JP2012214810A - Polystyrene-based resin foamed sheet, container, and method for producing polystyrene-based resin foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polystyrene-based resin foamed sheet having high heat resistance and controlling odor.SOLUTION: The method for producing the polystyrene-based resin foamed sheet, comprising extrusion-foaming a resin composition comprising the polystyrene-based resin and a polyphenylene ether-based resin and containing the polyphenylene ether-based resin in an amount of 10-50 pts.mass per 100 pts.mass of the total amount of the polystyrene-based resin and the polyphenylene ether-based resin to produce the polystyrene-based resin foamed sheet, is characterized in that the value obtained by subtracting the lowest temperature from the highest temperature in a temperature range from the center of a breaker plate to the outer peripheral portion is controlled to ≤20°C in the temperature of the resin, when the melted product prepared by melting the resin composition passes through the breaker plate.

Description

  The present invention relates to a polystyrene resin foam sheet, a container obtained by molding the polystyrene resin foam sheet, and a method for producing a polystyrene resin foam sheet.

  Conventionally, polystyrene-based resin foam sheets have been widely used as materials for food containers (food trays, cups, etc.). However, a food container formed of a polystyrene resin foam sheet made of a polystyrene resin is not sufficiently high in heat resistance, and thus has a problem of being deformed when heated by a microwave oven or the like. On the other hand, a polystyrene resin foam sheet (also referred to as a “foamed sheet”) formed by foaming a polyphenylene ether resin together with a polystyrene resin with a foaming agent has been proposed in order to improve heat resistance.

  However, such a polystyrene-based resin foam sheet has a problem that a peculiar odor is generated when the polyphenylene ether-based resin is contained, so that it is difficult to use as it is as a forming material for food containers and the like.

  From such a viewpoint, a polystyrene resin foam sheet containing a predetermined amount of a polystyrene resin, a polyphenylene ether resin, and a hydrophobic zeolite as an odorant has been proposed (Patent Document 1).

JP 2008-94919 A

However, other than hydrophobic zeolite, no deodorant capable of suppressing the peculiar odor derived from polyphenylene ether resin has been reported, and the effectiveness of hydrophobic zeolite has not been sufficiently confirmed. Absent.
Therefore, it is difficult to obtain a polystyrene resin foam sheet having high heat resistance and suppressed odor.

  In view of the above problems and demands, the present invention provides a polystyrene-based resin foam sheet having high heat resistance while suppressing odor, and thus providing a container with suppressed odor. To do.

  In order to solve the above-mentioned problems, the present invention contains a polystyrene resin and a polyphenylene ether resin, and the polyphenylene ether resin is 10 parts per 100 parts by mass of the total amount of the polystyrene resin and the polyphenylene ether resin. A method for producing a polystyrene-based resin foamed sheet by forming a polystyrene-based resin foamed sheet by extruding and foaming a resin composition containing ~ 50 parts by mass, wherein the melted resin composition passes through a breaker plate A method for producing a polystyrene-based resin foam sheet, characterized in that a value obtained by subtracting the minimum temperature from the maximum temperature from the center to the outer periphery of the breaker plate is 20 ° C. or less. I will provide a.

  In order to solve the above problems, the present invention includes a polystyrene resin and a polyphenylene ether resin, and the polyphenylene ether resin with respect to 100 parts by mass of the total amount of the polystyrene resin and the polyphenylene ether resin. Is a polystyrene-based resin foam sheet obtained by extruding and foaming a resin composition containing 10 to 50 parts by mass of the resin composition. The resin temperature when the melted resin composition passes through the breaker plate is as follows. Provided is a polystyrene-based resin foam sheet produced so that a value obtained by subtracting the minimum temperature from the maximum temperature from the center to the outer periphery is 20 ° C. or less.

  Furthermore, the present invention provides a container obtained by molding the polystyrene-based resin foam sheet as a means for solving the above problems.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the polystyrene-type resin foam sheet and container by which the odor was suppressed, having high heat resistance.

The figure which shows the TG / DTA chart of a hydrotalcite. The figure which shows the powder X-ray-diffraction pattern of a hydrotalcite. The figure which shows the powder X-ray-diffraction pattern of a hydrotalcite baked material. The figure which shows the front-end | tip part of the screw of the 2nd extruder used in the Example. ((A) Front view, (b) Side view).

  Hereinafter, an embodiment of the present invention will be described.

  The polystyrene-based resin foam sheet of the present embodiment is formed by extrusion foaming a resin composition containing a polystyrene-based resin, a polyphenylene ether-based resin, and a hydrotalcite fired product (also referred to as “fired product”). ing.

If the polystyrene-type resin foam sheet of this embodiment is a case where it is used for formation of the container for food packaging, for example, it is preferably 1.5-3.0 mm in thickness, and preferably 0.055-0.00. The density is 18 g / cm ³ .

Furthermore, the open cell ratio of the polystyrene resin foam sheet of the present embodiment is preferably 18% or less, more preferably 3 to 18%.
The polystyrene-based resin foam sheet of the present embodiment has the above-described characteristics related to the open cell ratio, so that the odor component inside can be gradually diffused to the extent that the user does not feel it. It has the advantage of being particularly excellent.

The open cell ratio can be calculated from the following formula from the volume V of the foam sheet specimen measured using an air-comparing hydrometer (manufactured by Tokyo Science Co., Ltd.).
Open cell ratio (%) = (V ₀ −V) / V ₀ × 100
In the above formula, V is the volume (cm ³ ) of the specimen measured by the above method, and V ₀ is the apparent volume (cm ³ ) of the specimen calculated from the external dimensions of the specimen used for the measurement. It is.

