JP4761936B2 - Polystyrene-based resin laminated foam sheet with excellent deep drawability - Google Patents

Description

  The present invention relates to a styrene-based resin laminated foam sheet having excellent strength used for a deep-drawn molded container such as an instant noodle container.

  Polystyrene resin foam sheet has a beautiful surface, light weight and strength, excellent moldability, low cost, hydrophobicity, hygiene, heat insulation and heat insulation. It is molded into cups and bowls and is widely used as various food packaging materials and simple containers. The molding is carried out by continuously plasticizing the polystyrene-based resin foam sheet and then continuously molding it into a container shape by a method such as press molding, vacuum molding or match molding. In molding, a mold, a wooden mold or the like is molded and the thermoplasticized sheet is cooled and solidified to form a container. In recent years, the pitch has been reduced due to cost reduction, high cycle, and increasing the number of containers, and container shapes have been diversified, deepened, and complicated due to the expansion of usage. . Furthermore, a polystyrene-based resin laminated foam sheet in which various films for imparting strength maintenance, beautification, designability, and functionality of a container are laminated is widely used. This tendency leads to a marked increase in the difficulty of molding, which naturally causes problems such as a decrease in the strength of the molded container and a failure associated with the rupture of the cell film called “Naki”. This problem is more noticeably affected in deep-drawn containers, for which demand has been increasing recently from the viewpoint of design. In order to obtain a deep-drawn molded container that does not cause a decrease in strength while avoiding these problems, a polystyrene resin foam sheet has a molecular weight distribution in a specific range, and a specific amount of a polystyrene resin composition is added. A method using a styrene resin (for example, Patent Document 1) has been proposed.

  Further, as a styrene resin composition having excellent fluidity, high melt tension, and reduced sheet width fluctuation during high-speed take-up and excellent in processing productivity, linear polystyrene having a mass average molecular weight of 25 to 450,000 And a mass average molecular weight of 150,000 to 10,000,000, and a mass ratio of linear polystyrene: multibranched polystyrene of 70:30 to 30:70 is 250,000 to A styrenic resin composition for a biaxially stretched sheet of 750,000 has been proposed (see Patent Document 2), and is a styrenic resin composition comprising the linear polystyrene and multi-branched polystyrene. The slope in the logarithmic graph with the weight average molecular weight as the horizontal axis and the inertial radius of the resin composition as the vertical axis is 0.35 to 0.45, and the depth (H) and the opening (W) Ratio of ( / W) is also proposed styrenic resin composition used to mold the foam containers to be 0.2 to 0.8 (see Patent Document 3.).

  However, in any of the above cases, it has been insufficient to solve the molding defects that occur in deep drawn containers having a drawing ratio of 0.6 or more, particularly 0.8 or more.

There has also been proposed a polystyrene-based resin foam sheet capable of obtaining good printability by setting the density of the surface layer portion from the surface on which the non-foamed film is laminated to the thickness direction of 100 μm to 0.35 g / cm ³ or more (see Patent Document 4). .) However, this improves the surface property on the side where the non-foamed sheets are laminated to obtain good printability, and does not solve the molding defects that occur in deep-drawn containers.
JP-A-3-103450 JP 2005-179389 A JP 2005-281405 A JP 2000-143863 A

  An object of this invention is to provide the styrene resin laminated foam sheet excellent in the deep drawability which can shape | mold the container excellent in intensity | strength.

As a result of earnestly studying a method for expressing excellent moldability in a container obtained by deep drawing with a drawing ratio of 0.8 or more, the inventors have obtained a specific melting characteristic. In order to express excellent moldability without causing a decrease in strength, in order to include a specific proportion of multi-branched polystyrene in the base resin, the basis weight of the foam sheet constituting the polystyrene resin laminated foam sheet The inventors have found that it is effective to adjust the density of the surface layer portion (particularly, the surface on which no film is laminated) and the amount of the remaining foaming agent to specific values, and have reached the present invention.

