JP4653338B2 - Container molding method - Google Patents

Description

【００３６】
【表２】

【００３７】
【発明の効果】
本発明によれば、容器からのスチレンダイマー及びスチレントリマーの溶出量の少ない容器を安定的に得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a container using a polystyrene-based resin laminated foam sheet.
[0002]
[Prior art]
Polystyrene resin foam sheets are excellent in thermoforming, the appearance of the resulting molded product is beautiful, lightweight, and excellent in heat insulation, so they have been used in large quantities in recent years for thermoforming food containers. ing. Instant noodle cups are also mainly made of polystyrene resin foam sheets. However, styrene dimers and styrene trimers, which are said to be partly suspected of environmental hormones, are included in the polystyrene resin sheet, and have a drawback of being eluted in the instant noodle soup. High impact manufactured by bulk polymerization on the inside of the container, especially for the purpose of cracking (punching processability) during container molding, generation of fine powder due to contact between noodles and the inner wall of the container during product transportation, and prevention of piercing by piercing chopsticks In a so-called laminated foamed sheet container in which films made of polystyrene are laminated, the amount of styrene dimer and styrene trimer eluted is remarkably large. In order to solve these problems, there is a method (Japanese Patent Application No. 2000-340236) in which a laminated film made of a polystyrene resin composition having a low content of styrene dimer and styrene trimer is laminated on a foamed sheet. Even if the method is used, a difference occurs in the elution amount of styrene dimer and styrene trimer in the container due to the difference in molding conditions when obtaining a container by secondary molding, and a container in which the elution amount of styrene dimer and styrene trimer is stably low There was a problem in getting.
[0003]
[Problems to be solved by the invention]
An object of this invention is to obtain stably the container from which a styrene dimer and a styrene trimer do not substantially elute in the instant noodle soup from a polystyrene-type resin laminated foam sheet.
[0004]
[Means for Solving the Problems]
When the polystyrene-based resin laminated foam sheet is heated and then molded with a mold, the heated polystyrene-based resin laminated foam sheet is stretched, cooled and solidified with a mold, and molded into a container shape. In that case, the film layer arrange | positioned inside a container receives extending | stretching and stress, and a countless very small craze generate | occur | produces in a film layer by the extending | stretching and stress. As a result, it is considered that when hot water is put in the container or when the test solvent is filled, the craze promotes the elution of the styrene dimer and the styrene trimer, and the elution amount increases. In particular, in a laminated foam sheet made of a resin composition in which a styrene rubber is mixed with a polystyrene resin in a film layer, the craze of the film layer increases when the stretching / stress at the time of molding of the container is increased, and the amount of elution rapidly increases accordingly. Increase. From this, the amount of crazing of the film layer changes as the stretching and stress received by the film layer change due to the temperature of the film layer during molding, and the elution amount of styrene dimer and styrene trimer from the container obtained by molding changes I found out that
[0005]
The crazing of the laminated film is micro deformation generated in the polymer when stress is concentrated on the laminated film, and is generated in a direction perpendicular to the stress. Then, it propagates through the resin layer and grows and propagates throughout the matrix. Eventually, when the molecular bundle in the craze breaks, it turns into a crack and breaks. In other words, craze is a pioneer of brittle fracture. This craze consists of molecular bundles in which polymer molecules are oriented and voids between them [Reference: Shin Polymer Library, Fumio Ide, Impact Polymer Material (top) (bottom)]. It is considered that styrene dimer and styrene trimer contained in the polystyrene-based resin laminated foamed sheet are eluted from this void.
[0006]
As described above, the present inventors have intensively studied to solve the above problems, and as a result, a method for forming a polystyrene-based resin laminated foam sheet into a container so that the laminated film is inside the container, the laminated film immediately before forming By defining the surface temperature on the side, it was found that a container having a low elution amount of styrene dimer and styrene trimer in food soup was stably obtained, and the present invention was completed.