Moreover, it is preferable that the polystyrene-type resin foam sheet of this embodiment sets an average cell diameter to 80-450 micrometers.
In addition, the average cell diameter of a polystyrene-type resin foam sheet can be measured based on the method described in ASTM D2842-69. That is, the test foam sheet sample was cut along a plane orthogonal to the extrusion direction, and cut along a plane extending in the extrusion direction and the thickness direction, and both outer sides 1/10 in the thickness direction of each cut surface. The portion excluding this portion is photographed with a scanning electron microscope (“S-3000N” manufactured by Hitachi, Ltd.) 17 to 20 times, and if necessary, enlarged up to 200 times. Each of the four captured images is printed on A4 paper, and along each direction of MD direction (extrusion direction), TD direction (direction orthogonal to the extrusion direction and along the sheet surface), and VD direction (thickness direction). Draw 6 parallel lines (length 60mm) for each A4 paper. From the number of bubbles overlapping such a line segment, the average chord length (t) of the bubbles in each direction is calculated by the following equation (1). However, the line segment is drawn as much as possible so that the bubbles do not touch only at the contact points, and if they are touched, they are included in the number of bubbles.
Average chord length (t) = 60 / (number of bubbles × photo magnification) (1)
And the bubble diameter in each direction is computed by following formula (2).
D = t / 0.616 (2)
Further, based on each bubble diameter (D _MD , D _TD , D _VD ) measured as described above, the average bubble diameter is calculated by the following formula (3).
Average bubble diameter (mm) = (D _MD + D _TD + D _VD ) / 3 (3)
In addition, when the thickness of the test foam sheet sample is thin and a line segment of 60 mm length cannot be drawn in the VD direction, the number of bubbles overlapping the 30 mm or 20 mm length line segment is counted, and the length of 60 mm Convert to the number of bubbles in the line.

In the polystyrene resin foam sheet of this embodiment, by setting the average cell diameter to 80 μm or more, the bubble film becomes thick, and the open cell rate tends to be lowered (the open cell rate tends to be 18% or less). And the effect that intensity | strength becomes high is exhibited by making an average bubble diameter 80 micrometers or more.
Moreover, when the average cell diameter is 450 μm or less, the polystyrene resin foam sheet of the present embodiment is not too large, the appearance is good, and excellent in smoothness and glossiness. There is an effect that it becomes difficult to break.

Moreover, it is preferable that content of normal butyric acid is less than 0.50 ppm, and, as for the polystyrene-type resin foam sheet of this embodiment, it is more preferable that it is less than 0.30 ppm.
When the content of normal butyric acid is less than 0.50 ppm, the polystyrene resin foam sheet of this embodiment has an advantage that odor is further suppressed.
In addition, content of this normal butyric acid can be confirmed by the method as described in an Example.

In addition, the polystyrene resin foam sheet of the present embodiment is obtained by placing the foam sheet (30 mm × 30 mm, weight 40 g) in a tetra bag (10 L), filling the tetra bag with 10 L of air through which activated carbon has been passed, and then at room temperature for 24 hours. The concentration of normal butyric acid contained in the gas in the tetrabag when left standing is preferably 1.5 ppb or less, and more preferably less than 0.30 ppm.
When the concentration is 1.5 ppb or less, the polystyrene resin foam sheet of the present embodiment has an advantage that odor is further suppressed.
This concentration can be confirmed by the method described in the examples.

  The polystyrene resin used for forming such a polystyrene resin foam sheet is preferably a polystyrene resin such as a styrene homopolymer from the viewpoint of compatibility with the polyphenylene ether resin.

  On the other hand, the polyphenylene ether-based resin is effective for imparting heat resistance, and a resin represented by the following general formula can be usually employed.

Here, R ¹ and R ² represent an alkyl group having 1 to 4 carbon atoms or a halogen atom, and n is a positive integer representing the degree of polymerization.
For example, poly (2,6-dimethylphenylene-1,4-ether), poly (2,6-diethylphenylene-1,4-ether), poly (2,6-dichlorophenylene-1,4-ether) Ether) or the like may be used in this embodiment.
The degree of polymerization n is usually in the range of 10 to 5000.

This polyphenylene ether resin is contained in a proportion of 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass in total with the polystyrene resin.
The polyphenylene ether-based resin is effective for improving heat resistance, and it is contained in a ratio of 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass in total with the polystyrene resin. If it is less than the range, the addition effect of the polyphenylene ether resin may not be sufficiently exerted. Conversely, even if the polyphenylene ether resin is included beyond the above range, the addition effect of the polyphenylene ether resin is further exhibited. This is because there is a risk of not being done.
Moreover, since it is generally more expensive than a polystyrene resin, if the polyphenylene ether resin is contained beyond the above range, there is a possibility of causing a problem in terms of material cost.

  Usually, the Vicat softening temperature of polystyrene resin (JIS K7206-1991, Method B, 50 ° C./h) is about 102 ° C., but by including the polyphenylene ether resin as described above, the Vicat softening temperature is reduced. It can be improved to a range of 110 to 155 ° C., and by using the polyphenylene ether resin and the polystyrene resin, the obtained polystyrene resin foam sheet, a product obtained by secondary processing of the polystyrene resin foam sheet, etc. The heat resistance can be improved.

In general, when heat resistance is required for a product made of polystyrene resin, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-maleimide having a higher Vicat softening temperature than styrene homopolymer Copolymers, copolymers such as polyparamethylstyrene resin, and the like are employed as the forming material.
On the other hand, the method of blending the polyphenylene ether-based resin as described above is excellent not only in imparting heat resistance to the product but also in imparting excellent toughness.

  Therefore, by using a polyphenylene ether resin and a polystyrene resin to form a container such as a foam tray, it is possible to form a foam tray that does not crack even if sudden deformation is applied.

In addition, the polystyrene resin foam sheet of this embodiment is formed by extruding and foaming a melt obtained by melting and mixing the polyphenylene ether resin and the polystyrene resin in an extruder. Moreover, as for the polystyrene-type resin foam sheet of this embodiment, the highest ultimate temperature of the said melt in the said extruder is preferably 220-340 degreeC.
In the polystyrene resin foam sheet of the present embodiment, when the maximum temperature of the melt in the extruder is 340 ° C. or less, the content of odor components, particularly the content of normal butyric acid is reduced, and the odor is reduced. It has the advantage of being suppressed. In addition, when the maximum temperature of the melt in the extruder is 220 ° C. or higher, the polyphenylene ether resin and the polystyrene resin are sufficiently melt-mixed, and the foamability of the resulting resin composition is It has the advantage of increasing.

  In the polystyrene-based resin foam sheet of the present embodiment, a resin composition containing the polystyrene-based resin and the polyphenylene ether-based resin in a predetermined ratio is melt-mixed in an extruder, and the melt-mixed material in the extruder is melt-mixed. It is formed by extrusion foaming from the extruder.

