JP2019111785A - Polystyrene resin multilayer foam sheet - Google Patents

Abstract

To provide a heat-resistant polystyrene resin multilayer foam sheet that is excellent in heat resistance and oil resistance and has improved brittleness, and obtains a molded body usable as application for microwave oven heating.SOLUTION: There is provide a multilayer foam sheet according to the present invention in which a polystyrene resin foam layer, an adhesive layer and a polypropylene resin layer are laminated by coextrusion, in which the foam layer is formed of a mixed resin (X) containing a polystyrene resin, a polypropylene resin and a styrene thermoplastic elastomer, the polystyrene resin contains a specific range of a methacrylic component as a copolymerization component, a content ratio of the polystyrene resin is within a specific range, a content ratio of the polypropylene resin is within a specific range, a content ratio of the elastomer is within a specific range, and the adhesive layer is formed of a mixed resin (Y) containing a polystyrene resin and a polypropylene resin.SELECTED DRAWING: None

Description

  The present invention relates to a polystyrene resin multilayer foam sheet in which a polypropylene resin layer is laminated and bonded to a polystyrene resin foam layer.

  Heretofore, molded articles obtained by thermoforming polystyrene-based resin foam sheets have been used as food containers for microwave oven heating. Furthermore, in recent years, the cooking heating application of heating food by microwave oven to a high temperature that can cook oil-based food stored in the obtained molded body beyond simply heating is increasing, and further heat resistance Improvement has come to be sought.

Therefore, as a resin having high heat resistance as compared to polystyrene, a molded article obtained from a foam sheet containing a methacrylic acid component as a copolymer component of a styrene monomer as a main component is used as a container for food Is being considered.
However, although the foam sheet which has this copolymer resin as a main component is excellent in heat resistance, it has the problem that impact resistance is inferior. In addition, when the foamed sheet is produced, when the foamed sheet extruded from the die lip opening is taken off, the problem is derived from the brittleness of the copolymer resin that sheeting property is also poor, such as breakage of the foamed sheet and cracking of the foam occur. There is also.

  In Patent Document 1, as a method of improving the brittleness of a polystyrene resin foamed sheet containing a methacrylic acid component, in addition to 50 to 80 wt% of a polystyrene resin containing a methacrylic acid component, 15 to 45 wt% of a polypropylene resin and It is disclosed that the foam layer is made of a heat-resistant polystyrene resin composition containing 3 to 10% by weight of a styrene elastomer.

JP, 2009-155557, A

  However, in the heat-resistant foam sheet of Patent Document 1, although the brittleness is improved, the oil resistance and the heat resistance become insufficient in the cooking heating application by the microwave, so the heat resistance and the oil resistance are maintained while maintaining the brittleness. It was difficult to satisfy

  The present invention is a multi-layer foamed sheet which solves the problems of the prior art and is improved in brittleness, which is excellent in thermoforming property, the obtained molded article is excellent in oil resistance and heat resistance, and cooked by a microwave It is an object of the present invention to provide a heat-resistant polystyrene resin multilayer foam sheet usable in heating applications and the like.

According to the present invention, the heat-resistant polystyrene resin multilayer foam sheet shown below is provided.
[1] A polystyrene-based resin foam sheet in which a polystyrene-based resin foam layer, an adhesive layer and a polypropylene-based resin layer are laminated by co-extrusion, the polystyrene-based resin foam layer comprises a polystyrene resin (x1) and a polypropylene resin It is composed of a mixed resin (X) containing (x2) and a styrenic thermoplastic elastomer (x3), and the polystyrene resin (x1) contains 10% by weight or more of a methacrylic acid component as a copolymerization component, The content of the polystyrene resin (x1) is more than 80 wt% and not more than 98.5 wt%, and the content ratio of the polypropylene resin (x2) is 1 wt% or more and less than 15 wt%. The content of the plasticizing elastomer (x3) is 0.5% by weight or more and 5% by weight or less (provided that the polystyrene resin (x1) and The total content of the polypropylene-based resin (x2) and the styrene-based thermoplastic elastomer (x3) is 100% by weight), the adhesive layer comprises a polystyrene-based resin (y1) and a polypropylene-based resin (y2) A polystyrene resin multilayer foam sheet comprising a mixed resin (Y) containing the resin.
[2] The difference [T _x2 −T _x1 ] between the Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) and the melting point (T _x2 ) of the polypropylene resin (x2) is 5 ° C. or more and 40 ° C. or less The heat-resistant polystyrene resin multilayer foam sheet according to the above 1, characterized in that
[3] The heat-resistant polystyrene resin multilayer described in 1 or 2 above, wherein the apparent density of the foam layer is 0.035 to 0.7 g / cm ³ and the closed cell ratio is 75% or more. Foam sheet.
[4] The heat-resistant polystyrene resin multilayer foam sheet according to any one of the above 1 to 3, wherein the basis weight of the resin layer is 25 g / m ² or more.
[5] The phase structure index PI representing the mixed state of the polystyrene resin (y1) and the polypropylene resin (y2) defined by the formula (1) is more than 1.3 and not more than 3 The heat resistant polystyrene resin multilayer foam sheet in any one of 1-4.
PI = (η _y2 × φ _y1 ) / (η _y1 × φ _y2 ) (1)
Melt viscosity of polystyrene resin at ° _y1 : 190 ° C, shear rate 100 sec- ¹ φ _y1 : Volume fraction of polystyrene resin in mixed resin (Y) _{y y2} : Polypropylene at shear rate 100 sec- ¹ Melt viscosity of resin-based resin φ _y2 : Volume fraction of polypropylene resin in mixed resin (Y) [6] Peeling strength at the time of peeling the resin layer from the polystyrene resin multilayer foam sheet is 80 cN / 25 mm or more 5. Polystyrene-based resin multilayer foamed sheet according to any one of the above 1 to 5, characterized in that
[7] The polystyrene resin multilayer foam sheet according to any one of the above 1 to 6, wherein the melting point of the polypropylene resin (z) constituting the resin layer is 150 ° C. or higher.
[8] The polystyrene resin multilayer foam sheet according to any one of the above 1 to 7, wherein the melting point of the polypropylene resin (x2) is 150 ° C. or higher.

  According to the present invention, a polystyrene-based resin foam layer is composed of a mixed resin (X) comprising a specific polystyrene-based resin (x1), a polypropylene-based resin (x2) and a styrene-based thermoplastic elastomer (x3). An adhesive layer is composed of a mixed resin (Y) composed of (y1) and a polypropylene resin (y2), a resin layer is composed of a polypropylene resin (z), and the foam layer, the adhesive layer and the resin layer are laminated by coextrusion Thus, the brittleness is improved, and a heat resistant multilayer foam sheet excellent in thermoforming can be obtained. Furthermore, the obtained molded article is excellent in heat resistance and oil resistance, and can be used as a food container which can be cooked and heated by a microwave oven in a state of containing an oily food.

Hereinafter, the heat-resistant polystyrene resin multilayer foam sheet of the present invention will be described in detail.
The heat-resistant polystyrene resin multilayer foam sheet (hereinafter, also simply referred to as multilayer foam sheet) of the present invention is a multilayer foam sheet in which a polystyrene resin foam layer, an adhesive layer and a polypropylene resin layer are laminated in this order by coextrusion. It is. Next, a polystyrene resin foam layer (hereinafter, also simply referred to as a foam layer), an adhesive layer, and a polypropylene resin layer (hereinafter, also simply referred to as a resin layer) will be described in this order.

