipment used for the coextrusion, one having a configuration as shown in FIG. 1 can be adopted.
As shown in FIG. 1, when producing a laminated foam sheet, the first extruder 10 for melt-kneading the first resin composition and the melt-kneading for the second resin composition are used. Two tandem extruders with the second extruder 20 are provided, and a merged mold XH into which melt-kneaded materials melted and kneaded in these extruders are merged, and a melt-kneaded material merged in the merged mold XH Can be used that has a circular die CD having an annular discharge port that is discharged as a cylindrical foam.

  Further, when manufacturing the laminated foam sheet, a cooling device CL for air-cooling the foam discharged from the circular die CD from the outside, and expanding the diameter of the cylindrical foam and cooling from the inside. Cylindrical mandrel MD, a slit device that continuously cuts the foam after passing through the mandrel MD along the extrusion direction and divides the foam into two long strips, and the long length obtained by the division A facility that is further provided with a winding roller 92 for winding the strip-shaped laminated foamed sheet 1 after passing the plurality of rollers 91 can be used.

  When a physical foaming agent such as hydrocarbon is employed as the foaming agent and a laminated foam sheet is produced using the above-described equipment as an example, a method for producing the laminated foam sheet will be described. First, the first extrusion A polystyrene resin or a high-impact polystyrene resin, which is the main component of the first resin composition, is introduced into a hopper of an extruder 10a upstream of the machine 10 together with a bubble regulator and the like, and an extruder 20a upstream of the second extruder 20 is used. The styrene- (meth) acrylic acid copolymer resin, which is the main component of the second resin composition, and the polyethylene resin are introduced into the hopper together with a cell regulator, and if necessary, a cyclic polyolefin resin or a styrenic heat A plastic elastomer or the like is introduced, and the resin introduced from the hopper is back-pressured by a screw inside the cylinder of each extruder. In addition proceeded, the melt-kneading is conducted by applying heat from the cylinder.

  And in this upstream side extruder, the material thrown in from the hopper to the blowing agent inlets 12 and 22 provided to introduce the blowing agent supplied from the blowing agent supply devices 11 and 21 into the cylinder of the extruder. In the region downstream of the foaming agent inlets 12 and 22, a melt-kneaded product adjusted so that the temperature becomes a temperature suitable for dispersing the foaming agent is reached. The foaming agent introduced from the foaming agent inlets 12 and 22 and the molten resin are continuously melt-kneaded.

  Next, the melt-kneaded material containing the foaming agent is transferred to the downstream extruders 10b and 20b, respectively, and while the melt-kneading continues while passing through the cylinders of the downstream extruders 10b and 20b, from the circular die. The temperature of the melt-kneaded product is adjusted so as to be in a state suitable for extrusion foaming, and the melt-kneaded product is supplied from the respective downstream side extruders 10b and 20b to the merging die XH.

In addition, as shown in the schematic sectional drawing in FIG. 2, the said confluence | merging die XH surrounds this flow path from the outer side in the middle of the flow path through which the melt-kneaded material supplied from the 1st extruder 10 passes. Thus, an annular slit is provided, and the melt-kneaded material supplied from the second extruder 20 can be discharged from the slit.
In this embodiment, a cylindrical flow is formed by the melt-kneaded material supplied from the first extruder 10 by this confluence mold, and the melt supplied from the second extruder 20 to the cylindrical flow. Two types of melt-kneaded materials are supplied toward the circular die CD with the outer skin covered with the kneaded materials.

In the circular die CD, the flow of the cylindrical melt-kneaded material supplied from the converging mold XH is changed into a cylindrical shape and discharged from an annular discharge port.
In this discharge, the melt-kneaded material is released from the pressure to cause foaming by the foaming agent, and so-called extrusion foaming is performed.
A cylindrical foam having an inner side as the first foam layer and an outer side as the second foam layer is formed by extrusion foaming in the coextrusion.

The cylindrical foam thus obtained is cooled from the inside by sliding the inner peripheral side of the cylindrical mandrel MD having an outer diameter larger than the discharge port of the circular die CD on the inner peripheral side. At the same time, the diameter is increased by the mandrel MD.
Thereafter, the expanded cylindrical foam is cut by a slitting device and used as a raw material for thermoforming as a laminated foam sheet having a first foam layer and a second foam layer.

