JP2016190905A - Poly-styrenic resin foam sheet, production method thereof, compact and fruit vegetable packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a poly-styrenic resin foam sheet having heightened flexibility and sufficient strength, and excellent in heat resistance and compactibility; and to provide a production method thereof, a compact and a fruit vegetable packaging container.SOLUTION: A poly-styrenic resin foam sheet includes a foamed resin layer in which a heterocyclic viscosity determined by viscoelasticity measurement under the condition of a temperature of 180°C and a frequency of 1 Hz is 3500-7000 Pa s. A fruit vegetable packaging container 10 is obtained by molding the poly-styrenic resin foam sheet. In the fruit vegetable packaging container 10, a plurality of recessed parts 12 are formed, which are opened to one surface 10a of the sheet and swollen semi-spherically to the other surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polystyrene-based resin foam sheet, a method for producing the same, a molded body, and a fruit vegetable packaging container.

For example, fruit vegetables such as apples, pears and peaches are housed in a fruit vegetable packaging container and transported or stored in order to prevent the surface from being damaged as much as possible. The fruit vegetable packaging container is formed with a plurality of recesses that open on one side of the sheet and swell in a semicircular shape on the other side of the sheet, and each of the fruit vegetables is accommodated in the recess.
In such a fruit vegetable packaging container, a molded body in which a polystyrene resin foam sheet is molded into a predetermined shape is used. The polystyrene-based resin foam sheet is excellent in moldability, heat insulation and light weight, has an appropriate rigidity, and is also suitably used as a material for fruit vegetable packaging containers.

Conventionally, studies have been made to improve the flexibility of polystyrene resin foam sheets so as not to damage the surface of fruit vegetables.
For example, Patent Document 1 proposes a fruit and vegetable tray (container for fruit and vegetables packaging) obtained by molding a laminated foam sheet in which a foam sheet and a thermoplastic resin film are laminated. For the foamed sheet described in Patent Document 1, a mixed resin of a polystyrene resin, a rubber-modified polystyrene resin, and a styrene elastomer resin is used.
Patent Document 2 proposes a fruit vegetable packaging container formed by molding a polystyrene resin foam sheet containing a polystyrene resin, a rubber-modified polystyrene resin, and a specific hydrogenated polystyrene elastomer.

JP 2004-299075 A JP 2012-097190 A

  However, in the vegetable vegetable packaging container described in Patent Document 1, sufficient strength cannot be obtained with only the foam sheet, and in order to ensure the strength, a thermoplastic resin film needs to be laminated and integrated with the foam sheet. . Moreover, although the softness | flexibility of a foamed sheet can be improved by mix | blending an elastomer with a foamed sheet, the heat resistance of the foamed sheet may fall, or the shaping | molding defect by lack of melt tension may arise.

  The vegetable vegetable packaging container described in Patent Document 2 has insufficient flexibility. For this reason, in the adjacent recesses of the fruit vegetable packaging container, when a slightly larger fruit vegetable is accommodated in one recess, the volume of the other recess decreases as the volume of the recess in which the fruit vegetables are accommodated increases. In some cases, the opening becomes narrow and it becomes difficult to accommodate the fruit vegetables in the other recess. In this case, if the fruit vegetables are forcibly accommodated in the other recess, the fruit vegetables are damaged.

  Therefore, the present invention has been made in view of the above circumstances, and has a high flexibility, sufficient strength, good heat resistance and moldability, a polystyrene-based resin foam sheet and a method for producing the same, and The object is a molded body and a container for fruit vegetables packaging.

  The polystyrene-based resin foam sheet according to the present invention includes a foamed resin layer having a complex viscosity of 3500 to 7000 Pa · s determined by viscoelasticity measurement under conditions of a temperature of 180 ° C. and a frequency of 1 Hz.

The foamed resin layer contains a resin component having a styrene monomer unit and an ethylene monomer unit, and is derived from a styrene monomer unit derived from a styrene monomer unit obtained from an infrared absorption spectrum of the surface of the foam resin layer. ^-1 absorbance (D698) and the absorbance of the ethylenic monomer unit derived from 2850cm ^-1 (D2850) to the absorbance ratio (D698 / D2850) is preferably a 7.0 to 15.0.

The foamed resin layer preferably contains a resin component containing an ionomer.
In addition, the foamed resin layer has a polystyrene resin of 45 to 75 mass%, an ionomer of 6 to 30 mass%, and a hydrogenated polystyrene elastomer of 5 to 20 mass with respect to the total amount (100 mass%) of the resin component. %, Polyethylene resin 0-15 mass%, and rubber-modified polystyrene resin 0-30 mass%.

Moreover, the manufacturing method of the polystyrene-type resin foam sheet of this invention is a manufacturing method of the said polystyrene-type resin foam sheet of this invention, Comprising: The raw material composition containing the resin component containing a polystyrene-type resin, and a foaming agent are included. It is characterized by being melt-kneaded, extruded and foamed.
The resin component further contains an ionomer, and the melt flow rate of the ionomer is preferably 0.8 to 5.0 g / 10 minutes.

  The said raw material composition is 45-75 mass% of polystyrene-type resins, 6-30 mass% of ionomers, 5-20 mass% of hydrogenated polystyrene-type elastomers with respect to the total amount (100 mass%) of the said resin component, It is preferable to contain 0 to 15% by mass of a polyethylene resin and 0 to 30% by mass of a rubber-modified polystyrene resin.

  Moreover, the molded article of the present invention is formed by molding the polystyrene resin foam sheet of the present invention.

  Moreover, the vegetable vegetable packaging container of this invention is provided with the foamed resin layer whose complex viscosity calculated | required by viscoelasticity measurement on the conditions of temperature 180 degreeC and frequency 1Hz is 3500-7000 Pa.s.

The polystyrene resin foam sheet of the present invention has enhanced flexibility, sufficient strength, and good heat resistance and moldability.
According to the method for producing a polystyrene resin foam sheet of the present invention, it is possible to produce a polystyrene resin foam sheet having improved flexibility, sufficient strength, good heat resistance and moldability.
The molded article of the present invention has enhanced flexibility, has sufficient strength, and good heat resistance.
According to the fruit vegetable packaging container of the present invention, the flexibility is enhanced, the strength is sufficient, the heat resistance is good, each fruit vegetable can be easily accommodated in the recess, and the fruit vegetables are not easily damaged. .

It is a perspective view which shows one Embodiment of the container for fruit vegetables packaging of this invention. It is XX sectional drawing of FIG.

(Polystyrene resin foam sheet)
The polystyrene resin foam sheet of the present invention (hereinafter also simply referred to as “foam sheet”) includes a foam resin layer containing a polystyrene resin.
Such a foamed sheet may have a single-layer structure composed only of a foamed resin layer, or may have a laminated structure in which a resin film or the like is provided on at least one surface of the foamed resin layer. In the foamed sheet of the present invention, even if it has a single-layer structure consisting only of the foamed resin layer, sufficient strength is ensured because the foamed resin layer has a predetermined complex viscosity.

  In the present invention, the complex viscosity is determined by viscoelasticity measurement under conditions of a temperature of 180 ° C. and a frequency of 1 Hz. Specifically, it is measured by the method described in Examples described later.

The complex viscosity of the foamed resin layer in the present invention is 3500 to 7000 Pa · s, preferably 4000 to 6500 Pa · s, and more preferably 4300 to 6500 Pa · s. s.
If the complex viscosity of a foamed resin layer is more than the lower limit of the said range, the softness | flexibility of a foam sheet will be improved. When the complex viscosity of the foamed resin layer is equal to or less than the upper limit of the above range, sufficient strength is easily secured. In addition, heat resistance is easily maintained and molding defects are less likely to occur.
The complex viscosity of the foamed resin layer is controlled, for example, by adjusting the composition of the resin component.

