JP2017177806A - Laminated foamed sheet and resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated foamed sheet which exhibits good moldability even at comparatively low temperature and is useful for forming a resin molding that is less likely to cause deformation even when heated, and to provide a resin molding made from a laminated foamed sheet such as a container for food storage excellent in production efficiency.SOLUTION: A polyethylene resin composition is adopted which has a relationship of a specific extrapolation glass transition initiation temperature, a specific midpoint glass transition temperature T, a specific extrapolation glass transition initiation temperature Tand a mid point glass transition temperature, as a formation material of a resin foamed layer and a resin non-foamed layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminated foam sheet provided with a resin foam layer and a resin non-foam layer formed of a polystyrene-based resin composition, and a resin molded product made of the laminate foam sheet.

Conventionally, polystyrene-based resin foam sheets (hereinafter also simply referred to as “foam sheets”) have been widely used as raw materials for resin molded products such as food containers, and are available in various types such as trays, cups, and bowls. It is molded into a shape.
When the resin molded product requires strength, a laminated foam sheet in which a polystyrene resin film is laminated on one side or both sides of the foam sheet is used as a raw material.
The laminated foam sheet is excellent in lightness and heat insulation by having a resin foam layer made of a foam sheet, and has excellent surface strength because it has a non-foamed resin layer made of the resin film.
Such a laminated foam sheet or a simple foam sheet not having a resin non-foamed layer is processed into a resin molded product by thermoforming such as vacuum forming or pressure forming (for example, Patent Documents 1 and 2).

JP-A-5-271456 JP 2009-263512 A

Incidentally, the resin molded product is required to improve the production efficiency.
For example, if the laminated foam sheet can be thermoformed at a lower temperature than conventional, energy required for heating the sheet at the time of thermoforming can be suppressed, and the production efficiency can be improved.
Further, if the laminated foam sheet can be molded at low temperature, the time (cooling time) required for demolding the resin molded product can be shortened.
However, simply thermoforming a laminated foamed sheet at a lower temperature than before would cause residual distortion in the resin molded product.
A resin molded product having a residual strain may be deformed due to the development of a restoring force against strain when heat is applied.

  In view of the above circumstances, the present invention provides a laminated foam sheet useful for forming a resin molded product that exhibits good moldability even at a relatively low temperature and that hardly deforms even when heated, and has excellent manufacturing efficiency. It is an object to provide a resin molded product.

  As a result of diligent research by the present inventor, the extrapolated glass transition start temperature and the midpoint glass transition temperature required when DSC measurement is performed on the resin composition constituting the resin foam layer of the laminated foam sheet are the laminated foam. It has been found that the relationship between the glass transition temperature of the resin composition constituting the resin foam layer and the resin non-foam layer affects the strain during molding, which affects the moldability of the sheet at low temperature thermoforming. . And this inventor can thermoform at a comparatively low temperature by selecting the formation material of a laminated foam sheet so that these intermediate point glass transition temperature and extrapolation glass transition start temperature may become in a specific range. It has been found that a laminated foam sheet can be provided, and that it is difficult to cause deformation at high temperatures for a resin molded product obtained by the thermoforming, and the present invention has been completed.

That is, the laminated foam sheet according to the present invention comprises a resin foam layer formed of the first polystyrene resin composition and a resin non-foam layer formed of the second polystyrene resin composition, It is a laminated foam sheet in which the resin non-foamed layer is laminated on at least one surface of the resin foam layer, and the extrapolated glass transition start temperature of the first polystyrene resin composition obtained by DSC measurement is “T _ig1 (° C. ) ”, When the intermediate point glass transition temperature is“ T _mg1 (° C.) ”and the intermediate point glass transition temperature of the second polystyrene resin composition is“ T _mg2 (° C.) ”, the following (1) to It satisfies all (3).

90 ° C. ≦ T _ig1 <100 ° C. (1)
95 ° C. ≦ T _mg1 <102 ° C. (2)
−5 ≦ (T _mg1 −T _mg2 ) <2 ° C. (3)

By satisfying the above (1) to (3), the laminated foam sheet can be easily thermoformed even at a relatively low temperature.
Moreover, such a laminated foam sheet and a resin molded product obtained by thermoforming the laminated foam sheet are unlikely to be deformed at high temperatures.

The laminated foam sheet having the above configuration preferably further satisfies the following (4).

98 ° C. ≦ T _mg2 (4)

  According to this structure, it can suppress more effectively that a laminated foam sheet and a resin molded product deform | transform at high temperature.

  In the laminated foam sheet having the above-described configuration, the first polystyrene-based resin composition contains an acrylate ester, and an absorbance ratio D1728 / D1600 obtained by infrared spectroscopic analysis by the ATR method is 0.2 or more and 0.9 or less. It is preferable that

  According to this configuration, when the absorbance ratio is within the above range, low temperature moldability and high temperature deformation suppression can be achieved at a higher level.

  Moreover, the laminated foam sheet of the said structure WHEREIN: It is preferable that a 1st polystyrene resin composition contains a polystyrene resin and a styrene-acrylic acid ester copolymer resin.

  According to this configuration, since the adjustment of the ratio of the polystyrene resin and the styrene-acrylate copolymer resin in the first polystyrene resin composition becomes easy, extrapolation of the first polystyrene resin composition is possible. It becomes easy to set the glass transition start temperature and the midpoint glass transition temperature within the above range.

In the laminated foam sheet having the above configuration, the resin foam layer has a thickness of 0.7 mm to 3.0 mm, a basis weight of 150 g / m ^{2 to} 400 g / m ² , and the resin non-foam layer is The thickness is preferably 0.05 mm or more and 0.3 mm or less.

  According to such a configuration, when the thickness and basis weight of each layer are within the above ranges, the laminated foam sheet can easily exhibit excellent strength and excellent thermoformability.

  In the laminated foam sheet having the above structure, the resin non-foamed layer preferably contains rubber particles, and the rubber particles preferably have an average particle size of 0.3 μm or more and 2.0 μm or less.

  According to this configuration, the strength of the resin non-foamed layer is improved, and in addition to the excellent strength of the laminated foamed sheet, a laminated foamed sheet having a beautiful appearance can be obtained.

  The resin molded product according to the present invention is a thermoformed product made of the laminated foam sheet as described above.

Since such a resin molded product can be manufactured by thermoforming at a relatively low temperature, it is excellent in productivity.
Moreover, such a resin molded product is unlikely to be deformed at a high temperature.

  The resin molded product having the above structure is a food container, and the non-foamed layer of the laminated foamed sheet is preferably disposed on the inner side of the container than the resin foamed layer.

  The resin molded product having such a configuration is unlikely to be deformed even when a high-temperature food is stored or when hot water is poured into the stored food and cooked. Moreover, the resin molded product of this structure is suitable as a container for food storage also in the point that the amount of oligomer elution is low. Furthermore, since the resin non-foamed layer is disposed on the inner side of the container than the resin foamed layer, the resin molded product can exhibit excellent strength on the inner side of the container.

  The food container having the above structure has a bottom wall portion, and the resin non-foamed layer disposed inside the container in the bottom wall portion contains rubber particles, and the rubber particles have an average particle diameter of 0.3 μm or more. It is preferable that it is 2.0 micrometers or less.

  According to this configuration, since the puncture strength of the container is improved, the container can be suitable for use as an instant noodle container.

  According to the present invention, it is possible to provide a laminated foamed sheet that can be thermoformed at a relatively low temperature and that can prevent the molded product from being deformed at a high temperature, and is excellent in production efficiency. A molded article can be provided.