  Here, the frictional force generated when the surface of the first foamed layer is slidably contacted with the outer peripheral surface of the mandrel MD can be made smaller than the second foamed layer, and the driving energy of the winding roller 92 can be saved. Coextrusion is carried out so that the second foam layer is on the outside in terms of preventing troubles such as sheet breakage, but if necessary, the coextrusion is carried out so that the second foam layer is on the inside. May be implemented.

Further, the laminated foam sheet thus obtained may be further laminated with a resin film for the purpose of improving the surface strength. For example, as shown in FIG. A resin film may be laminated on each of the foam layer.
The laminated foam sheet 1 illustrated in FIG. 3 includes a polystyrene resin film layer 1a, a first foam layer 1b, a second foam layer 1c, and a dry laminate film layer 1d in order from the bottom.

In addition, it is preferable to laminate | stack the resin film which shows the heat resistance equivalent to the said 2nd foam layer on the 2nd foam layer 1c excellent in heat resistance, The said dry laminate film layer in this embodiment is a polystyrene resin layer. It is preferable to use a dry laminate film in which 1d ₁ and a polypropylene resin layer 1d ₃ are laminated with an adhesive layer 1d ₂ interposed therebetween.
Further, the dry lamination film layer 1d is that the polystyrene resin layer 1d ₁ is thermally bonded to the second foam layer 1c, wherein the polypropylene resin layer 1d ₃ is formed such that the outermost surface of the laminated foam sheet Is preferable for exhibiting excellent heat resistance in the laminated foam sheet.

The polystyrene resin film layer 1a is preferably formed by adhering a stretched or non-stretched polystyrene resin film to the surface of the first foamed layer 1b by thermal lamination without using an adhesive or the like.
The polystyrene resin film layer 1a may be formed by co-extrusion when the first foam layer 1b and the second foam layer 1c are co-extruded.
That is, three layers (polystyrene resin film layer 1a / first foam layer 1b / second foam layer 1c) may be simultaneously coextruded to form the polystyrene resin film layer 1a.

  The thickness of each of the polystyrene resin film layer 1a and the dry laminate film layer 1d is usually 10 μm or more and 500 μm or less, and preferably 15 μm or more and 300 μm or less.

In addition, the dry laminate film and the polystyrene resin film may make the production environment of the laminated foam sheet clean in that it can be thermally bonded to the first foam layer and the second foam layer without using an adhesive or the like. it can.
However, if necessary, instead of these, for example, ethylene-vinyl acetate copolymer film, polyvinyl alcohol resin film, polyvinylidene chloride resin film, polyamide resin film, polyester resin film, polyacrylonitrile resin film, vinylidene chloride system -Acrylonitrile copolymer film, acrylonitrile-based methyl methacrylate-butadiene copolymer film, high-density polyethylene resin film, ionomer resin film, or metal vapor-deposited film with a metal vapor-deposited film formed on at least one side of these films You may make it laminate | stack using an adhesive agent etc. in any one of a foaming layer and a 2nd foaming layer, or both.

  When producing a foamed molded article using the laminated foam sheet of the present embodiment, for example, the laminated foamed sheet is softened by passing through a heating furnace set to a predetermined temperature, and then a desired mold is used. Appropriate thermoforming such as vacuum forming, pressure forming, vacuum / pressure forming, match mold forming, etc. may be performed.

In addition, since the foam molded product obtained by thermoforming the laminated foam sheet of this embodiment is excellent in lightness, toughness, heat resistance, etc., it is a container for refrigerated and frozen food, and it is electronic in a state where food is contained. A suitable range is a range-up container heated by a range.
In addition, since the foamed molded product of the present embodiment is also excellent in heat insulation, it is easy to handle with a bare hand even when the stored food is heated to a high temperature in a microwave oven, and the range can also be used to exhibit excellent heat retention. It can be said that it is suitable as an up container.
In producing a food container such as this range-up container, it is preferable to form the container so that the inside of the container becomes the second foam layer and the outside of the container becomes the first foam layer. It is preferable to perform thermoforming so as to be inside the first foam layer.