The polystyrene resin foam layer in the present invention is composed of the mixed resin (X). The mixed resin (X) contains a polystyrene resin (x1), a polypropylene resin (x2), and a styrene thermoplastic elastomer (x3).
Hereinafter, the styrene-based thermoplastic elastomer constituting the foam layer and the styrene-based thermoplastic resin elastomer blended in the adhesive layer described later are also simply referred to as a styrene-based elastomer.

  The polystyrene resin (x1) is made of a copolymer of a styrene component and a methacrylic acid component (hereinafter, also referred to as a styrene-methacrylic acid copolymer), and contains a methacrylic acid component as a copolymerization component of a styrene monomer. .

  Specific examples of the styrene-methacrylic acid copolymer include styrene-methacrylic acid copolymer and styrene-methacrylic acid-methacrylic acid methyl methacrylate copolymer, and the main component is styrene-methacrylic acid-methyl methacrylate copolymer It is preferable to These styrene-methacrylic acid copolymers may be used alone or in combination of two or more.

  The content of the methacrylic acid component in the styrene-methacrylic acid copolymer is 10% by weight or more, and preferably 12% by weight or more. When the methacrylic acid component satisfies the above range, it is possible to obtain a foam layer that is more excellent in heat resistance than a conventional heat resistant foam layer. The upper limit of the amount of methacrylic acid component is about 30% by weight.

  In the styrene-methacrylic acid copolymer, in addition to the above-mentioned methacrylic acid component, as a copolymer component other than the above-mentioned methacrylic acid component, acrylic acid, methyl acrylate as a copolymer component within the range of not inhibiting the object of the present invention and effects. And ethyl acrylate, maleic anhydride, methyl methacrylate, ethyl methacrylate and the like. 15 weight% or less is preferable in a polystyrene-type resin (x1), as for the quantity of another copolymerization component, 10 weight% or less is more preferable, and 7 weight% or less is more preferable.

  The polystyrene resin (x1) may contain a polystyrene resin other than the styrene-methacrylic acid copolymer. For example, polystyrene, rubber-modified polystyrene (high impact polystyrene), styrene-α-methylstyrene copolymer, Styrene-p-methylstyrene copolymer, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer, polyphenylene ether and the like are exemplified. 20 weight% or less is preferable in polystyrene resin (x1), as for content of polystyrene resin other than the said styrene- methacrylic acid copolymer, 15 weight% or less is more preferable, 10 weight% or less is more preferable, It is particularly preferable not to contain a polystyrene resin other than the styrene-methacrylic acid copolymer.

  The Vicat softening temperature of the polystyrene resin (x1) is preferably 120 ° C. or more, and more preferably 122 ° C. or more. The Vicat softening temperature is determined according to JIS K 7206 (Test load is method A, and the temperature rising rate of the heat transfer medium is 50 ± 5 ° C./hour). In addition, when a polystyrene-type resin (x1) contains 2 or more types of polystyrene-type resin, 2 or more types of polystyrene-type resin is mixed beforehand, a test piece is produced, and Vicat softening temperature shall be measured.

The measurement of the amount of methacrylic acid components in the styrenic copolymer can be obtained from the integral ratio of the spectrum measured by a proton nuclear magnetic resonance ( ¹ H-NMR) measuring device.

  The mixed resin (X) constituting the foam layer contains a polypropylene resin (x2). Since the content of the methacrylic acid component is 10% by weight or more, the polystyrene resin (x1) has a heat resistance when forming a foamed sheet more than a polystyrene resin having a content of the methacrylic acid component of less than 10% by weight Excellent but inferior in impact resistance. By containing the polypropylene resin (x2) in the mixed resin (X), it is possible to improve the impact resistance while maintaining the heat resistance of the foam layer higher than before. Further, at the time of thermoforming, even if the heating time of the multilayer foamed sheet is increased, a good molded product can be obtained, so that the range which can be thermoformed is broadened.

  As a polypropylene resin (x2), the copolymer of a propylene and the copolymerization component which can be copolymerized with propylene other than the homopolymer (h-PP) of a propylene is mentioned. Examples of copolymerization components copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1- Examples are ethylene or α-olefins having 4 to 10 carbon atoms, such as heptene and 3-methyl-1-hexene. The copolymer is not limited to a binary copolymer but may be a ternary copolymer. Moreover, these polypropylene resins can be used individually or in mixture of 2 or more types. Among these polypropylene resins, a homopolymer (h-PP) of propylene and an ethylene-propylene block copolymer (b-PP) are preferably used because the melting point is high and the brittleness improvement is excellent.

  The melting point of the polypropylene resin (x2) is preferably 150 ° C. or more, more preferably 155 ° C. or more, and more preferably 160 ° C. or more. By using a polypropylene resin having a melting point in this range, the heat resistance of the foam layer in the present invention can be improved more than the heat resistance of the conventional heat resistant foam layer. The upper limit of the melting point of the polypropylene resin is approximately 190 ° C.

  The melting point in the present invention can be measured by the method in accordance with JIS K 7121-1987. That is, pretreatment is carried out under the condition of conditioning (2) of the test piece according to JIS K 7 12 1-1987 (where the cooling rate is 10 ° C./min), and the melting peak is measured by raising the temperature at 10 ° C./min. Then, the temperature at the top of the obtained melting peak is taken as the melting point. When two or more melting peaks appear, the temperature of the top of the main melting peak (peak with the largest area) is used. When there is another peak having a peak area of 80% or more with respect to the peak area of the peak having the largest area, the phase of the peak temperature of the peak and the temperature of the peak of the largest area peak The mean value is adopted as the melting point. In addition, when the foam layer contains the recycle raw material mentioned later, suppose that the melting point of the polypropylene resin (x2) in a virgin raw material is measured.

  The melt flow rate (200 ° C., 5 kg load) of the polypropylene resin (x2) contained in the mixed resin (X) is preferably 2 to 20 g / 10 min, 3 to 18 g / 10 min More preferably, it is 4 to 16 g / 10 min. When a polypropylene resin (x2) having a melt flow rate in this range is used, it is possible to obtain a multilayer foam sheet having a good balance of flexural rigidity, brittleness and impact resistance.

  The melt flow rate in the present invention is measured based on JIS K 7210: 2014, and is measured under the conditions of 200 ° C., load 5 kg in the case of polystyrene resin, and 230 ° C., load 2.16 kg in the case of polypropylene resin. Ru.

In the present invention, the difference [T _x2 − of the Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) constituting the foam layer and the melting point (T _x2 ) of the polypropylene resin (x2) constituting the foam layer It is preferable that T _x1 ] be 40 ° C. or less. When this condition is satisfied, extrusion is performed in a state in which the polypropylene resin (x2) is sufficiently melted without excessively softening the polystyrene resin (x1) in the mixed resin (X) at the time of producing the multilayer foam sheet As a result, it is possible to obtain a multilayer foam sheet having a high single foam rate. From such a viewpoint, the difference is more preferably 38 ° C. or less. On the other hand, the lower limit of the difference [T _x2 −T _x1 ] is preferably 5 ° C., more preferably 10 ° C. When this condition is satisfied, it is possible to suppress the softening of the polypropylene resin (x2) in the mixed resin (X) at an earlier stage than the polystyrene resin (x1) at the time of thermoforming, so that molding is possible. Temperature range can be broadened, and stable thermoforming becomes possible. A multilayer foam sheet having a high single bubble rate can be stably obtained.

As said styrene-type thermoplastic elastomer (x3) which comprises the said mixed resin (X), a styrene butadiene copolymer, a styrene isoprene copolymer, these hydrogenated substances, and a partial hydrogenated substance are mentioned. The styrene-based thermoplastic elastomer (x3) can improve the mixed state of the polystyrene-based resin (x1) and the polypropylene-based resin (x2), and can increase the closed cell rate of the resulting multilayer foam sheet.
Incidentally, from the viewpoint of being able to further improve the mixed state of the polystyrene resin (x1) and the polypropylene resin (x2), one having a structural unit derived from styrene in the styrene elastomer of 10 to 65% by weight It is preferable to use, and it is more preferable to use the thing of 30 to 55 weight%.