The open cell ratio of the foamed resin layer in the present invention is preferably 20% or less, and more preferably 15% or less. When the open cell ratio of the foamed resin layer exceeds the preferable upper limit of the above range, the secondary foamability of the foamed sheet is deteriorated, and the moldability may be lowered.
In the present invention, the open cell ratio of the foamed resin layer can be measured by a method based on an air pycnometer (air comparison hydrometer) method (1-1 / 2-1 atmospheric pressure method) defined in ASTM D-2856. .

Apparent density of the foamed resin layer in the present invention, from the viewpoint of light weight, preferably ^{0.03~0.21g / cm 3, 0.05~0.09g / cm} 3 is more preferable.
There exists a possibility that the intensity | strength of a foamed sheet may fall that the apparent density of a foamed resin layer is less than the preferable lower limit of the said range. When the apparent density of the foamed resin layer exceeds the preferable upper limit of the above range, the flexibility of the foamed sheet may be lowered.
In the present invention, the apparent density of the foamed resin layer can be measured by a method based on JIS K 6767.

The thickness of the foamed resin layer in the present invention is preferably 0.5 to 3.0 mm, more preferably 0.5 to 2.5 mm, and further preferably 1.0 to 2.5 mm. If the thickness of the foamed resin layer is within the above range, the moldability becomes better.
In the present invention, the thickness of the foamed resin layer refers to an arithmetic average value of the thicknesses of the five portions measured at least five locations of the arbitrary portion of the foamed resin layer.

As for the basic weight of the foamed resin layer in this invention, 75-300 g / m < ² > is preferable and 85-200 g / m < ² > is more preferable.
If the basis weight of the foamed resin layer is equal to or greater than the preferred lower limit of the above range, the strength of the foamed sheet is easily maintained. If the basis weight of the foamed resin layer is equal to or less than the preferable upper limit of the above range, the flexibility of the foamed sheet is maintained and the buffering property is easily obtained.

The expansion ratio of the foamed resin layer in the present invention is preferably 5 to 30 times, more preferably 8 to 26 times, and still more preferably 12 to 21 times.
If the foaming ratio of the foamed resin layer is equal to or greater than the preferable lower limit of the above range, the foamed sheet can be easily reduced in weight. If the foaming ratio of the foamed resin layer is equal to or less than the preferable upper limit of the above range, the strength of the foamed sheet is further increased.

2-6 mass% is preferable and, as for the residual foaming agent amount (residual gas amount) of the 5th day in the foamed resin layer, 2-4 mass% is more preferable.
In the foamed resin layer, if the residual gas amount on the 5th day is more than the preferred lower limit of the above range, sufficient secondary foamability is obtained at the time of thermoforming, and there is no occurrence of perforation, tearing, etc. Can be obtained easily. If the amount of residual gas on the fifth day is less than or equal to the preferred upper limit of the above range, sagging (draw) due to heat during secondary foaming in thermoforming is unlikely to occur.
In the present invention, the amount of residual foaming agent (residual gas amount) on the fifth day of passage refers to the amount of gas present in the foamed resin layer when five days have elapsed since the manufacture of the foamed sheet. This amount of gas is obtained by allowing the residual gas in the foam sheet to dissipate in an oven at 150 ° C. for 1 hour and measuring the mass of the foam sheet before and after the test. Specifically, it is calculated | required by the method as described in the below-mentioned Example.

<Polystyrene resin>
The foamed resin layer constituting the foamed sheet of the present invention contains a polystyrene resin.
Examples of polystyrene resins include polymers of styrene monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethylstyrene, and bromostyrene. Or the copolymer of these styrene-type monomers and monomers other than this styrene-type monomer is mentioned.
In addition, the polystyrene-type resin here does not contain a conjugated diene as a monomer component.

  The polymer of the styrenic monomer may be one homopolymer of the styrenic monomer, or may be a copolymer of two or more styrenic monomers.

Examples of the monomer other than the styrene monomer include vinyl monomers copolymerizable with the styrene monomer, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, Alkyl (meth) acrylates such as butyl methacrylate, cetyl acrylate, cetyl methacrylate; acrylic acid, methacrylic acid; acrylonitrile, methacrylonitrile; maleic anhydride; dimethyl maleate; dimethyl fumarate; diethyl fumarate; ethyl fumarate; Is mentioned.
In addition, the said alkyl (meth) acrylate means alkyl acrylate or alkyl methacrylate.

When the polystyrene resin is a copolymer, 50% by mass or more with respect to the total amount (100% by mass) of monomers used in the copolymer is preferably a styrene monomer.
When a vinyl monomer copolymerizable with a styrenic monomer is used for the copolymer, the amount of the vinyl monomer is appropriately determined according to the use of the foam sheet, for example, the copolymer. 5 mass% or less is preferable with respect to the total amount (100 mass%) of the monomer used for a polymer.

The melt flow rate (MFR) of the polystyrene-based resin is preferably 0.5 to 6.0 g / 10 minutes, more preferably 0.7 to 3.0 g / 10 minutes.
When the MFR of the polystyrene-based resin is less than the preferable lower limit of the above range, the thickness of the foamed resin layer may be uneven. When the MFR of the polystyrene resin exceeds the preferable upper limit of the above range, the expansion ratio of the foamed resin layer may be lowered.

  In the present invention, the melt flow rate (MFR) of the resin is the same as the method described in JIS K 7210: 1999 “Plastic-thermoplastic melt mass flow rate (MFR) and melt volume flow rate (MVR) test method” B method. In conformity, it means a value measured under conditions of a test temperature of 200 ° C., a test load of 49.03 N, and a preheating time of 4 minutes.

The weight average molecular weight of the polystyrene-based resin is preferably 200,000 to 450,000, more preferably 300,000 to 400,000.
When the weight average molecular weight of the polystyrene-based resin is less than the preferable lower limit of the above range, it is difficult to obtain a foamed resin layer having a high expansion ratio and a low open cell ratio. When the weight average molecular weight of the polystyrene-based resin exceeds the preferable upper limit of the above range, the fluidity at the time of melting may decrease, and the productivity may decrease.

In the present invention, the resin has a weight average molecular weight of 30 mg of resin dissolved in 10 ml of chloroform, filtered through a non-aqueous 0.45 μm chromatodisc, and measured by chromatography using the filtrate as a sample. Mean value.
Specifically, it is measured under the following conditions.

Gas chromatograph: high performance liquid chromatography manufactured by Tosoh Corporation (pump: DP-8020, autosample: AS8020, detector: UV-8020, RI-8020).
Column: Two trade names “Shodex GPC K-806L (φ8.0 × 300 mm)” manufactured by Showa Denko KK
Column temperature: 40 ° C.
Carrier gas: chloroform.
Carrier gas flow rate: 1.2 ml / min.
Injection / pump temperature: room temperature.
Detection: UV254 nm.
Injection volume: 50 microliters.
Standard polystyrene for calibration curve: trade name “shodex” manufactured by Showa Denko KK, weight average molecular weight 1030000; weight average molecular weight 5480000, 3840000, 355000, 102000, 37900, 9100, 2630,495 manufactured by Tosoh Corporation.

As the polystyrene resin, those produced by a known production method can be used. For example, polystyrene resins include those produced by suspension polymerization, bulk polymerization, solution polymerization, emulsion polymerization, and the like.
When polymerizing a styrene-type monomer and the vinyl monomer used together as needed, a well-known polymerization initiator can be used. For example, as a polymerization initiator, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, benzoyl peroxide, lauryl peroxide, t-butylperoxybenzoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-t-butylperoxybutane, t-butylperoxy-3,3,5 trimethylhexanoate, Examples thereof include organic peroxides such as di-t-butylperoxyhexahydroterephthalate; azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. A polymerization initiator may be used individually by 1 type, and may be used in combination of 2 or more type.

Moreover, when manufacturing a polystyrene-type resin, a crosslinking agent may be used at the time of superposition | polymerization. Examples of this crosslinking agent include divinylbenzene. A crosslinking agent may be used individually by 1 type, and 2 or more types may be used in combination.
The compounding amount of the crosslinking agent is preferably more than 0 parts by mass and 1 part by mass or less with respect to 100 parts by mass of the total amount of monomers used in the polystyrene resin.