  In the present embodiment, the laminated foam sheet of the present invention is exemplified as described above. However, the laminated foam sheet of the present invention is not limited to the above example, and is described directly above. It is possible to adopt technical matters that do not significantly impair the effects of the present invention even if they are not.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Preliminary experiment)
(Test Example 1)
First, a tandem type extruder in which a downstream side extruder (L / D: 30, caliber: 65 mm) is connected to the tip of an upstream side extruder (L / D: 32, caliber φ: 50 mm) via a connecting pipe. Prepared.
And the raw material for foam sheets prepared so that it might become the following mixing | blending content was supplied to the upstream side extruder of the tandem type extruder, and melt-kneading was implemented in this extruder.

(A1) Styrene- (meth) acrylic acid copolymer resin: 90% by mass
Product name “G9001” manufactured by PS Japan
Representative properties Styrene unit content 92 mass%, methacrylic acid unit content 8 mass%
MFR: 1.8g / 10min

(B3) Ultra-low density polyethylene resin: 10% by mass
Product name "LUMITAC 12-1" manufactured by Tosoh Corporation
Typical characteristics MFR: 0.8g / 10min
Density: 0.900 g / cm ³

(D1) Styrene-ethylene-butylene-styrene copolymer (SEBS): [(A1) + (B3)] 2.0 parts by mass with respect to 100 parts by mass JSR's product name “Dynalon 9901C”
Typical characteristics MFR: 3.3 g / 10 min
Density: 0.970 g / cm ³

(X) Bubble regulator: [(A1) + (B3)] 2.0 parts by mass with respect to 100 parts by mass Toyo Styrene Co., Ltd. trade name “TM401A” (compound resin containing talc)

Next, butane was press-fitted as a foaming agent in the middle of the upstream side extruder, and further melt kneading was performed after adding the butane to the melt kneaded product.
Then, after butane is uniformly dispersed in the melt-kneaded material, the melt-kneaded material containing this foaming agent is continuously supplied to the downstream extruder to maintain the resin temperature suitable for foaming while continuing the melt-kneading. Cooled down.
Thereafter, the molten kneaded product is extruded and foamed from a circular die having a discharge port diameter of 70 mm attached to the tip of the downstream side extruder at a discharge rate of 30 kg / h and a resin temperature of 166 ° C., and is extruded and foamed from the die slit. The foam was placed on a cooled mandrel, and air was blown from the air ring to cool the outer surface of the foam, and the foam was cut by a cutter to produce a flat sheet-like foam sheet.
In producing the foam sheet, the take-up speed and the butane gas injection amount were adjusted so that the basis weight was 200 g / m ² and the thickness was 2 mm.
The specific value of the resin temperature is a value obtained by measuring the temperature of the breaker plate at the tip of the downstream side extruder, and the temperature of the breaker plate inserted with a resin thermometer at a depth of ¼ in the diameter direction. It is a measured value.

(Test Example 2)
A foamed sheet was produced in the same manner as in Test Example 1 except that the take-up speed and the butane gas injection amount were changed so that the basis weight was 130 g / m ² and the thickness was 1.6 mm.

(Test Example 3)
Further use of the following styrenic thermoplastic elastomer (D4), styrene- (meth) acrylic acid copolymer resin, ultra-low density polyethylene (LUMITAC12-1), styrene-ethylene-butylene-styrene copolymer The mass ratio of the coalesced styrene thermoplastic elastomer (A1: B3: D1: D4) was set to 90: 5: 5: 5 instead of 90: 10: 5: 0, and the resin temperature in extrusion foaming was changed. A foamed sheet was produced in the same manner as in Test Example 1 except that the temperature was changed to 167 ° C. instead of 166 ° C.

(D4) Styrenic thermoplastic elastomer (SBS)
Asahi Kasei Chemicals Co., Ltd. trade name “Toughprene 125”
Styrene / butadiene mass ratio = 40/60

(Test Example 4)
A foam sheet was prepared in the same manner as in Test Example 3 except that the take-up speed and the butane gas injection amount were changed so that the basis weight was 130 g / m ² and the thickness was 1.6 mm.