[0007]
That is, the present invention is (1) laminating a polystyrene resin laminated film having a content of 1000 ppm or less of a styrene dimer and a styrene trimer made of a mixture of a polystyrene resin and a styrene rubber on at least one surface of a polystyrene resin foam sheet. When the molded polystyrene resin laminated foam sheet is secondarily heated and molded into a container so that the laminated film is inside the container, the surface temperature T on the laminated film immediately before molding is 80 ° C. <T <130 ° C. Styrene-butadiene block copolymer having a melt flow rate of 5 to 30 g / 10 min at 200 ° C. and a load of 5 kgf and a butadiene component content of 30 to 90% by weight. Noll styrene dimer and styrene trimer, characterized in that it is Container forming process the amount of elution of the Ruheputan is less than 300 ppb (claim 1), (2) after heating the polystyrene-based resin laminate foam sheet in a heating furnace, when forming the forming die, the surface temperature The container molding method according to claim 1 (Claim 2), (3) wherein the resin composition of the polystyrene-based resin laminated film is polystyrene. The container molding method according to claim 1 or 2, wherein the total rubber component amount in the resin composition is 1 to 30% by weight, comprising a mixture of a styrene resin and a styrene rubber. (4) The container-forming method according to claim 1, 2 or 3, wherein the polystyrene resin of the laminated film is produced by suspension polymerization (Claim 4), ( 5 ) of the polystyrene-based resin laminated film Tree To fat 100 parts by weight of the composition, according to claim 1, 2, 3 or 4 container forming method, wherein said adding a stabilizer 0.01 to 0.5 parts (claim 5), (6 ) stabilizer a phenolic antioxidant and / or relates to claim 1, 2, 3, 4 or 5 container forming method according a stabilizer consisting of a phosphorus-based processing heat stabilizer (claim 6).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the polystyrene resin and styrene rubber constituting the film resin composition preferably laminated on the inside of the container are preferably those produced by suspension polymerization or solution polymerization, and others are not particularly limited. Absent.
[0009]
The polystyrene resin may be a copolymer as long as it contains 50% by weight or more of styrene as long as the effects of the present invention are not impaired. Copolymerization components include conjugated dienes such as 1,3-butadiene and isoprene, styrene derivatives such as α-methylstyrene, paramethylstyrene, t-butylstyrene and chlorostyrene, methyl acrylate, butyl acrylate, methyl methacrylate, ethyl Examples include acrylic acid and methacrylic acid esters such as methacrylate and cetyl methacrylate, and various monomers such as acrylonitrile, dimethyl fumarate, and ethyl fumarate. These monomers may be used alone or in combination. Can do. Moreover, you may use together bifunctional monomers, such as divinylbenzene and alkylene glycol dimethacrylate. As such, polystyrene, which is a styrene homopolymer, and high impact polystyrene, which is a copolymer with 1,3-butadiene, are preferable in terms of balance of heat resistance, mechanical properties, cost, and the like.
[0010]
The weight average molecular weight of such a polystyrene resin is preferably 200,000 or more and 500,000 or less, more preferably 250,000 or more and 450,000 or less. If the weight average molecular weight is less than 200,000, the resulting laminated resin becomes brittle, which is not preferable. On the other hand, if the weight average molecular weight exceeds 500,000, the workability at the time of lamination is lowered. As a method for polymerizing polystyrene-based resins, suspension polymerization is preferable from the viewpoint of low content of styrene dimer and styrene trimer and cost.
[0011]
Styrenic rubber used mixed with the polystyrene as a laminated film resin includes cracks during container molding (punching processability), generation of fine powder due to contact between noodles and the inner wall of the product during transportation, puncture by piercing chopsticks, etc. A styrene-butadiene block copolymer is preferable because it has a large effect of preventing the above, and is advantageous in terms of adhesiveness to the polystyrene resin, which is the base resin of the foamed sheet, and cost. For example, a styrene-butadiene block copolymer can be polymerized by solution polymerization (living anion polymerization method) using an alkali-based initiator .
[0012]
The styrene rubber preferably has a melt flow rate (hereinafter abbreviated as MFR) at 200 ° C. and a load of 5 kgf in the range of 5 to 30 g / 10 minutes , and the butadiene component content is preferably 30 to 90% by weight. Styrenic rubbers outside this range cannot be said to have sufficient dispersibility in polystyrene resins, cracking during container molding (punching processability), generation of fine powder due to contact between noodles and the container inner wall during product transportation, and piercing of chopsticks The prevention effect such as perforation due to may not be great.
