JP2016036946A - Polystyrenic resin foam body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel polystyrenic resin foam body having beautiful strip-like pattern by colored resin laminated with stripe-like, having no risk of detachment and dropout of the colored resin and of which manufacturing is simple and inexpensive.SOLUTION: There is provided a polystyrene resin foam body where a colored resin 3 containing a polystyrene resin and a coloring agent is laminated with strip-like on at least single face of a polystyrene resin foam layer 2, the colored resin contains further at least one kind of polyethylene resin selected from linear low density polyethylene, branched low density polyethylene, ultra low density polyethylene and high density polyethylene, and the content of the polyethylene resin in the colored resin is 4 to 40 wt.%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a novel polystyrene-based resin foam having a streak pattern such as wood grain on the surface.

  Since a polystyrene resin foam, for example, a thin polystyrene resin foam (sheet-like foam) having a thickness of about 0.5 to 3 mm is excellent in light weight and heat insulation, it is also excellent in thermoformability. It is widely used as a foam sheet for thermoforming for processing food distribution packaging materials such as tray containers, instant noodle containers, lunch boxes, and natto containers.

  Moreover, since a plate-like polystyrene resin foam (plate-like foam) having a thickness of 3 to 10 mm is excellent in lightness, heat insulation, rigidity, etc., raw materials such as lunch boxes, confectionery boxes and folding boxes are used. It is widely used as a signboard.

  Furthermore, foams having a streak pattern on the surface are excellent in design and have a high-class feeling, so that there is a high consumer need and is currently produced in large quantities.

  Conventionally, as such a foam, for example, the following (1) to (3) are known.

(1) A pattern printed directly on the surface of a polystyrene resin foam (Patent Document 1).
(2) A film on which a pattern is printed is laminated on the surface of a polystyrene resin foam with an adhesive or the like (Patent Document 2).
(3) The polystyrene resin foam layer B colored on the surface of the polystyrene resin foam A is laminated in a streak shape or a strip shape by a coextrusion method (Patent Document 3).

JP 2007-7966 A Japanese Patent Laid-Open No. 5-38752 JP 2003-94896 A

  However, as in (1), the pattern directly printed on the surface of the foam has a problem in that its use is limited because the printed surface may be in direct contact with the package.

  In addition, since the manufacturing requires two steps, a foam manufacturing process and a pattern printing process, the manufacturing process becomes complicated and the manufacturing cost is high.

  In addition, as in (2), a film with a pattern printed on the surface of a foam is laminated with an adhesive, and the film is laminated with the printed surface facing the foam. Although there was no contact with the product, there was room for further improvement, such as recycling becoming difficult.

  In addition, the manufacturing process requires a foam manufacturing process, a film manufacturing process, a pattern printing process on the film, and a process in which the foam and the pattern-printed film are bonded together. And problems in terms of manufacturing costs.

  In addition, a structure in which the foamed layer colored on the outer peripheral surface of the foam core layer is coextruded in a streak shape or a strip shape as in (3) is a structure in which the colored foam layer is laminated on the foam core layer Then, since the surface has irregularities, there is a possibility that a part of the colored foam layer may be peeled off when rubbed strongly, and its use may be limited.

  As described above, each of the conventional polystyrene resin foams such as sheet-like foams having a streak pattern has major problems and problems to be solved. Development of a practical polystyrene-based resin foam in which dropout is suppressed has been eagerly desired, but no satisfactory proposal has been made yet.

  The present invention has been made in view of the circumstances as described above, and has a beautiful streak pattern made of colored resin laminated in a streak shape, and there is no fear of detachment of the colored resin or dropping of the colorant. Furthermore, another object of the present invention is to provide a novel polystyrene resin foam that is simple and inexpensive to produce.

  According to this invention, the polystyrene-type resin foam as described in the following <1> to <6> is provided.

<1> A polystyrene-based resin foam in which a colored resin containing a polystyrene-based resin and a colorant is layered on at least one surface of a polystyrene-based resin foam layer,
The colored resin further includes at least one polyethylene-based resin selected from linear low-density polyethylene, branched low-density polyethylene, ultra-low-density polyethylene, and high-density polyethylene,
A polystyrene-based resin foam, wherein the content of the polyethylene-based resin in the colored resin is 4 to 40% by weight.
<2> The polystyrene resin foam according to <1>, wherein the density of the polyethylene resin is 0.94 g / cm ³ or less.
<3> The ratio (η2 / η1) of the melt viscosity (η2) of the polyethylene resin to the melt viscosity (η1) of the polystyrene resin in the colored resin is 0.5 to 1.5. <1> or a polystyrene resin foam according to <2>.
<4> The polystyrene resin foam according to any one of <1> to <3>, wherein the polyethylene resin is a linear low density polyethylene.
<5> The polystyrene type according to any one of <1> to <4>, wherein a lamination amount of the colored resin is in a range of 3 to 50 g / m ² per one side of the polystyrene resin foam. Resin foam.
<6> Any one of <1> to <5>, wherein the polystyrene resin foam has an apparent density of 0.04 to 0.35 g / cm ³ and a thickness of 0.5 to 10 mm. The polystyrene resin foam described in 1.