  Polystyrene resin may be used individually by 1 type, and 2 or more types may be used in combination.

<Optional component>
The foamed resin layer constituting the foamed sheet of the present invention may contain other components (arbitrary components) in addition to the polystyrene-based resin as long as the complex viscosity is in the range of 3500 to 7000 Pa · s.
Examples of such optional components include resin components other than polystyrene-based resins, bubble regulators, colorants, shrinkage inhibitors, flame retardants, lubricants, and deterioration inhibitors.
Examples of resin components other than polystyrene resins include rubber-modified polystyrene resins, hydrogenated polystyrene elastomers, polyethylene resins, ionomers, and the like.

≪Rubber modified polystyrene resin≫
The rubber-modified polystyrene resin in the present invention includes a polymer alloy obtained by mixing a conjugated diene polymer with a polystyrene resin, and a graft copolymer obtained by graft copolymerizing a conjugated diene polymer with a polystyrene resin. Respectively.
The rubber-modified polystyrene resin has a sea-island structure in which particles (islands) made of a conjugated diene polymer having a particle size of 0.3 to 10 μm are dispersed in a continuous phase (sea) of a polystyrene resin. Generally referred to as high impact polystyrene.
In the rubber-modified polystyrene resin, hydrogenation is not performed on the double bond of the conjugated diene polymer portion (conjugated diene block).

As the polystyrene-based resin in the rubber-modified polystyrene-based resin, the same one as the above-mentioned polystyrene-based resin is used.
Examples of the conjugated diene polymer include a polymer or copolymer of a conjugated diene, and a copolymer of a conjugated diene and an aromatic vinyl compound. When the conjugated diene polymer is a conjugated diene copolymer or a copolymer of a conjugated diene and an aromatic vinyl compound, the conjugated diene polymer may be a block copolymer or a random copolymer. Any of polymers may be used. Examples of the conjugated diene include butadiene, isoprene and chloroprene, and butadiene is preferred. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethylstyrene, bromostyrene, and the like, and styrene is preferable.

The content of the styrene monomer unit in the rubber-modified polystyrene resin is preferably 75 to 99% by mass, and 80 to 97% by mass with respect to the total amount (100% by mass) of the monomer units constituting the resin. % Is more preferable.
There exists a possibility that the moldability of a foamed sheet may fall that content of a styrene-type monomer unit is less than the preferable lower limit of the said range. If the content of the styrene monomer unit exceeds the preferable upper limit of the above range, the foamed sheet or the molded product thereof may not have sufficient impact resistance.

The MFR of the rubber-modified polystyrene resin is preferably 1.5 to 4.0 g / 10 minutes, more preferably 2.0 to 3.5 g / 10 minutes.
When the MFR of the rubber-modified polystyrene resin is less than the preferable lower limit of the above range, the thickness of the foamed resin layer may be uneven. When the MFR of the rubber-modified polystyrene resin exceeds the preferable upper limit of the above range, the foaming ratio of the foamed resin layer may decrease.

The weight average molecular weight of the rubber-modified polystyrene resin is preferably from 150,000 to 350,000, and more preferably from 200,000 to 300,000.
If the weight average molecular weight of the rubber-modified polystyrene-based resin is less than the preferable lower limit of the above range, the closed cell ratio of the foamed resin layer is lowered, and the thickness of the foamed resin layer may be insufficient. When the weight average molecular weight of the rubber-modified polystyrene resin exceeds the preferable upper limit of the above range, the fluidity at the time of melting may decrease, and the productivity may decrease.

  The rubber-modified polystyrene resin may be used alone or in combination of two or more.

≪Hydrogenated polystyrene elastomer≫
The hydrogenated polystyrene elastomer in the present invention is a hydrogenated product of a styrene-conjugated diene block copolymer.
Examples of the conjugated diene here include butadiene, isoprene and chloroprene, and butadiene is preferred.

  Preferable examples of the hydrogenated polystyrene elastomer include styrene-ethylene / butadiene-styrene (SEBS) block copolymers and styrene-butadiene / butylene-styrene (SBBS) block copolymers.

The hydrogenation rate of the double bond of the conjugated diene block in the hydrogenated polystyrene elastomer is preferably 60 to 95 mol%, more preferably 65 to 95 mol%.
If such a hydrogenation rate is within the above range, the flexibility of the foamed sheet can be enhanced by using a hydrogenated polystyrene elastomer. For example, when transporting fruit vegetables in a recess of a vegetable packaging container formed by forming a foam sheet, even if the fruit vegetables stored in the recess receive an impact force such as vibration during transport, Since it does not rotate (around the ball) in the recess, it is possible to prevent the fruit vegetables from being damaged.

The hydrogenation rate of the conjugated diene block in the hydrogenated polystyrene elastomer can be measured according to the following procedure.
Procedure 1) Using a nuclear magnetic resonance apparatus, a ¹ H-NMR spectrum of a resin to be measured is obtained.
Procedure 2) Based on the ¹ H-NMR spectrum, the amount of hydrogenated conjugated diene (hydrogenated conjugated diene) and the amount of unconjugated hydrogenated conjugated diene (unhydrogenated conjugated diene) were calculated. To do.
Procedure 3) The hydrogenation rate is calculated from the following formula from the above-mentioned amount of added conjugated diene and the amount of unhydrogenated conjugated diene.
Hydrogenation rate (mol%)
= 100 × (amount of hydrogenated conjugated diene) / {(amount of hydrogenated conjugated diene) + (amount of unhydrogenated conjugated diene)}

The measurement by the nuclear magnetic resonance apparatus in the procedure 1 is performed under the following conditions.
Nuclear magnetic resonance apparatus: trade name “ECX-400P type” manufactured by JEOL Ltd.
Measurement nucleus: ¹ H.
Observation range: 8000 (20 ppm).
Pulse width: 45 ° (9.0 μsec).
Pulse interval: 9 sec.
Number of measurements: 2400 times.
Set temperature: 55 ° C.
Measurement solvent: CDCl ₃ .
Measurement concentration: 50 mgr / 0.4 mL.
Internal reference material: tetramethylsilane (TMS).

The rebound resilience of the hydrogenated polystyrene elastomer is preferably 10% or less, more preferably 8% or less, and particularly preferably 3 to 6%.
When the rebound resilience is equal to or less than the preferable upper limit of the above range, the flexibility of the foamed sheet is enhanced. In addition, the impact resistance of the foam sheet can be improved. For example, when transporting fruits and vegetables in a recess of a vegetable packaging container formed by forming a foam sheet, the fruits are less likely to be damaged.
In the present invention, the rebound resilience of the hydrogenated polystyrene elastomer refers to a value measured by a method based on JIS K 6255.

The durometer type A hardness (HDA) of the hydrogenated polystyrene elastomer is preferably 90 or less, and more preferably 50 to 90.
When the durometer type A hardness (HDA) is equal to or less than the preferable upper limit of the above range, the flexibility of the foam sheet is further enhanced. For example, fruit vegetables accommodated in a concave part of a fruit vegetable packaging container formed by forming a foam sheet are less likely to be rubbed with the concave part, and the fruit vegetables are less likely to be damaged.
In the present invention, the durometer type A hardness (HDA) of the hydrogenated polystyrene elastomer refers to a value measured by a method according to JIS K7215.

The MFR of the hydrogenated polystyrene elastomer is preferably 2 to 20 g / 10 minutes, and more preferably 3 to 15 g / 10 minutes.
When the MFR of the hydrogenated polystyrene elastomer is less than the preferred lower limit of the above range, the thickness of the foamed resin layer may be nonuniform. When the MFR of the hydrogenated polystyrene elastomer exceeds the preferable upper limit of the above range, the expansion ratio of the foamed resin layer may be lowered.

The weight average molecular weight of the hydrogenated polystyrene elastomer is preferably from 100,000 to 350,000, more preferably from 150,000 to 250,000.
If the weight average molecular weight of the hydrogenated polystyrene-based elastomer is less than the preferred lower limit of the above range, the closed cell ratio of the foamed resin layer is lowered, and the thickness of the foamed resin layer may be insufficient. When the weight average molecular weight of the hydrogenated polystyrene elastomer exceeds the preferable upper limit of the above range, the fluidity at the time of melting may decrease, and the productivity may decrease.