Next, the content ratio of each component in the mixed resin (X) will be described.
In the present invention, the ratio of each component in the mixed resin (X) constituting the foam layer is as follows in order to obtain a multilayer foam sheet which is more excellent in heat resistance and oil resistance and superior in brittleness than the conventional heat resistant multilayer foam sheet. It is important to have a specific range.

  In the mixed resin (X), the content ratio of the polystyrene resin (x1) is more than 80 wt% and 98.5 wt% or less (however, the polystyrene resin (x1) and the polypropylene resin (x2) The total content of the styrenic thermoplastic elastomer (x3) is 100% by weight). By setting the content ratio in this range, it is possible to stably obtain a multilayer foam sheet having good heat resistance and flexural rigidity. From such a viewpoint, the lower limit of the content ratio is more preferably 86% by weight, and still more preferably 87% by weight. The upper limit of the content ratio is more preferably 95% by weight, still more preferably 94% by weight.

The content ratio of the polypropylene resin (x2) in the mixed resin (X) is 1% by weight or more and less than 15% by weight. (However, the total content of the polystyrene resin (x1), the polypropylene resin (x2) and the styrene thermoplastic elastomer (x3) is 100% by weight. When the content ratio of the polypropylene resin (x2) in the foam layer is too large, the closed cell ratio of the foam layer may be reduced, and the thermoformability of the resulting multilayer foam sheet may be reduced.
On the other hand, when the content ratio is too small, improvement of the brittleness in the foam layer is insufficient, and the impact resistance of the multilayer foam sheet may be insufficient. From such a viewpoint, the lower limit of the content is preferably 3% by weight, and more preferably 5% by weight. The upper limit of the content is preferably 12% by weight, more preferably 10% by weight.

  The content ratio of the styrene-based elastomer (x3) in the mixed resin (X) is 0.5% by weight or more and 5% by weight or less (provided that the polystyrene-based resin (x1) and the polypropylene-based resin (x2) The total content of the styrenic thermoplastic elastomer (x3) is 100% by weight). When the content of the styrenic elastomer is too small, the brittleness improving effect of the foam layer and the multilayer foam sheet may be insufficient. In addition, when the content of the styrenic elastomer is too large, it becomes difficult to improve the heat resistance of the foam layer and the multilayer foam sheet, and there is a possibility that the cost increases. From such a viewpoint, the content of the styrene-based elastomer constituting the foam layer is preferably 1% by weight or more, and more preferably 1.5% by weight or more. On the other hand, 4 weight% is preferable and less than 3 weight% is more preferable.

The recycled raw material derived from a multilayer foam sheet can be mix | blended with mixed resin (X) which comprises a foam layer. Examples of the recycled raw material include scraps and the like generated at the time of thermoforming of a multilayer foam sheet in which a polypropylene resin layer is laminated on the foam layer, and recycled as a raw material.
That is, in thermoforming for obtaining a molded article such as straw, a multi-layer foamed sheet having a large area is used to secure production efficiency, and from a sheet material on which a plurality of molded articles are formed by one thermoforming The final shaped body is obtained by trimming the shaped body. After thermoforming, the remaining portion of the multilayer foam sheet from which the molded body has been cut becomes a scrap called trimming waste or the like. The scrap is a scrap of a multilayer foam sheet in which a polypropylene resin layer is laminated on a heat-resistant foam layer, and therefore, the raw material obtained by recycling the trimming scrap is styrene-methacrylic as a main component. It is a mixed resin containing an acid copolymer and a polypropylene resin.

From the viewpoint of efficiently using recycled raw materials, it is preferable that the polypropylene-based resin (x2) constituting the foam layer and the polypropylene-based resin (z) constituting the resin layer described later are the same type of resin.
In addition, when mix | blending a recycle raw material with mixed resin (X), the content rate of mixed resin (X) is set so that it may become the content rate of each component in the said mixed resin (X) by mix | blending a new raw material suitably. It can be adjusted. In addition, when mix | blending a recycling raw material with a foaming layer, the polystyrene-type resin in a recycling raw material, a polypropylene-type resin, and a styrene-type thermoplastic elastomer are respectively polystyrene-type resin (x1) in a mixed resin (X), polypropylene-type resin (X2) and the content of each component in the mixed resin (X) are determined as those constituting the styrenic thermoplastic elastomer (x3).

  In the multilayer foam sheet of the present invention, when the recycled raw material is blended into the mixed resin (X), the upper limit of the blending ratio is preferably 40% by weight in 100% by weight of the mixed resin (X), Preferably, it is 30% by weight, more preferably 25% by weight. On the other hand, the lower limit is preferably 3% by weight, more preferably 5% by weight, and still more preferably 10% by weight. If recycled raw materials are used in this composition, it is possible to stably obtain a multilayer foam sheet having good impact resistance and a wide range of thermoformability while effectively utilizing the recycled raw materials.

Next, the mixed resin (Y) constituting the adhesive layer will be described.
The mixed resin (Y) constituting the adhesive layer contains a polystyrene resin (y1) and a polypropylene resin (y2). Since the adhesive layer contains the polystyrene resin (y1) and the polypropylene resin (y2), the foam layer containing a large amount of the polystyrene resin (x1) and the resin layer made of the polyolefin resin (z) are favorably adhered. It can be done.

  The polystyrene-based resin (y1) means a resin containing 50% by weight or more of a styrene-based resin monomer component, and in addition to polystyrene, high-impact polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolyester Polymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methyl acrylate copolymer, styrene-acrylic acid Styrene-based copolymers such as ethyl copolymer, styrene-maleic anhydride copolymer, styrene-α-methylstyrene copolymer, styrene-p-methylstyrene copolymer, polystyrene-polyphenylene ether copolymer, polystyrene and polyphenylene Mixing of compatible systems such as mixtures with ether Objects are exemplified. These can be used as 1 type, or 2 or more types of mixtures.

  Furthermore, it is preferable to use the thing whose total content (total content of a styrene oligomer) of a styrene dimer and a styrene trimer is 1500 ppm or less as a polystyrene resin (y1). The amount of styrene oligomers extracted from the container obtained by shape | molding a multilayer foam sheet as the content of styrene oligomers content in polystyrene-type resin (y1) is the said range can be decreased. From this viewpoint, the content of the styrene oligomer is preferably 1400 ppm or less, more preferably 1300 ppm or less, still more preferably 1200 ppm or less, and particularly preferably 1100 ppm or less.

  Examples of polystyrene resins (y1) having a total content of styrene oligomers of 1,500 ppm or less include polystyrene "G0002", "G0302", "G0501" manufactured by PS Japan, and "HRM 52M" manufactured by Toyo Styrene. In addition, the suspension polymerization method is adopted, the polymerization temperature is divided into two steps of the low temperature side and the high temperature side, and the polymerization rate of styrene is increased by prolonging the polymerization time on the high temperature side, the total content of styrene oligomers It is also possible to use a polystyrene-based resin manufactured so as to be 1500 ppm or less.