  The polystyrene resin foam of the present invention has a streak pattern of colored resin laminated in a streak pattern on at least one side of the foamed layer, and the colored resin can be peeled off even under severe friction conditions. Dropping is prevented and suppressed, and the moldability is also good.

  Further, unlike the conventional product, the manufacturing process is very simple, and the manufacturing cost can be greatly reduced.

  Accordingly, the polystyrene resin foam of the present invention is used as a sheet (sheet-like foam) for thermoforming, such as tray containers, instant noodle containers, lunch boxes, food distribution packaging materials such as natto containers and rice cakes, or lunch boxes. Demand is widely expected as raw materials (plate-like foam) such as candy boxes and confectionery boxes.

It is explanatory drawing of the typical polystyrene-type resin foam of this invention. It is a schematic sectional drawing of the polystyrene-type resin foam of this invention. It is explanatory drawing of the manufacturing method of the typical polystyrene-type resin foam of this invention. It is the schematic of the die | dye for manufacture of the typical polystyrene-type resin foam of this invention.

<Polystyrene resin foam>
1 and 2 are schematic sectional views in the thickness direction of a typical polystyrene resin foam 1 (hereinafter simply referred to as foam 1) according to the present invention.

  The foam 1 is a colored resin including a polystyrene resin foam layer 2 (hereinafter simply referred to as a foam layer 2) and a polystyrene resin and a colorant laminated in a streak pattern on at least one surface of the foam layer 2. 3 (hereinafter simply referred to as colored resin 3).

  Here, the streaks in the present invention means, for example, a linear shape having a certain width or changing width along the longitudinal direction (extrusion direction) of the foam as shown in FIG. However, due to the difference in hue and color tone between the foam layer and the colored resin layered in the foam layer, for example, a wood grain pattern or a stripe pattern is given to the foam.

<Foaming layer 2>
The foamed layer 2 can be formed by foaming a foamed layer-forming melt containing a polystyrene-based resin, a physical foaming agent, and, if necessary, a cell regulator and other additives. Below, each component of the material used in order to form the foaming layer 2 is explained in full detail.

(Polystyrene resin)
The polystyrene resin can be used without particular limitation as long as it is a polystyrene resin usually used for a polystyrene foam. For example, polystyrene (GPPS), high impact polystyrene (HIPS), styrene-acrylonitrile copolymer. Styrene-acrylic acid copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Examples thereof include a polymer, a styrene-maleic anhydride copolymer, a styrene-α-methylstyrene copolymer, a polystyrene-polyphenylene ether copolymer, and a mixture thereof.

  In the present invention, in addition to the polystyrene resin, the foam layer may be made of a propylene homopolymer, a polypropylene resin such as an ethylene-propylene copolymer, a high density polyethylene, a low density polyethylene, or the like, depending on the desired purpose. Polymers such as polyethylene resins, thermoplastic elastomers such as styrene-conjugated diene block copolymers and hydrogenated products thereof, and rubbers such as ethylene-propylene rubber and butadiene rubber can be blended. The ratio is preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and still more preferably 10 parts by weight or less with respect to 100 parts by weight of the polystyrene-based resin. Moreover, when high heat resistance is requested | required, what contains polyphenylene ether-type resin as a polystyrene-type resin can be used, The ratio is 5-100 weight part with respect to 100 weight part of polystyrene-type resin. It is preferable that it is 10 to 80 parts by weight.

From the viewpoint of foamability, the melt viscosity (200 ° C., shear rate 100 sec ⁻¹ ) of the polystyrene-based resin for forming the foamed layer is preferably 800 to 2500 Pa · s, more preferably 1000 to 2200 Pa · s, and further Preferably it is 1200-2000 Pa.s.

(Physical foaming agent)
Examples of the physical foaming agent include aliphatic hydrocarbons having 2 to 7 carbon atoms, such as ethane, propane, normal butane, isobutane, normal pentane, isopentane, isohexane, cyclohexane, heptane, methyl chloride, ethyl chloride, 1,1. Halogenated aliphatic hydrocarbons having 1 to 4 carbon atoms such as 1,2,2-tetrafluoroethane, 1,1-difluoroethane, aliphatic alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol, and butanol; Examples thereof include organic physical foaming agents such as aliphatic ethers having 2 to 8 carbon atoms such as dimethyl ether, diethyl ether and dipropyl ether, and inorganic physical foaming agents such as nitrogen, carbon dioxide and water.