The resin composition contains a hydrotalcite fired product as a deodorant in addition to the polystyrene resin and the polyphenylene ether resin.
Hydrotalcite is a kind of naturally occurring clay mineral and is usually a double hydroxide represented by the following general formula.

M ¹ _8-x M ² _x (OH) ₁₆ CO ₂ · nH ₂ O

Here, the ^{M 1, Mg 2+, Fe 2+} , Zn 2+, Ca 2+, Li 2+, Ni 2+, Co 2+, is any of Cu ^2+, as M ² is Any one of Al ³⁺ , Fe ³⁺ and Mn ³⁺ , x is preferably 2 to 5, and n is an integer of 0 or more.

  In recent years, synthetic products are also commercially available. For example, an aqueous suspension of basic magnesium carbonate particles and an aqueous suspension of aluminum hydroxide have a ratio of magnesium atom to aluminum atom (Mg / Al). The mixture is mixed so as to have a predetermined ratio (for example, 2.6 to 3.2), and caustic alkali such as sodium hydroxide, potassium hydroxide, ammonium hydroxide is further added to obtain a reaction solution having a pH of 8.5 to 11.5. The step of obtaining, the step of heating and aging the reaction solution obtained by the step at, for example, 50 to 100 ° C. for 0.5 to 20 hours, and hydrotalcite particles from the solution after heating and aging in the step Products manufactured through solid-liquid separation, washing, dehydration and drying processes are commercially available, and the calcined product obtained by firing such hydrotalcite is also natural hydrotalcite. It can be used as well as form calcined product.

  As can be seen from the TG / DTA chart shown in FIG. 1, hydrotalcite releases adsorbed water or crystal water when heated, and adsorbed water is released by firing at 200 ° C. or higher. When calcined at 400 ° C. or higher, for example, 550 ° C., carbonate radicals and hydroxyl groups are eliminated, and analyzed by powder X-ray diffractometer (manufactured by Rigaku Corporation, RAD system) at 2θ = 10 to 70 degrees, It is a substance which shows a chart result as shown in FIG.

The hydrotalcite fired product is a compound obtained by firing at a temperature as described above, and is a compound that retains anion exchange ability even after firing.
As the hydrotalcite fired product, for example, a material represented by the following general formula is preferably employed.

Mg _0.7 Al _0.3 O _1.15

The calcined hydrotalcite exhibits three peaks characteristic of a powder X-ray diffraction pattern analyzed at 2θ = 10 to 70 degrees with a powder X-ray diffractometer (manufactured by Rigaku Corporation, RAD system). FIG. 3 is a substance showing a chart result as shown in FIG.

The content of the hydrotalcite fired product in the resin composition is advantageous in that the larger the polystyrene resin foam sheet according to the present invention, the odor can be further suppressed. When there is too much content, there exists a possibility of reducing the foamability of this resin composition.
Therefore, preferable content of the calcined hydrotalcite with respect to 100 parts by mass of the total amount of the polystyrene resin and the polyphenylene ether resin in that a good foaming state can be imparted to the polystyrene resin foam sheet while suppressing odor. Is 0.05 to 20 parts by mass, more preferable content is 0.1 to 10 parts by mass, and still more preferable content is 0.12 to 2.9 parts by mass.
The smaller the particle size of the fired hydrotalcite, the easier it is to disperse in the resin composition and the odor control effect becomes higher, but those with an excessively small particle size are commercially available. In addition to being difficult to obtain, it is likely to float up and be difficult to handle.
Accordingly, the particle diameter (volume average diameter) of the fired product employed in the present embodiment is preferably 1 to 100 μm in that the polystyrene-based resin foam sheet with suppressed odor can be easily manufactured. More preferably, the thickness is 20 μm.
Furthermore, the specific surface area of the fired hydrotalcite is preferably 130 m ² / g or more. When the specific surface area is 130 m ² / g or more, the resin composition is easily contacted and the odor suppressing effect is enhanced. The specific surface area means that measured by the BET method.
Further, the resin composition may contain a deodorant other than the silica-based or zeolite-based fired hydrotalcite, and it is preferable to contain silica as a deodorant.

  Furthermore, you may make the said resin composition contain the component for foaming, such as a foaming agent and a bubble regulator, and the various additives currently utilized as a raw material of a general polystyrene-type resin foam sheet.

As said foaming agent, a volatile foaming agent, an inorganic gas type foaming agent, a decomposable foaming agent, etc. are used individually or in combination of 2 or more, respectively. Examples of the volatile blowing agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, pentane and hexane, and cyclic aliphatic hydrocarbons such as cyclobutane and cyclopentane. As the inorganic gas-based foaming agent, an inert gas such as carbon dioxide, nitrogen or air is used. Examples of the decomposable foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate, and the like. However, it is desirable to use a volatile foaming agent as the main foaming agent from the viewpoint of improving secondary foamability during heating prior to thermoforming of the polystyrene resin foam sheet. The amount of foaming agent added depends on the type of foaming agent, the base resin, the target foaming ratio, etc., so select the desired foaming ratio according to the type of foaming agent and base resin. do it.
Examples of the air conditioner used in combination with the foaming agent include inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, and reaction mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate. It is preferable that the addition amount of a bubble regulator is 0.5-5 mass parts with respect to a total of 100 mass parts of the said polystyrene-type resin and the said polyphenylene ether resin.
Examples of the additive include a stabilizer, an ultraviolet absorber, an antioxidant, and a colorant.

  In order to form the polystyrene resin foam sheet according to the present embodiment, equipment generally used for extrusion foaming can be used. In the method for producing a polystyrene resin foam sheet of the present embodiment, A resin composition such as the above is melt-kneaded using a tandem extruder equipped with a first extruder and a second extruder to produce a melt, and the melt is extruded and foamed. Can be formed.