(Test Example 5)
Styrenic thermoplastic elastomer was not contained, and the mass ratio (A1: B3) of styrene- (meth) acrylic acid copolymer resin and ultra-low density polyethylene (LUMITAC 12-1) was 90:10, extrusion foaming A foamed sheet was prepared in the same manner as in Test Example 1 except that the resin temperature was changed to 167 ° C. instead of 166 ° C.

(Test Example 6)
Without containing a styrene-based thermoplastic elastomer, the styrene- (meth) acrylic acid copolymer resin was changed to the following resin (T080), and the polyethylene resin was changed to the following linear low density polyethylene (UH411). A foamed sheet was produced in the same manner as in Test Example 1 except that.

(A2) Styrene- (meth) acrylic acid copolymer resin: 90% by mass
Product name “Toyostyrene T080” manufactured by Toyo Styrene Co., Ltd.
Representative properties Styrene unit content 92 mass%, methacrylic acid unit content 8 mass%
Weight average molecular weight 230,000 MFR: 1.7 g / 10 min

(B2) Linear low density polyethylene resin: 10% by mass
Product name "Novatec LL UH411" made by Nippon Polyethylene
Typical characteristics MFR: 0.3g / 10min
Density: 0.924 g / cm ³

(Test Example 7)
Further use of the following styrenic thermoplastic elastomer (D2), mass ratio of styrene- (meth) acrylic acid copolymer resin, linear low density polyethylene resin (UH411), and styrenic thermoplastic elastomer (A2: B2: D2) was changed to 90: 10: 0 instead of 90: 10: 0, the resin temperature in extrusion foaming was changed to 165 ° C instead of 166 ° C, the basis weight was 130 g / m ² and the thickness was A foamed sheet was produced in the same manner as in Test Example 6 except that the take-up speed and the amount of butane gas injected were changed so that became 1.6 mm.

(D2) Styrene-butadiene-butylene-styrene copolymer (SBBS)
Product name “Tough Tech P2000” manufactured by Asahi Kasei Chemicals
Typical characteristics Density: 0.98 g / cm ³

(Test Example 8)
The mass ratio of the styrene- (meth) acrylic acid copolymer resin (T080) and the linear low density polyethylene resin (UH411) was set to 85:15 instead of 90:10, and the resin temperature in extrusion foaming A resin foam sheet for thermoforming was prepared in the same manner as in Test Example 6 except that the temperature was changed to 167 ° C. instead of 166 ° C.

(Test Example 9)
Further use of the following cyclic olefin resin, mass ratio of styrene- (meth) acrylic acid copolymer resin, linear low density polyethylene resin (UH411), and cyclic olefin resin (A2: B2: C) The resin foam sheet for thermoforming was the same as in Test Example 6 except that the ratio was changed to 80: 15: 5 instead of 90: 10: 0, and the resin temperature in extrusion foaming was changed to 165 ° C. instead of 166 ° C. Was made.

(C) Cyclic Olefin Resin Product Name “TOPAS COC 6013F” (copolymer obtained by copolymerizing norbornene and ethylene with a metallocene catalyst)
Typical characteristics Density: 1.02 g / cm ³

(Test Example 10)
Further use of the following high-density polyethylene resin, mass ratio of styrene- (meth) acrylic acid copolymer resin, linear low-density polyethylene resin (UH411), and high-density polyethylene resin (A2: B2 ( LLDPE): B1 (HDPE)) was changed from 90: 10: 0 to 90: 5: 5, and the resin temperature in extrusion foaming was changed to 165 ° C. instead of 166 ° C. Similarly, a resin foam sheet for thermoforming was prepared.

(B1) High-density polyethylene resin Product name "Novatec HD HB530" manufactured by Nippon Polyethylene
Typical characteristics MFR: 0.3g / 10min
Density: 0.964 g / cm ³

(Test Example 11)
The ratio (A2: D4) of the styrene-based thermoplastic elastomer (D4: tufprene 125) to the styrene- (meth) acrylic acid copolymer resin (T080) is 95: 5 without including a polyethylene resin. That the blended resin (trade name “CM140” manufactured by Toyo Styrene Co., Ltd.) blended with epoxidized soybean oil with respect to 100 parts by mass of these (A2 + D4) was used in a proportion of 3.0 parts by mass, A thermoformed resin foam sheet was produced in the same manner as in Test Example 6 except that the resin temperature in extrusion foaming was 177 ° C.