[0013]
The laminated resin composition for a polystyrene resin foam sheet according to the present invention comprises a mixture of a polystyrene resin and a styrene rubber, and the total amount of rubber components in the resin composition (the content of components such as diene rubbers such as butadiene) ) Is preferably 1 to 30% by weight, more preferably 2 to 15% by weight. If the total rubber content is less than 1% by weight, cracks in the laminated film during film lamination and winding, cracks during molding of the container, generation of fine powder due to contact between the noodles and the container inner wall during product transportation, and holes due to piercing of chopsticks It is difficult to obtain an effect such as perforation, and when it exceeds 30% by weight, the laminating workability is lowered.
[0014]
Addition of a stabilizer to the polystyrene resin is effective in reducing the amount of styrene dimer and trimer eluted into the food soup in the molded container. Stabilizers used in the present invention include phenolic antioxidants and phosphorus processing heat stabilizers. Examples of phenolic antioxidants include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis (3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate (available as Ciba Special Chemicals, Inc. Irganox 1010), 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, In addition to commercially available common products such as 2 (1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl) -4,6-di-t-pentylphenyl acrylate, vitamin C , Vitamin E, catechin, etc., which are particularly suitable for food use are also used. Commercially available products such as 4-di-t-butylphenyl) phosphite (available as Ciba Special Chemicals, Inc. Irgafos 168) can be used The stabilizer should be blended into the resin before extrusion. Although generally used, it may be impregnated during suspension polymerization, although phenolic antioxidants and phosphorus processing heat stabilizers can be used alone, the laminated film resin composition is used as a polystyrene resin foam sheet. Two types of combination are preferred from the viewpoint of the processability when laminating on the surface and the amount of elution of styrene dimer and styrene trimer in the food soup is small. 0.01 to 0.5 parts by weight, preferably 0.03 to 0.4 parts by weight, more preferably 100 parts by weight of the mixture of If the added amount is less than 0.01 parts by weight, the decrease in the amount of styrene dimer and styrene trimer dissolved in the food soup is small. If added in a large amount, no further effect on the processability at the time of lamination and the elution amount of styrene dimer and styrene trimer in the food soup is seen, and it is not preferable from the viewpoint of cost.
[0015]
The laminated resin composition thus obtained can be laminated in a film state by various methods on the polystyrene-based resin foam sheet described below, but it is normal from a molded container obtained from the laminate resin foam sheet. The total content of styrene dimer and styrene trimer in the laminated film is preferably 1000 ppm or less, more preferably 600 ppm or less, from the viewpoint that the amount of styrene dimer and styrene trimer eluted into heptane is small.
[0016]
The polystyrene-based resin foamed sheet on which the laminated film of the present invention is laminated is one that uses a polystyrene-based resin as a base resin and is manufactured by ordinary extrusion foaming. The polystyrene-based resin used here is not particularly limited and is not particularly limited as long as it is produced by a usual polymerization method such as bulk polymerization, suspension polymerization, solution polymerization, etc. Among these, suspension polymerization, solution polymerization Is preferable in that the content of styrene dimer and styrene trimer is low.
[0017]
Examples of foaming agents used in the production of the polystyrene resin foam sheet include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane, and hexane, cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane, and the like. And hydrocarbons such as methyl chloride, methylene chloride, dichlorofluoromethane, chlorofluoromethane, chlorodifluoromethane, trichlorofluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, and the like. The amount of the foaming agent is preferably 2 to 5 parts by weight with respect to 100 parts by weight of the polystyrene resin. These may be used singly or in combination of two or more, and may be added and impregnated at the time of producing a polystyrene resin, or may be added at the time of forming an extruded foam sheet.