The specific procedure in the case of using a volatile foaming agent will be described below. First, a polystyrene resin and a fired product of hydrotalcite are melt-kneaded with an extruder, and the polystyrene resin foam sheet according to this embodiment is used. A master batch is produced in which the concentration of the fired hydrotalcite is higher than that of the resin composition constituting the composition. At this time, a part of the polyphenylene ether resin to be included in the polystyrene resin composition is previously contained in the masterbatch in that the component causing the odor can be removed from the polyphenylene ether resin. May be.
Then, using the master batch, all the materials except the foaming agent in the blend are supplied to the first extruder, and the highest ultimate temperature of the melt in the first extruder is preferably 220 to 340. It heats so that it may become 0 degreeC, These are melt-kneaded and a melt is produced.
The method for producing a polystyrene resin foam sheet according to this embodiment includes a fired product of polystyrene resin and hydrotalcite, and is more hydrotalcite than the resin composition constituting the polystyrene resin foam sheet according to this embodiment. By producing a masterbatch having a high concentration of the baked product and mixing the masterbatch, a polystyrene resin, and a polyphenylene ether resin, the following advantages are obtained. That is, there is an advantage that the odor is further suppressed because the calcined product of hydrotalcite is more easily dispersed and present in the polystyrene-based resin composition. Also, unlike the case where the powdered hydrotalcite fired product is supplied directly to the extruder, the advantage is that the hydrotalcite fired product can be prevented from being scattered in the work site environment due to the hot air of the extruder. There is also. In addition, you may produce | generate a resin composition by mixing a powdery hydrotalcite baking thing, a polystyrene resin, and a polyphenylene ether resin directly, without using the said masterbatch.
When the masterbatch further contains a polyphenylene ether-based resin, the method for producing a polystyrene-based resin foam sheet of this embodiment suppresses the odor of the polyphenylene ether-based resin contained in the masterbatch at the stage of the masterbatch, Further, since the fired hydrotalcite is more easily dispersed and present in the polystyrene resin composition, there is an advantage that the odor is further suppressed.
The master batch preferably contains 5 to 40% by mass of a fired hydrotalcite.

And in the said 1st extruder, a foaming agent is introduce | transduced into this 1st extruder inside from the injection port provided in the middle, and this foaming agent is melt-mixed with the said melt, and a foaming agent containing melt is produced.
Next, the foaming agent-containing melt is fed from the first extruder to the second extruder. And about the temperature (it is also called "resin temperature") of the foaming agent containing melt which cools the said foaming agent containing melt and is extruded in a column shape from the said 2nd extruder from the center part in the cross section of a cylinder. A value obtained by subtracting the minimum temperature from the maximum temperature up to the outer periphery (hereinafter also referred to as “resin temperature difference”) is preferably 20 ° C. or less, and the value is increased from the outer periphery of the cylinder toward the center. The temperature at a position that is 1/4 of the inner diameter of the cylinder from the outer periphery is preferably set within the range from the glass transition temperature of the obtained foamed sheet + 30 ° C. to the glass transition temperature + 70 ° C., and a circular die is used. The foaming agent-containing melt is extruded and foamed to form a cylindrical foam.
Specifically, the temperature of the resin passes through the thermistor through the hole of the breaker plate provided at the outlet of the second extruder and has a hole in the radial direction, and the thermistor is moved little by little (by 5 mm). The temperature distribution from the center to the outer periphery in the cross section is measured.
In addition, as a specific method for setting the difference in resin temperature to 20 ° C. or less, there is a method for increasing the kneadability of the foam-containing melt at the tip of the screw.
For example, the tip surface of a screw generally has a conical shape with a central portion protruding, but a groove or protrusion is provided on the tip surface, and the blowing agent-containing melt flowing toward the breaker plate is transferred to the protrusion or What is necessary is just to make it stir by the said groove | channel.
More specifically, as a shape in which a plurality of grooves extending radially from the outer peripheral portion to the center of the tip of the screw of the second extruder are provided, the blowing agent-containing melting from the central portion of the cylinder to the outer peripheral portion By increasing the kneadability of the product, the difference in resin temperature can be reduced. By the way, a 2nd extruder makes a polystyrene-type resin, a polyphenylene ether-type resin, and a foaming agent heat with a 1st extruder, and is made to contact the wall surface and screw of a cylinder with the foaming agent containing melt obtained. Thus, the foaming agent-containing melt is cooled to a temperature exhibiting a melt tension suitable for foaming. Therefore, when the blowing agent-containing melt in the second extruder is rapidly cooled, particularly when the blowing agent-containing melt is rapidly cooled on the outlet side of the second extruder, the tip of the screw Even if the kneadability at the part is increased, the difference in the resin temperature may not be sufficiently reduced. Therefore, it is preferable that the temperature of the second extruder is set so that the blowing agent-containing melt is gradually cooled from the first extruder side to the mold side.
Furthermore, air is blown to the foam immediately after extrusion with an air-cooling ring installed inside and outside of the foam to cool, and the obtained cylindrical foam is cut along the extrusion direction to obtain a polystyrene resin foam sheet ( A foam sheet is produced.

In addition, it is preferable to employ | adopt the above temperature conditions in a 1st extruder, The polystyrene-type resin obtained by suppressing the highest ultimate temperature of the said melt in this 1st extruder to 340 degrees C or less This is because the odor of the foam sheet can be further suppressed.
Although the mechanism is not clearly understood, when heated so that the temperature in the first extruder is 340 ° C. or lower, decomposition of polystyrene due to heat is suppressed and odor components are generated. It is thought that it becomes difficult to be done.
Further, in the method for producing a polystyrene resin foam sheet of the present embodiment, as described above, the temperature at a position at a depth of 1/4 of the inner diameter of the cylinder from the outer peripheral portion toward the center portion from the outer peripheral portion of the cylinder is set. By setting the glass transition temperature of the foamed sheet to 30 ° C. or higher, the viscosity of the foaming agent-containing melt does not become too high, and it becomes easy to extrude the foaming agent-containing melt from an extruder and the extrusion conditions are stabilized. There are advantages. Moreover, since the external appearance of the obtained foamed sheet becomes favorable, there is an advantage that the yield is improved and the productivity is improved.

  Further, in the method for producing a polystyrene-based resin foam sheet of the present embodiment, the temperature at a position at a depth of ¼ of the inner diameter of the cylinder from the outer periphery to the center of the cylinder is measured. By making the glass transition temperature + 70 ° C. or less, the viscosity of the foaming agent-containing melt does not become too low, and it becomes easy to lower the open cell ratio of the obtained foam sheet (the open cell ratio is easily set to 18% or less). ).