  A hydrogenated polystyrene type elastomer may be used individually by 1 type, and may be used in combination of 2 or more type.

≪Polyethylene resin≫
In the foamed sheet of the present invention, the foamed resin layer contains a polyethylene-based resin, whereby the flexibility of the foamed sheet is enhanced. For example, the fruit vegetables contained in the recesses of the fruit vegetable packaging container formed by molding the foamed sheet. It becomes hard to be damaged.
Examples of the polyethylene resin include ultra-low density polyethylene resin, low density polyethylene resin, medium density polyethylene resin, high density polyethylene resin, linear low density polyethylene resin, and linear medium density polyethylene resin. And linear high-density polyethylene resin.

The MFR of the polyethylene resin is preferably from 0.1 to 5 g / 10 minutes, and more preferably from 0.4 to 4 g / 10 minutes.
When the MFR of the polyethylene resin is less than the preferable lower limit of the above range, the fluidity at the time of melting may be lowered, and the productivity may be easily lowered. When the MFR of the polyethylene resin exceeds the preferable upper limit of the above range, foamability or moldability may be deteriorated, or compatibility with polystyrene may be deteriorated.

The weight average molecular weight of the polyethylene resin is preferably from 50,000 to 300,000, more preferably from 100,000 to 200,000.
If the weight average molecular weight of the polyethylene resin is less than the preferred lower limit of the above range, it may be difficult to obtain a foamed resin layer having a low open cell ratio. When the weight average molecular weight of the polyethylene resin exceeds the preferable upper limit of the above range, the fluidity at the time of melting may be lowered, and the productivity may be lowered.

  Polyethylene resin may be used individually by 1 type, and may be used in combination of 2 or more type.

≪Ionomer≫
The ionomer in the present invention is a resin in which a polymer is aggregated by utilizing the cohesive force of metal ions.
In the foamed sheet of the present invention, the foamed resin layer contains an ionomer, whereby the flexibility of the foamed sheet is enhanced.
Examples of the metal ion in the ionomer include sodium ion, potassium ion, and zinc ion.
Examples of the polymer in the ionomer include a copolymer of ethylene and an acidic group-containing monomer. Examples of the acidic group-containing monomer include acrylic acid and methacrylic acid.
As an ionomer, a resin in which a copolymer of acrylic acid or methacrylic acid and ethylene is aggregated using the cohesive force of sodium ions; a copolymer of acrylic acid or methacrylic acid and ethylene by zinc ions Examples thereof include resins made into aggregates by utilizing the cohesive force.

The ionomer MFR is preferably 0.8 to 5.0 g / 10 min, and more preferably 0.8 to 2.0 g / 10 min.
If the MFR of the ionomer is at least the preferred lower limit of the above range, the production stability of the foamed sheet will be better. If the MFR of the ionomer is less than or equal to the preferable upper limit of the above range, the foamability is easily maintained.

  An ionomer may be used individually by 1 type, and may be used in combination of 2 or more type.

In the polystyrene resin foam sheet of the present invention, the foamed resin layer preferably contains a resin component having a styrene monomer unit and an ethylene monomer unit from the viewpoint of imparting flexibility.
The absorbance ratio (D698 / D2850) of the foamed resin layer is preferably 7.0 to 15.0, more preferably 7 from the viewpoint of the balance of flexibility, strength, heat resistance and moldability of the foamed sheet. It is 0.0-12.0, More preferably, it is 7.0-10.0.
When the absorbance ratio (D698 / D2850) is equal to or greater than the preferable lower limit of the above range, the strength and heat resistance of the foamed sheet are easily maintained, and the moldability is further improved. When the absorbance ratio (D698 / D2850) is equal to or less than the preferable upper limit of the above range, the flexibility of the foamed sheet is further enhanced.
In the present invention, the absorbance ratio (D698 / D2850) of the foamed resin layer is measured by infrared spectroscopy (IR). Absorbance ratio (D698 / D2850) means the absorbance of the styrene-based monomer unit derived from 698cm ^-1 and (D698), the absorbance of 2850 cm ^-1 derived from ethylene monomer units and (D2850), the ratio of . Specifically, it is calculated | required by the method as described in the below-mentioned Example.

Such a foamed resin layer preferably contains a resin component including an ionomer in addition to the polystyrene-based resin because flexibility is further improved.
Moreover, this foamed resin layer is 45-75 mass% of polystyrene-type resin with respect to the total amount (100 mass%) of the said resin component from the point of the softness | flexibility of a foam sheet, intensity | strength, heat resistance, and a moldability. It is preferable to contain 6-30 mass% of ionomers, 5-20 mass% of hydrogenated polystyrene elastomer, 0-15 mass% of polyethylene resin, and 0-30 mass% of rubber-modified polystyrene resin.

In such a foamed resin layer, in addition to the resin component, it is preferable that a foam regulator is further contained. By containing the cell regulator, it is easy to obtain a foam sheet having a low open cell ratio and good moldability.
Examples of the air conditioner include inorganic fillers such as talc, mica, mica, and montmorillonite.
A bubble regulator may be used individually by 1 type, and may be used in combination of 2 or more type.
0.5-5 mass parts is preferable with respect to 100 mass parts of resin components, and, as for content of the bubble regulator in a foamed resin layer, 0.5-3 mass parts is more preferable.

The polystyrene-based resin foam sheet of the present invention described above is flexible by including a foam resin layer having a complex viscosity of 3500 to 7000 Pa · s determined by viscoelasticity measurement under conditions of a temperature of 180 ° C. and a frequency of 1 Hz. Is increased, has sufficient strength, and has good heat resistance and moldability.
The polystyrene resin foam sheet of the present invention also has good gas retention.

(Method for producing polystyrene resin foam sheet)
The method for producing a polystyrene-based resin foam sheet of the present invention is the above-described method for producing the polystyrene-based resin foam sheet of the present invention, comprising: a raw material composition containing a resin component containing a polystyrene resin; and a foaming agent. This is a method of melt kneading, extruding and foaming.
As a suitable method for producing such a polystyrene resin foam sheet, a known foam sheet production method can be employed, and examples thereof include the following production method (A) and production method (B). Among these, as a manufacturing method of such a polystyrene-type resin foam sheet, a manufacturing method (A) is more preferable from the point of extrusion foamability and thermoformability.

Manufacturing method (A):
A circular die attached to the tip of the extruder after supplying a raw material composition containing a polystyrene-based resin and other resins and a raw material composition containing other components and a physical foaming agent to the extruder and melt-kneading them. After extrusion foaming from above, a cylindrical foam is obtained, and then the cylindrical foam is expanded and supplied to a mandrel for cooling, and then the cylindrical foam is placed between its inner and outer peripheral surfaces. A method for producing a polystyrene-based resin foam sheet by continuously cutting and developing in the extrusion direction.

Manufacturing method (B):
By melt-kneading the raw material composition and the chemical foaming agent in an extruder and then extruding from a T-die attached to the tip of the extruder to produce a foamable sheet, and heating and foaming the foamable sheet A method for producing a polystyrene resin foam sheet.

In the production method (A), the physical foaming agent is not particularly limited, and examples thereof include hydrocarbons such as propane, butane, and pentane; and inert gases such as nitrogen and carbon dioxide.
A physical foaming agent may be used individually by 1 type, and may be used in combination of 2 or more type.
2-7 mass parts is preferable with respect to 100 mass parts of raw material compositions, and, as for the compounding quantity of a physical foaming agent, 2-6 mass parts is more preferable.

In the production method (B), the chemical foaming agent is not particularly limited, and examples thereof include azodicarbonamide.
A chemical foaming agent may be used individually by 1 type, and 2 or more types may be used in combination.
2-7 mass parts is preferable with respect to 100 mass parts of raw material compositions, and, as for the compounding quantity of a chemical foaming agent, 2-6 mass parts is more preferable.