(Test Example 12)
A thermoformed resin foamed sheet was prepared in the same manner as in Test Example 6 except that 100 parts by mass of styrene- (meth) acrylic acid copolymer resin (T080) was used and the resin temperature in extrusion foaming was 180 ° C.

(Test Example 13)
The take-up speed and butane gas injection amount were changed so that the basis weight was 130 g / m ² and the thickness was 1.6 mm. As a result, a foam sheet could not be obtained.

(Test Example 14)
The mass ratio of styrene- (meth) acrylic acid copolymer resin (T080) and linear low density polyethylene resin (UH411) was set to 70:30, and the resin temperature in extrusion foaming was changed to 166 ° C. A thermoformed resin foam sheet was prepared in the same manner as in Test Example 4 except that the temperature was 163 ° C.

(Test Example 15)
Further use of the following styrenic thermoplastic elastomer (D3), mass ratio of styrene- (meth) acrylic acid copolymer resin, linear low density polyethylene resin (UH411), and styrenic thermoplastic elastomer (A2: B2: D3) was changed from 90: 10: 0 to 70: 30: 5, except that the resin temperature in extrusion foaming was changed to 165 ° C. instead of 166 ° C. A foam sheet was prepared.

(D3) Styrenic thermoplastic elastomer (SBC)
Product name "Lavalon ME5301CS" manufactured by Mitsubishi Chemical Corporation
Representative characteristics MFR: 5.0 g / 10 min
Density: 0.9 g / cm ³

(Evaluation)
(Basis weight / foaming ratio)
The basis weight and expansion ratio of the foamed sheet of each test example were determined as follows.
First, the basis weight (M / S) of the foam sheet was determined by calculation from the size (area: S) of the sample obtained by cutting the foam sheet into a predetermined size and the mass (M) of the sample.
Next, the thickness (t) of the sample is measured, the apparent volume (V = S × t) of the sample is obtained, and the apparent density (d = M / V) of the foamed sheet is calculated from the mass (M) of the sample. Then, the density (ρ) of the mixed resin forming the foamed sheet was divided by the apparent density (d) to obtain the foaming ratio by the following formula.
For the density (ρ) of the mixed resin forming the foamed sheet, the weighted average of the density and blending ratio of individual resins such as styrene- (meth) acrylic acid copolymer resin and polyethylene resin is calculated. Asked.

Foaming ratio = density of mixed resin (ρ) ÷ apparent density of foamed sheet (d)

(High temperature oil resistance)
A one-side vacuum type match mold with a tray container shape (outside of container opening: 115 mm × 185 mm, outside of bottom: 70 mm × 115 mm, outside of container depth: 30 mm), mold atmosphere temperature 165 ° C., male The mold temperature was set to 165 ° C. and the female mold temperature was set to 50 ° C., and the foam sheet of each test example was preheated in the mold for 15 seconds and then press-molded to prepare a tray container.
Salad oil heated to a predetermined temperature up to about 70% of the tray depth was poured into the tray container, and after 30 seconds, the salad oil was removed and the surface condition was visually checked.
If the surface state hardly changed from before oil injection, the oil resistance was good (OK), and if there was a change, the state was recorded.

(Shock resistance: energy required for punching)
The strength evaluation by the film impact tester (Brand name "No.181 film impact tester" by Yasuda Seiki Seisakusyo Co., Ltd.) was implemented with respect to the foam sheet of each test example.
At the time of evaluation, each 100 mm × 90 mm evaluation sample was taken from the foamed sheet, and each of the impact ball size was 12.7 mmR and the pendulum angle was 90 degrees in an environment adjusted to a temperature of 22 ° C. and a relative humidity of 40%. The energy required for punching the sample (unit: J) was determined.
Specifically, a sample for determining the energy required for punching was set between the sample plate and the sample holder, the pointer was placed on the 3.0 J line, the pendulum stop handle was tilted, and the pendulum was dropped.
Then, the sample was broken, and the scale indicated by the pendulum pushing the pointer was read.
The above operation was performed 5 times each for the front and back of the foam sheet, and the average value was obtained.
The energy required for punching was determined together with the thickness of each foam sheet and the expansion ratio.