Graph showing an example of a DSC curve Graph showing an example of a DSC curve The partial notch schematic perspective view of the resin molded product (container for instant noodles). Transmission electron micrograph showing the state of the resin non-foamed layer on the bottom wall of the resin molded product (food container), and explanatory diagram showing how to determine the particle diameter of the rubber particles (upper figure) ). The transmission electron micrograph showing the state of the resin non-foamed layer of a laminated foam sheet. 9 is a transmission electron micrograph showing the state of rubber particles in a rubber-modified polystyrene resin used for forming a resin non-foamed layer of the laminated foamed sheet of Example 5. FIG. 7 is a transmission electron micrograph showing the state of rubber particles in a rubber-modified polystyrene resin used for forming a resin non-foamed layer of the laminated foamed sheet of Example 6. FIG. 9 is a transmission electron micrograph showing the state of rubber particles in a rubber-modified polystyrene resin used for forming a resin non-foamed layer of the laminated foamed sheet of Example 7. FIG.

The laminated foam sheet and the resin molded product according to the embodiment of the present invention will be described below.
In the following, the present invention will be described by taking as an example a case where the laminated foam sheet has a two-layer structure in which a resin non-foamed layer is provided on one side of the resin foam layer.
In the following, the present invention will be described by taking as an example the case where the resin molded product is a food container such as an instant noodle container.

The laminated foam sheet of this embodiment includes a resin foam layer formed of a first polystyrene resin composition and a resin non-foam layer formed of a second polystyrene resin composition, and the resin foam It is a laminated foam sheet in which the resin non-foamed layer is laminated on one side of the layer.
The laminated foam sheet of the present embodiment has an extrapolated glass transition start temperature of the first polystyrene resin composition obtained by DSC measurement of “T _ig1 (° C.)” and an intermediate glass transition temperature of “T _mg1 ( C) ”and satisfying all of the following (1) to (3) when the intermediate glass transition temperature of the second polystyrene resin composition is“ T _mg2 (° C.) ”.

90 ° C. ≦ T _ig1 <100 ° C. (1)
95 ° C. ≦ T _mg1 <102 ° C. (2)
−5 ≦ (T _mg1 −T _mg2 ) <2 ° C. (3)

The laminated foam sheet of this embodiment further satisfies the following (4).

98 ° C. ≦ T _mg2 (4)

The extrapolated glass transition start temperature (T _ig ) and midpoint glass transition temperature (T _mg ) of the polystyrene-based resin composition are measured based on the method described in JIS K7121: 1987 “Plastic transition temperature measurement method”. can do.

The extrapolated glass transition start temperature (T _ig ) is a differential according to “9.3 Determination of glass transition temperature” of the same standard based on the method described in JIS K7121: 1987 “Method for measuring plastic transition temperature”. It can be measured using a scanning calorimeter (DSC).
More specifically, for example, a model name “DSC6220 type” manufactured by SII Nanotechnology Co., Ltd. is used, and a sample is placed on the DSC sample side so that there is as little gap as possible at the bottom of the aluminum measurement container. Place a 6.5 mg filled sample, and place an aluminum measuring vessel with alumina on the reference side, and increase the temperature from 30 ° C to 200 ° C at a temperature increase rate of 20 ° C / min under a nitrogen gas flow rate of 20 mL / min. From the DSC curve obtained when the temperature was raised to 200 ° C. at a rate of temperature increase of 20 ° C./min. The extrapolated glass transition start temperature (T _ig ) can be determined using the attached analysis software (Muse).
As shown in FIG. 1, the extrapolated glass transition start temperature (T _ig ) is a straight line obtained by extending the base line on the low temperature side of the DSC curve obtained by the above measurement to the high temperature side, and the stepwise change portion of the glass transition. It can be determined as the temperature of the intersection with the tangent drawn at the point where the slope of the curve is maximum.
In addition, as shown in FIG. 2, the extrapolated glass transition start temperature (T _ig ) is a straight line obtained by extending the low-temperature base line to the high-temperature side when the resulting DSC curve has two or more steps. And the temperature of the intersection with the tangent drawn at the point where the slope of the step-like change portion at the first stage (low temperature side) of the glass transition becomes maximum.

The intermediate glass transition temperature (T _mg ) can be measured using a differential scanning calorimeter (DSC) based on the method described in JIS K7121: 1987 “Method for Measuring Plastic Transition Temperature”.
More specifically, for example, a DSC curve is obtained in the same manner as the measurement of the extrapolation glass transition start temperature (T _ig ) described above, and the midpoint glass transition temperature (T _mg ) is obtained from the obtained DSC curve. it can.
Specifically, as shown in FIG. 1 and FIG. 2, the midpoint glass transition temperature (T _mg ) is the low temperature side and high temperature side baseline of the DSC curve (see FIG. 1 and FIG. 2) obtained by the above measurement. The temperature at the point where the straight line equidistant from the straight line extending in the direction of the vertical axis and the curve of the step-like change part of the glass transition intersect can be obtained.

Extrapolated glass transition start temperature (T _ig1 (° C.)) of the first polystyrene resin composition, intermediate glass transition temperature (T _mg1 (° C.)), and intermediate glass of the second polystyrene resin composition The transition temperature (T _mg2 (° C.)) is determined by carrying out the above measurement on a sample collected from a laminated foam sheet, a resin foam layer or a resin non-foam layer of a resin molded product.

  The laminated foam sheet exhibits excellent formability even in thermoforming at a relatively low temperature because the extrapolated glass transition start temperature and the midpoint glass transition temperature satisfy the above-mentioned regulations (1) to (3). Moreover, deformation at high temperatures is difficult to occur. In addition, the resin molded product (food storage container) obtained by thermoforming the laminated foamed sheet also satisfies the provisions of (1) to (3), so that thermal deformation hardly occurs.

From the viewpoints of moldability in thermoforming at low temperatures and prevention of deformation at high temperature storage, the extrapolated glass transition start temperature (T _ig1 ) of the first polystyrene resin composition is preferably 91 ° C. or higher and 98 ° C. or lower. More preferably, the temperature is 92 ° C. or higher and 97 ° C. or lower.
The midpoint glass transition temperature (T _mg1 ) of the first polystyrene-based resin composition is preferably 96 ° C. or higher and _lower than 102 ° C., and more preferably 97 ° C. or higher and 100 ° C. or lower.
Furthermore, the difference (T _mg1 -T _mg2 ) between the midpoint glass transition temperature (T _mg1 ) of the first polystyrene resin composition and the midpoint glass transition temperature (T _mg2 ) of the second polystyrene resin composition is The temperature is preferably -4 ° C or higher and 0 ° C or lower, and more preferably -3.5 ° C or higher and -1 ° C or lower.

The first polystyrene resin composition and the second polystyrene resin composition preferably contain 80% by mass or more of polystyrene resin, and more preferably contain 85% by mass or more.
By including 80% by mass or more of the polystyrene-based resin, excellent mechanical properties resulting from the polystyrene-based resin in the laminated foam sheet produced using these polystyrene-based resin compositions and resin molded products There is an advantage that the moldability is more easily exhibited.

The polystyrene resin is a polymer having a styrene monomer as a constituent unit in the molecule, and usually has a styrene monomer as a main constituent unit.
Examples of the polystyrene resins include homopolymers of styrene monomers (polystyrene resins) and copolymers of styrene and other monomers.
Examples of such a copolymer include a styrene-acrylic acid ester copolymer, a styrene-vinyl chloride copolymer, a styrene-butadiene copolymer, and a styrene-butadiene-acrylonitrile copolymer.
Examples of the styrene-acrylic acid ester copolymer include a styrene-maleic anhydride copolymer, a styrene-acrylic acid copolymer, a styrene-methyl acrylate copolymer, a styrene-ethyl acrylate copolymer, and a styrene-acrylic copolymer. Examples include butyl acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, and styrene-butyl methacrylate copolymer.
In addition, as such a copolymer, in order to more effectively exhibit excellent mechanical properties and moldability derived from a styrene polymer in a laminated foam sheet, the styrene monomer is 60% by mass or more and the other monomer is 40% by mass or less. These copolymers are preferred.

  The first polystyrene resin composition and the second polystyrene resin composition have a mass ratio of styrene units in the resin of 60% or more when the mass of all the resins contained is 100%. It is preferable.

  The polystyrene-based resin preferably has a mass average molecular weight of 240,000 or more, and preferably 400,000 or less.