  These physical foaming agents may be used individually by 1 type, and may use 2 or more types together. Moreover, what has a normal butane, isobutane, or these mixtures as a main component can be used suitably from a viewpoint of compatibility with a polystyrene-type resin and foaming efficiency.

  The amount of the physical foaming agent added can be appropriately adjusted according to the apparent density of the foam, etc., but usually 0.15 to 1 kg in 1 kg of the foamed resin melt for forming the foamed layer 2. 0.8 mol is preferable, 0.3 to 1.5 mol is more preferable, and 0.4 to 1.2 mol is even more preferable. In addition to the physical foaming agent, a chemical foaming agent may be used in combination as the foaming agent.

(Bubble conditioner)
As the bubble adjusting agent, either an organic type or an inorganic type can be used. Examples of the inorganic air conditioner include metal borates such as zinc borate, magnesium borate, borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate and the like. .
Examples of the organic foam regulator include sodium phosphate-2,2-methylenebis (4,6-tert-butylphenyl), sodium benzoate, calcium benzoate, aluminum benzoate, and sodium stearate. Can do. Also, a combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate, or the like can be used. These bubble regulators may be used alone or in combination of two or more.

  The addition amount of the cell regulator is preferably in the range of 0.05 to 10 parts by weight, more preferably 0.2 to 5 parts by weight per 100 parts by weight of the foamed layer forming resin melt. .

(Other additives)
As a material component for molding the foam layer 2, various additives can be added in addition to the above components. Examples of the additive include an antioxidant, a heat stabilizer, a weathering agent, an ultraviolet absorber, a flame retardant, an inorganic filler, an antibacterial agent, and a colorant. In addition, when mix | blending a coloring agent, it is desirable to adjust the kind and compounding quantity of a coloring agent so that it may become lighter than a colored resin from a viewpoint of improving the texture of a foam.

<Coloring resin 3>
The foam 1 has a colored resin 3 laminated in a streak form on at least one side of the foam layer 2. The colored resin 3 uses a polystyrene-based resin as a base resin and includes a polyethylene-based resin together with a colorant.
Although the colored resin 3 may be in a foamed state or in a non-foamed state, it is preferably in a non-foamed state in order to obtain a foam having a clear pattern made of the colored resin 3. Note that a part of the bubbles may be locally formed in the non-foamed colored resin 3. Further, in order to make the colored resin non-foamed, a volatile plasticizer described later is within a specific range, a method of cooling by blowing air to the colored resin immediately after extrusion, or a coloring agent for the colored resin. The resin layer can be more reliably brought into a non-foamed state by using in combination with a method that does not add as much as possible cell nuclei other than the above and a method that reduces the basis weight of the colored resin.
Further, the end in the width direction of the foam is not thermoformed when it is a sheet-like foam for thermoforming, and is cut off when it is a plate-like foam. May not be used as. As long as the intended purpose of the present invention can be achieved, it is not necessary for the colored resin 3 to cover all one side of the foamed layer 2, and there may be a non-laminated portion in part. Further, the non-laminated portion may be formed in a portion other than the end portion in the width direction. When the end portions of the streak pattern are in contact with each other, it is preferable that the streak pattern is expressed by color shading due to a change in the thickness of the continuous colored resin 3 in the foam width direction.

  The colored resin 3 is a resin for forming a colored resin, in which a foamed layer forming resin melt is blended with a polystyrene resin, a specific polyethylene resin and a colorant, and more preferably a compatibilizer, a plasticizer and other additives. Preferably, the melt is formed by laminating and joining the melted resin for forming a foamed layer in a coextrusion die in a streaky manner and coextruding them at intervals. Further, from the viewpoint of surface smoothness, the colored resin 3 is desirably formed in such a form that the colored resin 3 is embedded in the foamed layer 2 as shown in FIG.

  Below, each component of the material used in order to shape | mold the colored resin 3 is explained in full detail.

(Polystyrene resin)
As the polystyrene resin forming the colored resin 3, the same resin as the polystyrene resin forming the foamed layer can be used.
The melt viscosity (200 ° C., shear rate 100 sec ⁻¹ ) of the polystyrene resin in the colored resin is preferably 500 to 2000 Pa · s, more preferably 700 to 1700 Pa · s, and still more preferably 800 to 1500 Pa. -S.

  In this invention, it is preferable that the compounding quantity of the said polystyrene-type resin is the range of 60 to 95 weight% with respect to the total weight of colored resin, More preferably, it is 70 to 94 weight%, More preferably, it is 80 to 93% by weight.

(Polyethylene resin)
A polyethylene resin is added to the colored resin of the present invention together with the polystyrene resin. By blending the polyethylene resin, the colored resin 3 can be prevented from being peeled off or dropped out due to excessive rubbing or contact.