45-75 mass% is preferable with respect to the total amount (100 mass%) of a resin component, and, as for the compounding quantity of a polystyrene-type resin, 50-70 mass% is more preferable.
When the blending amount of the polystyrene-based resin is equal to or more than the preferable lower limit of the above range, the strength and heat resistance of the foamed sheet are increased, and the moldability is further improved. If the blending amount of the polystyrene-based resin is equal to or less than the preferable upper limit of the above range, the flexibility of the foamed sheet is easily maintained.

When a rubber-modified polystyrene resin is used as a resin component other than the polystyrene resin, the blending amount of the rubber-modified polystyrene resin is preferably 0 to 30% by mass with respect to the total amount (100% by mass) of the resin component, 30 mass% is more preferable, and 10-25 mass% is further more preferable.
When the blending amount of the rubber-modified polystyrene resin is equal to or more than the preferable lower limit of the above range, an impact force such as vibration applied to the foamed sheet is easily absorbed. When the blending amount of the rubber-modified polystyrene resin is equal to or less than the preferable upper limit of the above range, the rubber-modified polystyrene resin becomes more difficult to aggregate and the appearance of the foamed sheet becomes better.

The blending ratio of the polystyrene resin (PS system) and the rubber-modified polystyrene resin (rubber-modified) is also expressed as a mass ratio represented by polystyrene-based resin / rubber-modified polystyrene resin (hereinafter referred to as “PS-based / rubber-modified”). ) Is preferably 1.5 to 14.0, and more preferably 1.5 to 7.0.
If PS system / rubber modification is not less than the preferable lower limit of the above range, the flexibility of the foam sheet is easily maintained. If PS system / rubber modification is less than or equal to the preferable upper limit of the above range, the strength and heat resistance of the foamed sheet are easily maintained, and the moldability is further improved.

When a hydrogenated polystyrene elastomer is used as a resin component other than the polystyrene resin, the blending amount of the hydrogenated polystyrene elastomer is preferably 5 to 20% by mass with respect to the total amount (100% by mass) of the resin component. 20 mass% is more preferable.
When the blending amount of the hydrogenated polystyrene elastomer is equal to or more than the preferable lower limit of the above range, the flexibility of the foam sheet is easily maintained, and, for example, it is accommodated in a recess of a fruit vegetable packaging container formed by molding the foam sheet. Fruit vegetables are less likely to be damaged. When the blending amount of the hydrogenated polystyrene elastomer is not more than the preferable upper limit of the above range, the strength and heat resistance of the foamed sheet are easily maintained, and the moldability is further improved.

The blending ratio of the polystyrene-based resin (PS-based) and the hydrogenated polystyrene-based elastomer (hydrogenated) is also expressed as a mass ratio represented by polystyrene-based resin / hydrogenated polystyrene-based elastomer (hereinafter referred to as “PS-based / hydrogenated”). ) Is preferably 2.0 to 5.0, more preferably 2.5 to 4.0.
If PS system / hydrogenation is more than the preferable lower limit of the said range, the heat resistance of a foam sheet will be maintained easily and a softness | flexibility will also improve more. If PS system / hydrogenation is less than or equal to the preferred upper limit of the above range, the compatibility between the polystyrene resin and the polyethylene resin is further improved, and the foamability and thermoformability are further improved.

When a polyethylene resin is used as the resin component other than the polystyrene resin, the blending amount of the polyethylene resin is preferably 0 to 15% by mass, and 5 to 10% by mass with respect to the total amount (100% by mass) of the resin component. More preferred.
When the blending amount of the polyethylene resin is equal to or more than the preferable lower limit of the above range, the flexibility of the foam sheet is easily maintained. For example, the fruit vegetables contained in the recesses of the fruit vegetable packaging container formed by forming the foam sheet It becomes hard to be damaged. When the blending amount of the polyethylene resin is equal to or less than the preferable upper limit of the above range, the strength and heat resistance of the foamed sheet are easily maintained, and the moldability is further improved.

The blending ratio of the polystyrene resin (PS system) and the polyethylene resin (PE system) is a mass ratio represented by polystyrene resin / polyethylene resin (hereinafter also referred to as “PS system / PE system”). 0-7.0 are preferable and 4.0-5.5 are more preferable.
If PS system / PE system is more than the preferable lower limit of the said range, the intensity | strength of a foamed sheet and a moldability will become easy to be maintained. If PS system / PE system is below the preferable upper limit of the said range, the softness | flexibility of a foam sheet will be easy to be maintained.

The raw material composition preferably contains a resin component containing an ionomer in addition to the polystyrene resin. As the ionomer, it is preferable to use one having a melt flow rate of 0.8 to 5.0 g / 10 min.
Ionomer is trade name “Himiran 1601” (metal ion: sodium ion, polymer: copolymer of acrylic acid or methacrylic acid and ethylene) manufactured by Mitsui DuPont Polychemical Co., Ltd., trade name “Himiran 1855” ( Commercially available products such as metal ions: zinc ions, polymers: copolymers of acrylic acid or methacrylic acid and ethylene) can be used.

When using an ionomer as a resin component, the blending amount of the ionomer is preferably 6 to 30% by mass and more preferably 10 to 25% by mass with respect to the total amount (100% by mass) of the resin component.
If the blending amount of the ionomer is equal to or more than the preferable lower limit of the above range, the flexibility of the foamed sheet is further enhanced. If the blending amount of the ionomer is less than or equal to the preferable upper limit of the above range, the heat resistance of the foamed sheet is easily secured.

The blending ratio of the polystyrene resin (PS system) and the ionomer is preferably 1.6 to 5.5 in terms of mass ratio represented by polystyrene resin / ionomer (hereinafter also referred to as “PS system / ionomer”). .2 to 5.3 is more preferable.
If PS type | system | group / ionomer is more than the preferable lower limit of the said range, the intensity | strength of a foamed sheet and heat resistance will become easy to be maintained. If PS type | system | group / ionomer is below the preferable upper limit of the said range, the softness | flexibility of a foamed sheet will be improved more.

The said raw material composition contains the resin component containing a polystyrene-type resin.
The resin component preferably contains an ionomer in addition to the polystyrene resin. In addition to the polystyrene resin, the resin component preferably contains an ionomer and a hydrogenated polystyrene elastomer.
Furthermore, the resin component preferably includes a polystyrene resin, an ionomer, a hydrogenated polystyrene elastomer, and one or more selected from the group consisting of a polyethylene resin and a rubber-modified polystyrene resin.
As the raw material composition, since the effect of the present invention is further enhanced, 45 to 75% by mass of polystyrene resin and 6 to 30% by mass of ionomer with respect to the total amount (100% by mass) of the resin component, What contains 5-20 mass% of hydrogenated polystyrene-type elastomer, 0-15 mass% of polyethylene-type resin, and 0-30 mass% of rubber-modified polystyrene-type resins is preferable.

  According to the method for producing a polystyrene resin foam sheet of the present invention described above, a polystyrene resin foam sheet having improved flexibility, sufficient strength, good heat resistance and moldability can be produced.

(Molded body)
The molded body of the present invention is formed by molding the polystyrene-based resin foam sheet of the present invention into a desired shape using a known molding method or the like.
Examples of the method for forming the polystyrene-based resin foam sheet include vacuum forming and pressure forming. As vacuum forming or pressure forming, plug forming, free drawing forming, plug and ridge forming, matched mold forming, straight forming, drape forming, reverse draw forming, air slip forming, plug assist forming, plug assist reverse drawing forming Etc.
The molded body of the present invention has increased flexibility, has sufficient strength, has good heat resistance, and in particular for fruit vegetables packaging in which a plurality of recesses for accommodating fruit vegetables are formed on one surface of the sheet. It is useful as a container.

(Container for fruit vegetables packaging)
The container for fruit vegetables packaging of this invention is provided with the foamed resin layer whose complex viscosity calculated | required by the viscoelasticity measurement on the conditions of temperature 180 degreeC and frequency 1Hz is 3500-7000 Pa.s.