In the present specification, the content of styrene dimer and styrene trimer in the raw material or adhesive layer can be determined as follows.
First, 0.1 g of a styrenic resin is dissolved in 10 ml of tetrahydrofuran, and dropped into about 250 ml of heptane at 23 ° C. to precipitate the resin. Next, after adding triphenylmethane as an internal standard to the filtrate from which the resin is filtered out, the solution is concentrated to about 20 ml, and measurement is performed by a gas chromatograph mass spectrometer to contain styrene dimer and styrene trimer. You can determine the quantity. In addition, the measurement conditions of gas chromatograph mass spectrometry are as follows.
Equipment used: Shimadzu gas chromatograph mass spectrometer GC / MS QP50A, column: J & W Scientific DB-5 MS 0.25 mm × 30 m (stationary phase: 5% diphenyl-95% dimethyl-polysiloxane), carrier gas: helium column Flow rate: 1.6 ml / min, sample injection amount: 1 μL.

  As a polypropylene resin (y2) which comprises an adhesive layer, the copolymer of a propylene and the copolymerization component copolymerizable with propylene other than a polypropylene is mentioned. Examples of copolymerization components copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1- Examples are ethylene or α-olefins having 4 to 10 carbon atoms, such as heptene and 3-methyl-1-hexene. The copolymer may be a random copolymer or a block copolymer, and the copolymer is not limited to a binary copolymer and may be a ternary copolymer. Moreover, these polypropylene resins can be used individually or in mixture of 2 or more types.

The weight ratio (W _y1 : W _y2 ) of the polystyrene resin (y1) to the polypropylene resin (y2) constituting the adhesive layer is preferably 95: 5 to 30:70. When the weight ratio is in the above range, the amount of the styrene oligomer extracted can be reduced while improving the adhesion between the adhesive layer and the resin layer. From this viewpoint, the weight ratio (W _y1 : W _y2 ) is more preferably 85:15 to 40:60, still more preferably 75:25 to 60:40.

  In the present invention, a compatibilizer can be added to the mixed resin constituting the adhesive layer. As a compatibilizer in this case, any one capable of making a polystyrene resin and a polypropylene resin compatible with each other may be used, and various conventionally known ones can be used. Among these, the use of styrenic thermoplastic elastomers is particularly preferred. The styrenic thermoplastic elastomers include styrene-butadiene-styrene block copolymers (SBS) or styrene-isoprene-styrene block copolymers (SIS) and their fully hydrogenated products or partially hydrogenated products.

  The compatibilizer is preferably added in a proportion of 0.1 to 25 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight in total of the polystyrene resin and the polypropylene resin in the adhesive layer. It is preferable to do. By setting the addition amount of the compatibilizer in the above-described range, the polystyrene resin and the polypropylene resin constituting the adhesive layer can be appropriately dispersed to easily form an adhesive layer having a uniform thickness.

  The phase structure index PI (hereinafter, also simply referred to as PI) representing the mixed state of the mixed resin (y) is preferably more than 1.3. The phase structure (sea-island structure) in which the polystyrene resin (y1) and the polypropylene resin (y2), the polystyrene resin (y1) is a sea, and the polypropylene resin (y2) is an island by having PI in the above range Is likely to be formed. When forming the sea-island structure, since the polypropylene resin (y2) is dispersed like islands in the sea of the polystyrene resin (y1), in the heptane extraction test for the molded product, in the polystyrene resin (y1) It is thought that the styrene oligomer contained in is difficult to elute. From the above viewpoint, the lower limit of PI is preferably 1.4 or more, more preferably 1.5 or more. On the other hand, the upper limit is about three. If the PI value is 3 or less, the adhesive strength between the foam layer and the resin layer can be maintained, and the delamination of the resin layer at the time of thermoforming and the delamination at the time of cooking heating by a microwave oven are stabilized. It can prevent.

  When the sea-island structure in which the phase structure index PI is in the above range and the polypropylene resin (y2) is an island is formed, the adhesion between the adhesive layer and the resin layer may be reduced. However, in the present invention, the adhesive layer and the resin layer exhibit adhesion that can withstand practical use. The reason for this is the influence of high die internal pressure at the time of extrusion molding, and the resin layer to be described later is made of a polypropylene resin having a melting point of 150 ° C. or more, and the foam layer is made of a polystyrene resin having excellent heat resistance. It is believed that extrusion at high temperatures is possible and good adhesion can be maintained.

  The phase structure index PI indicates a mixed state of a polystyrene resin (y1) and a polypropylene resin (y2) constituting an adhesive layer, and is defined by the following formula (1). Also, when the adhesive layer contains a compatibilizer, PI is calculated without considering the compatibilizer. The volume fraction of each resin component in the mixed resin can be determined by dividing the compounding ratio (weight ratio) of each resin by the resin density of each resin.

PI = (η _y2 × φ _y1 ) / (η _y1 × φ _y2 ) (1)
η _y1: 190 ℃, the melt viscosity of the polystyrene resin (y1) at a shear rate 100 sec ^-1 phi _y1: volume fraction of polystyrene resin of the mixed resin _{(y1) η y2: 190 ℃} , shear rate 100 sec ^- Melt viscosity of polypropylene resin (y2) at ¹ φ _y2 : volume fraction of polypropylene resin (y2) in the mixed resin

In the present invention, the melt viscosity of the polystyrene resin, the polypropylene resin and the styrene thermoplastic elastomer is a nozzle having a nozzle inner diameter (D) of 1.0 mm and a nozzle length (L) of 10 mm, and a shear rate of 100 sec. ^-1 , measured at a resin temperature of 190 ° C.

  Next, the resin layer will be described. In the multilayer foam sheet of the present invention, the oil resistance is improved by providing the resin layer, and the molded product obtained by thermoforming is a foam layer when heated by a microwave oven in a state of containing a food containing oil. Can be prevented from dissolving by oil.

  The resin layer is made of a polypropylene resin (z). By laminating the resin layer by coextrusion, the brittleness of the resulting multilayer foam sheet is improved, the sheeting properties are improved, and a multilayer foam sheet can be easily produced. As polypropylene resin (z) which comprises a resin layer, resin similar to polypropylene resin (x2) which comprises the said foaming layer can be used. Among the polypropylene resins, polypropylene and ethylene-propylene block copolymers are preferably used because they have a high melting point and are excellent in oil resistance.

  The melting point of the polypropylene resin (z) constituting the resin layer is preferably 150 ° C. or more. If the melting point is 150 ° C. or more, the resin layer is locally broken even if cooking heating is performed with a microwave oven in a state where the oily food is contained in the molded product obtained by molding the foam sheet of the present invention It is possible to prevent the erosion due to the edible oil or the like soaking into the foam layer. From the above viewpoint, the melting point of the polypropylene-based resin constituting the polypropylene-based resin layer is more preferably 155 ° C. or more, more preferably 157 ° C. or more, and still more preferably 160 ° C. or more. On the other hand, the upper limit of the melting point is about 170 ° C. The melting point of the polypropylene resin (z) can be determined from the melt flow rate by the method described above, as in the case of the polypropylene resin (x2).

Next, the physical properties of the multilayer foam sheet of the present invention and each layer will be described.
It is preferable that the peeling strength at the time of making a resin layer peel from a multilayer foam sheet is 80 cN / 25 mm or more. If the peel strength is within this range, the adhesion between the foam layer and the resin layer is sufficient, and the occurrence of delamination from the foam layer of the resin layer is prevented during thermoforming or cooking with a microwave oven Be done. From this viewpoint, the peel strength is more preferably 100 cN / 25 mm or more, further preferably 200 cN / 25 mm or more, and particularly preferably 300 cN / 25 mm or more. The upper limit of the peel strength is approximately 700 cN / 25 mm.