The mass average molecular weight means those conventionally defined in the field of polymer chemistry, and is determined by the following molecular weight measurement.
Specifically, the mass average molecular weight is determined by gel permeation chromatography (GPC).
More specifically, the polystyrene-based resin has a mass average molecular weight of about 30 mg of a sample dissolved in 10 mL of chloroform, filtered through a non-aqueous 0.45 μm chromatographic disk, and then subjected to polystyrene using Waters HPLC (Detector 484, Pump 510). It can be determined by measuring the converted molecular weight.
Regarding the measurement conditions, two columns “Shodex GPC K-806L (φ8.0 × 300 mm)” (manufactured by Showa Denko) were used, the column temperature was 40 ° C., the mobile phase was chloroform, and the mobile phase flow rate was 1. The injection pump temperature can be room temperature, the detection wavelength can be 254 nm, and the injection volume can be 50 μL.
Standard polystyrene for preparing a calibration curve has a molecular weight of 1,030,000 from Showa Denko KK, and molecular weights of 5,480,000, 3,840,000, 355,000, 102,000, manufactured by Tosoh Corporation. 37,000, 9,100, 2,630, and 495.

In the laminated foam sheet of this embodiment, it is preferable that the 1st polystyrene type resin composition which comprises a resin foam layer contains acrylic acid ester.
The first polystyrene-based resin composition may contain an acrylate ester in a state such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, or the like.
The first polystyrene resin composition preferably contains an acrylic ester as a copolymer unit, and preferably contains a polystyrene resin and a styrene-acrylic ester copolymer resin.
The first polystyrene resin composition preferably has an absorbance ratio D1728 / D1600 of 0.2 or more and 0.9 or less obtained by performing infrared spectroscopic analysis by ATR method on the resin foam layer.

  When the absorbance ratio is less than 0.2, the laminated foam sheet may not exhibit sufficiently good low-temperature formability. When the absorbance ratio is larger than 0.9, it may not be possible to sufficiently prevent the laminated foam sheet or the resin molded product from being deformed at a high temperature. On the other hand, when the absorbance ratio is 0.2 to 0.9, the low-temperature moldability is excellent, and the low-temperature moldability and the suppression of the container dimensional change during high-temperature storage can be compatible at a higher level. Considering this point, a more preferable absorbance ratio is in the range of 0.2 to 0.8, a more preferable absorbance ratio is in the range of 0.3 to 0.7, and a most preferable absorbance ratio is in the range of 0.4 to The range is 0.6.

Absorbance ratio D1728 / D1600 is infrared in the absorption spectrum as measured by infrared spectroscopic analysis by ATR method, it means the ratio of the absorbance at 1728 cm ^-1 to the absorbance at 1600 cm ^-1. Here, the absorption at 1728 cm ⁻¹ shows a peak derived from stretching vibration between C═O of the ester group contained in the acrylate ester. The absorption at 1600 cm ⁻¹ indicates the presence of a peak derived from the in-plane vibration of the benzene ring contained in the polystyrene resin.

Here, the infrared spectroscopic analysis is an analysis method for measuring an infrared absorption spectrum by a single reflection type ATR method using total reflection absorption (Attenuated Total Reflectance). This analysis method is a method in which an ATR prism having a high refractive index is brought into close contact with a sample, infrared light is irradiated to the sample through the ATR prism, and light emitted from the ATR prism is spectrally analyzed.
ATR infrared spectroscopic analysis includes organic materials such as polymer materials because of the simplicity of being able to measure the spectrum simply by bringing the sample and the ATR prism into close contact with each other, and the ability to perform surface analysis up to a depth of several μm. It is widely used for surface analysis of various substances.

The resin foam layer of this embodiment is a kneaded product obtained by melt-kneading a first polystyrene resin composition containing a polystyrene resin, which is a styrene homopolymer resin, and a styrene-acrylate copolymer resin. The foamed sheet is preferably formed of a foamed sheet, and the content of the acrylic ester in the styrene-acrylic ester copolymer is preferably 1% by mass or more and less than 15% by mass. When the content of the acrylic ester is less than 1% by mass, excellent low-temperature formability tends not to be exhibited. When the acrylic ester content is 15% by mass or more, the dispersion state of the polystyrene resin and melt-kneaded styrene-acrylic ester copolymer may be deteriorated, resulting in poor appearance on the surface of the foam sheet. This is not preferable because the thermal stability of the resin molded product is lowered. The resin foam layer is obtained by extrusion foaming a resin composition in which a polystyrene resin and a styrene-acrylic acid ester copolymer resin are melt-kneaded, so that the intermediate glass transition temperature is more reliably 95 ° C. or higher. It becomes possible to make it less than 102 degreeC. Moreover, it becomes possible for the resin foam layer to more reliably set the extrapolated glass transition start temperature to 90 ° C. or more and less than 100 ° C. when the acrylic ester content is within the above range.
Moreover, it is more preferable that the content of the acrylate ester in the styrene-acrylate copolymer is 3% by mass or more and less than 12% by mass in terms of further suppressing changes in the container dimensions during high-temperature storage. More preferably, it is 5 mass% or more and less than 8 mass%.
The content of the acrylic ester in the styrene-acrylic ester copolymer can be determined by the following calibration curve formula from the absorbance ratio determined by the method of measuring the absorbance ratio of styrene-acrylic ester described later.

Y = 5.737X-0.692

Y: Acrylic acid ester content (% by mass)
X: Absorbance ratio of styrene-acrylate

The calibration curve here is such that the mass ratio of styrene monomer / butyl acrylate monomer is 99/1, 97/3, 95/5, 93/7, 90/10, 85/15, 80/20. The styrene-butyl acrylate copolymer resin obtained by the above-described adjustment and suspension polymerization can be prepared from the absorbance ratio determined by the method for measuring the absorbance ratio of styrene-acrylate ester described below.

In the case where the resin foam layer of the laminated foam sheet of the present embodiment is formed by a foam sheet obtained by an extrusion method, the styrene-acrylic acid ester system is easy in that it is easy to form a dense foam state in the resin foam layer. The copolymer resin preferably exhibits strain hardening.
In addition, since the styrene-acrylic acid ester copolymer resin exhibits strain-hardening properties, the first polystyrene-based resin composition constituting the resin foam layer exhibits strain-hardening properties. This is advantageous for good moldability.

  As the styrene-acrylic acid ester copolymer resin exhibiting strain hardening, a styrene-acrylic acid ester copolymer resin having a plurality of branched structures in the molecule (hereinafter referred to as “multi-branched styrene-acrylic acid ester copolymer”). Also referred to as “union resin”).

In the laminated foam sheet of the present embodiment, the mass ratio (polystyrene resin / styrene-acrylate copolymer resin) between the polystyrene resin and the styrene-acrylate copolymer resin in the first polystyrene-based resin composition is It is preferable that it is 30 / 70-70 / 30.
The mass ratio of the polystyrene resin and the styrene-acrylic acid ester copolymer resin in the first polystyrene-based resin composition in that the laminated foamed sheet is further excellent in low-temperature moldability and high-temperature deformation suppression. 60/40 to 30/70 is more preferable.

On the other hand, even if the second polystyrene resin composition constituting the resin non-foamed layer of the laminated foam sheet contains the styrene-acrylate copolymer resin as described above, the styrene-acrylate copolymer It does not need to contain a coalesced resin.
The second polystyrene resin composition preferably has a styrene-acrylic acid ester copolymer resin content (mass ratio) lower than that of the first polystyrene resin composition, and is substantially styrene. -It is preferable not to contain acrylic ester copolymer resin.
Therefore, the second polystyrene resin composition preferably has an absorbance ratio D1728 / D1600 lower than the first polystyrene resin composition, and more preferably the absorbance ratio is less than 0.2. It is particularly preferable that the absorbance ratio is 0.1 or less.

The second polystyrene resin composition preferably contains butadiene, and preferably contains an impact-resistant polystyrene resin (HIPS) that is a copolymer of styrene and butadiene.
The second polystyrene-based resin composition preferably contains a polystyrene resin (GPPS) and an impact-resistant polystyrene resin.
The mass ratio (GPPS / HIPS) of polystyrene resin (GPPS) and impact-resistant polystyrene resin (HIPS) in the second polystyrene-based resin composition is preferably 40/60 to 0/100.