That is, the present invention relates to a container in which a polystyrene resin non-foamed film having a basis weight of 100 to 210 g / m ² is laminated on one side of a polystyrene resin foam sheet and the drawing ratio is 0.8 or more . A polystyrene-based resin laminated foam sheet used for molding, wherein the polystyrene-based resin foam sheet has a base resin of linear polystyrene having a mass average molecular weight of 25 to 450,000 and a mass average molecular weight of 1,000,000 to 1,000,000. A styrene-based resin composition containing 10 million hyperbranched polystyrene, having a mass ratio of linear polystyrene: multibranched polystyrene of 70:30 to 30:70 and a mass average molecular weight of 250,000 to 750,000. Table extrusion foaming becomes, the basis weight 250~400g / m ^2, the residual blowing agent weight 2.1 to 3.0 wt%, not laminating the non-foam film surface Polystyrene-based resin laminate foam sheet, wherein (claim 1) the density of the surface layer portion of the thickness of 150μm is 0.25~0.40g / cm ³ from. The “mass average molecular weight” is determined by the GPC-MALLS method.

Further, the present invention is the polystyrene resin foam sheet (Claim 2) wherein the base resin of the polystyrene resin foam sheet has a melt tension at 180 ° C. of 50 g or more and a take-up speed at break of 20 m / min or more. .

Furthermore, the present invention is a Thickness is 1.5~2.2mm the polystyrene-based resin laminate foam sheet (claim 3).

  Further, in the present invention, the polystyrene-based resin laminated foamed sheet has a maximum elongation of 200% or more at which a crack does not occur on a non-laminated surface when a tensile test is performed in an extrusion direction under an atmosphere of 110 ° C. (Claim 4). It is.

  Moreover, this invention is a container (Claim 5) whose drawing ratio obtained by shape | molding a polystyrene-type resin laminated foam sheet is 0.8 or more.

By using the port polystyrene based resin laminated foamed sheet of the present invention, excellent fluidity moldability of the resin, and deep drawing vessel does not cause strength reduction is obtained.

  The styrene resin composition used for the polystyrene resin foam sheet of the present invention is disclosed in Japanese Patent Application Laid-Open No. 2005-179389 (Patent Document 2), and has an average molecular weight of 25 to 450,000. And a polybranched polystyrene having a weight average molecular weight of 1,000,000 to 10,000,000, and a weight average molecular weight of a linear polystyrene: multibranched polystyrene of 70:30 to 30:70 is 250,000 to This is an extruded foam of a multi-branched polystyrene resin which is a styrene resin composition of 750,000. The weight average molecular weight of the linear polystyrene contained in the styrenic resin composition is 250,000 to 450,000, and the weight average molecular weight of the multi-branched polystyrene is 1 million to 10 million, more preferably 2 million to 5 million. It is. If the weight average molecular weight of the multi-branched polystyrene is less than 1 million, sufficient strength cannot be obtained, and if it exceeds 10 million, good moldability cannot be obtained. Furthermore, the weight average molecular weight of the styrene resin composition is 250,000 to 700,000, more preferably 350,000 to 500,000. The mass ratio of linear polystyrene to hyperbranched polystyrene in the resin composition is 70:30 to 30:70, preferably 60:40 to 40:60, for linear polystyrene: multibranched polystyrene. When the mass ratio applied to the multi-branched polystyrene is less than 30, sufficient melt tension cannot be obtained, and reduction in container strength is inevitable. On the other hand, if it exceeds 70, the moldability associated with the decrease in fluidity deteriorates. As such a multi-branched polystyrene resin, for example, Dainippon Ink and Chemicals, Inc. sells, for example, a styrene resin composition having a weight average molecular weight of 290,000 as a trade name “HP-500M”.

  The melt tension at 180 ° C. of the base resin used in the polystyrene resin foam sheet of the present invention is 50 g or more, and the take-up speed at break is 20 m / min or more. The melt tension of the base resin of the polystyrene-based resin foam sheet and the take-off speed at break are measured using a Capillograph manufactured by Toyo Seiki. A cylinder having a diameter of 10 mm and a length of 350 mm with an orifice having a diameter of 1 mm, a length of 10 mm, and an inflow angle of 45 degrees is heated at 180 ° C. at the tip of the capilograph, filled with about 20 g of polystyrene resin, and preheated for 5 minutes. After preheating, polystyrene resin is extruded at a speed of 10 mm / min using a piston having the same diameter as the cylinder, and the extrudate is passed through a tension detection pulley and accelerated at a rate of 200 m / 5 min from a speed of 2 m / min. The tension required for taking-up until the extrudate is cut and the speed at that time are measured. The tension at the time of breaking was used as the melt tension of the polystyrene-based resin, and the speed at that time was taken as the take-up speed at the time of breaking. When the melt tension thus obtained is lower than 50 g, the strength of the deep-drawn container obtained by molding is insufficient. On the other hand, when the take-off speed at the time of breakage is lower than 20 m / min, a crack (crack) on the inside of the container and cracks (cracks) occur, and a good molded product cannot be obtained.