[0018]
The nucleating agent used in the production of the polystyrene resin foam sheet is not particularly limited, and any nucleating agent that can be usually used can be used. Specific examples include inorganic compounds such as talc, calcium carbonate, barium sulfate, silica, titanium oxide, clay, aluminum oxide, bentonite, diatomaceous earth, and an average particle size of 0.1 to 20 microns, preferably 1 to Examples include organic acids such as citric acid, tartaric acid, and oxalic acid; and combinations of acids such as boric acid and bicarbonates or carbonates such as sodium, potassium, and ammonium. These nucleating agents are usually used alone, but may be used in combination of two or more. Of these, inorganic compounds such as talc, calcium carbonate, silica, and alumina are preferable because they are inexpensive and easy to handle. The polystyrene resin foam sheet may contain a filler, a flame retardant, a colorant, an ultraviolet absorber, an antioxidant, and the like.
[0019]
The method of laminating the laminated film resin composition of the present invention so as to be inside the container of the polystyrene resin foam sheet is not particularly limited. For example, a method of adhering to a foam sheet supplied with a resin composition previously formed into a film shape by a hot roll or the like so as to be inside the container, a foam sheet supplied with a resin composition previously formed into a film shape , A method of adhering via an adhesive so as to be inside the container, and laminating the laminated resin composition supplied from the extruder so as to be inside the container on the supplied foamed sheet in a plastic state For example, a method of fixing the laminated resin with a cooling roll or the like can be used. Among these, the method of laminating and fixing the laminated resin composition supplied from the extruder in a layered manner is preferable from the viewpoint of cost because the number of manufacturing steps is small.
[0020]
Using the above-mentioned polystyrene-based resin laminated foam sheet, various containers can be produced by vacuum / compression molding or the like in the same manner as ordinary foam sheet molding. In particular, molding using a male / female fitting mold is preferable in terms of mold determination.
[0021]
In the method for forming a container by secondarily foaming the polystyrene-based resin laminated foam sheet according to the present invention, the surface temperature T on the side of the laminated film immediately before molding when the container is molded so that the laminated film is inside the container is 80 ° C. Heating is performed so that <T <130 ° C.
[0022]
Adjustment of the surface temperature on the side of the laminated film immediately before molding is performed by methods such as the heater temperature of the heating furnace, the heating time, the distance between the heater and the sheet surface, the cooling around the molding position by suppressing the flow of air, etc. Yes.
[0023]
Moreover, the measurement of the surface temperature just before shaping | molding can be performed using a non-contact thermometer (for example, THERMO-HUNTER PT-3LF by OPTEX). However, in a non-contact type temperature sensor, the measurement temperature may differ depending on the distance and angle from the object to be measured. Therefore, when measuring the surface temperature on the laminated film side of the sheet, it is preferable to measure from the same distance and angle.
[0024]
When the surface temperature T on the side of the laminated film immediately before molding is 80 ° C. or lower, the amount of styrene dimer and styrene trimer eluted from the molding container tends to be large. In addition, there may be a case where a good molded body cannot be obtained, for example, the laminated film is not sufficiently stretched during molding and the sheet is torn.
[0025]
On the other hand, when the surface temperature T on the laminated film side is 130 ° C. or higher, although the elution amount of styrene dimer and styrene trimer from the molding container tends to be low, a molded product that can withstand actual use can be obtained because the laminated film surface becomes rough. It may not be possible.
[0026]
From the above points, in the method of secondarily foaming the polystyrene-based resin laminated foamed sheet, the surface temperature T immediately before molding the laminated film when the container is molded so that the laminated film is inside the container is 80. ° C <T <130 ° C is preferable, and 90 ° C <T <120 ° C is more preferable.
[0027]
In the present invention, when the polystyrene-based resin laminated foam sheet is heated in a heating furnace and then molded in a molding die, the surface temperature is molded in a mold whose temperature is adjusted to 60 ° C. or more and 120 ° C. or less. It is characterized by. When the mold temperature is less than 60 ° C., the foamed laminated sheet is cooled and stretched by the mold at the same time. As a result, the stress received by the laminated foamed sheet may increase and the amount of elution may increase. When the mold temperature is higher than 120 ° C., the container may be greatly deformed when the mold is allowed to cool after being released, and the amount of elution may increase.
[0028]
The elution amount of styrene dimer and styrene trimer from the laminated foamed sheet molding container thus obtained is extremely small, and the elution amount into normal heptane is preferably 300 ppb or less, more preferably 200 ppb or less.