The measurement of peel strength is performed as follows. A test piece of 25 mm in width is cut out from the multilayer foam sheet along the extrusion direction, and the resin layer is peeled off from the multilayer foam sheet in a 90 ° peel test of 300 mm / min according to JIS Z0237: 2009. Measure the peel strength of
In addition, two interfaces between the foam layer and the adhesive layer, and two interfaces between the adhesive layer and the resin layer are assumed as interfaces where peeling occurs when the peel test is performed, and depending on the adhesive force between the layers, the foam layer Material failure or cohesive failure of the adhesive layer may occur. The peel strength in the present invention means the weakest of them. For example, in the peeling test, when the foam layer is fixed with one jig and the adhesive layer and the resin layer are fixed with the other jig and the peeling test is performed, peeling occurs at the interface with the weak adhesive strength, The peel strength determined in the first test is the adhesive strength between the foam layer and the adhesive layer or the adhesive layer and the resin layer, whichever is weaker. If the resin layer is too thin to be fixed by a jig or if the resin layer is broken during the test, the resin layer may be lined with a reinforcing film.
In addition, it is preferable to peel between an adhesive layer and a resin layer, when a peeling test is performed from a viewpoint that the extraction amount of a styrene oligomer can be restrained lower. In such a case, it is considered that in the adhesive layer, a good morphology capable of suppressing the extraction amount lower is formed.

The basis weight of the foam layer is preferably 80 to 400 g / m ² , more preferably 100 to 330 g / m ² , still more preferably 200, from the viewpoint of the balance between mechanical strength and lightness as a packaging container. It is -340 g / m < ² >, Especially preferably, it is 250-350 g / m < ² >.
For the same reason, the basis weight of the entire multi-layer foam sheet is preferably 100 to 600 / ^{m 2,} more preferably 150~500g / ^{m 2,} more preferably 200~450g / ^{m 2,} particularly preferably Is 300 to 400 g / m ² .

The basis weight of the adhesive layer is preferably 5 g / m ² or more, more preferably 7 g / m ² or more from the viewpoint of adhesion. On the other hand, the basis weight of the adhesive layer is preferably 50 g / m ² or less, more preferably 40 g / m ² or less, from the viewpoint that light-weighting and foam having a favorable cell structure are easily obtained.

The basis weight of the resin layer is preferably 10 g / m ² or more. When the basis weight of the resin layer is too small, the effect of improving the brittleness by the resin layer is small, and there is a possibility that the multilayer foamed sheet may become brittle depending on the molding conditions. Furthermore, when the basis weight of the resin layer is too small, depending on the conditions, when the molded body containing the oily food is cooked and heated by a microwave oven, there is a possibility that corrosion by an edible oil or the like may occur. From the above viewpoint, the basis weight of the resin layer is more preferably 25 g / m ² or more, still more preferably 40 g / m ² or more, and particularly preferably 45 g / m ² or more. On the other hand, the upper limit of the basis weight of the resin layer is preferably 100 g / m ² or less, more preferably 80 g / m ² or less, and still more preferably 70 g / m ² or less. When coextruding the foam layer and the resin layer with the upper limit of the basis weight being in the above-mentioned range, the heat of the resin layer is not transmitted to the foam layer and the closed cell rate of the foam layer is not lowered. It is preferable because the rate can be maintained.

  The total thickness of the multilayer foam sheet is preferably 0.5 to 4 mm, more preferably 0.7 to 3.5 mm, further preferably from the viewpoint of improving brittleness and balancing mechanical strength and handleability as a packaging container. Is 1 to 3 mm, particularly preferably 2 to 2.8 mm.

For the same reason, the apparent density of the multilayer foamed sheet is preferably 0.035 to 0.7 g / cm ³ , more preferably 0.05 to 0.5 g / cm ³ .

The closed cell rate of the foam layer is preferably 70% or more. When the closed cell rate satisfies the above range, the range in which thermoforming can be performed can be broadened. From such a viewpoint, the closed cell rate of the foam layer is more preferably 75% or more, still more preferably 77% or more, and particularly preferably 80% or more.
As a method of increasing the closed cell rate of the foam layer, a method of co-extrusion using a resin having a low melt viscosity in the extrusion temperature range as a resin constituting the adhesive layer, volatilization to molten resin for forming an adhesive layer during extrusion There is a method in which a co-extrusion is carried out by adding an organic plasticizer.
In addition, when the foam layer and resin layer which consist of mixed resin (X) which mix | blended polypropylene resin with a co-extrusion layer and a resin layer are laminated | stacked, it exists in the tendency for the closed cell rate of a foam layer to fall easily. This is considered to be one of the causes of the narrowing of the thermoformable range of the multilayer foam sheet.
In the present invention, it is considered that a foamed layer having a high closed cell rate could be obtained by lowering the melt viscosity of the molten resin for forming an adhesive layer during extrusion and laminating the adhesive layer at a temperature close to the foamed layer. .

  The closed cell ratio is measured according to procedure C of ASTM-D 2856-70, for example, using a dry automatic densimeter Accupyt II 1340 manufactured by Shimadzu Corporation (a cut sample cut into 25 mm x 25 mm x 20 mm from a multilayer foam sheet If the multi-layer foam sheet is too thin to cut out the cut sample of the above size, multiple samples of 25 mm × 25 mm × multi-layer foam sheet thickness are cut out and stacked. Therefore, using the true volume Vx of the multilayer foam sheet (cut sample) subjected to measurement of 25 mm × 25 mm × about 20 mm, the closed cell rate S (%) is calculated by the following equation (2) Do.

S (%) = (Vx-W / ρ) × 100 / (Va-W / ρ) (2)
Vx: the true volume (cm ³ ) of the cut sample measured by the above method, which corresponds to the sum of the volume of the resin constituting the cut sample and the total bubble volume of the closed cell portion in the cut sample.
Va: Apparent volume (cm ³ ) of cut sample calculated from outer dimensions of cut sample used for measurement.
W: Total weight of cut sample used for measurement (g).
ρ: Density of resin obtained by defoaming the foam sheet (g / cm ³ )

Next, the manufacturing method of the multilayer foam sheet of this invention is demonstrated.
In the multilayer foam sheet of the present invention, a co-extrusion method is carried out using an adhesive layer consisting of a specific mixed resin (Y) on one surface of a foamed layer consisting of a specific mixed resin (X) and a resin layer consisting of a polypropylene resin (z) Can be obtained by laminating and bonding a resin layer, an adhesive layer, and a foam layer in this order from the surface. Specifically, a coextrusion die is attached to the outlet of the foam layer forming extruder, and the coextrusion die is connected to the adhesive layer forming extruder and the resin layer forming extruder using the apparatus. A molten resin for forming a foam layer comprising a specific mixed resin (X), a molten resin for forming an adhesive layer comprising a specific mixed resin (Y) and a volatile plasticizer, and a resin layer comprising a polypropylene resin (z) In the molding die for coextrusion, the molten resin for forming a foam layer, the molten resin for forming an adhesive layer, and the molten resin for forming a resin layer are joined in this order in the die for co-extrusion, laminated and then extruded and drawn. A multilayer foam sheet is produced, in which an adhesive layer and a resin layer are further formed on the surface of a foam layer formed by foaming a molten resin for layer formation.

  According to the co-extrusion method, the process is simple and cost reduction is possible as compared to other methods for producing a multilayer foam sheet. In addition, it is possible to obtain a multi-layer foam sheet having high adhesive strength between the foam layer and the adhesive layer and high adhesive strength between the adhesive layer and the resin layer. A multilayer foam sheet in which the phenomenon of peeling (delamination) is suppressed can be obtained.

  In the method of forming a multilayer foam sheet by the coextrusion method, a method of coextruding molten resin constituting each layer into a sheet shape using a coextrusion flat die to make a multilayer foam sheet, or an annular die for coextrusion Molten resin constituting each layer is co-extruded to form a tubular multilayer foam, and then the tubular multilayer foam is expanded along a cylindrical widening device, and then it is cut open while being pulled to form a multilayer foam sheet etc. There is. Among these, a method using a coextrusion annular die is the preferred method because it can produce a multilayer foam sheet with high productivity.