  The foamed sheet manufacturing process by extrusion foaming when obtaining the polystyrene-based resin foamed sheet of the present invention can be performed by a widely used method. For example, a resin composition in which a nucleating agent is mixed with a polystyrene resin is melt-mixed using an extruder, and after the foaming agent is pressed in, the molten resin is further cooled to a temperature suitable for foaming. , Extrude into the low pressure range from the circular die (ie foaming by pressure release) to obtain a cylindrical foam, located inside the cylindrical foam to cool from the inner surface side of the cylindrical foam A method is known in which a foamed sheet can be obtained after being molded by a cylindrical cooling cylinder.

  Examples of the foaming agent used in the production of the polystyrene resin foam sheet of the present invention include physical foaming agents such as propane, butane and pentane, and chemical foaming agents such as sodium bicarbonate-citric acid. Industrially, butane is frequently used. Especially, it is preferable to use the mixed butane which consists of 70-100 weight% of isobutane and 0-30 weight% of normal butane from the viewpoint of the thermoformability of a sheet | seat, and the retainability of a foaming agent gas.

  The nucleating agent used in the production of the polystyrene resin foam sheet of the present invention includes porous inorganic powders such as calcium carbonate, barium sulfate, silica, titanium oxide, clay, aluminum oxide, bentonite, diatomaceous earth, talc. Etc. can be used. Further, if necessary, in order to improve dispersion of the nucleating agent in the resin, a fatty acid metal salt such as ethylene bisstearylamide and magnesium stearate, a lubricant such as a fatty acid ester, and the like may be added.

The basis weight of the polystyrene resin foam sheet of the present invention is 250 g / m ² or more. If the basis weight is less than 250 g / m ² , a container satisfying the container strength cannot be obtained. In addition, an increase in the basis weight of the polystyrene resin foam sheet leads to an improvement in container strength, but increases the cost. Therefore, it is preferable to set the amount to 400 g / m ² or less.

  The amount of the remaining foaming agent in the polystyrene-based resin foamed sheet is mainly determined by the amount of the foaming agent injected during production by extrusion foaming of the polystyrene-based resin and the resin temperature of the polystyrene-based resin during foaming. Moreover, raising the density of the surface layer part of the polystyrene-type resin foam sheet mentioned later also has the effect which suppresses dissipation of the foaming agent from the polystyrene-type resin foam sheet surface, and is effective in ensuring the amount of residual foaming agents. The greater the amount of residual foaming agent (gas) in the polystyrene resin foam sheet, the higher the gas pressure in the cell of the polystyrene resin foam sheet and the better the container strength. In order to obtain a sufficiently strong container, the amount of residual foaming agent is preferably 2.1 to 3.0% by weight, and more preferably 2.3 to 2.6% by weight. If the residual foaming agent amount is less than 2.1% by weight, the container strength of the resulting container tends to decrease. In addition, when the amount of the remaining foaming agent exceeds 3.0% by weight, the foaming agent gas is dissipated from the polystyrene resin foam sheet during lamination with the polystyrene resin non-foamed film, and voids are generated at the lamination interface between the two. When the molding is heated, the interface between the non-foamed polystyrene resin film and the foamed polystyrene resin sheet is peeled off, causing a so-called blistering phenomenon, and the container appearance tends to be greatly impaired.

In the polystyrene resin foam sheet of the present invention, the density of the surface layer portion having a thickness of 150 μm from the surface on which the film is not laminated is 0.25 to 0.40 g / cm ³ . By controlling the density of the surface layer portion of the polystyrene resin foam sheet as described above, a rigid layer can be formed on the surface of the polystyrene resin foam sheet, thereby improving the compressive strength of the resulting container. If the density of the surface layer is less than 0.25 g / cm ³ , the reinforcing effect will be insufficient, and the strength, particularly the lip compression strength will be reduced. On the other hand, if it exceeds 0.40 g / cm ³ , the elongation of the surface of the polystyrene-based resin foamed sheet is extremely lowered, and there is a tendency that the obtained molded product has a crack (a phenomenon in which the foamed sheet is stretched locally). . In addition, the density of the surface layer part of a polystyrene-type resin foam sheet is calculated | required by cutting out a surface layer part (150 micrometers from the surface), and measuring the weight.