FIG. 1 shows an embodiment of a fruit vegetable packaging container according to the present invention, and FIG. 2 is a cross-sectional view taken along line XX of FIG.
The fruit vegetable packaging container 10 of this embodiment is for accommodating fruit vegetables such as apples, pears, and peaches.
The fruit vegetable packaging container 10 has a substantially rectangular shape in plan view, and is formed with twelve recesses 12 that open on one surface 10a of the sheet and swell in a semicircular shape on the other surface 10b of the sheet. .
One concave portion 12 has a size in which about half of one fruit vegetable is buried.
As shown in FIG. 2, a partition 15 is formed between the adjacent recesses 12. The partition portion 15 includes each peripheral wall 12 b of the adjacent recesses 12 and a connection portion 14 provided between the recesses 12.
At the center of the inner bottom surface of the concave portion 12, a convex portion 12a is formed that protrudes in the direction of the open surface 10a and follows the concave portion of the fruit vegetables.

For example, the fruit vegetable packaging container 10 is formed of a polystyrene-based resin foam sheet having a foamed resin layer having a complex viscosity of 3500 to 7000 Pa · s determined by viscoelasticity measurement under conditions of a temperature of 180 ° C. and a frequency of 1 Hz. It is manufactured by thermoforming. A preferable range of the complex viscosity is 4000 to 6500 Pa.s. s, and a more preferable range is 4300 to 6500 Pa.s. s.
The fruit vegetable packaging container 10 is provided with a foamed resin layer having a complex viscosity of 3500 to 7000 Pa · s, thereby exhibiting high flexibility, and has sufficient strength and heat resistance.

  When fruit vegetables are stored in the recess 12, the lower half of the fruit vegetables is buried in the recess 12. Since the flexibility of the fruit vegetable packaging container 10 is enhanced, the peripheral wall 12b of the recess 12 comes into contact with the fruit vegetables, so that the fruit vegetables are stably accommodated in the recess 12 in close contact with the peripheral wall 12b.

When fruit vegetables of a size larger than the opening diameter of the recesses are accommodated in one of the adjacent recesses, in the conventional fruit vegetable packaging container, the volume of the recesses in which such large size vegetables are accommodated increases, and the opening is As it spreads, the partitioning part falls into the other concave part, the opening part of the other concave part becomes narrow, and it is difficult to accommodate fruit vegetables in the other concave part.
In the fruit vegetable packaging container 10 of the present embodiment, since the flexibility of the peripheral wall 12b and the connection portion 14 (partition portion 15) is enhanced, even when such a large size fruit vegetable is accommodated in the recess 12, the recess 12 The partition portion 15 is compressed as the opening portion of the first portion expands. Thereby, the volume of the other adjacent recess is maintained, and the opening is not narrowed. For this reason, fruit vegetables can be easily accommodated in the adjacent recesses 12 respectively.

  In addition, the foamed resin layer constituting the fruit vegetable packaging container 10 can be appropriately elastically deformed as the flexibility is increased. For this reason, even if the fruit vegetables accommodated in the recess 12 in close contact with the peripheral wall 12b are subjected to an impact force such as vibration during transportation or storage, they are less likely to cause ball rotation and damage to the fruit vegetables.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
The raw materials used in this example are shown below.

Resin component Polystyrene (MFR: 1.5 g / 10 min, weight average molecular weight: 340,000, product name: HRM26, manufactured by Toyo Styrene Co., Ltd.).

  Polyethylene resin (ultra low density polyethylene, MFR: 0.8 g / 10 min, weight average molecular weight: 110,000, product name: Lumitac 12-1, manufactured by Tosoh Corporation).

Hydrogenated polystyrene elastomer (styrene-ethylene / butadiene-styrene block copolymer, hydrogenation rate: 95 mol%, rebound resilience: 4%, durometer type A hardness: 87, MFR: 3.5 g / 10 min, weight Average molecular weight: 150,000, product name: SOE-S1605, manufactured by Asahi Kasei Chemicals Corporation).
In addition, the durometer type A hardness about the above-mentioned raw material was measured as follows.

[Durometer type A hardness]
The durometer type A hardness of the hydrogenated polystyrene elastomer was measured by a method based on JIS K7215 using a durometer ASKER A type (manufactured by Kobunshi Keiki Co., Ltd.) and a constant pressure loader to which a load of 10 N was applied.
Specifically, 12 plane rectangular test pieces of length 30 mm × width 50 mm × thickness 4 mm made of hydrogenated polystyrene elastomer were prepared, and two of them were stacked to obtain a measurement sample having a thickness of 8 mm. Individually produced.
About each measurement sample, the value (HDA) of durometer type A hardness was measured 6 times, and the arithmetic mean value was computed.

  Rubber-modified polystyrene resin (styrene monomer unit: 94% by mass, MFR: 2.7 g / 10 min, weight average molecular weight: 240,000, product name: E640N, manufactured by Toyo Styrene Co., Ltd.).

Ionomer A (metal ion Na ⁺ , MFR: 1.3 g / 10 min, product name: High Milan 1601, manufactured by Mitsui DuPont Polychemical Co., Ltd.).
Ionomer B (metal ion Zn ⁺ , MFR: 1.0 g / 10 min, product name: High Milan 1855, manufactured by Mitsui DuPont Polychemical Co., Ltd.).

-Bubble regulator talc (powder talc, product name: DSM-1401A, manufactured by Toyo Styrene Co., Ltd.).

Example 1
[Production of polystyrene resin foam sheet]
Polystyrene (HRM26) 100 parts by mass, polyethylene resin (Lumitac 12-1) 10 parts by mass, hydrogenated polystyrene elastomer (SOE-S1605) 15 parts by mass, rubber-modified polystyrene resin (E640N) 15 parts by mass, and ionomer A raw material composition containing a resin component containing 10 parts by mass of A (High Milan 1601) and talc (1.5 parts by mass with respect to 100 parts by mass of the resin component) as a bubble regulator was prepared.
Next, the raw material composition is supplied to an extruder and melt-kneaded so that the maximum temperature is 245 ° C., and butane gas (isobutane / normal butane = 68/32) is used as a physical foaming agent in the raw material composition in a molten state. (Mass ratio)) 5.3 parts by mass (with respect to 100 parts by mass of the raw material composition) were injected, and butane gas was uniformly dispersed in the raw material composition.
Then, after cooling the raw material composition until its temperature reaches 138 ° C., it is extruded and foamed from a circular die having a diameter of 180 mm attached to the tip of the extruder with a clearance of 0.28 mm, to form a cylindrical foam Got the body. Subsequently, the cylindrical foam was expanded in diameter and then supplied to a cooling mandrel to be cooled.
After cooling, two polystyrene-based resin foam sheets are obtained by continuously cutting and developing the cylindrical foam in the extrusion direction across the inner and outer peripheral surfaces at two locations facing the diameter direction. Obtained.

[Manufacture of fruit vegetable packaging containers]
The obtained polystyrene-based resin foam sheet was left under normal temperature and normal pressure conditions for 14 days in order to completely replace the butane gas in the bubbles with air.
Thereafter, the polystyrene-based resin foam sheet is cut into a flat rectangular shape having a length of 470 mm and a width of 350 mm, and then thermoformed using a plug assist molding method, so that twelve recesses are provided to accommodate each fruit vegetable. A vegetable packaging container according to the embodiment shown in FIGS.

(Examples 2-5 and Comparative Examples 1-4)
Except having changed the compounding composition of the resin component as shown in Table 1, a polystyrene-based resin foam sheet was produced in the same manner as in Example 1, and this was molded to obtain a fruit vegetable packaging container.

About the manufactured polystyrene-based resin foam sheet, complex viscosity (Pa · s), thickness (mm), basis weight (g / m ² ), expansion ratio (times), absorbance ratio (D698 / D2850), day 5 The amount of residual foaming agent (% by mass) of the eyes was determined. In addition, the manufactured polystyrene-based resin foam sheet was evaluated for heat resistance, flexibility, and moldability.
Moreover, the transport test was done about the manufactured fruit vegetable packaging container.
The above results are shown in Table 1.