[0029]
The laminated sheet of the present invention can be suitably used as a bowl or cup for foods such as ramen, udon, and fried noodles.
[0030]
【Example】
EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.
[Measurement of surface temperature of laminated film just before molding]
Using a fixed non-contact temperature sensor, the surface temperature of the laminated film immediately before being molded was measured when the laminated foam sheet was heated in a heating furnace and brought to a molding position and stopped.
Non-contact temperature sensor: THERMO-HUNTER PT-3LF manufactured by Optex
[Measurement of styrene dimer and styrene trimer]
The laminated resin composition film was dissolved in chloroform and measured by GC.
GC: Hewlett-Packard's GC-5890 Series II
Column: J & W Scientific DB-5MS 0.25 mm i.d. × 30 m Film thickness 0.25 micron Column temperature: 40 ° C. (0.5 min) → 10 ° C./min→100° C. → 20 ° C./min→280° C. (15 minutes)
[Measurement of elution amount of styrene dimer and styrene trimer]
Measurements were performed in accordance with the provisions of the Food Sanitation Law, the standards for equipment and container packaging, and the preparation of test solutions in dissolution tests.
[0031]
580 cc of normal heptane is placed in a polystyrene-based resin-laminated foam sheet container (contained in a truncated cone shape with an inner volume of 850 cm ^{3 having} a diameter of 155 mm, a bottom diameter of 140 mm, and a depth of 50 mm) and left at 25 ° C. for 60 minutes. The amount of styrene dimer and styrene trimer was measured by GC / MS-SIM.
[0032]
GC / MS: HP6890 series II / HP5973 made by Hewlett-Packard.
[0033]
Column: DB-5MS 0.25 mm i.d. × 30 m manufactured by J & W Scientific Co., Ltd. Column thickness: 40 ° C. (0.5 min) → 10 ° C./min→100° C. → 20 ° C./min→ 280 ° C (15 minutes)
[Punching workability]
When a container molded from a laminated resin foam sheet was punched out with a Thomson blade, the case where cracks occurred in the punched portion was indicated as x (failed), and the case where it did not was marked as o (passed).
[Surface property of molded container]
The state of the surface roughness of the container molded from the laminated resin foam sheet was visually observed, and the case where the surface roughness was recognized and could not withstand actual use was evaluated as x (failed), and the case where it was not satisfied was evaluated as ○ (passed).
(Production Example) In a reactor equipped with a stirrer, 700 kg of pure water, 1.05 kg of tribasic calcium phosphate, 46 g of sodium dodecylbenzenesulfonate and 3.3 kg of sodium chloride were stirred to form an aqueous suspension, and then polymerized to 700 kg of styrene. As an initiator, 1.33 kg of benzoyl peroxide and 0.7 kg of 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane are dissolved, added to the reactor, and heated to 98 ° C. To polymerize over 4 hours. Next, the temperature was raised to 120 ° C. and held for 2 hours, followed by cooling. The contents were taken out, dehydrated and dried to obtain a polystyrene resin.
(Example 1) A T-die was formed on the surface of a foamed sheet having a thickness of 2 mm, an expansion ratio of 8 times, and 10 cells in the thickness direction, which was produced from the suspension-polymerized polystyrene resin obtained in the production example by a usual method. The suspension-polymerized polystyrene resin and styrene-butadiene block copolymer obtained in the production example were mixed and mixed together as shown in Table 1 (types of each compounding agent are shown in Table 2), and extruded to 120 microns. The films were laminated. The amount of styrene dimer and styrene trimer in the laminated film portion of the obtained sheet was measured by gas chromatography.