The above evaluation results are shown in Table 1 below.
In Test Examples 13 to 15, evaluation of the obtained foamed sheets was not performed because a foamed sheet in a good state could not be obtained.

According to the preliminary experiment, as compared with Test Example 12 using only a styrene- (meth) acrylic acid copolymer, Test Example 11 containing a styrene-based thermoplastic elastomer has improved impact resistance. It has been shown.
Moreover, in the test examples 1-10 which contained the polyethylene resin which is an essential component of the 2nd foam layer in this invention, it became a result that the further outstanding impact resistance was exhibited.
Since the second foamed layer of the laminated foam sheet of the present invention is formed by the foamed sheets of Test Examples 1 to 10, according to this preliminary experiment, the laminated foamed sheet of the present invention has excellent strength. It turns out that it becomes.

(Evaluation of laminated foam sheet)
Example 1
An extruder (first extruder) for forming the first foamed layer was prepared, and the raw materials prepared so as to have the following blending contents were supplied thereto, and these melt-kneading was carried out with the first extruder. .

(1) Polystyrene resin: 80% by mass
Product name "Toyostyrene HRM26" manufactured by Toyo Styrene Co., Ltd.

(2) High impact polystyrene resin: 20% by mass
Product name "Toyostyrene HI E640N" manufactured by Toyo Styrene Co., Ltd.

(X) Bubble regulator: [(1) + (2)] 1.0 part by mass with respect to 100 parts by mass Toyo Styrene Co., Ltd. trade name “TM401A” (compounded resin containing talc)

Next, butane was press-fitted from the middle of the first extruder as a foaming agent, and the melt was further kneaded after adding the butane to the melt-kneaded product.
Then, after butane was uniformly dispersed in the melt-kneaded product, the melt-kneaded product containing this foaming agent was supplied to the confluence mold.
In a second extruder different from this, the same compounded material as in Test Example 1 of the preliminary experiment ((A1) styrene- (meth) acrylic acid copolymer resin: (B3) ultra-low density polyethylene resin: (D1 ) Styrenic thermoplastic elastomer = 90: 10: 5 parts) is melt-kneaded so that the resin temperature is 166 ° C., and the obtained melt-kneaded product is supplied from the first extruder in the merging die. A cylindrical foam is extruded from a circular die so that the outer side is the second foam layer with excellent heat resistance and the inner side is the first foam layer with excellent toughness. Immediately after the extrusion, the inside and the outside were cooled by cooling, and further cooled by a mandrel, and then the cylindrical foam was cut open to produce a laminated foam sheet.

(Example 2)
The second foamed layer was blended in Preliminary Experiment Example 3 ((A1) :( B3) :( D1) Styrenic thermoplastic elastomer: (D4) Styrenic thermoplastic elastomer = 90: 5: 5: 5) A laminated foamed sheet was produced in the same manner as in Example 1 except that the resin temperature was changed to 165 ° C. instead of 166 ° C.

(Example 3)
Except that the second foamed layer was blended as in Test Example 5 ((A1) :( B3) = 90: 10) of the preliminary experiment, and the resin temperature in extrusion foaming was changed to 163 ° C. instead of 166 ° C. A laminated foam sheet was produced in the same manner as in Example 1.

Example 4
Except that the second foamed layer was blended in Preliminary Experiment Example 6 ((A2) :( B2) LLDPE = 90: 10), and the resin temperature in extrusion foaming was changed to 163 ° C. instead of 166 ° C. Produced a laminated foam sheet in the same manner as in Example 1.

(Example 5)
(D2) Styrenic thermoplastic elastomer (trade name “Tuftec P2000”) is added to the formulation of Test Example 6, and the resin mass ratio ((A2) :( B2) :( D2)) is (90: 10: 3). The laminated foam sheet was produced in the same manner as in Example 4 except that the second foamed layer was formed by changing the resin temperature to 165 ° C. instead of 166 ° C.