  When the polystyrene resin foam sheet is produced by extrusion foaming, the density of the surface layer portion of the polystyrene resin foam sheet is controlled by blowing air onto the surface of the polystyrene resin foam sheet to rapidly cool the polystyrene resin foam sheet. The density of the surface layer portion of the sheet can be increased. In order to obtain the target density of the surface layer portion, the temperature of the cooling air, the air volume, the wind speed, and the spraying position may be appropriately adjusted according to the sheet surface temperature immediately after extrusion, the extrusion resin discharge amount, the sheet take-up speed, etc. .

  In addition, the closed cell ratio of the polystyrene resin foam sheet of the present invention is preferably 85% or more in order to suppress the dissipation of the foaming agent gas in the polystyrene resin laminated foam sheet and maintain strength properties over a long period of time. 90% or more is more preferable. When the closed cell ratio is less than 85%, the remaining foaming agent in the foam sheet is quickly dissipated, the pressure inside the bubbles cannot be maintained, the strength is greatly reduced, and the secondary foaming force due to heating during molding is also reduced. Since it falls, there exists a tendency for favorable shaping | molding to become impossible. The closed cell ratio of the polystyrene resin foam sheet can be measured using an Air Comparison Pycnometer (for example, model 1930 manufactured by BECKMAN).

  As the resin of the styrene resin non-foamed film laminated on the surface of the polystyrene resin foam sheet of the present invention, those exemplified as the styrene resin used in the styrene resin foam sheet can be used. The same type of resin as the sheet or a different type of resin may be used. Among them, styrene resin film containing a rubber component made of copolymer resin with styrene monomer and diene monomer, especially film made from high impact polystyrene resin, has the adhesiveness to foamed sheet and the impact resistance of the film. From the viewpoint of

  As a method for laminating the polystyrene resin non-foamed film on the surface of the polystyrene resin foam sheet, a known dry laminating method, extrusion laminating method, co-extrusion method or the like can be used and is not particularly limited. However, the extrusion laminating method, that is, the method of extruding and laminating a thermoplastic resin in a molten state on the surface of the polystyrene resin foam sheet using a T die is preferable from the viewpoint of securing moldability. .

  Only one non-foamed extruded film layer of polystyrene-based resin may be laminated on the surface of the polystyrene-based resin foamed sheet, or a thermoplastic resin non-foamed film may be laminated on the outer surface through the extruded film layer. .

  In the lamination method by the extrusion lamination method, it is preferable to appropriately select the temperature of the film-like polystyrene resin extruded from the T-die according to the fluidity of the resin used. If the resin temperature of the film-like polystyrene-based resin is too low relative to the temperature required for melt-compression bonding with the polystyrene-based resin foam sheet, there is a tendency that the adhesive force with the polystyrene-based resin foam sheet cannot be secured. On the other hand, if it is too high, fine bubbles are generated on the surface of the polystyrene resin foam sheet on the side where the polystyrene resin film is bonded due to the heat of the film-like polystyrene resin, causing blistering during molding. In addition, other thermoplastic resin non-foamed films laminated on the outer surface tend to expand and contract to cause wrinkles. For this reason, it is necessary to select suitably the temperature of the film resin extruded from a T-die according to the fluidity of the resin used. For example, in the case of a high impact polystyrene resin, the temperature is preferably 210 to 240 ° C.

In the polystyrene-based resin laminated foam sheet of the present invention, when only one extruded film is laminated as the polystyrene-based resin non-foamed film, the basis weight of the non-foamed film is preferably 100 to 210 g / m ² , and 120 to 150 g / m ^2. m ² is more preferable. When the basis weight of the non-foamed film is less than 120 g / m ² , the curved surface printing suitability tends to be impaired. On the other hand, if it exceeds 210 g / m ² , the cost increases, but the container strength tends not to be improved as much as the increase in the basis weight of the non-foamed film.

  Moreover, in the polystyrene-based resin laminated foam sheet of the present invention, as a material for the thermoplastic resin non-foamed film laminated on the outer surface through the extruded film layer, in addition to the styrene resin, polyolefin resins such as polyethylene and polystyrene, Any material applicable to food packaging applications such as polyethylene terephthalate can be used.