  The container of the present invention can be produced, for example, by subjecting a polystyrene resin foam sheet obtained by the above production method to molding such as thermoforming or bending. By using a polystyrene resin foam sheet having a low content of odor components, the container of the present invention has odor suppressed as the container.

Examples of the thermoforming method include vacuum forming, pressure forming, vacuum pressure forming, press forming, and the like.
Moreover, as said bending molding, the method of giving a V-groove process to a polystyrene-type resin foam sheet, and bend | folding via this V-groove, etc. are mentioned.

  The polystyrene resin foam sheet, the container, the method for producing the polystyrene resin foam sheet, and the method for producing the container of the present embodiment have the advantages described above, but the polystyrene resin foam of the present invention. The manufacturing method of a sheet | seat, a container, and a polystyrene-type resin foam sheet is not limited to the said structure, A design change is possible suitably.

  Next, the present invention will be described more specifically with reference to examples and comparative examples.

  The measurement of each characteristic value of the polystyrene-type resin foam sheet (foamed sheet) of an Example and a comparative example was implemented as follows.

<Basis weight>
The basis weight was obtained by cutting the foamed sheet with a width of 20 cm in the extrusion direction in the direction orthogonal to the extrusion direction, and calculating from the weight W (g) and the area S (cm ² ) of the section by the following formula.
Basis weight (g / m ² ) = W / S × 10000

<Contents of normal butyric acid, styrene, toluene, and ethylbenzene (weight generated per unit sample weight)>
Gas chromatograph mass spectrometry by a purge and trap (P & T) method was performed to evaluate volatile organic compounds generated when the foamed sheet was heated at a temperature of 250 ° C.
First, after thinly slicing the foam sheet, about 5 mg of a sample was precisely weighed, wrapped in aluminum foil, and set in a glass-lined stainless steel tube (GLT tube).
In this state, the GLT tube is heated at a temperature of 250 ° C. for 5 minutes, the generated gas is cold trapped in the cryofocus section, and then thermally desorbed to introduce volatile components into a gas chromatograph mass spectrometer (GC / MS). Measurements were made.
For measurement, GC / MS (model name “JMS-Q1000GC”) manufactured by JEOL Datum is combined with P & T Autosampler (model name “TD-4J”) manufactured by Liquid Chloroscience, and Phenomenex is used. Column (ZB-1 (10 μm × 0.25 mmφ × 60 m)).
The P & T conditions were as follows.
ChargeTime (10s), InjectionTime (20s), DesorbTime (300s), DelayStartTime (10s), Desheater (250 ° C), CryoTemperating (200 ° C), CryoTemp Cooling (-40 ° C)
Furthermore, the measurement conditions were as follows.
・ Column temperature:
Hold at 40 ° C. for 3 minutes, heat up to 200 ° C. at 15 ° C./min, heat up to 250 ° C. at 25 ° C./min, hold for 6.33 minutes at 250 ° C. ・ Carrier gas: helium (flow rate: 1 mL / min)
・ Inlet temperature: 250 ° C
・ Interface temperature: 250 ℃
・ Detector voltage: -1146V
・ Split ratio: 1/10
-Ion source temperature: 250 ° C
・ Ionization current: 300 μA
・ Ionization energy: 70 eV

<Odor measurement using tetra-back>
Each of the foam sheets (30 mm × 30 mm, weight 40 g) of Examples and Comparative Examples was placed in a Tedlar bag (10 L), 10 L of air through activated carbon was filled in the Tedlar bag, and left at room temperature for 24 hours. In addition, in order to reduce the influence of the butane gas odor in a foam sheet, the foam sheet of an Example and a comparative example put the thing of 30 days after extrusion in a tetra bag.
(1) Measurement of concentration of normal butyric acid contained in gas in tetrabag The gas in tetrabag was introduced into a gas chromatograph mass spectrometer (GC / MS), and the concentration of normal butyric acid was measured.
The measurement apparatus used the apparatus used for the measurement of the content of normal butyric acid, and the measurement conditions were the same as those for the measurement of the content of normal butyric acid.
(2) Measurement of 6-step odor intensity by an odor judger The odor intensity in the Tedlar bag is measured by a total of 5 people who have passed the odor judger and odor judger test by the 6-step odor intensity display method shown below. The arithmetic average value of 6-step odor intensity of 5 persons was calculated | required.
・ 6-level odor intensity display method 0: Odorless 1: Smell that can be finally detected 2: Weak odor that understands what odor is 3: Smell that can be easily detected 4: Strong odor 5: Strong odor (3) Measurement by odor sensor Cosmos Portable odor sensor XP-329III R (high-sensitivity indium oxide-based hot-wire sintered semiconductor sensor) (measuring range: 0 to 2000) (larger value indicates stronger odor) is inserted into the Tedlar bag. Then, the numerical value was measured.
(4) Measurement of 5 levels of unpleasant odor intensity with a monitor 10 unmonitored odor intensity levels in the Tedlar bag were measured by 10 monitors (5 men and 5 men) according to the 5 level unpleasant odor intensity display method shown below. The arithmetic mean value of the stage unpleasant odor intensity was obtained.
1: Odorless 1: Slight odor that does not matter at all 3: Odor that does not bother (not uncomfortable) 4: Odor that is anxious (slightly uncomfortable) 5: Unpleasant odor