  Examples of the polyethylene resin used in the present invention include at least one ethylene homopolymer selected from linear low density polyethylene, branched low density polyethylene, ultra low density polyethylene, and high density polyethylene.

In the present invention, the linear low density polyethylene (PE-LLD) is composed of a copolymer of ethylene and an α-olefin, and includes a linear polyethylene main chain and a short chain branch having about 2 to 6 carbon atoms. having a density of 0.91 g / cm ³ or more 0.94 g / cm ³ or less degree of the polyethylene, it is preferred that its melting point is below 127 ° C. exceed 105 ° C.. In addition, as the linear low-density polyethylene, those polymerized by a metallocene polymerization catalyst have a large tensile elongation at break of the resin, hardly cause cracking even with little heating, and can widen the moldable temperature range. Therefore, it is preferably used.

In the present invention, the branched low-density polyethylene is a polyethylene having a long chain branch, generally called a low-density polyethylene (PE-LD), having a density of about 0.91 to 0.94 kg / m ³ , and its melting point is It is about 95-120 degreeC.

In the present invention, ultra-low density polyethylene (PE-VLD) is a copolymer of an ethylene resin and an α-olefin, and is a linear low density polyethylene having a large content of α-olefin. Density is generally less than 0.91 g / cm ^3, the lower limit of the density is approximately 0.88 g / cm ³ order. Moreover, melting | fusing point is about 65-120 degreeC.

The high-density polyethylene in the present invention (PE-HD), obtained in the process called slurry method or solution method, commonly density 0.94 g / cm ³ Ultra 0.97 g / cm ³ or less degree of linear Polyethylene. Moreover, melting | fusing point is about 125-135 degreeC.

  The melting point of the polyethylene resin is such that when the polystyrene resin laminated foam sheet of the present invention is used as a food container, the resin is not softened and the rigidity of the container is reduced, or the colored resin is not easily detached. It is preferable. Therefore, from the viewpoint of heat resistance, the melting point is preferably 70 ° C or higher, more preferably 80 ° C or higher, and still more preferably 90 ° C or higher. On the other hand, the upper limit of the melting point is preferably 140 ° C. or less, more preferably 138 ° C. or less, and still more preferably 136 ° C. or less from the viewpoint of preventing crystallization during extrusion.

Among these polyethylene-based resins, a resin having a density of less than 0.95 g / cm ³ is preferable, a resin having a density of 0.94 g / cm ³ or less is more preferable, and 0.93 g / cm ³ is more preferable from the viewpoint of preventing dropping of the colored resin. A resin having ³ or less is more preferable.

  The melt flow rate (hereinafter also referred to as MFR) of the polyethylene resin used in the present invention is preferably from 0.1 to 30 g from the viewpoint of the film-forming property of the colored resin and the durability of the effect of preventing the colored resin from falling off. / 10 minutes, more preferably 1 to 20 g / 10 minutes, still more preferably 3 to 10 g / 10 minutes. The melt flow rate (MFR) of the polyethylene resin in this specification is a value measured at a test temperature of 190 ° C. and a load of 21.18 N based on JIS K7210 (1999) A method.

Moreover, it is preferable that the melt viscosity (190 degreeC, shear rate 100sec < ^-1 >) of the said polyethylene-type resin is the range of 100-3500 Pa * S.
From the viewpoint of facilitating formation by laminating the colored resin on the foamed layer, 300 to 2500 Pa · S is preferable, and 500 to 1500 Pa · S is more preferable.

The ratio of the melt viscosity of the polystyrene resin and the polyethylene resin in the colored resin constituting the colored resin 3 affects the dispersibility of each other. If the ratio of the melt viscosity is small, they are finely dispersed with each other, and the colored resin film can be formed satisfactorily and the color fading prevention can be excellent.
From the above viewpoint, the ratio (η2 / η1) of the melt viscosity (η2) of the polyethylene resin to the melt viscosity (η1) of the polystyrene resin is preferably in the range of 0.1 to 2.5, 0.3-2 are more preferable, 0.5-1.5 are more preferable, and 0.5-1.0 are the most preferable. Regarding the ratio of melt viscosity, the melt viscosity of polystyrene resin (η1, [200 ° C., shear rate 100 sec ⁻¹ ]) and the melt viscosity of polyethylene resin (η2, [190 ° C., shear rate 100 sec ⁻¹ ]) And the ratio.

  In this invention, the compounding quantity of the said polyethylene-type resin is 4 to 40 weight% with respect to the total weight of colored resin. When the blending amount of the polyethylene resin is within the above range, it is possible to effectively suppress peeling of the colored resin and dropping off of the colorant contained therein even by excessive rubbing. The lower limit of the blending amount of the polyethylene resin is preferably 5% by weight, more preferably 6% by weight. On the other hand, the upper limit of the amount of the polyethylene resin is preferably 30% by weight, more preferably 20% by weight.