  In the polystyrene-based resin laminated foam sheet of the present invention, the thermoplastic resin non-foamed film laminated on the outer surface through the extruded film layer is manufactured by a known method such as a T-die method or an inflation method. Since a certain amount of stretching is performed in the manufacturing process, an effect of improving the container strength can be expected by laminating the thermoplastic resin non-foamed film. In the polystyrene resin laminated foam sheet of the present invention, it is also possible to impart design properties to the molded container by laminating the thermoplastic resin non-foamed film film that has been previously printed by a known method such as a gravure method. It is.

In a polystyrene-based resin laminate foam sheet of the present invention, the basis weight of the thermoplastic resin non-foamed film laminated via the extruded film layer is preferably from 20 to 40 g / m ^2, and more preferably 25 to 35 g / m ^2. When the basis weight of the thermoplastic resin non-foamed film is less than 20 g / m ² , wrinkles are easily generated in the thermoplastic resin non-foamed film during lamination, and stable production tends to be difficult. On the other hand, if it exceeds 40 g / m ² , the cost of the film itself tends to increase.

  When the polystyrene-based resin laminated foam sheet of the present invention is subjected to a tensile test in the extrusion direction under an atmosphere of 110 ° C., the maximum elongation at which no cracks are generated on the non-laminated surface needs to be 200% or more. The tensile test of the polystyrene-based resin laminated foam sheet is measured using a tensile test apparatus (manufactured by A & D) having a thermostatic bath. Tensile test is performed under the conditions that the atmospheric temperature in the thermostatic chamber is 110 ° C., the sample size is 100 mm long × 10 mm wide, the distance between chucks is 50 mm, and the test speed is 500 mm / min. did. When the tensile elongation is lower than 200%, when molding a container having a large squeezing ratio such as a container, there is a crack (crack) on the inside of the container that is a non-laminated film surface of the polystyrene resin foam sheet. Will occur.

In order to give the above-mentioned mechanical characteristics to the polystyrene resin laminated foam sheet of the present invention, it is necessary to adjust the surface cooling conditions performed at the time of sheet extrusion. Surface cooling is necessary to give a predetermined density to the surface layer portion. However, if excessively rapid cooling is performed, the residual strain in the surface layer portion increases and the tensile fracture displacement of the surface layer portion decreases. In addition, fine bubbles of 100 μm or less may be generated by heating in the surface layer portion where the density is increased by cooling. When these fine cells are generated, the surface layer portion is cracked from the cells, so that the formability of the sheet is greatly impaired. From the above, it is necessary to relax the cooling of the sheet in order to satisfy the mechanical properties of the sheet while giving a predetermined density. That is, the wind temperature is increased, the wind speed is decreased, and the density is adjusted by the air volume. As an example, a discharge amount of 200 to 300 kg / Hr is 200 g / m ^2.
When producing the above foam sheet, it is preferable to set the air volume to 3.0 to 4.0 m ³ / min after setting the air temperature to 30 to 50 ° C. and the wind speed to 50 to 150 m / min.

  The polystyrene-based resin laminated foam sheet obtained by the present invention can be formed into a container by a heat forming method that is widely and generally performed. That is, after heating with an infrared heater or the like to secondarily foam the polystyrene-based resin laminated foam sheet, the container is shaped by fitting with a mold and then punching out the container from the sheet. Specific examples of thermoforming include plug molding, match molding, straight molding, drape molding, plug assist molding, plug assist reverse draw molding, air slip molding, snapback molding, reverse draw molding, and free molding. Examples of the method include drawing molding, plug-and-ridge molding, and ridge molding. Match-mold molding is preferable from the viewpoint of the container shape and surface properties.

  In general, the appropriate secondary foam thickness of the polystyrene-based resin laminated foam sheet is determined by the mold design used for thermoforming. Generally, when thermoforming to obtain a molded body having a bowl shape, the secondary thickness of the polystyrene resin laminated foam sheet is required to be about 4.5 to 6.0 mm, and in accordance with this, the polystyrene type is required. It is necessary to determine the primary thickness of the resin laminated foam sheet.