The resin non-foamed layer of the laminated foamed sheet of the present embodiment preferably has a microphase separation structure derived from polybutadiene contained in the impact-resistant polystyrene resin in order to exhibit excellent strength.
That is, the resin non-foamed layer preferably has a microphase separation structure in which domains containing polybutadiene are dispersed in a matrix containing polystyrene resin.
Moreover, it is preferable that the said domain contains the polystyrene resin particle smaller than the said particle | grain in the particle | grains containing polybutadiene, and it is preferable to have a salami structure.

In order to exhibit excellent strength to the resin molded product, it is preferable that the resin non-foamed layer has rubber particles dispersed in an appropriate size.
Larger rubber particles are advantageous in terms of exerting a rubber-like texture in the resin non-foamed layer, but the larger the rubber particles, the easier it is to crack between the resin surrounding the rubber particles and the rubber particles are too small. However, impact resistance and piercing strength are reduced.
Therefore, in giving excellent impact resistance and toughness to the resin non-foamed layer, the average particle diameter of the rubber particles is preferably 0.3 μm or more, more preferably 0.35 μm or more, More preferably, it is 0.4 μm or more.
In imparting excellent tensile strength to the resin non-foamed layer, the particle size of the rubber particles is preferably 2.0 μm or less, more preferably 1.5 μm or less, and 1.0 μm or less. More preferably.

In a general laminated foamed sheet, rubber particles having a cross section when cut along the extrusion direction (MD cross section) and a cross section when cut along the direction orthogonal to the extrusion direction (TD cross section) There may be differences in the size of
Therefore, the average particle diameter of the rubber particles is determined for the MD cross section and the TD cross section, and the average particle diameter (DM _AVE ) of the rubber particles in the MD cross section and the average particle diameter (DT _AVE ) of the rubber particles in the TD cross section. Both measurement results can be obtained by further averaging ((DM _AVE + DT _AVE ) / 2).
Furthermore, when it is unclear which direction is the extrusion direction, the average particle diameter may be obtained in two cross sections orthogonal to each other, such as the MD cross section and the TD cross section, and these may be averaged.
In addition, the average particle diameter of the rubber particles of the resin non-foamed layer can be obtained as follows.

First, a slice is collected so that a cross section (MD cross section) when cut along the extrusion direction can be observed.
Thereafter, the cut section was embedded in an epoxy resin, and then the epoxy resin was cured at a temperature of 60 ° C. for 24 hours. Is used to prepare ultrathin sections (thickness, about 70 nm).
The cutting direction of the slice is the sheet thickness direction (VD), and the staining agent is osmium tetroxide.
Next, using a transmission electron microscope (TEM) (manufactured by Hitachi High-Technologies Corporation, model name “H-7600”, “ER-B” CCD camera system manufactured by AMT), the observation magnification so that the surface of the resin non-foamed layer is reflected. The photograph is taken at 2000 times.
A photograph taken under the above conditions is printed, and the length of the scale bar on the photograph is measured to 1/100 mm with “Digimatic Caliper” manufactured by Mitutoyo. From the measured value of the scale bar and the displayed value of the scale bar Obtain the average particle size of the rubber particles.
First, for each rubber particle, the maximum chord length of the rubber particle and the chord length orthogonal to each other through the midpoint of the maximum chord are calculated, and the average value is taken as the rubber particle diameter.
Next, the rubber particle diameter is measured for 200 rubber particles, and the average particle diameter of the rubber particles is determined from the average value of the 200 rubber particle diameters.
The measurement of the rubber particle diameter is performed on rubber particles having a maximum chord length of 0.2 μm or more.

More specifically, based on an actual TEM photograph, when obtaining the particle diameter of the rubber particle indicated by the block arrow A in FIG. 4, the length of the straight line among the straight lines connecting two different points on the contour line of the rubber particle is The longest two points a1 and a2 are determined, a straight line connecting the two points is set as the maximum chord, and the length is set as the maximum chord length (D1).
Then, an intermediate point a3 of these two points (a1, a2) is determined, and a distance D2 between the two points through which the straight line orthogonal to the maximum chord intersects the contour line of the rubber particle is determined. The average value ((D1 + D2) / 2) of the distance D2 and the maximum chord length D1 is defined as the particle diameter of the rubber particle indicated by the arrow A.
The average particle diameter in the MD cross section of the rubber particle diameter can be obtained by arithmetically averaging the results of carrying out such an operation on 200 rubber particles.
Moreover, the average particle diameter of the rubber particle diameter in the TD section can be obtained in the same manner as described above except that the section is collected so that the TD section can be observed.

Examples of the resin molded article that is preferably reinforced with rubber particles include a container for instant noodles (yakisoba) as shown in FIG.
The instant noodle container A has a rectangular tray shape, the outer side of the container is formed by the resin foam layer Ax, and the inner side of the container is formed by the resin non-foamed layer Ay.
In the instant noodle container A, an accommodation recess A0 is defined for the purpose of using the contents by a bottom wall portion A1 and a peripheral side wall portion A2 rising from the outer peripheral edge of the bottom wall portion A1.
In this type of instant noodle container A, the tip of a chopstick tip or fork collides with the inside of the container when used, and therefore the inside of the container is reinforced by a resin non-foamed layer Ay containing rubber particles.

The instant noodle container A of the present embodiment exhibits excellent piercing strength because rubber particles are dispersed in an appropriate size in the resin non-foamed layer.
The piercing strength is strength in a direction perpendicular to the resin non-foamed layer Ay, and is a value obtained as follows.
In the instant noodle container A, it is preferable that the rubber particles have the size as described above at least in the resin non-foamed layer Ay disposed on the inner surface side of the bottom wall portion.

(Puncture strength measurement method)
The puncture strength of a resin molded product such as a container is determined in accordance with a pinhole test prescribed in ASTM-D1164.
The piercing strength can be measured, for example, by cutting a strip-shaped test piece having a size of about 25 mm × 100 mm from the bottom wall portion or the peripheral wall portion of the container.
More specifically, using a compression tester (manufactured by A & D, model name “Tensilon RTC-1210A”), a test needle having a round bar shape with a diameter of 1 mm and a tip having a radius of curvature of 0.5 mm is used as a test speed of 50 mm Puncture under the condition of / min, and the maximum load observed until the needle penetrates the test piece is evaluated as the puncture strength.
The measurement is carried out at least 10 times in total to obtain the arithmetic average value.

  In order to more reliably exhibit the above-described strength with respect to the resin non-foamed layer, the second polystyrene-based resin composition forming the resin non-foamed layer has rubber particles of 2% by mass or more and 15% by mass. It is preferably contained in the following ratio, and more preferably in the ratio of 4% by mass or more and 10% by mass or less.

  The polystyrene resin or impact-resistant polystyrene resin contained in the second polystyrene-based resin composition is preferably a low oligomer content, generally referred to as a “low oligomer product”, specifically styrene. The total content of dimer and trimer is preferably 5000 ppm or less, and more preferably 2000 ppm or less.

In the laminated foam sheet formed using the above polystyrene-based resin composition, the thickness of the resin foam layer is 0.7 mm or more and 3.0 mm or less, and the thickness of the resin non-foam layer is 0.05 mm or more and 0.00. It is preferable that it is 3 mm or less.
The resin foam layer preferably has a basis weight of 150 g / m ² or more and 400 g / m ² or less.
In the present embodiment, the laminated foam sheet is exemplified by a resin foam layer provided with a resin non-foam layer only on one side of the resin foam layer. For example, a resin non-foam layer is provided on both sides of the resin foam layer. In the laminated foam sheet, it is preferable that each resin non-foamed layer has the above thickness.
In such a case, the first resin non-foamed layer provided on one side of the resin foam layer and the second resin non-foamed layer provided on the other side share the same thickness and forming material. These may be different.