<Example 1>
First, a hydrotalcite fired product (hereinafter also referred to as “baked product”) (manufactured by Toagosei Co., Ltd., deodorant “Kesmon NS-70”, average particle size 6 μm) and polystyrene resin (manufactured by DIC, product name) : "XC-515") is supplied to a twin screw extruder (caliber: 30 mm, L / D = 35) maintained at a cylinder temperature of 200 to 220 ° C, melt kneaded, and the tip of the twin screw extruder A master batch of a fired product containing 10% by mass of the fired product was obtained by extruding into a strand form from a die (diameter 3 mm, number of holes: 4) attached to the substrate at an extrusion rate of 10 kg / h.
Further, silica (manufactured by Toagosei Co., Ltd., deodorant “Kesmon NS-100”, average particle diameter 6 μm) and polystyrene resin (manufactured by DIC, product name: “XC-515”) are used at a cylinder temperature of 200 to 200 ° C. A die (3 mm diameter, number of holes: 4) attached to the tip of the twin screw extruder, supplied to a twin screw extruder (caliber: 30 mm, L / D = 35) held at 220 ° C., melted and kneaded. Was extruded into a strand at an extrusion rate of 10 kg / h to obtain a silica masterbatch containing 10% by mass of silica.
And 70 parts by mass of a polystyrene resin (manufactured by DIC, product name: “XC-515”) and a mixed resin of polyphenylene ether resin (PPE) and polystyrene resin (PS) (manufactured by SABIC, product name: “ Nozzle EFN4230 ", (PPE / PS = 70 parts by mass / 30 parts by mass) 100 parts by mass of the resin, bubble regulator (polystyrene with talc kneaded, content of talc: 40 masses) %) (Manufactured by Toyo Styrene Co., Ltd., product name “DSM1401A”) is 1 part by mass, the calcined product is 0.5 part by mass, and silica is 0.5 part by mass. : "XC-515"), the mixed resin, the master batch of the fired product, and the master batch of silica were put into a first extruder (φ115 mm). The maximum temperature of the melt (hereinafter, simply referred to as "maximum temperature".) In the heated so that 295 ° C. to obtain a melt and melt-kneading them.
Next, from an injection port provided in the middle of the first extruder, 3.0 parts by mass of butane gas (having isobutane and normal butane as a composition) as a foaming agent is added to 100 parts by mass of the resin composition. The melt was injected into the first extruder, and the melt and the butane gas were mixed to obtain a foaming agent-containing melt.
Then, the foaming agent-containing melt is supplied from the first extruder to the second extruder (diameter 150 mm), the foaming agent-containing melt is cooled and extruded from the second extruder. Regarding the temperature, a value obtained by subtracting the minimum temperature from the maximum temperature from the center to the outer periphery in the cross section of the second extruder (hereinafter also referred to as “resin temperature difference”) is set to 13.4 ° C. The temperature at a position at a depth of 1/4 of the inner diameter of the cylinder from the outer periphery to the center is made 176 ° C., and the foam-containing melt is extruded and foamed using a circular die. Obtained. Next, air was blown onto the foam immediately after extrusion with an air-cooling ring installed inside and outside the foam to cool it, thereby obtaining a cylindrical body. The obtained cylindrical body was cut along the extrusion direction to obtain a polystyrene resin foam sheet (foam sheet) having a basis weight of 220 g / m ² , a thickness of 1.60 mm, and a width of 1050 mm.
In addition, the fired hydrotalcite used here shows the same X-ray diffraction pattern as FIG.
Further, as the cylindrical cylinder of the second extruder, a cylinder having an inner diameter of 150 mm was used. Furthermore, as the screw of the second extruder, as shown in FIG. 4, a screw having a shape in which a plurality of grooves 1 extending from the outer peripheral portion toward the center is provided radially is used.

<Example 2>
A foamed sheet was produced in the same manner as in Example 1 except that the maximum temperature reached was 270 ° C. and the difference in resin temperature was changed to 12.6 ° C.

<Example 3>
A foamed sheet was produced in the same manner as in Example 1 except that silica was not used and the difference in resin temperature was changed to 12.5 ° C.

<Example 4>
A foamed sheet was produced in the same manner as in Example 1 except that the maximum temperature reached was changed to 245 ° C and the difference in height of the resin temperature was changed to 12.7 ° C.

<Example 5>
A foamed sheet was produced in the same manner as in Example 1 except that silica was not used, the maximum temperature reached was changed to 225 ° C, and the difference in height of the resin temperature was changed to 13.1 ° C.

<Example 6>
A foamed sheet was produced in the same manner as in Example 1 except that silica was not used, the maximum temperature reached was changed to 335 ° C, and the difference in height of the resin temperature was changed to 15.7 ° C.

<Example 7>
A foamed sheet was produced in the same manner as in Example 1 except that silica was not used, the maximum temperature reached was changed to 305 ° C, and the difference in height of the resin temperature was changed to 19.6 ° C.

<Example 8>
Instead of silica, a polyamine compound (deodorant “Kesmon NS-241” manufactured by Toagosei Co., Ltd.) is used, and the fired product is 0.3 parts by mass and the polyamine compound is 0.3 parts per 100 parts by mass of the resin. A foamed sheet was produced in the same manner as in Example 1 except that the mass part was changed, the maximum temperature reached was changed to 305 ° C, and the difference in height of the resin temperature was changed to 12.4 ° C. .

<Example 9>
With respect to 100 parts by mass of the resin, the calcined product was 0.3 parts by mass, the silica was 0.3 parts by mass, and the maximum temperature reached was changed to 305 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 12.2 ° C.

<Example 10>
With respect to 100 parts by mass of the resin, the fired product was 0.25 parts by mass, the silica was 0.25 parts by mass, and the maximum temperature reached was changed to 305 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 12.3 ° C.

<Example 11>
The silica was not used, the fired product was 0.20 parts by mass with respect to 100 parts by mass of the resin, and the maximum temperature reached was changed to 305 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 3 ° C.

<Example 12>
The silica was not used, the fired product was 0.12 parts by mass with respect to 100 parts by mass of the resin, and the maximum temperature reached was changed to 305 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 4 ° C.

<Example 13>
The silica was not used, the fired product was 0.12 parts by mass with respect to 100 parts by mass of the resin, and the maximum temperature reached was changed to 335 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 5 ° C.

<Example 14>
The silica was not used, the fired product was 0.12 parts by mass with respect to 100 parts by mass of the resin, and the maximum temperature reached was changed to 335 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 7 ° C.

<Example 15>
Except that silica was not used, that the fired product was 2.0 parts by mass with respect to 100 parts by mass of the resin, and that the difference in resin temperature was changed to 12.7 ° C. A foamed sheet was produced in the same manner as in Example 1.

<Example 16>
Except that silica was not used, that the fired product was 2.9 parts by mass with respect to 100 parts by mass of the resin, and that the difference in resin temperature was changed to 13.0 ° C. A foamed sheet was produced in the same manner as in Example 1.

<Example 17>
Except that silica was not used, that the fired product was 2.9 parts by mass with respect to 100 parts by mass of the resin, and that the difference in height of the resin temperature was changed to 19.7 ° C. A foamed sheet was produced in the same manner as in Example 1.

<Example 18>
A foamed sheet was produced in the same manner as in Example 1 except that silica was not used, the maximum temperature reached was changed to 225 ° C, and the difference in height of the resin temperature was changed to 19.8 ° C.