  In order to sufficiently bring out the strength of the polystyrene-based resin laminated foam sheet, a secondary thickness of about 80 to 90% of the maximum secondary thickness of the laminated foam sheet (secondary foam thickness immediately before heating and burning of the sheet). It is desirable to perform molding by heating so that the thickness of the polystyrene-based resin laminated foam sheet is preferably 1.5 to 2.2 mm, and more preferably 1.7 to 2.0 mm. If the thickness of the polystyrene-based resin laminated foam sheet is less than 1.5 mm, it is necessary to increase the heating at the time of molding, which tends to cause a decrease in container strength and poor appearance due to excessive heating. When the thickness exceeds 2.2 mm, sufficient heating cannot be performed at the time of molding, and due to insufficient heating, the expansion of the polystyrene-based resin laminated foam sheet is insufficient. There is a tendency to cause molding defects such as a phenomenon that is elongated.

  A container obtained by molding a polystyrene-based resin laminated foam sheet has specific top-and-bottom compression strength and lip strength, so that it can be safely used even in a container shape with a high drawing ratio.

  The vertical compression strength of the container obtained by molding the polystyrene-based resin laminated foam sheet in the present invention is preferably 80 N or more, more preferably 85 N or more, and particularly preferably 100 N or more. When the vertical compression strength of the container is less than 80 N, wrinkles tend to occur at the bottom. In addition, although the top-and-bottom compressive strength of a container is one measuring method of the buckling strength which a container has, it can be measured as follows. That is, using an autograph (manufactured by Shimadzu Corporation, DSS-1000), the container was compressed at a rate of 100 mm / min from the bottom with the container being sandwiched between two plates with the mouth of the container facing down. The yield strength at the time was measured and used as the vertical compression strength of the container.

  The lip strength of the container obtained by molding the polystyrene-based resin laminated foam sheet in the present invention is preferably 8N or more, and more preferably 10N or more. When the lip strength of the container is less than 8N, the container after hot water supply has insufficient rigidity, and the container may be deformed during eating, which may cause hot water leakage.

Hereinafter, specific examples will be described.
Evaluation methods for polystyrene resin foam sheets, polystyrene resin laminated foam sheets or containers obtained in Examples and Comparative Examples are shown below.

(Measurement of lip strength of container)
Using an autograph (manufactured by Shimadzu Corporation, DSS-1000), the yield strength when the mouth of the obtained container was compressed at a speed of 100 mm / min with the container sandwiched between two plates was measured. . The measurement was performed on 36 shots, and the average value was obtained.

(Measurement of vertical compression strength of container)
Using an autograph (manufactured by Shimadzu Corporation, DSS-1000), the container was compressed at a rate of 100 mm / min from the bottom with the container being sandwiched between two plates with the mouth of the container facing down The yield strength was measured. The measurement was performed on 36 shots, and the average value was obtained.

(Formability)
Cracking (cell rupture phenomenon), Naki (a phenomenon in which the foamed sheet is stretched locally) or blistering (polystyrene during molding and heating) during thermoforming into a container using the obtained polystyrene resin laminated foam sheet The phenomenon of peeling between the resin-based resin foam sheet and the film) did not occur, and it was visually evaluated whether molding with a good appearance was possible (note that measurement was performed for 36 shots). The evaluation criteria at that time are as follows.
○: Cracks, cracks and blisters are not observed.
X: Generation | occurrence | production of a crack, a crack, or a blister is recognized.

  In Table 1, it shows to the resin characteristic of the polystyrene resin used for the Example and the comparative example.

Example 1
Using a multi-branched polystyrene resin (HP-500M, manufactured by Dainippon Ink & Chemicals, Inc.) having a mass average molecular weight of 290,000 determined by the GPC-MALLS method, isobutane 85 wt% / normal butane 15 wt% butane gas is a blowing agent. Used to produce an extruded foam sheet with a width of 1050 mm under the production conditions shown in Table 2 (foaming agent press-in amount, sheet take-up speed, and cooling air flow at 30 ° C. on the non-foamed film surface of the sheet) did. In addition, the density of the surface layer part (within 150 μm) on the surface (non-laminar surface) side where the non-foamed film is not laminated is as shown in Table 2 in the obtained polystyrene-based resin foam sheet. The closed cell ratio was 90% or more (Example 1).