  The colored resin may contain a resin other than the polystyrene-based resin and the polyethylene-based resin as long as the objects and effects of the present invention are not impaired. Specifically, the ratio is preferably 20% by weight or less, more preferably 15% by weight or less, further preferably 10% by weight or less, and more preferably 5% by weight with respect to the total weight of the colored resin. The following are particularly preferred:

  In the present invention, when a specific amount of a specific polyethylene-based resin is added to the colored resin, it is possible to effectively suppress the colored resin from being scraped and dropped even by excessive rubbing. The reason for this is not clear at this time, but is presumed to be due to the following reason. Since the polyethylene resin is softer and has higher toughness than the polystyrene resin of the base material, it is considered that the polyethylene resin is mixed with the polystyrene resin, thereby preventing the colored resin from falling off. Further, among polyethylene resins, it is speculated that the polyethylene homopolymer was more effective because the Tg (glass transition point) was lower.

(Compatibilizer)
In the colored resin of the present invention, it is preferable to use a compatibilizing agent in order to increase the affinity and dispersibility of the polyethylene resin to the polystyrene resin. As such a compatibilizing agent, any compatibilizer may be used as long as it can compatibilize polystyrene resin and polyethylene resin, and various conventionally known ones can be used. As such, it is particularly preferable to use a styrene-based thermoplastic elastomer.

In the present invention, among the styrenic thermoplastic elastomers, preferred are those comprising the styrene-diene block copolymer (a), or at least a part of the ethylenic double bonds in the styrene-diene block copolymer. What consists of a hydrogenation block copolymer (b) obtained by reduction | restoration by hydrogenation with an organic or inorganic metal compound catalyst is mentioned.
Examples of the styrene-diene block copolymer (a) include a styrene-1,3-butadiene block copolymer (SBS), a styrene-1,3-pentadiene block copolymer, and a styrene-isoprene block copolymer ( SIS), styrene- (2,3-dimethyl-1,3-butadiene) block copolymer, styrene- (3-methyl-1,3-octadiene) block copolymer, styrene- (4-ethyl-1, Examples include 3-hexadiene) block copolymers.
On the other hand, examples of the hydrogenated block copolymer (b) include those obtained by a reduction reaction by hydrogenation of at least part of the ethylenic double bond in the styrene-diene block copolymer (a). Specifically, styrene-butadiene-butylene-styrene (SBBS) in which double bond of SBS is partially reduced, styrene-ethylene-butylene-styrene copolymer (SEBS) in which double bond of SBS is completely reduced, Examples thereof include styrene-ethylene-propylene-styrene (SEPS) in which a double bond of SIS is reduced.

  Although the compounding quantity of a compatibilizing agent is arbitrary, it is preferable that it is 1 to 10 weight% with respect to the total weight of colored resin, and 2 to 7 weight% is more preferable.

(Coloring agent)
As the colorant to be blended in the colored resin 3, for example, inorganic or organic pigments or dyes such as brown, black, gray, yellow, red, pink, green, and blue can be used. Examples of organic pigments include, for example, condensed azos such as monoazo, chromoftal red, anthraquinone, isoindolinone, heterocyclic, perinone, quinacridone, perylene, thioindigo, dioxazine, phthalocyanine Nitroso, phthalocyanine pigments, organic fluorescent pigments, and the like.

  Examples of the inorganic pigment include titanium oxide, carbon black, titanium yellow, iron oxide, ultramarine blue, cobalt blue, calcined pigment, metallic pigment, mica, pearl pigment, zinc white, precipitated silica, cadmium red and the like. .

Examples of the organic dye include anthraquinone, heterocyclic, perinone, basic dye, acid dye, and mordant dye. Among these, the use of an inorganic pigment is preferable because it can be produced at low cost.
Moreover, a coloring agent may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  The resin layer 3 has a brown color by using iron oxide or a brown colorant containing iron oxide as a colorant, for example, a colorant composed of a mixture of iron oxide, carbon black, and titanium oxide. The foam 1 having a high-quality feeling with a higher design can be obtained.

The amount of the colorant added is appropriately adjusted according to various conditions such as a required color tone, but is 0.05 to 3.0% by mass with respect to the total weight of the color resin constituting the color resin 3. preferable. Moreover, More preferably, it is 0.05-2.5 mass%, More preferably, it is 0.1-2.0 mass%. Within the above range, it is easy to form a streak pattern with a beautiful appearance.
In addition, when used as a food container, it is necessary to determine the physical properties and addition amount of the colorant according to the values of the voluntary standards set by the Sanitation Council for Polyolefins.