<Example 19>
The silica was not used, the fired product was 0.12 parts by mass with respect to 100 parts by mass of the resin, and the maximum temperature reached was changed to 225 ° C. A foamed sheet was produced in the same manner as in Example 1 except that the temperature was changed to 8 ° C.

<Example 20>
A foamed sheet in the same manner as in Example 1 except that the difference in height of the resin temperature was changed to 14.5 ° C., and that the cylindrical cylinder of the second extruder used an inner diameter of 200 mm. Was made.

<Example 21>
A foamed sheet in the same manner as in Example 1 except that the difference in height of the resin temperature was changed to 13.7 ° C. and that the cylindrical cylinder of the second extruder had an inner diameter of 115 mm. Was made.

<Comparative Example 1>
A foamed sheet was prepared in the same manner as in Example 1 except that the fired product and silica were not used, the maximum temperature reached was changed to 305 ° C, and the difference in resin temperature was changed to 12.2 ° C. did.

<Comparative example 2>
A foamed sheet was produced in the same manner as in Example 1 except that the fired product was not used, the maximum temperature reached was changed to 305 ° C, and the difference in height of the resin temperature was changed to 12.5 ° C.

<Comparative Example 3>
A foamed sheet was produced in the same manner as in Example 1, except that the fired product was not used, the maximum temperature reached was changed to 305 ° C, and the difference in resin temperature was changed to 13.5 ° C.

<Comparative example 4>
A foamed sheet was produced in the same manner as in Example 1 except that the fired product was not used, the maximum temperature reached was changed to 270 ° C., and the difference in resin temperature was changed to 12.8 ° C.

<Comparative Example 5>
Example 1 except that no calcined product was used, that silica was 1.0 part by mass with respect to 100 parts by mass of the resin, and that the resin temperature difference was changed to 12.5 ° C. In the same manner, a foam sheet was produced.

<Comparative Example 6>
A foamed sheet was produced in the same manner as in Example 1 except that the fired product and silica were not used, the maximum temperature reached was changed to 345 ° C, and the difference in resin temperature was changed to 12.5 ° C. did.

  Deodorant blending amount of Examples and Comparative Examples, maximum temperature reached, difference in resin temperature, normal butyric acid content, normal butyric acid concentration, odor intensity, odor sensor value, unpleasant odor intensity, styrene, toluene The total content of ethylbenzene is shown in Table 1.

As shown in Table 1, the foam sheet of the example within the scope of the present invention is one of the causative substances that greatly affect the odor compared to the foam sheet of the comparative example that does not use the fired hydrotalcite. As a result, the content of normal acetic acid was low. From this, it can be seen that according to the present invention, a polystyrene resin foam sheet with reduced odor can be obtained.
In addition, the foamed sheet of Example 10 containing the fired product and silica as the deodorant was the same as in Examples 3, 5-7, and 18 where the total amount of the deodorizer was the same and only the fired product was contained as the deodorant. The content of styrene, toluene and ethylbenzene, which are volatile components derived from styrene, was lower than that of the foam sheet. From this, when the foam sheet contains the fired product and silica as a deodorant, the odor caused by styrene, toluene, and ethylbenzene can be suppressed, and when the foam sheet is molded, it is used in this process. The adhesion of these components to the mold and other equipment can be suppressed. Therefore, it is preferable to contain a fired product and silica as a deodorant.