[0034]
Next, the surface of the laminated film immediately before molding the sheet is set to 100 ° C. using a small single molding machine for molding the polystyrene foam sheet so that the laminated film is inside the container. A container having a diameter of 155 mm, a bottom diameter of 140 mm, and a depth of 50 mm was formed with a male and female fitting mold heated and adjusted to a surface temperature of 80 ° C., and the obtained container was punched out with a Thomson blade and taken out. The amount of elution of styrene dimer and styrene trimer into normal heptane from the obtained polystyrene-based resin laminated foam sheet container was measured by gas chromatography. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Example 2) A laminated film, a laminated foamed sheet, and a container were produced in the same manner as in Example 1 except that a mixture of a phosphorus processing stabilizer and a phenolic antioxidant was added as a stabilizer. Table 1 shows the results of blending, processability during lamination, container punchability, container surface properties, and elution amount (Table 2 shows the types of each compounding agent).
(Examples 3 to 5) A laminated film, a laminated foamed sheet and a container were produced in the same manner as in Example 2 except that heating was performed so that the surface temperature of the laminated film immediately before forming the laminated foamed sheet was 90 ° C. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Examples 6 to 8) A laminated film, a laminated foamed sheet and a container were produced in the same manner as in Example 2 except that heating was performed so that the surface temperature of the laminated film immediately before forming the laminated foamed sheet was 110 ° C. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Comparative Example 1) A laminated film and a laminated foamed sheet container were prepared in the same manner as in Example 1 except that the laminated film was produced from a commercially available bulk polymerized high impact polystyrene (Asahi Kasei; Stylon HIPS, rubber content 7% by weight). Produced. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Comparative Example 2) A laminated film, a laminated foamed sheet and a container were produced in the same manner as in Example 1 except that the laminated film was produced only from the suspension-polymerized polystyrene obtained in the production example. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Comparative Example 3) A laminated film, a laminated foamed sheet, and a container were produced in the same manner as in Example 1 except that heating was performed so that the surface temperature of the laminated film immediately before forming the laminated foamed sheet was 70 ° C. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Comparative Example 4) A laminated film, a laminated foamed sheet, and a container were produced in the same manner as in Example 1 except that heating was performed so that the surface temperature of the laminated film immediately before forming the laminated foamed sheet was 130 ° C. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
(Comparative Example 5) A laminated film, a laminated foamed sheet, and a container were produced in the same manner as in Example 1 except that the mold surface temperature was adjusted to 40 ° C. The results of blending, container punchability, container surface properties, and elution amount are shown in Table 1 (types of each compounding agent are Table 2).
[0035]
[Table 1]

[0036]
[Table 2]

[0037]
【The invention's effect】
According to the present invention, a container with a small amount of elution of styrene dimer and styrene trimer from the container can be stably obtained.

Claims (6)

A polystyrene resin laminated foam sheet in which a polystyrene resin laminated film having a content of 1000 ppm or less of a styrene dimer made of a mixture of a polystyrene resin and a styrene rubber is laminated on at least one surface of the polystyrene resin foam sheet. When the container is formed such that the secondary foam is heated and the laminated film is inside the container, the surface temperature T on the side of the laminated film immediately before molding is heated to 80 ° C. <T <130 ° C. The rubber is a styrene-butadiene block copolymer having a melt flow rate of 5 to 30 g / 10 min at 200 ° C. and a load of 5 kgf, and a butadiene component content of 30 to 90% by weight. Elution amount of dimer and styrene trimer into normal heptane Method of molding the container is 00ppb or less.   When the polystyrene-based resin laminated foam sheet is heated in a heating furnace and then molded in a molding die, the surface temperature is molded in a mold whose temperature is adjusted to 60 ° C or higher and 120 ° C or lower. Item 2. A method for forming a container according to Item 1.   The resin composition of the polystyrene-based resin laminated film comprises a mixture of a polystyrene-based resin and a styrene-based rubber, and the total rubber component amount in the resin composition is 1 to 30% by weight. 2. The method for forming a container according to 2.   The method for forming a container according to claim 1, 2 or 3, wherein the polystyrene-based resin of the laminated film is produced by suspension polymerization. The method for forming a container according to claim 1, 2, 3, or 4 , wherein 0.01 to 0.5 part of a stabilizer is added to 100 parts by weight of the resin composition of the polystyrene-based resin laminated film. The method for forming a container according to claim 1, 2, 3, 4, or 5 , wherein the stabilizer is a stabilizer comprising a phenol-based antioxidant and / or a phosphorus-based processing heat stabilizer.