[Complex viscosity of polystyrene resin foam sheet, complex viscosity of fruit vegetables packaging container]
For the foamed sheet or container, dynamic viscoelasticity measurement is performed by combining the viscoelasticity measuring device “PHYSICA MCR301” manufactured by Anton Paar, the temperature control system “CTD450”, and the software “Leoplus” to determine the complex viscosity (η *). Asked.
Specifically, the dynamic viscoelasticity measurement was performed according to the following procedure.
The raw material composition used for the production of the foamed sheet or container, or a sample collected from the foamed sheet or container was heated at a temperature of 150 ° C. for 5 minutes, and the number of presses was 5 times. A disk-shaped sample having a thickness of 3 mm was produced.
Next, the sample was set on a plate of a viscoelasticity measuring apparatus heated to a measurement start temperature of 200 ° C., and allowed to stand for 5 minutes in a nitrogen atmosphere to be melted.
Thereafter, the interval was crushed to 2.0 mm with a parallel plate having a diameter of 25 mm, and the melted material protruding from the plate was removed.
Furthermore, after standing for 5 minutes after reaching the measurement start temperature of 200 ± 1 ° C, the conditions of 5% strain, frequency 1Hz, temperature drop rate 2 ° C / min, measurement interval 30 seconds, normal force 0N, measurement temperature 200-100 ° C The complex viscosity η * (Pa · s) was measured below, and the complex viscosity η * (Pa · s) value at 180 ° C. was read.
The complex viscosity η * (Pa · s) value measured for the foamed sheet was almost the same as each complex viscosity η * (Pa · s) value measured for the raw material composition and the vegetable vegetable packaging container. . The complex viscosity η * (Pa · s) value measured for the foamed sheet is shown as “complex viscosity (Pa · s)” in Table 1.

[Thickness of polystyrene resin foam sheet]
The thickness (mm) of the foamed sheet was determined by measuring the thickness of an arbitrary portion of the foamed sheet at five locations and calculating the arithmetic average value of the thicknesses at the five locations.

[Basis weight of polystyrene resin foam sheet]
The basis weight of the foamed sheet was determined as follows.
Except 20 mm in the width direction at both ends of the foamed sheet, 10 sections of 10 cm × 10 cm were cut out at equal intervals in the width direction, and the mass (g) of each section was measured to 0.001 g unit. A value obtained by converting an average value of the mass (g) of each section into a mass per 1 m ² was defined as a basis weight (g / m ² ) of the foamed sheet.

[Expansion ratio of polystyrene resin foam sheet]
The expansion ratio (times) of the foam sheet was determined as follows.
About the sample which cut out the foamed sheet to the predetermined | prescribed magnitude | size, the magnitude | size (area: S) and thickness (t) are measured, and these are multiplied and the apparent volume (V = Sxt (cm < ³ >) of a sample. )), And the apparent density (d = M / V (g / cm ³ )) of the foamed sheet was calculated from this and the mass (M (g)) of the sample.
Then, the density of the mixed resin forming the foamed sheet (ρ: 1.05 g / cm ³ ) is divided by the apparent density (d) of the foamed sheet to obtain the foaming ratio (times) of the foamed sheet. It was.
Foaming ratio (times) = density of mixed resin (ρ) ÷ apparent density of foamed sheet (d)

[Absorbance ratio of polystyrene resin foam sheet (D698 / D2850)]
The absorbance ratio (D698 / D2850) of the foamed sheet was determined as follows.
About the surface of the foam sheet (foamed resin layer) of three each selected at random, surface analysis was performed by the infrared spectroscopic analysis ATR measuring method, and the infrared absorption spectrum was obtained.
An absorbance ratio (D698 / D2850) was calculated from each infrared absorption spectrum, and an arithmetic average of the calculated absorbance ratios was obtained. This was used as the absorbance ratio (D698 / D2850) of the foamed sheet.
Absorbance (D698) and absorbance (D2850) are measured by a measurement apparatus sold under the trade name “Fourier transform infrared spectrophotometer MAGN-560” by Nicolet, respectively, and “Thunder Dome” manufactured by Spectra-Tech as an ATR accessory. ”And measured.

ATR-FTIR measurement was performed under the following conditions.
High refractive index crystal species: Ge (germanium).
Incident angle: 45 ° ± 1 °.
Measurement region: 4000 cm ^{−1 to} 675 cm ⁻¹ .
Fraction dependency of measurement depth: No correction.
Number of reflections: 1 time.
Detector: DTGS KBr.
Resolution: 4 cm ⁻¹ .
Integration count: 32 times.
Others: A process that is not related to the measurement spectrum is performed with the infrared absorption spectrum measured without contacting the sample as the background.
In the ATR method, the intensity of the obtained infrared absorption spectrum changes depending on the degree of adhesion between the sample and the high refractive index crystal. For this reason, the ATR accessory “Thunder Dome” was subjected to a maximum load and the degree of adhesion was controlled almost uniformly to perform measurement. The foam sheet was used without any pretreatment and set on a thunder dome, and this measurement was performed.

  Absorbance (D698) and absorbance (D2850) were obtained by performing peak processing on the infrared absorption spectrum obtained under the above conditions as follows.

The absorbance at 698 cm ⁻¹ (D698) obtained from the infrared absorption spectrum is the absorbance corresponding to the absorption spectrum derived from the out-of-plane deformation vibration of the benzene ring contained in the styrene monomer unit. In this measurement of absorbance, no peak separation is performed even when other absorption spectra overlap at 698 cm ⁻¹ . Absorbance (D698) is a straight line connecting the 2000 cm ^-1 and 815 cm ^-1 as a baseline, means the maximum absorbance between 710 cm ^-1 and 685cm ^-1.

The absorbance at 2850 cm ⁻¹ (D2850) obtained from the infrared absorption spectrum is the absorbance corresponding to the absorption spectrum derived from the C—H stretching vibration contained in the ethylene monomer unit. In this measurement of absorbance, no peak separation is performed even when other absorption spectra overlap at 2850 cm ⁻¹ . Absorbance (D2850) is a straight line connecting the 3130Cm ^-1 and 2620cm ^-1 as a baseline, it means the maximum absorbance between 2875cm ^-1 and 2800 cm ^-1.
The absorbance ratio (D698 / D2850) is a value obtained by dividing the absorbance (D698) by the absorbance (D2850).

[Amount of residual foaming agent on the fifth day of the day in the polystyrene resin foam sheet]
The amount (% by mass) of the remaining foaming agent on the fifth day of the foamed sheet was determined as follows.
The foam sheet on the fifth day after manufacture was used. Except for 20 mm at both ends in the width direction of the foam sheet, 10 pieces of 10 cm × 10 cm were cut out at equal intervals in the width direction, and the total mass of 10 pieces was measured to obtain “sheet weight before heating (g)”.
These sections were overlapped and wrapped with aluminum foil to prepare a sample, and the mass was measured to obtain “sheet mass before heating + aluminum mass (g)”.
Next, the sample was put into an oven, and the foaming agent in the foamed sheet was dissipated under the conditions of 150 ° C. × 1 hour.
Thereafter, the sample was taken out of the oven and stored in a desiccator for 1 hour, and then the mass was measured to obtain “heated sheet mass + aluminum mass (g)”.
And about the foam sheet, the amount (mass%) of the residual foaming agent of the 5th day was calculated | required by following Formula.
Residual foaming agent amount (% by mass) = {(sheet mass before heating + aluminum mass) − (sheet mass after heating + aluminum mass)} ÷ sheet mass before heating × 100

[Heat resistance of polystyrene resin foam sheet]
Cut out 5 pieces of 10 cm × 10 cm each from the foamed sheet of each example, stack the 5 pieces, and further sandwich the top and bottom with two aluminum plates of the same size of about 1 mm in thickness, at 70 ° C. It was left horizontally in the set oven. Next, a 5 kg weight was placed on the upper aluminum plate and heated in that state for 24 hours.
Then, it took out from oven and investigated the peelability (fusion-peeling property) between slices (foamed sheets). The five slices (foamed sheets) that have been stacked are peeled off one by one, and the degree of peeling at that time is determined in four stages of A, B, C, and D according to the following evaluation criteria, and the heat resistance of the foamed sheet Evaluated.
Evaluation criteria A: The sections are peeled off with little force applied, and there is almost no sound at that time (very good).
B: A slight force is required to start peeling between the sections, but after the sections start to peel off, there is almost no sound and no force is required (further better).
C: When the slices are peeled off, a sound of crispy sound is produced, but not much force is required to peel the slices (good).
D: When the slices are peeled off, a sound is heard and the slices are not peeled off unless a force is applied (defect).