The oligomer content (total content of styrene dimer and trimer) contained in the resin non-foamed layer of the laminated foamed sheet can be determined as follows.
<Measurement of oligomer content>
A sample of about 0.2 g is taken from the non-foamed resin layer laminated on one side of the laminated foamed sheet, dissolved in 10 mL of methyl ethyl ketone, dropped into 35 mL of methanol, re-precipitated, and stirred for about 1 hour.
Next, the reprecipitation liquid is No. Filter into a 50 mL volumetric flask with 5A filter paper and dissolve to 50 mL with methanol.
Next, 10 μL of internal standard solution pyrene (1000 ppm methanol solution) is put into a 2 mL volumetric flask, and the sample solution is prepared by dissolving in 2 mL with a methanol solution in a 50 mL volumetric flask.
Next, using this sample solution, GC / MS measurement is performed under the following conditions.
In the obtained chromatogram, the peak areas of 3 peaks of styrene dimer and 5 peaks of styrene trimer were quantified with a calibration curve of styrene oligomer prepared in advance as relative sensitivity to the peak area of pyrene as an internal standard substance. To do.
Calibration curves for dimers and trimers can be prepared using standard materials made by Kanto Chemical.

(GC / MS measurement conditions)
Apparatus: Gas chromatograph mass spectrometer QP2010SE (GC-17A) manufactured by Shimadzu Corporation
Column: ZB-5MS (Phenomenex, 0.25 μm × 0.25 mmφ × 30 m)
GC oven temperature rising condition: initial temperature 100 ° C. (1 minute)
First stage heating rate 10 ° C / min (holds -190 min to 190 ° C)
Second stage heating rate 10 ° C / min (holding -2.5 min to 300 ° C)
Inlet temperature: 300 ° C
Detector temperature: 260 ° C
Detector: 1.00 kV
Carrier gas: Helium Total flow rate: 52 mL / min Column flow rate: 1.0 mL / min Carrier gas pressure: 75 kPa
Test solution injection volume: 2 μL (using an autosampler)
Split ratio: 1/50

The thickness [mm] of the laminated foam sheet can be measured using a thickness gauge (for example, “Dial Thickness Gauge H” manufactured by Ozaki Seisakusho Co., Ltd.).
The basis weight [g / m ² ] of the laminated foamed sheet can be measured by cutting the laminated foamed sheet into 10 cm × 10 cm, measuring the mass [g] of this slice, and converting this mass to the mass per square meter.
The thickness (mm) of the resin foam layer is determined by removing the resin non-foamed layer from the boundary surface where the resin foam layer and the resin non-foamed layer of the laminated foam sheet are in contact with each other. (Ozaki Mfg. Co., Ltd.).
The basis weight [g / m ² ] of the resin foam layer is 10 cm after removing the resin non-foamed layer from the boundary surface where the resin foam layer and the resin non-foamed layer of the laminated foam sheet are in contact with each other. It cut | disconnects in * 10cm, the mass [g] of this section | slice is measured, and this mass can be converted into the mass per square meter, and can be measured.
The thickness (mm) of the resin non-foamed layer is determined by removing the resin foam layer from the boundary surface where the resin foam layer and the resin non-foam layer of the laminated foam sheet are in contact with each other. It can be measured using “H” (manufactured by Ozaki Seisakusho).
The basis weight [g / m ² ] of the resin non-foamed layer is determined by removing the resin foam layer from the boundary surface where the resin foam layer and the resin non-foam layer of the laminated foam sheet are in contact with each other. It can be cut into 10 cm × 10 cm, the mass [g] of this slice is measured, and this mass can be measured by converting it to the mass per square meter.
Alternatively, the thickness [mm] of the resin foam layer can also be measured by subtracting the thickness of the resin non-foamed layer from the thickness of the laminated foam sheet.
The basis weight [g / m ² ] of the resin foam layer can also be measured by subtracting the basis weight of the resin non-foamed layer from the basis weight of the laminated foam sheet.
The thickness [mm] of the resin non-foamed layer can also be measured by subtracting the thickness of the resin foamed layer from the thickness of the laminated foamed sheet.
The basis weight [g / m ² ] of the resin non-foamed layer can also be measured by subtracting the basis weight of the resin foam layer from the basis weight of the laminated foam sheet.

The laminated foam sheet of this embodiment is suitable as a forming material for a resin molded product having shapes such as a bag, a cup, and a tray, and is suitable as a forming material for a food container.
The resin molded product such as a food container is preferably a thermoformed product made of a laminated foam sheet.
That is, the resin molded product is preferably a product obtained by subjecting a laminated foamed sheet to thermoforming such as vacuum forming, pressure forming, vacuum pressure forming, match mold forming, press forming or the like.

  When the resin molded product is a food container, it is preferable that the resin non-foamed layer is disposed on the inner side of the container than the resin foam layer. And the total elution amount of trimmer) is preferably 500 ppb or less, more preferably 100 ppb or less, and even more preferably 50 ppb or less.

The oligomer elution amount (total elution amount of styrene dimer and trimer) can be determined as follows.
<Measurement of oligomer elution amount>
Using the obtained polystyrene-based resin laminated foam sheet, a food product having a rectangular shape with a length of 170 mm × width of 155 mm × depth of 50 mm, the outer surface of which is formed of a resin foam layer and the inner surface of which is formed of a resin non-foam layer. A storage container is prepared.
570 mL of distilled heptane is added to the test vessel as an elution solvent, and elution is performed at 25 ° C. for 1 hour.
Thereafter, 300 mL is taken from the elution solvent in the test container and concentrated to 1 mL at 50 ° C. using a fully automatic concentrator (product name: Turbobop 500, manufactured by ZY Mark).
The obtained concentrated solution is transferred to a 2 mL volumetric flask, 10 μL of pyrene (1000 ppm heptane solution) is added as an internal standard substance, and the volume is adjusted to 2 mL with n-heptane (measured up) to obtain a test solution.
In the obtained chromatogram, the peak areas of 3 peaks of styrene dimer and 5 peaks of styrene trimer were quantified with a calibration curve of styrene oligomer prepared in advance as relative sensitivity to the peak area of pyrene as an internal standard substance. To do.
Calibration curves for dimers and trimers can be prepared using standard materials made by Kanto Chemical.

(GC / MS measurement conditions)
Apparatus: Gas chromatograph mass spectrometer QP2010SE (GC-17A) manufactured by Shimadzu Corporation
Column: ZB-5MS (Phenomenex, 0.25 μm × 0.25 mmφ × 30 m)
GC oven temperature rising condition: initial temperature 100 ° C. (1 minute)
First stage heating rate 10 ° C / min (holds -190 min to 190 ° C)
Second stage heating rate 10 ° C / min (holding -2.5 min to 300 ° C)
Inlet temperature: 300 ° C
Detector temperature: 260 ° C
Detector: 1.00 kV
Carrier gas: Helium Total flow rate: 52 mL / min Column flow rate: 1.0 mL / min Carrier gas pressure: 75 kPa
Test solution injection volume: 2 μL (using an autosampler)
Split ratio: 1/50

In the laminated foam sheet of the present embodiment, since the first polystyrene resin composition and the second polystyrene resin composition approximate the value of the midpoint glass transition temperature, the deformation of the resin foam layer in thermoforming The behavior and the deformation behavior of the resin non-foamed layer can be approximated.
Therefore, the laminated foam sheet of the present embodiment can exhibit excellent followability with respect to the molding surface of the mold during thermoforming.
In addition, the laminated foam sheet may cause residual strain in the resin non-foamed layer or the resin foam layer during thermoforming, or shear fracture (interfacial separation) may occur between the resin non-foamed layer and the resin foamed layer. Low.
That is, the laminated foam sheet of this embodiment is suitable for efficiently producing a resin molded product that is excellent in appearance and mechanical properties and hardly causes problems such as thermal deformation.