(Additional example 1)
A foamed sheet was produced in the same manner as in Example 3 except that the maximum temperature reached was changed to 345 ° C. and the difference in resin temperature was changed to 13.1 ° C. Content is 0.77 ppm, the concentration of normal butyric acid in the tetra-back test is 1.66 ppb, the odor intensity is 3.6, the odor sensor value is 682, and the unpleasant odor intensity is 3.8. It was a high value compared with Examples 1-17 whose temperature is 340 degrees C or less, and the highest ultimate temperature was the same, and was a low value compared with the comparative example 6 which does not contain a baked product.
(Additional example 2)
A foamed sheet was produced in the same manner as in Example 15 except that the maximum temperature reached was changed to 345 ° C. and the difference in resin temperature was changed to 12.5 ° C. Content of 0.58 ppm, normal butyric acid concentration in the tetra-back test is 1.65 ppb, odor intensity is 3.2, odor sensor value is 689, unpleasant odor intensity is 3.4, and all values reach the maximum It was a high value compared with Examples 1-17 whose temperature is 340 degrees C or less, and the highest ultimate temperature was the same, and was a low value compared with the comparative example 6 which does not contain a baked product.
From the additional examples 1 and 2, it can be seen that the highest achieved temperature is preferably 340 ° C. or lower.
(Additional example 3)
Except for changing the maximum temperature to 215 ° C., a foamed sheet was produced in the same manner as in Example 3. As a result, the polyphenylene ether resin and the polystyrene resin were not sufficiently melt-mixed, and the resulting foamed sheet was The foamability was not sufficient as compared with the foamed sheets of Examples 1 to 17 having a maximum ultimate temperature of 220 ° C. or higher.
From addition example 3, it can be seen that the maximum temperature reached is preferably 220 ° C. or higher.
(Additional example 4)
Except that the screw having no groove extending from the outer peripheral portion toward the center is used as the screw of the second extruder, the height difference of the resin temperature is changed to 20.8 ° C. In the same manner as in Example 3, a foam sheet was produced. This foam sheet has a normal acetic acid content of 0.55 ppm, a normal butyric acid concentration in the tetra-back test of 1.52 ppb, an odor intensity of 3.2, an odor sensor value of 610, and an unpleasant odor intensity of 3.5. All values were higher than those of Examples 1 to 17 in which the maximum temperature reached was 340 ° C. or lower.
(Additional example 5)
Except that the screw having no groove extending from the outer peripheral portion toward the center is used as the screw of the second extruder, the height difference of the resin temperature is changed to 20.8 ° C. In the same manner as in Example 15, a foam sheet was produced. This foam sheet has a normal acetic acid content of 0.67 ppm, a normal butyric acid concentration in the tetra-back test of 1.83 ppb, an odor intensity of 3.2, an odor sensor value of 711, an unpleasant odor intensity of 3.5, All values were higher than those of Examples 1 to 17 in which the maximum temperature reached was 340 ° C. or lower.
The foamed sheets of additional examples 4 and 5 were not sufficiently foamable as compared with the foamed sheets of Examples 1 to 17 in which the difference in resin temperature was 20 ° C. or less. From this, it can be seen that the difference in height of the resin temperature is preferably 20 ° C. or less.
(Additional example 6)
As the screw of the second extruder, the difference in the resin temperature is changed to 20.7 ° C. by using a screw not provided with a groove extending from the outer peripheral portion toward the center on the front end surface, and further, the highest temperature reached A foamed sheet was produced in the same manner as in Example 3 except that was changed to 225 ° C. This foam sheet has a normal acetic acid content of 0.63 ppm, a normal butyric acid concentration in the tetra-back test of 1.62 ppb, an odor intensity of 3.4, an odor sensor value of 666, and an unpleasant odor intensity of 3.5. All the values were higher than those of Examples 1 to 17 in which the difference in height of the resin temperature was 20 ° C. or less.
(Additional example 7)
As the screw of the second extruder, the difference in the resin temperature is changed to 21.2 ° C. by using a screw not provided with a groove extending from the outer peripheral portion toward the center on the front end surface. A foamed sheet was produced in the same manner as in Example 3 except that was changed to 345 ° C. This foam sheet has a normal acetic acid content of 1.05 ppm, a normal butyric acid concentration of 2.66 ppb, an odor intensity of 4.2, an odor sensor value of 823, and an unpleasant odor intensity of 4.0. All the values were higher than those of Examples 1 to 17 in which the difference in height of the resin temperature was 20 ° C. or less.
(Additional Example 8)
As the screw of the second extruder, the difference in the resin temperature is changed to 20.7 ° C. by using a screw not provided with a groove extending from the outer peripheral portion toward the center on the front end surface, and further, the highest temperature reached Was changed to 225 ° C., and a foamed sheet was produced in the same manner as in Example 3 except that a cylindrical cylinder of the second extruder was used having an inner diameter of 200 mm. The foamed sheet has a normal acetic acid content of 0.63 ppm, a normal butyric acid concentration in the tetra-back test of 1.62 ppb, an odor intensity of 3.4, an odor sensor value of 666, and an unpleasant odor intensity of 3.6. All the values were higher than those of Examples 1 to 17 in which the difference in height of the resin temperature was 20 ° C. or less.
(Additional example 9)
As the screw of the second extruder, the difference in the resin temperature is changed to 21.2 ° C. by using a screw not provided with a groove extending from the outer peripheral portion toward the center on the front end surface. A foamed sheet was produced in the same manner as in Example 3 except that the temperature was changed to 225 ° C. and that the cylindrical cylinder of the second extruder was a cylinder having an inner diameter of 115 mm. This foam sheet has a normal acetic acid content of 0.71 ppm, a normal butyric acid concentration in the tetra-back test of 1.66 ppb, an odor intensity of 3.4, an odor sensor value of 680, and an unpleasant odor intensity of 3.6, All the values were higher than those of Examples 1 to 17 in which the difference in height of the resin temperature was 20 ° C. or less.
It can be seen from the additional examples 6 to 9 that the difference in the resin temperature is preferably 20 ° C. or less.
In addition, in the additional examples 4 to 9, the temperature in the flow direction of the foaming agent-containing melt in the cylinder of the second extruder was drastically decreased on the outlet side of the second extruder.
(Additional examples 10 and 11)
Moreover, without using the master batch of the fired product, the fired product was charged into the first extruder in a powder state, the silica was 1.0 part by weight with respect to 100 parts by weight of the resin, and A foamed sheet was prepared in the same manner as in Example 3 except that the difference in resin temperature was changed to 12.4 ° C., and the fired product remained in powder form without using the master batch of the fired product. The foamed sheets were produced in the same manner as in Example 3 except that these were put into the first extruder. These foamed sheets were compared with the foamed sheets of Examples 1 to 17 using a fired master batch. Thus, the foamability was not sufficient. From this, it is understood that it is preferable to use a master batch of the fired product when the fired product is charged into the first extruder.

In order to solve the above-mentioned problems, the present invention contains a polystyrene resin and a polyphenylene ether resin, and the polyphenylene ether resin is 10 parts per 100 parts by mass of the total amount of the polystyrene resin and the polyphenylene ether resin. A method for producing a polystyrene-based resin foamed sheet by forming a polystyrene-based resin foamed sheet by extruding and foaming a resin composition containing ~ 50 parts by mass, wherein the melted resin composition passes through a breaker plate A method for producing a polystyrene-based resin foam sheet, characterized in that a value obtained by subtracting the minimum temperature from the maximum temperature from the center to the outer periphery of the breaker plate is 20 ° C. or less. I will provide a.
As the resin composition, a resin composition further containing a fired hydrotalcite is used.

Moreover, this invention provides the polystyrene-type resin foam sheet produced with the manufacturing method of the said polystyrene-type resin foam sheet as a solution means of the said subject .

Claims (3)

A resin composition comprising a polystyrene resin and a polyphenylene ether resin and 10 to 50 parts by mass of the polyphenylene ether resin with respect to 100 parts by mass of the total amount of the polystyrene resin and the polyphenylene ether resin. A method for producing a polystyrene resin foam sheet, which is formed by extrusion foaming to form a polystyrene resin foam sheet,
About the resin temperature when the melted product of the resin composition passes through the breaker plate, the value obtained by subtracting the minimum temperature from the maximum temperature from the center to the outer periphery of the breaker plate is 20 ° C. or less. A method for producing a polystyrene-based resin foam sheet characterized by comprising: A resin composition containing a polystyrene resin and a polyphenylene ether resin and containing 10 to 50 parts by mass of the polyphenylene ether resin with respect to a total amount of 100 parts by mass of the polystyrene resin and the polyphenylene ether resin is extruded and foamed. A polystyrene resin foam sheet,
Regarding the resin temperature when the melted product of the resin composition passes through the breaker plate, the value obtained by subtracting the minimum temperature from the maximum temperature from the center to the outer periphery of the breaker plate is set to 20 ° C. or less. A polystyrene-based resin foam sheet characterized by being produced by   A container obtained by molding the polystyrene resin foam sheet according to claim 2.

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