  As the extruder, co-extrusion annular die, cylindrical widening device, device for cutting cylindrical multi-layered foam, etc., known ones used in the field of extrusion foaming can be used.

  The molten resin for forming the foam layer is a polystyrene resin (x1) containing 10% by weight or more of a methacrylic acid component as a copolymerization component, a polystyrene resin (x2), and the styrene thermoplastic elastomer (x3) And an additive such as a cell regulator, which is blended according to need, to an extruder for forming a foam layer, which can be obtained by heating, melting, kneading, pressing in physical blowing agents and further kneading . As described above for the foam layer, the content ratio of the polystyrene resin (x1), the polypropylene resin (x2), and the styrene thermoplastic elastomer (x3) exceeds 80 wt%. It is 98.5 wt% or less, the content ratio of the polypropylene resin (x2) is 1 wt% or more and less than 15 wt%, the content ratio of the styrene thermoplastic elastomer (x3) is 0.5 wt% or more and 5 wt% % Or less (however, the total content of the polystyrene resin (x1), the polypropylene resin (x2) and the styrene thermoplastic elastomer (x3) is 100% by weight).

Usually, a cell regulator is added to the molten resin for forming a foam layer. As a cell regulator, either an organic type or an inorganic type can be used. Examples of inorganic cell regulators include zinc borate, magnesium borate, metal salts of boric acid such as borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate and the like. Moreover, phosphoric acid 2, 2- methylene bis (4, 6-tert- butylphenyl) sodium, a sodium benzoate, a calcium benzoate, an aluminum benzoate, sodium stearate etc. are mentioned as an organic type cell regulator.
Further, a combination of citric acid and sodium bicarbonate, a monoalkali salt of citric acid and sodium bicarbonate or the like can also be used as the cell regulator. These cell regulators can be used in mixture of 2 or more types.

  Examples of the foaming agent used for producing the foam layer include propane, n-butane (normal butane), i-butane (isobutane), a mixture of n-butane and i-butane, and aliphatic hydrocarbons such as pentane and hexane. Halogenated such as trichlorofluoromethane, dichlorodifluoromethane, 1,1-difluoroethane, 1,1-difluoro-1-chloroethane, 1,1,1,2-tetrafluoroethane, methyl chloride, ethyl chloride, methylene chloride and the like Inorganic blowing agents such as hydrocarbons, carbon dioxide, nitrogen, water and the like can be mentioned. Furthermore, decomposable foaming agents such as azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium hydrogen carbonate and the like can also be used. These foaming agents can be used in combination as appropriate. Among these, from the viewpoint of extrusion foamability, a foaming agent containing an aliphatic hydrocarbon as a main component is preferable, and among aliphatic hydrocarbons, i-butane or a mixture of i-butane and n-butane is more preferable. The amount of the foaming agent used is not particularly limited, but can be selected freely for the apparent density of the intended foamed sheet in the range of about 0.1 to 1 mole per 1 kg of resin.

The molten resin for forming an adhesive layer supplies the polystyrene resin (y1) and the polypropylene resin (y2) to an extruder for forming an adhesive layer, heats, melts, kneads and press-fits a volatile plasticizer. It can be obtained by further kneading.
The content ratio of the polystyrene resin (y1) and the polypropylene resin (y2) may be as described for the adhesive layer.

Preferably, a volatile plasticizer is added to the adhesive layer-forming molten resin, and co-extrusion is performed in a state in which the adhesive layer-forming molten resin contains the volatile plasticizer.
As a result of studies by the present inventors, when the foam layer made of a mixed resin compounded with a polypropylene resin and the resin layer are laminated by coextrusion via an adhesive layer, the closed cell ratio of the foam layer tends to be reduced. It turned out that there was a tendency. The decrease in the closed cell rate is considered to be one of the causes of the narrowing of the thermoformable range of the multilayer foam sheet. In the present invention, in particular, a volatile plasticizer is added at the time of extrusion, and co-extrusion is performed in a state in which the molten resin for forming an adhesive layer contains the volatile plasticizer, thereby increasing the closed cell rate of the foam layer. It is possible to stably obtain a multilayer foam sheet having a wide range of heat-formable properties.
The reason why the closed cell rate of the foam layer can be increased by co-extrusion in the state where the adhesive layer-forming molten resin contains a volatile plasticizer is not clear, but the plasticity of the volatile plasticizer is not clear. Since the temperature of the molten resin for forming the adhesive layer can be lowered by extrusion effect, even if the adhesive layer is laminated to the foamed layer which is composed of the mixed resin (X) and the closed cell rate tends to decrease. It is considered that the closed cell rate can be maintained high without significantly deteriorating the foaming state of the foam layer in the vicinity of the adhesive layer.

The volatile plasticizer is not particularly limited as long as it volatilizes from the multilayer foam sheet after producing the multilayer foam sheet and does not impair the intended purpose of the present invention, but is saturated with 2 to 7 carbon atoms 1 type or 2 types selected from hydrocarbon, halogenated aliphatic hydrocarbon having 1 to 3 carbon atoms, aliphatic alcohol having 1 to 4 carbon atoms, aliphatic ether having 2 to 8 carbon atoms, etc. What is constituted by the above is illustrated.
Examples of the saturated hydrocarbon having 2 or more and 7 or less carbon atoms as an example of the volatile plasticizer include ethane, propane, normal butane, isobutane, normal pentane, isopentane, isohexane, cyclohexane and heptane.

  Examples of the halogenated aliphatic hydrocarbon having 1 or more and 3 or less carbon atoms include methyl chloride, ethyl chloride, 1,1,1,2-tetrafluoroethane, and 1,1-difluoroethane.

  Examples of the aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol and tert-butyl alcohol.

  Examples of the aliphatic ether having 2 to 8 carbon atoms include methyl ether, ethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, methyl isobutyl ether and methyl amyl ether And methyl isoamyl ether, ethyl propyl ether, ethyl isopropyl ether, ethyl butyl ether, ethyl isobutyl ether, ethyl amyl ether, ethyl amyl ether, ethyl isoamyl ether, vinyl ether, allyl ether, methyl vinyl ether, methyl allyl ether, ethyl vinyl ether, ethyl allyl ether.

  The boiling point of the volatile plasticizer is preferably 80.degree. C. or less, more preferably 60.degree. C. or less, because it is easily volatilized from the adhesive layer. The lower limit of the boiling point is approximately -50 ° C.

It is preferable that the addition amount of the said volatile plasticizer is 0.05-2 mol with respect to 1 kg of mixed resin (Y), More preferably, it is 0.1-1 mol.
In addition, it is preferable to use butane as a volatile plasticizer since it is excellent in the handling property and the plasticizing effect with respect to resin.

  In the resin composition for forming each layer of the multilayer foam sheet of the present invention, a nucleating agent, an antioxidant, a heat stabilizer, an antistatic agent, a conductive agent, as needed, as long as the object of the present invention is not impaired. Additives such as additives, weathering agents, UV absorbers, colorants, flame retardants and inorganic fillers can be added.

  The present invention will next be described in more detail by way of examples and comparative examples. However, the present invention is not limited to the examples.