[Flexibility of polystyrene resin foam sheet]
Using Tensilon UCT-10 manufactured by Orientec, a partial compression test was performed as follows to evaluate the flexibility of the foam sheet.
The foam sheet was cut out to 50 mm × 50 mm and used as a sample sample.
To measure the partial compression displacement, a load cell with a maximum load of 25 kgf was used, and the load cell was fitted with a hemispherical φ20 mm, 25 mm long straight rod-shaped pushing jig with a tip of R = 10 mm. went.
The above four sample samples were stacked, and the sample sample on which the four sheets were stacked was set in close contact with the measuring device carrier so that there was no gap in the measuring device carrier. The thickness at this time was measured sample thickness (unit: mm).
Using the state where the lower end of the pressing jig was in contact with the upper end of the sample sample in the thickness direction, the pressing jig was lowered at a speed of 10 mm / min to compress the sample sample.
At that time, the displacement (mm) from the base point of the jig when the load on the sample sample was 1 kgf was defined as the partial compressive displacement amount when the sample sample was loaded with 1 kgf. The average of the measured values of 5 samples was defined as the partial compression displacement (unit: mm) of the sample sample when loaded with 1 kgf.
And the softness | flexibility (%) of the foam sheet was calculated | required by the following Formula.
Flexibility (%) = partial compression displacement of sample sample under 1 kgf load (unit: mm) / measured sample thickness (unit: mm) × 100
The higher the value of the flexibility (%), the higher the flexibility of the foam sheet.
The flexibility of the foam sheet was evaluated according to the following evaluation criteria.
Evaluation criteria A: More than 13% flexibility and less than 18% (flexibility is particularly good).
○: Flexibility of 10 to 13% or flexibility of 18 to 24% (good flexibility).
X: Softness less than 10% (poor inferior in flexibility) or softness in excess of 24% (too soft and poor).

[Moldability of polystyrene resin foam sheet]
Using a mold having twelve recesses with an opening diameter of 100 mm and a depth of 40 mm, the temperature in the heating furnace is set to 130 ° C., the foamed sheet is thermoformed, and the fruit vegetable packaging container of the embodiment shown in FIG. Got.
And the state of this molded object surface and the molded object thickness were observed, and the moldability of the foam sheet was evaluated according to the following evaluation criteria.
Evaluation criteria ○: No defects were found (good).
X: The surface was in a state of being burned, tearing occurred, or only a molded product having an insufficient thickness was obtained (defect).

[Transport test for fruit vegetable packaging containers]
After storing 12 apples one by one in one recess of the molded body obtained above (container for fruit vegetables packaging of the embodiment shown in FIG. 1), a seal is placed on the upper surface of each apple for marking. Sticked. In that case, the ease of accommodation of the apple in a recessed part was evaluated.
Next, the fruit vegetable packaging container was placed in a cardboard box, and this cardboard box was placed on a truck and transported from Nagano Prefecture to Nara Prefecture.
After the transportation, the damaged state of the fruit vegetable packaging container was visually observed to evaluate the strength of the container.
Furthermore, the position of the mark seal was determined by visual observation as to whether or not the apple housed in the concave portion of the fruit vegetable packaging container vibrated and rotated in the concave portion (produced a ball circumference).
Each apple was observed from vertically above, and the case where the sticker that had been attached in advance was moved 90 ° or more in the horizontal direction around the core of the apple was determined to be “having a ball-around”.
And according to the following evaluation criteria, the bitterness of the fruit vegetables in the fruit vegetable packaging container was evaluated.
Evaluation criteria A: The apples were easily accommodated in the recesses, and the number of apples that produced the ball circumference was less than 3 (very good).
B: The apples were easily accommodated in the recesses, and the number of apples that caused the ball rotation was 3 or more and less than 5 (further better).
C: The apples were easily accommodated in the recesses, and the number of coral that caused the ball rotation was 5 or more and less than 7 (good).
D: It was not easy to accommodate the apples in the recesses, and the number of apples that caused the ball rotation was 7 or more (defect).

From the results shown in Table 1, it can be confirmed that the polystyrene resin foam sheets of Examples 1 to 5 to which the present invention is applied have all of flexibility, heat resistance and moldability.
Moreover, the vegetable packaging container formed by shape | molding the polystyrene-type resin foam sheet of Examples 1-5 was able to accommodate the apple easily in the adjacent recessed part.
In addition, it was confirmed that the fruit vegetable packaging containers obtained by molding the polystyrene-based resin foam sheets of Examples 1 to 5 were not damaged in the transportation test and had no problem in strength. Moreover, according to the container for fruit vegetables packaging of Examples 1-4, it was also confirmed that in this transportation test, it is hard to produce the ball circumference and the fruit vegetables are hardly damaged.

10 Container for fruit and vegetables packaging, 12 recessed part, 14 connection part, 15 partition part.

Claims (9)

  A polystyrene-based resin foam sheet comprising a foam resin layer having a complex viscosity of 3500 to 7000 Pa · s determined by viscoelasticity measurement under conditions of a temperature of 180 ° C. and a frequency of 1 Hz. The foamed resin layer contains a resin component having a styrene monomer unit and an ethylene monomer unit,
The foamed resin layer surface of the infrared absorbing styrene obtained from the spectrum monomer units absorbance derived 698cm ^-1 of (D698) ethylene monomer units absorbance derived 2850cm ^-1 (D2850) and the absorbance ratio of The polystyrene-based resin foamed sheet according to claim 1, wherein (D698 / D2850) is 7.0 to 15.0.   The polystyrene-based resin foam sheet according to claim 1, wherein the foamed resin layer contains a resin component including an ionomer.   The foamed resin layer has a polystyrene resin of 45 to 75 mass%, an ionomer of 6 to 30 mass%, and a hydrogenated polystyrene elastomer of 5 to 20 mass% with respect to the total amount (100 mass%) of the resin component. The polystyrene-based resin foam sheet according to claim 3, comprising 0 to 15% by mass of a polyethylene-based resin and 0 to 30% by mass of a rubber-modified polystyrene-based resin. A method for producing a polystyrene resin foam sheet according to any one of claims 1 to 4,
A method for producing a polystyrene-based resin foam sheet, comprising melting and kneading a raw material composition containing a resin component including a polystyrene-based resin and a foaming agent, and extruding and foaming. The resin component further includes an ionomer,
The manufacturing method of the polystyrene-type resin foam sheet of Claim 5 whose melt flow rate of the said ionomer is 0.8-5.0 g / 10min.   The said raw material composition is 45-75 mass% of polystyrene-type resins, 6-30 mass% of ionomers, 5-20 mass% of hydrogenated polystyrene-type elastomers with respect to the total amount (100 mass%) of the said resin component, The manufacturing method of the polystyrene-type resin foam sheet of Claim 5 or 6 containing 0-15 mass% of polyethylene-type resins, and 0-30 mass% of rubber-modified polystyrene-type resins.   The molded object formed by shape | molding the polystyrene-type resin foam sheet as described in any one of Claims 1-4.   A fruit vegetable packaging container comprising a foamed resin layer having a complex viscosity of 3500 to 7000 Pa · s determined by viscoelasticity measurement under conditions of a temperature of 180 ° C. and a frequency of 1 Hz.

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