The laminated foam sheet of the present embodiment is produced by a coextrusion method in which the first polystyrene resin composition and the second polystyrene resin composition are extruded into a sheet shape in a state where they overlap each other from a flat die or a circular die. obtain.
In addition, the laminated foam sheet of the present embodiment is prepared by extruding and foaming the first polystyrene resin composition to produce a foam sheet of a single resin foam layer, and then using a flat die on the surface of the foam sheet. It can be produced by a method (extrusion laminating method) in which the polystyrene-based resin composition is extruded into a sheet shape and laminated and integrated.
Further, in the laminated foam sheet of the present embodiment, a foamed sheet is produced with the first polystyrene resin composition and a resin film is produced with the second polystyrene resin composition, and then the foamed sheet and the resin film are laminated. Further, it can be produced by a method (thermal laminating method) in which these are integrated by passing through a heated nip roll.
Regardless of these, the laminated foam sheet of the present embodiment can be produced by various methods.

  In order to make the first polystyrene resin composition exhibit good extrusion foamability, the first polystyrene resin composition includes a foaming agent, a bubble adjusting agent, etc. in addition to the polystyrene resin as described above. Additives may be included.

  Examples of the foaming agent include volatile foaming agents and decomposable foaming agents.

Examples of the volatile blowing agent include hydrocarbons such as propane, butane, pentane, cyclopentadiene, and hexane, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol, and isopropyl alcohol, dimethyl ether, diethyl ether, and diene. Examples thereof include ether compounds such as propyl ether, methyl ethyl ether and petroleum ether.
Further, as the volatile foaming agent, carbon dioxide, nitrogen, ammonia, water and the like can be employed.
The volatile blowing agent is preferably a hydrocarbon having a boiling point at atmospheric pressure of −45 to 40 ° C., and preferably propane, butane, pentane and the like.
In addition, the said volatile foaming agent may be used individually by 1 type or in combination of 2 or more types.
Among them, the volatile foaming agent is preferably a butane mixture such as normal butane or isobutane, or a butane mixture in which normal butane and isobutane are mixed in an arbitrary ratio.

Examples of the decomposable foaming agent include organic decomposable foaming agents such as azodicarbonamide and dinitrosopentamethylenetetramine, an organic acid such as citric acid or a salt thereof, and a bicarbonate such as sodium bicarbonate. Inorganic decomposable foaming agents and the like.
The decomposable foaming agent can also be used alone or in combination of two or more.

  As the foaming agent, only one of the volatile foaming agent and the decomposable foaming agent may be used, or these may be used in combination.

  The said foaming agent can be normally used in the ratio of 1-10 mass parts, when the total amount of all the resins contained in a 1st polystyrene-type resin composition is 100 mass parts.

  Examples of the additive include a bubble adjusting agent such as talc, an inorganic filler, an organic pigment, a flame retardant, a flame retardant aid, a lubricant, and a plasticizer.

The resin foam layer preferably has an open cell ratio of 15% or less, more preferably 5 to 12%.
When the open cell ratio of the resin foam layer is 15% or less, the laminated foam sheet hardly changes in volume due to heating and has excellent strength.
Note that the open cell ratio can be measured by the 1-1 / 2-1 atmospheric pressure method in accordance with ASTM D-2856-87.

The foamed resin layer is preferably an apparent density of 0.05~0.57g / cm ^3, more preferably 0.1 to 0.3 g / cm ^3.
When the apparent density is 0.05 g / cm ³ or more, it is easy to make the laminated foamed sheet excellent in strength, and the resin molded product molded using the laminated foamed sheet can be made more excellent in preservative formation. .
Moreover, when an apparent density is 0.57 g / cm < ³ > or less, a laminated foam sheet becomes lighter and there exists an advantage that the bulkiness of a laminated foam sheet can be suppressed.

  The apparent density of the resin foam layer can be measured by the method described in JIS K7222: 1999 “Foamed Plastics and Rubber—Measurement of Apparent Density”.

The resin molded product obtained by thermoforming the laminated foam sheet of the present embodiment preferably has a heating dimensional change rate of less than 1.5% when heated at 60 ° C. for 24 hours, and in particular, as a food container. When used, it is preferable to have such a heating dimensional change rate (less than 1.5%). When the heating dimensional change rate is 1.5% or more, the amount of deformation increases when storing in the warehouse in the summer or when a high-temperature product of 60 ° C. or higher is put in the container. The sealing property at the time of sealing with a wrap film may fall. On the other hand, the food container, which is a resin molded product of the present embodiment, has a smaller rate of deformation during high-temperature storage due to a heating dimensional change rate of less than 1.5. Excellent sealing performance with film.
The heating dimensional change rate is calculated on the basis of the dimension of the container in the short direction in plan view. That is, the dimensions of the container before heating are, for example, dimensions in the direction in which the distance from one point on the contour line of the container in plan view to the opposite contour line through the center point of the contour shape is shortest (container (Distance between contour lines).
And after taking out the container for 24 hours in a hot air circulation dryer at 60 ° C., the dimensions of the same part after being left in a standard state (25 ° C., 1 atm) for 1 hour are the dimensions after heating, The heating dimensional change rate is obtained by the following formula.

S = | (L ₁ −L ₀ ) | / L ₀ × 100

S: heating dimensional change rate (%), L ₁ : average dimension after heating (mm), L ₀ : average dimension before heating

  In addition, the food container of the present embodiment having a small heating dimensional change rate can be suitably used as a container for instant noodles for storing instant noodles because deformation due to hot water supply into the container is also suppressed.

The laminated foam sheet and resin molded product of the present invention are not limited to the specific forms and applications exemplified above.
Moreover, in this invention, it is possible to employ | adopt the various form employ | adopted in a conventionally well-known laminated foam sheet and resin molded product in the range which the effect of this invention is not impaired remarkably.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to the following.

<Synthesis of Styrene-Acrylate Ester Copolymer Resin (Synthesis Example 1)>
As a polymerization initiator, 295 g of benzoyl peroxide (purity 75%, manufactured by NOF Corporation, trade name Nyper BW) and 268 g of t-butylperoxy-2-ethylhexyl monocarbonate (manufactured by NOF Corporation, trade name Perbutyl E) ) And prepared.
This polymerization initiator (total 563 g) was dissolved in a mixed monomer of 130.2 kg of styrene monomer and 9.8 kg of butyl acrylate monomer, and the autoclave with a stirrer having an internal volume of 500 liter (hereinafter also referred to as “reactor”). I put it in. Further, 802 g of magnesium pyrophosphate, 21 g of sodium dodecylbenzenesulfonate, and 268 kg of distilled water were added to the reactor, and then the mixed solution in the reactor was dissolved and dispersed with stirring at 47 rpm to form a suspension. .
Subsequently, the temperature in the autoclave was raised to 90 ° C. and then held at 90 ° C. for 9 hours.
Then, after stirring at 85 rpm, the temperature in the autoclave was further raised to 125 ° C., held at 125 ° C. for 3 hours, then the temperature in the autoclave was cooled to 40 ° C., and the polymerization slurry was taken out from the autoclave and dehydrated. By washing and drying, a styrene-butyl acrylate copolymer resin containing 7% of a butyl acrylate component was obtained.

<Production of foam sheet>
<Example 1>
A foam sheet was produced as follows.
90 parts by mass of polystyrene-based resin (A1) (polystyrene resin by DIC, trade name: “Dick Styrene XC-515”) and 10 mass of styrene-acrylate copolymer resin (A2) (resin of Synthesis Example 1) To 100 parts by mass of a mixed resin (X1) containing styrene, polystyrene blended with talc as a foam regulator (polystyrene resin: 60% by mass, talc content: 40% by mass) (trade name: “DSM1401A, manufactured by Toyo Styrene Co., Ltd.) ]) 0.6 parts by mass were dry blended to prepare a blended raw material (Y1).
Next, using a tandem extruder to which two extruders are connected (the upstream first extruder is a φ115 mm single screw extruder, and the downstream second extruder is a φ150 mm single screw extruder), and The blended material (Y1) was supplied to the hopper of the first extruder, and the blended material (Y1) was heated and melt-kneaded in the first extruder so that the maximum temperature setting was 230 ° C.
Further, butane gas (mixed butane gas of isobutane and normal butane) as a foaming agent was pressed into the first extruder so that the ratio with respect to 100 parts by mass of the mixed resin (X1) was 3.5 parts by mass, and the blended raw materials ( Melt kneading with Y1) was continued.
Subsequently, the temperature of the melt-kneaded product is lowered to 158 ° C. by a second extruder, and a foaming agent is applied from a circular die (caliber: φ175 mm, slit clearance: 0.5 mm) attached to the tip of the second extruder. The melt-kneaded material containing slag was extruded and foamed at a discharge rate of 200 kg / h to form a cylindrical foam, and then cooling air was sprayed on the inner side and the outer side of the foam, and then φ675 mm The outer peripheral surface of the cooling mandrel having a length of 800 mm is brought into sliding contact with the inner surface of the foam to cool the foam from the inside, and the two left and right portions of the cylindrical foam are extruded in the rear side of the cooling mandrel. The foam was divided into upper and lower parts to obtain two long strip foam sheets, each of which was wound into a roll.