The following raw materials were used in Examples and Comparative Examples.
[Polystyrene resin (x1) for forming foam layer]
(1) PS Japan Co., Ltd. styrene-methacrylic acid-methacrylic acid methyl methacrylate copolymer “MM 290” (83 wt% of styrene component, 12 wt% of methacrylic acid component, 5 wt% of methyl methacrylate component) (abbreviation: MM 290, Melt viscosity 3948 Pa · s, MFR (200 ° C, load 5 kg) 1.0 g / 10 min, Vicat softening temperature 123 ° C.)
(2) PS Japan Co., Ltd. styrene-methacrylic acid copolymer "G 9001" (93% by weight of styrene component, 7% by weight of methacrylic acid component) (abbreviation: G9001, melt viscosity: 2646 Pa · s, MFR (200 ° C., Load 5 kg): 1.6 g / 10 min, Vicat softening temperature: 118 ° C.)

[Polypropylene-based resin (x 2) for forming a foam layer]
(1) Japan Polypropylene Corporation homopolypropylene resin "FY4" (abbreviation: FY4 melt viscosity: 761 Pa · s, MFR (230 ° C, load 2.16 kg): 5.0 g / 10 min, melting point 160 ° C.)
(2) Block Polypropylene Resin “BC3AD” (abbreviation: BC3AD, melt viscosity: 532 Pa · s, MFR (230 ° C., load 2.16 kg): 10 g / 10 min, melting point 158 ° C.)

[Styrenic thermoplastic elastomer (x 3) for forming a foam layer]
(1) JSR Co., Ltd. styrene-ethylene-butylene-styrene block copolymer, grade name "DYNARON9901P" (abbreviation: 9901P, melt viscosity 1284 Pa · s, styrene component content 53% by weight)

[Recycled material for foam layer formation]
(1) A recycled raw material obtained by heating and melting the multilayer foamed sheet obtained in Example 1 (abbreviation: RE1, 79.1 wt% of a polystyrene resin, 19.2 wt% of a polypropylene resin, a styrene thermoplastic elastomer 1.7) weight%)

[Polystyrene resin (y1) for forming an adhesive layer]
(1) PS Japan Co., Ltd. product polystyrene "G0002" (abbreviation: G0002, styrene oligomer content: 1056 ppm by weight, melt viscosity 1580 Pa · s)

[Polypropylene-based resin (y2) for forming an adhesive layer]
(1) Prime Polymer Co., Ltd. polypropylene resin “E111G” (abbreviation: E111G, melt viscosity: 1512 Pa · s, MFR (230 ° C., load 2.16 kg): 0.5 g / 10 min, melting point: 160 ° C.)
(2) Polypropylene resin “EC 9” (abbreviation: EC 9, melt viscosity 1900 Pa · s, MFR (230 ° C., load 2.16 kg): 0.5 g / 10 min, melting point 161 ° C.)

[Styrenic thermoplastic elastomer for adhesive layer formation]
The same one as the styrene-based elastomer for forming a foam layer was used.

[Polypropylene-based resin (z) for forming a resin layer]
The same polypropylene-based resin for forming a foam layer was used.

  As physical blowing agent and volatile plasticizer, mixed butane consisting of 70% by weight of normal butane and 30% by weight of isobutane was used.

[Air bubble regulator]
Talc: Matsumura Sangyo Co., Ltd., grade name "High Filler # 12" was used.

[apparatus]
Use a tandem extruder consisting of a first extruder with a barrel inner diameter of 90 mm and a second extruder with a barrel inner diameter of 120 mm as the extruder for foam layer formation, and a barrel extruder with a barrel inner diameter of 40 mm as the extruder for adhesive layer formation. As the extruder used for forming the resin layer, a barrel with an inner diameter of 65 mm was used. Furthermore, the outlet of each of the second extruder, the third extruder and the fourth extruder was connected to the coextrusion annular die so that each molten resin could be laminated in the coextrusion annular die.

Examples 1, 3 to 5, Comparative Examples 1 to 3, 5
90.6 wt% of "MM 290" as polystyrene resin (x1) constituting the foamed layer, 7.5 wt% of "FY4" as polypropylene resin (x2), and "9901 P as styrene thermoplastic elastomer (x3) Is used as mixed resin (x) by using 1.9% by weight of the mixture resin (x) and 1.7 parts by weight of talc is blended with 100 parts by weight of mixed resin (x). Mixed butane was injected at a rate of 0.31 mol / kg into this to make a molten resin for forming a foam layer, and then transferred to a second extruder to adjust the resin temperature to 183 ° C., as shown in Table 3 It was introduced into a coextrusion annular die so as to have a basis weight configuration.

  At the same time, the polystyrene resin (y1), the polypropylene resin (y2) and the thermoplastic elastomer of the types and weight ratios shown in Table 1 are supplied to a third extruder, heat-kneaded, and the proportions shown in Table 2 A mixed butane as a volatile plasticizer is injected and further kneaded to form a molten resin for forming an adhesive layer, and then the resin temperature is adjusted to 183 ° C., and the annular die for coextrusion is made to have a basis weight configuration shown in Table 1. Introduced to

  At the same time, the polypropylene-based resin shown in the column of resin layer in Table 1 is supplied to the fourth extruder and heat-kneaded to form a resin melt for forming a resin layer, and the resin temperature is adjusted to 183 ° C. It was introduced into the coextrusion annular die in an amount configuration.

In the annular die for coextrusion, a resin melt for forming an adhesive layer is laminated on the outer peripheral surface of the resin flow for forming a foam layer flowing in a cylindrical shape, and a resin melt for resin layer formation is further laminated on the outer peripheral surface. Then, an annular die lip having a diameter of 90 mm was extruded into the atmosphere to form a three-layered tubular laminated foam of foam layer / adhesion layer / resin layer. The extruded cylindrical laminated foam was cut along the extrusion direction while being pulled up with a diameter expansion blow-up ratio of 3.0 to obtain a multilayer foam sheet having a width of 850 mm.
The Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) constituting the foam layer is 123 ° C., and the melting point (T _x2 ) of the polypropylene resin (x2) constituting the foam layer is 160 ° C. From that, the difference [T _x2 -T _x1 ] was 37 ° C.

Example 2
A multilayer foamed sheet was obtained in the same manner as in Example 1 except that the polypropylene resin constituting the resin layer was "BC3AD" and the polypropylene resin constituting the adhesive layer was "EC9". The Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) constituting the foam layer is 123 ° C., and the melting point (T _x2 ) of the polypropylene resin (x2) constituting the foam layer is 158 ° C. From the above, the difference [T _x2 -T _x1 ] was 35 ° C.

Example 6
74.8 wt% of "MM290" as polystyrene resin constituting the foam layer, 3.6 wt% of "FY4" as polypropylene resin, 1.6 wt% of "9901 P" as styrenic elastomer, and further recycling 20% by weight of “RE1” as a raw material, 90.6% by weight of polystyrene resin (x1) constituting the foam layer, 7.5% by weight of polypropylene resin (x2), styrenic thermoplastic elastomer (x3) The multilayer foamed sheet was obtained in the same manner as in Example 1 except that the content of the copolymer was 1.9% by weight. The Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) constituting the foam layer is 123 ° C., and the melting point (T _x2 ) of the polypropylene resin (x2) constituting the foam layer is 160 ° C. From that, the difference [T _x2 -T _x1 ] was 37 ° C.

Comparative example 4
A multilayer foam sheet was obtained in the same manner as in Example 1 except that “G9001” was used as the polystyrene resin constituting the foam layer, and the compounding amount was 90.6% by weight.
Note that the Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) constituting the foam layer is 118 ° C., and the melting point (T _x2 ) of the polypropylene resin (x2) constituting the foam layer is 160 ° C. From the above, the difference [T _x2 -T _x1 ] was 42 ° C.

  Table 3 shows the results of measurement of various physical properties of the obtained multilayer foam sheet.

  Each physical property in an Example and evaluation were performed as follows.