(Examples 2 to 4)
On the polystyrene resin foam sheet obtained in Example 1, a film using a high impact polystyrene resin (manufactured by PS Japan, HIPS475D) is laminated by an extrusion laminating method so as to have a basis weight shown in Table 2, The polystyrene resin laminated foam sheets of Examples 2 to 4 were obtained. In addition, as a result of measuring the surface temperature of the extruded film-like polystyrene resin at the time of extrusion lamination using the non-contact-type surface thermometer (PT-3LF made from APTUS), it was 225 +/- 3 degreeC in the width direction.

The polystyrene-based resin foam sheet and polystyrene-based resin laminated foam sheet obtained in Examples 1 to 4 were subjected to a container having a drawing ratio of 0.85 (mouth inner diameter 130 mmφ and bottom surface) using a continuous molding machine (FLC type 3 manufactured by Asano Laboratory). Using a mold having a diameter of 86 mmφ × depth of 110 mm, 36 pieces / shot), the polystyrene resin non-foamed film laminated surface of the polystyrene resin laminated foam sheet is molded by a match mold method so that it is outside the container, A molded body was obtained. The heating conditions were adjusted so that the secondary foam thickness during molding of the polystyrene-based resin laminated foam sheet by the match molding method was 4.5 to 5.0 mm. About the obtained container, the lip strength and the top and bottom compression strength were measured. The results obtained are summarized in Table 2.
From the results shown in Table 2, it can be seen that the container obtained from the polystyrene resin foam sheet and the polystyrene resin laminated foam sheet of the present invention has sufficient strength and a good product can be obtained.

(Comparative Examples 1-2)
Except for changing the production conditions as shown in Table 2, a polystyrene-based resin laminated foam sheet was prepared by the same method as in Examples 1 to 3, and the container was molded by the same method as in the example. It implemented and evaluated regarding the obtained laminated foam sheet and container. The results obtained are summarized in Table 2.
In Comparative Example 1, since the surface density of the foam sheet was too high, fine cells were generated in the surface layer due to secondary foaming during molding, and therefore internal cracks occurred. On the other hand, in Comparative Example 2, the container strength was insufficient.

(Comparative Examples 3-5)
Comparative Examples 3 and 4 use a polystyrene resin with a molecular weight of 310,000 (PS810 G8102) that does not contain multibranched polystyrene, and Comparative Example 5 uses a polystyrene resin with a molecular weight of 230,000 (PS Japan that does not contain multibranched polystyrene). A predetermined sample was collected using HH102). In Comparative Examples 4 and 5, a laminated foam sheet was prepared in the same manner as in Example 2, and the container was molded in the same manner as in the Example. The obtained container was evaluated. The results obtained are summarized in Table 2.

  In Comparative Examples 3 and 4, the take-up speed when the base resin was broken was slower than that of the Example, and internal cracks occurred. In Comparative Example 5, the melt tension was low and the strength was insufficient.

Claims (5)

On one side of the polystyrene-based resin foam sheet, the basis weight is laminated to a polystyrene resin non-foamed film is a 100~210g / m ^2, and aperture ratio is polystyrene used in the molding of the container is 0.8 or more A resin-laminated foam sheet ,
The polystyrene-based resin foamed sheet contains linear polystyrene having a mass average molecular weight of 25 to 450,000 and multi-branched polystyrene having a mass average molecular weight of 1,000,000 to 10,000,000. A polystyrene-based composition having a mass average molecular weight of 250,000 to 750,000, and a basis weight of 250 to 400 g / y. m ^2, the residual blowing agent weight 2.1 to 3.0 wt%, the density of the surface layer portion of the thickness of 150μm from the surface of the surface without laminating the non-foam film is 0.25~0.40g / cm ³ A polystyrene-based resin laminated foam sheet characterized by the following . The polystyrene resin laminated foam sheet according to claim 1, wherein the base resin of the polystyrene resin foam sheet has a melt tension at 180 ° C of 50 g or more and a take-up speed at break of 20 m / min or more. The polystyrene-based resin laminated foam sheet according to claim 1 or 2, wherein the thickness is 1.5 to 2.2 mm. The polystyrene-based resin laminated foam according to any one of claims 1 to 3, wherein the maximum elongation at which cracks do not occur on a non-laminated surface when a tensile test is performed in an extrusion direction under an atmosphere of 110 ° C is 200% or more. Sheet. The container whose drawing ratio obtained by shape | molding the polystyrene-type resin laminated foam sheet of any one of Claims 1-4 is 0.8 or more.