<Production of laminated foam sheet>
<Example 1>
The foamed sheet was cured at room temperature (20 ° C. to 40 ° C.) for 21 days.
70 parts by mass of a rubber-modified polystyrene resin (A3) (rubber content 8%, midpoint glass transition temperature 101 ° C.) and 30 parts by mass of a polystyrene resin (A4) (PS Japan, polystyrene, trade name “G0002”) The mixed resin (X2) contained was heated and melt-kneaded in a φ90 mm single-screw extruder under conditions where the resin temperature was 240 ° C.
This melt-kneaded product was extruded from a T-die and laminated on one side of a foamed sheet, and provided with a resin non-foamed layer having a thickness of 133 μm (basis weight 140 g / m ² ) and a resin foamed layer made of the foamed sheet. A laminated foam sheet was produced.
The state of rubber particles in the resin non-foamed layer of the laminated foamed sheet collected from the bottom wall portion of the food container described later, and the state of rubber particles in the resin non-foamed layer in the laminated foamed sheet before molding are transmissive. Observed with an electron microscope.
Photographs taken with a transmission electron microscope are shown in FIG. 4 (container) and FIG. 5 (laminated foam sheet), respectively.

<Molding evaluation>
Next, the laminated foamed sheet was thermoformed to produce a container for containing food.
This thermoforming was performed so that the resin non-foamed layer was inside the container.
That is, the prepared food container was one having an outer surface formed of a resin foam layer and an inner surface formed of a resin non-foam layer.
The container had a rectangular shape with a length of 170 mm × width of 155 mm × depth of 50 mm.
For thermoforming, a press molding apparatus having a cavity (concave) having a recess corresponding to the outer shape of the container and a plug having a recess corresponding to the inner shape of the container (convex) was used.
The thermoforming was performed with the set temperature of the heater on the cavity side being 250 ° C and the set temperature of the heater on the plug side being 330 ° C.
The molding timing is set so that the cavity and the plug almost simultaneously contact the laminated foam sheet to start molding, and the thickness of the foam sheet before thermoforming is 4.3 mm ± 0.2 mm. The heating time was adjusted appropriately.
The obtained container was evaluated visually and by heating seconds, and the high cycle moldability was determined according to the following criteria.
○: No cracks or wrinkles were observed, and the heating time was 10 to 12 seconds (good).
Δ: No cracks or wrinkles were observed, but the heating time was 13 to 14 seconds (somewhat good).
X: Cracks or wrinkles were observed in a part of the container, or the heating time was 15 seconds or more (defect).

<Evaluation of hot water supply deformation>
Boiling hot water (100 ° C., 600 cc) was poured into the rectangular container obtained as described above, covered with a polycarbonate resin plate (thickness: 2 mm, dimensions: 200 mm × 200 mm), and held for 5 minutes.
After throwing out the hot water in the container, leave it at 23 ° C for 1 hour with the container opening facing up, and then place it on a table with a horizontal top so that the container opening faces down. The gap between the table and the table was measured with calipers on four sides, and the maximum value was shown as the flange floating height.
Hot water deformation resistance was evaluated according to the following criteria.
A: The flange floating height was less than 1.0 mm (excellent).
○: The flange floating height was 1.0 mm or more and 2.0 mm or less (good).
(Triangle | delta): The flange floating height exceeded 2.0 mm and was less than 3.0 mm (slightly favorable).
X: The flange floating height was 3.0 mm or more (defect).

<Container puncture strength>
The puncture strength was measured according to the pinhole test specified in ASTM-D1164 (n = 10).
The test piece was collected from the bottom wall, and the needle piercing direction was outward from the inside of the container.

<Comprehensive judgment>
Based on the evaluation results of molding evaluation and hot water supply deformation evaluation, comprehensive evaluation was performed according to the following evaluation criteria.
Comprehensive evaluation criteria A: Two evaluation results had 2 or more (very good).
○: The two evaluation results had no x and one Δ (good).
X: There was one x in the two evaluation results (defective).

<Measurement method of styrene-acrylic ester absorbance ratio>
The absorbance ratio of styrene and acrylate was measured by the following method.
Specifically, an infrared absorption spectrum was obtained only for the surface of the foamed sheet cut into 3 cm × 3 cm by a single reflection ATR method using the following measuring apparatus and measurement conditions.
Measurement apparatus: Fourier transform infrared spectrophotometer Nicolet iS10 (manufactured by Thermo SSCIENTIFIC) and single reflection type horizontal ATR Smart-iTR (manufactured by Thermo SSCIENTIFIC)
-ATR crystal: Diamond affixed KRS-5 (angle = 45 °)
・ Measuring method: One-time ATR method ・ Measured wave number region: 4000 cm ^{−1 to} 400 cm ⁻¹
-Wavenumber dependence of measurement depth: No correction-Detector: Deuterated triglycine sulfate (DTGS) detector and KBr beam splitter-Resolution: 4 cm ^-1
・ Number of integration: 16 times (same for background measurement)

The absorbance ratio of styrene and acrylate ester = D1728 / D1600 was determined from the obtained infrared absorption spectrum.
D1728 is an infrared absorption spectrum and the lowest absorption position of wave number 1770 cm ^-1 ± ^{5 cm -1} in the curve, infrared lowest absorption position and the baseline a line connecting the wavenumber 1515cm ^-1 ± ^{5cm -1} in the absorption spectrum curve The maximum absorbance (absorbance at wave number 1728 cm ⁻¹ ) of the absorbance difference between the infrared absorption spectrum curve in the region of wave number 1728 cm ⁻¹ ± 5 cm ⁻¹ and the baseline (measured absorbance−absorbance at baseline) D1728).
Further, the D1600, a straight line connecting the lowest absorption position of wave number 1770 cm ^-1 ± ^{5 cm -1} in the infrared absorption spectrum curve, and a minimum absorption position in wavenumber 1515cm ^-1 ± ^{5cm -1} in the infrared absorption spectrum curve Is the maximum value of the difference in absorbance between the infrared absorption spectrum curve in the region of wave number 1600 cm ⁻¹ ± 5 cm ⁻¹ and the baseline (measured absorbance−absorbance of the baseline) at a wave number of 1600 cm ⁻¹ . Absorbance D1600).
In addition, the obtained styrene and acrylate absorbance ratio is a value only for polystyrene.

<Example 2>
70 parts by mass of polystyrene-based resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC-515”), and 30 of styrene-acrylate copolymer resin (A2) (resin of Synthesis Example 1) A foamed sheet, a laminated foamed sheet, and a resin molded product were prepared in the same manner as in Example 1 except that parts by mass were used, and evaluation was performed in the same manner as in Example 1.

<Example 3>
60 parts by mass of polystyrene resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC-515”) and 40 of styrene-acrylate copolymer resin (A2) (resin of Synthesis Example 1) Except that the mass part was used and the temperature of the melt-kneaded product of the resin composition was lowered to 156 ° C. in the second extruder after the melt-kneading of the mixture and the foaming agent in the first extruder, A foamed sheet, a laminated foamed sheet, and a resin molded product were produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1.