(Plasticizer)
In order to mold the non-foamed colored resin 3, it is preferable to add a plasticizer. By adding the plasticizer, when the colored resin-forming melt is laminated, it can be adjusted to an appropriate melt elongation that allows the colored resin-forming melt to follow the foam layer. When the colored resin forming melt and the foam layer forming melt are produced by coextrusion, the melt elongation of the colored resin forming melt at an appropriate foaming temperature can be remarkably improved. It is preferable because the elongation of the forming melt can correspond to the elongation of the resin melt for forming the polystyrene-based resin foam layer.

  As the plasticizer, a volatile plasticizer is preferably used. In the state where the volatile plasticizer is present in the resin melt for forming the colored resin, the melt viscosity of the polystyrene resin is lowered, and the volatile plasticizer is in a range suitable for laminating the colored resin melt on the foam layer. After the extrusion, it is volatilized from the colored resin and can be easily removed from the colored resin, and there is no possibility that the rigidity of the colored resin 3 is lowered due to the remaining plasticizer. In addition, when using a volatile plasticizer, it is preferable not to add a bubble regulator.

In addition, a volatile plasticizer is preferably used because the plasticizer remains after the extrusion and the rigidity of the colored resin 3 is not lowered.
Examples of the volatile plasticizer include aliphatic hydrocarbons having 2 to 7 carbon atoms, halogenated aliphatic hydrocarbons having 1 to 4 carbon atoms, aliphatic alcohols having 1 to 4 carbon atoms, or 2 to 8 carbon atoms. Those composed of one or two or more selected from the following aliphatic ethers are preferably used, and those mainly composed of normal butane, isobutane or a mixture thereof can be suitably used.

  The boiling point of the volatile plasticizer is preferably 120 ° C. or lower, more preferably 80 ° C. or lower, from the viewpoint of volatility from the resin layer. If the boiling point of the volatile plasticizer is within this range, the volatile plasticizer is a resin due to heat immediately after extrusion and gas permeation at room temperature in a state where the obtained foam is left after extrusion. Naturally stripped from the layer and removed naturally. The lower limit of the boiling point is approximately -50 ° C.

  The addition amount of the volatile plasticizer is preferably 0.1 to 1.5 mol, more preferably 0.2 to 1.2 mol, relative to 1 kg of the polystyrene resin forming the colored resin. By setting the addition amount within this range, the colored resin can be plasticized well during production.

  In addition, if it is the addition amount of the grade which does not produce the physical property fall of the polystyrene resin which comprises colored resin, a normal plasticizer can also be used, The addition amount becomes like this. Preferably it is less than 3 mass%, More preferably, it is 2 %.

  Below, the foam 1 formed by laminating the foam layer 2 and the colored resin 3 will be described in detail.

(Apparent density of foam 1)
The apparent density of the foam 1 is preferably 0.04 to 0.35 g / cm ³ . When the apparent density is within the above range, the balance between lightness and strength is excellent. The lower limit of the apparent density is more preferably 0.05 g / cm ^3, more preferably from 0.07 g / cm ^3. On the other hand, the upper limit of the apparent density is more preferably 0.21 g / cm ³ , and still more preferably 0.15 g / cm ³ .

(Foam 1 thickness)
The thickness of the foam 1 is not particularly limited, but is preferably 0.5 to 10 mm.
A sheet-like foam (sheet-like foam) having a thickness of 0.5 to 3 mm is a high-quality tray container, instant noodle container, lunch box container that is thermoformed and has a streak pattern, It can be suitably used as a food container such as a natto container, a frozen container or a koji.

  In addition, a plate-like foam (plate-like foam) having a thickness of 3 to 10 mm can be suitably used as a folding box, a display core, or the like.

  The thickness of the polystyrene resin foam can be determined by the following method. The thickness (mm) of the foam is measured at 10 points in the width direction at equal intervals, and the arithmetic average value of the thickness (mm) of the foam at each measured point is taken as the thickness (mm) of the foam.

Next, one embodiment of the method for producing a foam of the present invention is shown in FIGS.
As shown in FIG. 3, in the method for producing a foam of the present invention, first, a polystyrene resin 9, which is a material for molding the foam layer 2 described above, and other bubble adjustments added as necessary. An additive such as an agent is supplied to the first extruder 13 and heated and kneaded. The physical foaming agent 10 is press-fitted and further kneaded to obtain a foamed layer-forming resin melt 11 in the first extruder 13.

  At the same time, polystyrene resin 4, polyethylene resin 5 and colorant 6, and other additives added as necessary, which are materials for forming the colored resin 3 described above, are added to the second extruder 12. The volatile plasticizer 7 is supplied and further kneaded to obtain a colored resin-forming resin melt 8 in the second extruder 12.

  And the foam 1 is obtained by introduce | transducing the said molten resin 11 for foamed layer formation and the resin melt 8 for colored resin formation into the cyclic | annular die | dye 14, combining lamination | stacking, and coextruding.

  Below, the coextrusion of the resin melt 11 for foam layer formation and the resin melt 8 for colored resin formation is explained in full detail.