(Example 6)
The compounding resin which mix | blended the same epoxidized soybean oil with what was further used for the test example 11 for the mixing | blending of the test example 6 was used, and the mass ratio of a resin ((A2) :( B3) :( D1): Large epoxidation) Bean oil) is (90: 10: 3: 3), the resin foam is changed to 168 ° C. instead of 166 ° C., and the second foamed layer is formed in the same manner as in Example 4 to obtain a laminated foam sheet Was made.

(Comparative Example 1)
(D4) Styrenic thermoplastic elastomer used in Test Example 11 and styrene- (meth) acrylic acid copolymer resin (T080) for forming the second foamed layer without including a polyethylene resin in the second foamed layer (Trade name “Tufprene 125”) was used so that the mass ratio (A2: D4) was 95: 5, and the resin temperature was 177 ° C., and the laminated foam sheet as in Example 1. Was made.

(Comparative Example 2)
The second foamed layer was set to Test Example 15 ((A2) :( B2) :( D3) = 70: 30: 5) of the preliminary experiment, and the resin temperature in extrusion foaming was changed to 163 ° C. instead of 166 ° C. A laminated foam sheet was produced in the same manner as in Example 1 except that.

This laminated foam sheet was evaluated in the same manner as in the preliminary experiment.
However, the energy value required for punching was evaluated in two ways: when an impact ball was applied from the first foam layer side and when an impact ball was applied from the second foam layer side.
The results are shown in Table 2 below.
In Comparative Example 2, the foamed sheet obtained was not evaluated because a foamed sheet in a good state could not be obtained.

  From the results shown in Table 2 above, according to the present invention, the laminated foam sheet having a foam layer mainly composed of a styrene- (meth) acrylic acid copolymer resin has a higher bending strength and impact strength than ever before. It can be seen that an excellent laminated foam sheet can be provided.

Claims (6)

A first polystyrene resin composition mainly composed of polystyrene resin or high impact polystyrene resin and a second polystyrene resin composition mainly composed of styrene- (meth) acrylic acid copolymer resin are coextruded. A laminated foamed sheet having a laminated structure of two or more layers including a first foamed layer made of the first polystyrene resin composition and a second foamed layer made of the second polystyrene resin composition. There,
The second polystyrene resin composition further contains a polyethylene resin (B) together with the styrene- (meth) acrylic acid copolymer resin (A), and the styrene- (meth) acrylic acid copolymer. A laminated foamed sheet characterized in that the polyethylene resin (B) is contained so that the ratio to the total (A + B) with the polymer resin is 3% by mass or more and 20% by mass or less.   The second polystyrene-based resin composition further contains a cyclic polyolefin resin (C), the cyclic polyolefin resin (C), the styrene- (meth) acrylic acid copolymer resin (A), and the polyethylene. The ratio of the cyclic polyolefin resin (C) in the total (A + B + C) of the resin (B) is more than 0% by mass and 15% by mass or less, and the cyclic polyolefin resin and the polyethylene resin are in the total (A + B + C) The laminated foam sheet according to claim 1, wherein the total (B + C) ratio exceeds 3 mass% and is 20 mass% or less.   The melt mass flow rate (MFR) measured under the conditions of a temperature of 190 ° C. and a load of 2.16 kgf of the polyethylene resin (B) is 0.1 g / 10 min or more and 1.5 g / 10 min or less. Laminated foam sheet.   A dry laminate film layer comprising a dry laminate film in which a polystyrene resin layer and a polypropylene resin layer are laminated via an adhesive layer is further provided, and the polystyrene resin layer is adhered to the second foam layer, and in order, The laminated foam sheet according to any one of claims 1 to 3, wherein the laminated foam sheet has a laminated structure that becomes one foam layer, a second foam layer, and a dry laminate film layer, and the polypropylene resin layer is provided on the outermost surface side.   A foamed molded product obtained by thermoforming the laminated foamed sheet according to claim 1.   The foam molded product according to claim 5, wherein the foam molded product is a container for food storage and is thermoformed so that the second foam layer is inside the first foam layer.

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