<Example 4>
50 parts by mass of polystyrene-based resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC-515”), and 50 of styrene-acrylate copolymer resin (A2) (resin of Synthesis Example 1) Except that the mass part was used and the temperature of the melt-kneaded product of the resin composition was lowered to 155 ° C. by the second extruder after the melt-kneading of the mixture and the foaming agent in the first extruder, A foamed sheet, a laminated foamed sheet, and a resin molded product were produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1.

<Example 5>
Instead of rubber-modified polystyrene resin (A3) (rubber content 8%, midpoint glass transition temperature 101 ° C), another rubber-modified polystyrene resin (A5) (rubber content 6%, midpoint glass transition temperature 101 ° C) was used. A laminated foam sheet and a resin molded product were produced in the same manner as in Example 2 except that they were used, and evaluated in the same manner as in Example 1.
In addition, the microscope picture which showed the mode of the rubber particle of rubber-modified polystyrene-type resin (A5) is shown in FIG.

<Example 6>
Instead of the rubber-modified polystyrene resin (A3) (rubber content 8%, midpoint glass transition temperature 101 ° C), another rubber-modified polystyrene resin (A6) (rubber content 6%, midpoint glass transition temperature 96 ° C) is used. A laminated foam sheet and a resin molded product were produced in the same manner as in Example 2 except that they were used, and evaluated in the same manner as in Example 1.
In addition, the microscope picture which showed the mode of the rubber particle of rubber-modified polystyrene-type resin (A6) is shown in FIG.

<Example 7>
Instead of rubber-modified polystyrene resin (A3) (rubber content 8%, midpoint glass transition temperature 101 ° C.), another rubber-modified polystyrene resin (A7) (rubber content 13%, midpoint glass transition temperature 98 ° C.) A laminated foam sheet and a resin molded product were produced in the same manner as in Example 2 except that they were used, and evaluated in the same manner as in Example 1.
In addition, the microscope picture which showed the mode of the rubber particle of rubber modified polystyrene resin (A7) is shown in FIG.

<Comparative Example 1>
30 parts by mass of polystyrene resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC-515”), and 70 of styrene-acrylate copolymer resin (A2) (resin of Synthesis Example 1) Except that the mass part was used, and after the melt kneading of the mixture and the foaming agent in the first extruder, the temperature of the melt kneaded product of the resin composition was lowered to 154 ° C. in the second extruder, A foamed sheet, a laminated foamed sheet, and a resin molded product were produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1.

<Comparative example 2>
95 parts by mass of polystyrene resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC-515”) and 5 parts of styrene-acrylate copolymer resin (A2) (resin of Synthesis Example 1) A foamed sheet, a laminated foamed sheet, and a resin molded product were prepared in the same manner as in Example 1 except that parts by mass were used, and evaluation was performed in the same manner as in Example 1.

<Comparative Example 3>
Using the foamed sheet produced in Example 3, 30 parts by mass of rubber-modified polystyrene resin (A3) and polystyrene resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC” -515 ") was made 70 parts by mass, and a laminated foamed sheet and a resin molded product were produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1.

<Comparative Example 4>
After 100 parts by mass of polystyrene resin (A1) (polystyrene resin manufactured by DIC, trade name: “Dick Styrene XC-515”) and after melt-kneading the mixture and foaming agent in the first extruder, Except that the temperature of the melt-kneaded product of the resin composition was lowered to 159 ° C. in the second extruder, a foamed sheet, a laminated foamed sheet, and a resin molded product were produced and carried out in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1.
The results are shown in Table 1.

<Comparative Example 5>
A resin molded product was prepared in the same manner as in Comparative Example 3 except that the molding time at the time of container preparation was changed, and evaluation was performed in the same manner as in Example 1.

<Comparative Example 6>
Instead of the rubber-modified polystyrene resin (A3) (rubber content 8%, midpoint glass transition temperature 101 ° C), another rubber-modified polystyrene resin (A6) (rubber content 6%, midpoint glass transition temperature 96 ° C) is used. A laminated foamed sheet and a resin molded product were produced in the same manner as in Example 1 except that they were used, and evaluated in the same manner as in Example 1.

  From the above results, according to the present invention, a laminated foamed sheet useful for the formation of a resin molded product that can be satisfactorily thermoformed at a relatively low temperature and is not easily deformed at a high temperature, and a resin excellent in production efficiency. It turns out that a molded article is obtained.

Claims (12)

A resin foam layer formed of the first polystyrene resin composition;
A resin non-foamed layer formed of a second polystyrene-based resin composition,
A laminated foam sheet in which the resin non-foamed layer is laminated on at least one surface of the resin foam layer,
The extrapolated glass transition start temperature of the first polystyrene resin composition obtained by DSC measurement is “T _ig1 (° C.)”, the midpoint glass transition temperature is “T _mg1 (° C.)”, and the second polystyrene resin A laminated foam sheet satisfying all of the following (1) to (3) when the intermediate point glass transition temperature of the composition is “T _mg2 (° C.)”.

90 ° C. ≦ T _ig1 <100 ° C. (1)
95 ° C. ≦ T _mg1 <102 ° C. (2)
−5 ≦ (T _mg1 −T _mg2 ) <2 ° C. (3) The laminated foam sheet according to claim 1, further satisfying the following (4).

98 ° C. ≦ T _mg2 (4)
  The first polystyrene resin composition contains an acrylate ester, and an absorbance ratio D1728 / D1600 obtained by infrared spectroscopic analysis by an ATR method is 0.2 or more and 0.9 or less. Laminated foam sheet.   The laminated foam sheet according to any one of claims 1 to 3, wherein the first polystyrene-based resin composition includes a polystyrene resin and a styrene-acrylate copolymer resin. The resin foam layer has a thickness of 0.7 mm or more and 3.0 mm or less, and a basis weight of 150 g / m ² or more and 400 g / m ² or less,
The laminated foam sheet according to any one of claims 1 to 4, wherein the resin non-foamed layer has a thickness of 0.05 mm or more and 0.3 mm or less.   The laminated foam sheet according to any one of claims 1 to 5, wherein the resin non-foamed layer includes rubber particles, and the rubber particles have an average particle size of 0.3 µm to 2.0 µm. It is a thermoformed product made of a laminated foam sheet,
The laminated foam sheet is
A resin foam layer formed of the first polystyrene resin composition;
A resin non-foamed layer formed of a second polystyrene-based resin composition,
The resin non-foamed layer is laminated on at least one side of the resin foam layer,
and,
The extrapolated glass transition start temperature of the first polystyrene resin composition obtained by DSC measurement is “T _ig1 (° C.)”, the midpoint glass transition temperature is “T _mg1 (° C.)”, and the second polystyrene resin A resin molded product that satisfies all of the following (1) to (3) when the intermediate point glass transition temperature of the composition is “T _mg2 (° C.)”.

90 ° C. ≦ T _ig1 <100 ° C. (1)
95 ° C. ≦ T _mg1 <102 ° C. (2)
−5 ≦ (T _mg1 −T _mg2 ) <2 ° C. (3)
The laminated foam sheet is
The resin molded product according to claim 7, further satisfying the following (4).

98 ° C. ≦ T _mg2 (4)
  The first polystyrene resin composition contains an acrylate ester, and an absorbance ratio D1728 / D1600 obtained by infrared spectroscopic analysis by an ATR method is 0.2 or more and 0.9 or less. Resin molded products.   The resin molded product according to any one of claims 7 to 9, wherein the first polystyrene-based resin composition includes a polystyrene resin and a styrene-acrylate copolymer resin.   The resin molded product according to any one of claims 7 to 10, which is a container for food storage, wherein the resin non-foamed layer of the laminated foamed sheet is disposed on the inner side of the container than the resin foamed layer.   The container for containing food has a bottom wall portion, and the resin non-foamed layer disposed inside the container in the bottom wall portion includes rubber particles, and the average particle diameter of the rubber particles is 0.3 μm or more 2 The resin molded product according to claim 11, which is 0.0 μm or less.