(Melt viscosity)
The measurement of the melt viscosity was performed by the above method using Capirograph 1D manufactured by Toyo Seiki Seisaku-sho, Ltd. as a measuring device (n = 3).

(Vicat softening temperature of polystyrene resin)
The Vicat softening temperature of the polystyrene resin was measured by the above method.

(Melting point of polypropylene resin)
The melting point of the polypropylene resin was measured by the above method.

(Phase structure index PI)
The value of the phase structure index PI indicating the mixed state of the mixed resin (Y) in the adhesive layer was measured by the above method.

(Basic weight composition)
Cut out a test piece of 100 mm in width (test piece size: 100 mm × 1040 mm) across the entire width from the multilayer foam sheet, divide the weight of the test piece by its area (10400 mm ² ), and convert to g / m ² The basis weight of the multilayer foam sheet was determined according to (n = 3).
The basis weight constitution was determined from the discharge amount ratio of each layer based on the total basis weight of the multilayer foam sheet.

(Thickness of multilayer foam sheet)
The thickness was measured at intervals of 10 mm across the width direction of the multilayer sheet, and the average thickness was determined by arithmetic averaging.

(Apparent density of multilayer foam sheet)
The apparent density of the multilayer foam sheet was determined by dividing the basis weight of the multilayer foam sheet by its average thickness and converting it to g / cm ³ .

(Closed cell rate)
Using a dry automatic densimeter Accupyt II 1340 manufactured by Shimadzu Corporation, the measurement was performed according to the above-mentioned method except that the measurement pressure was 10 KPa (gauge pressure) and the equilibrium pressure rate was 0.05 KPa / min.

Brittle improvement (Charpy impact strength)
Test pieces of length 80 mm × width 10 mm × thickness: thickness of multilayer foam sheet, with the width direction of the multilayer foam sheet matched with the length direction of the test piece from 10 randomly selected locations of the multilayer sheet Ten pieces were cut out respectively. The test piece was placed in a constant temperature and humidity chamber at 23 ° C. and a relative humidity of 50% for 24 hours to condition the test piece. Using a conditioned test piece (without a notch), the resin layer becomes a striking surface by flatwise vertical impact according to JIS K7111-1: 2012 in a constant temperature and humidity chamber at 23 ° C and a relative humidity of 50%. Thus, the Charpy impact strength of the test piece was measured, and the arithmetic mean value of the measured values was taken as the Charpy impact strength of the multilayer sheet. The measured values of Charpy impact strength obtained are entered in the column of “Improvement of brittleness (Charpy impact strength)” in Table 3.

Thermoforming (The range where thermoforming is possible)
The evaluation of the thermoformability was performed based on the following criteria. In addition, after aging the multilayer foam sheet obtained by the Example and the comparative example for 21 days at the temperature of 25 degreeC, the following thermoforming was performed.
A thermoforming machine (manufactured by Asano Laboratory: product number “FKS-0631-10”) is used, and the surface on which the resin layer is laminated is inside the molded body by match mold vacuum forming, and the heater temperature is 315 ° C. Thermoforming using a cup-shaped forming die (3 rows × 3 steps) capable of taking 9 pieces of a molded article having a diameter of 142 mm and a spreading ratio of 2.6 after heating the multilayer foam sheet for a predetermined number of seconds in Did. By changing the heating time and measuring the heating time at which a good molded body can be obtained with respect to the molded body formed by the mold located at the central portion of the 9-piece mold, the good molded body is obtained The heating time range was calculated from the shortest heating time (shortest heating time) and the longest heating time (longest heating time) that could be achieved. The resulting heating time range is entered in the thermal formation column of Table 3.

(Oil resistance)
First, the multi-layer foam sheet was thermoformed with the resin layer facing the inner surface side to obtain a plate-shaped molded article (container) having an opening 142 mm × bottom 95 mm × height 86 mm. The vessel was charged with 300 ml of salad oil heated to each temperature (85-165 ° C., 5 ° C. interval). After holding for 1 minute, the presence or absence of oil erosion on the foam layer on the inner surface of the container was observed, and the maximum temperature at which oil erosion on the foam layer did not occur was entered in the oil resistance column of Table 3.

(Heat-resistant)
First, the multi-layer foam sheet was thermoformed with the resin layer facing the inner surface side to obtain a plate-shaped molded article (container) having an opening 142 mm × bottom 95 mm × height 86 mm. The vessel was charged with 300 ml of salad oil heated to each temperature (85-165 ° C., 5 ° C. interval). After holding for 1 minute, the presence or absence of container deformation was observed. The maximum temperature at which container deformation does not occur is entered in the heat resistance column of Table 3.

Claims (8)

In a polystyrene resin foam sheet in which a polystyrene resin foam layer, an adhesive layer and a polypropylene resin layer are laminated by coextrusion,
The polystyrene-based resin foam layer comprises a mixed resin (X) containing a polystyrene-based resin (x1), a polypropylene-based resin (x2), and a styrene-based thermoplastic elastomer (x3), and the polystyrene-based resin (x1) But contains 10% by weight or more of a methacrylic acid component as a copolymerization component, and the content of the polystyrene resin (x1) is more than 80% by weight and 98.5% by weight or less, and the polypropylene resin (x2) The content ratio of the styrene thermoplastic elastomer (x3) is 1 wt% or more and less than 15 wt%, and the content ratio of the styrenic thermoplastic elastomer (x3) is 0.5 wt% or more and 5 wt% or less (however, the polystyrene resin (x1) And the total content of the polypropylene-based resin (x2) and the styrene-based thermoplastic elastomer (x3) is 100% by weight. Polystyrene resin multilayer foamed sheet characterized by comprising a polyalkylene-based resin (y1) and the polypropylene resin (y2) and a mixed resin containing (Y).
The difference [T _x2 −T _x1 ] between the Vicat softening temperature (T _x1 ) of the polystyrene resin (x1) and the melting point (T _x2 ) of the polypropylene resin (x2) is 5 ° C. or more and 40 ° C. or less The polystyrene resin multilayer foam sheet according to claim 1.
The polystyrene resin multilayer foam sheet according to claim 1 or 2, wherein the apparent density of the multilayer foam sheet is 0.035 to 0.7 g / cm ³ and the closed cell ratio is 75% or more.
The basis weight of the said resin layer is 25 g / m < ² > or more, The polystyrene-type resin multilayer foam sheet in any one of the Claims 1-3 characterized by the above-mentioned.
The phase structure index PI representing the mixed state of the polystyrene resin (y1) and the polypropylene resin (y2) defined by the formula (1) is more than 1.3 and 3 or less. The polystyrene-based resin multilayer foam sheet according to any one of 4.

PI = (η _y2 × φ _y1 ) / (η _y1 × φ _y2 ) (1)
Melt viscosity of polystyrene resin (y1) at η _y1 : 190 ° C, shear rate 100 sec ^-1 _{y y1} : Volume fraction of polystyrene resin (y1) in mixed resin (Y) y _y2 : 190 ° C, shear rate Melt viscosity of polypropylene resin (y2) at 100 sec ^-1 φ _y2 : volume fraction of polypropylene resin (y2) in mixed resin (Y)

The peel strength at the time of making a resin layer peel from the said polystyrene resin multilayer foam sheet is 80 cN / 25 mm or more, The polystyrene resin multilayer foam sheet in any one of Claims 1-5 characterized by the above-mentioned.
The melting point of the polypropylene resin (z) which comprises the said resin layer is 150 degreeC or more, The polystyrene-type resin multilayer foam sheet in any one of Claims 1-6 characterized by the above-mentioned.
The melting point of a polypropylene resin (x2) is 150 degreeC or more, The polystyrene resin multilayer foam sheet in any one of the Claims 1-7 characterized by the above-mentioned.