  For example, as shown in FIGS. 3 and 4, the foamed layer forming resin melt 11 and the colored resin forming resin melt 8 are adjusted to appropriate temperatures and then introduced into the die 14 for coextrusion. The colored resin-forming resin melt 8 is formed into a large number of streaks at intervals on one side of the foam-layer-forming resin melt 11 in the die 14 via a large number of internal lips having hole-shaped outlets. After merging and laminating, the laminate is coextruded and the foamed layer forming resin is foamed to produce a laminated foam in which the colored resin 3 is formed on the surface of the foamed layer 2. The colored resin forming resin melt 8 may be laminated on both sides of the foamed layer forming resin melt 11.

  When an annular die is used as the die for coextrusion, the sheet-like foam 1 can be obtained by cutting open the cylindrical laminated foam. Moreover, the plate-like foam 1 can be obtained by sandwiching this cylindrical laminated foam with a pinch roll and joining the inner surfaces of the foam layer 2 to each other.

  In addition, when manufacturing by a co-extrusion method, the foam of high closed cell ratio is obtained by making the temperature of the resin melt 11 for foamed layer formation and the resin melt 8 for colored resin formation as close as possible, and is desirable.

(Lamination amount of colored resin 3)
The amount of the colored resin 3 laminated is appropriately set by adjusting the surface of the foamed layer 2 so that a streak pattern of the colored resin 3 is exposed in the extrusion direction. Usually, the range of 3 to 50 g / m ² is set. More preferably, it is 5-40 g / m < ² >, More preferably, it is the range of 10-30 g / m < ² >. By setting the amount of lamination within the above range, it is possible to form a non-foamed colored resin 3 having a small thickness. In addition, the lamination amount of the colored resin 3 refers to the total lamination amount of the colored resin 3 per unit area existing on one side of the foam.

The amount of the colored resin 3 laminated is expressed by the following formula (1), where L (kg / hr) is the discharge amount of the colored resin 3 through the extruder, the foam take-up speed M (m / min), and the foam full width N (m). It can ask for.
Stacking amount of colored resin (g / m ² ) = L × 10 ³ / (M × N × 60) (1)
Moreover, when joining the inner surface of a foam layer with a pinch roll and making a plate shape into a plate shape, sheet-like foaming is carried out by making the width | variety of a plate-like foam in Formula (1) twice. It can be obtained in the same manner as the body.

(Stacking amount per 1 m of extrusion direction per colored resin 3)
When the colored resin-forming resin melt 8 is linearly laminated on the foamed-layer-forming resin melt 11 and coextruded, the amount of each colored resin 3 to be laminated per 1 m in the extrusion direction is laminated. The resin melt 8 for forming the colored resin is streaked so as to be 0.01 to 0.6 g / m, preferably 0.02 to 0.5 g / m, more preferably 0.03 to 0.4 g / m. It is preferable to join and laminate in a shape. By setting the amount of lamination within the above range, a foam with less thickness unevenness can be obtained.

The amount of lamination of each colored resin 3 per 1 m in the extrusion direction is X (kg / hr) for the discharge amount of the resin melt 8 for forming the colored resin, and Y (m / min) for the foam take-up speed. ), The number Z of the colored resin forming resin melts 8 per the entire width of the foam can be obtained by the following equation (2).
(X × 10 ³ ) / (Y × Z × 60) (2)

(Average center distance of colored resin 3)
In the colored resin 3, the average center-to-center distance between adjacent colored resins laminated in a streak shape can be set by appropriately selecting the annular die 18 of the manufacturing apparatus, but the streak shape in the foam extrusion direction. It is preferably in the range of 2 to 30 mm, more preferably 2 to 25 mm, and even more preferably 3 to 15 mm so that the pattern can be clearly expressed.

  As the annular die 14, the colored resin-forming resin melt is placed on the outer peripheral surface of the foamed layer-forming resin melt through a large number of internal lips having hole-like outlets arranged on the circumference of the annular die. It is preferable to use a structure that can be laminated in a streak shape.

  For the internal lip for forming the colored resin 3 processed in the annular die 14, if the resin melt for forming the colored resin can be joined and laminated in a streak pattern on the outer peripheral surface of the resin melt for forming the foam layer, The shape and the like are not particularly limited. Examples of the cross-sectional shape of the outlet of the internal lip include a rectangular shape, a triangular shape, a semicircular shape, and a circular shape. The maximum width of the inner lip outlet is preferably 0.4 to 6.0 mm, more preferably 0.5 to 5.0 mm, and still more preferably 0.6 to 4.0 mm. .

  In addition, in the laminated portion of the colored resin forming resin melt 8 and the foamed layer forming resin melt 11, the average center-to-center length between adjacent internal lips is preferably 1 to 12 mm, and 2 to 11 mm. It is more preferable to do.

  Hereinafter, the polystyrene resin foam of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

  As a production apparatus, as a first extruder, a tandem type foam layer forming extruder composed of an extruder having a barrel inner diameter of 90 mm and an extruder having a barrel inner diameter of 120 mm connected to the downstream side of the extruder is used. Co-extrusion in which a co-extrusion annular die (lip diameter 67 mm, lip gap 0.6 mm) is attached to the outlet of the extruder, and a colored resin forming second extruder (inner diameter 65 mm) is connected to the co-extrusion annular die. A device was used.

  Polystyrene resin for forming a foam layer shown in Table 3-5, talc (parts by weight shown in the table as a weight ratio with respect to 100 parts by weight of polystyrene resin) is supplied as a foam regulator, heated and kneaded, and a physical foaming agent is added thereto. The amount shown in Table 3-5 (number of moles relative to 1 kg of polystyrene resin) is press-fitted and adjusted to a resin temperature suitable for foaming in the first extruder to obtain a resin melt for forming a foam layer, and a co-extrusion ring Introduced into the die.

  At the same time, the polystyrene resin for forming the colored resin, the polyethylene resin and various colorants shown in Table 3-5 (weight% with respect to the total weight of the colored resin) are supplied to the second extruder and heated and kneaded. The amount of the volatile plasticizer shown in Table 3-5 (number of moles relative to 1 kg of polystyrene resin) was press-fitted to form a colored resin-forming resin melt and introduced into a co-extrusion annular die.

  In the annular die for coextrusion, the resin melt for forming the foam layer and the width (circumferential direction) 0.8 mm and the height (direction perpendicular to the width direction) 1.9 mm on the circumferential outer edge of the foam layer flow path A foamed layer is formed by joining a colored resin-forming resin melt extruded at an interval from an internal lip having a hole-like outlet disposed at 163 locations with an average center-to-center distance of 2.0 mm. After laminating the resin melt for forming colored resin on the resin melt for forming a streak and co-extruding it into a cylindrical shape, it is taken out through a 270 mm ψ mandrel (blow-up ratio 4) and incised to make a sheet form Foam was obtained. The colored resin was laminated on one side of the foamed layer in a non-foamed state with a space spaced apart.

In Table 3-5, the raw materials PS (1) and PS (2) used for the foamed layer and the colored resin mean the following polystyrene resins.
PS (1): Polystyrene (PS Japan, 680, melt viscosity 930 Pa · s)
PS (2): Polystyrene (GX154 manufactured by PS Japan, melt viscosity 1430 Pa · s)

In addition, the melt viscosity of polystyrene resin is based on JIS K7199 (1999), using a flow characteristic measuring machine of Capillograph 1D (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at a temperature of 200 ° C. and a shear rate of 100 seconds− ¹ . It is a value measured under conditions.

  Moreover, in Table 3-5, the polyethylene-type resin etc. which were used for colored resin mean what was described in the following Table 1.

All melt viscosities were measured with Capillograph 1D (manufactured by Toyo Seiki) based on JIS K 7199 (1999) under the conditions of a measurement temperature of 190 ° C. and a shear rate of 100 seconds- ¹ .
The melting point was measured by a method according to JIS K7121 (1987). That is, a pretreatment was performed according to the condition adjustment conditions of the test piece in JIS K7121 (1987) (however, the cooling rate was 10 ° C./min), and the temperature was raised at 10 ° C./min to obtain a melting peak. The temperature at the top of the obtained melting peak was taken as the melting point.

  In Table 3-5, the colorant used for the colored resin means the following.

In Table 3-5, the compatibilizer used for the colored resin is Tuftec P2000 (SEBS: styrene / butadiene / butylene ratio = 67/33; melt viscosity 394 Pa · S) manufactured by Asahi Kasei Emicals. The melt viscosity is a value measured with Capillograph 1D (manufactured by Toyo Seiki Co., Ltd.) according to JIS K7199 (1999) under the conditions of a measurement temperature of 190 ° C. and a shear rate of 100 seconds- ¹ .

Example 1
According to the production conditions shown in Table 3, PE-LLD1 (linear low density) is used as a polystyrene resin and a polyethylene resin on the outer peripheral surface of a foamed layer forming resin melt obtained by kneading a polystyrene resin and a physical foaming agent. Polyethylene resin), compatibilizer, colorant 1 and volatile plasticizer are kneaded together to form a colored resin-forming resin melt that forms a streak and laminates by coextrusion. A foam was obtained.

  In addition, the coloring agent 1 was added as a masterbatch so that the addition amount of the coloring agent 1 might be 0.6 weight part with respect to 100 weight part of polystyrene resins.

  The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 2)
In Example 1, a foam was obtained in the same manner except that the blending amount of PE-LLD1 was 10% by weight and the compatibilizer was removed. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 3)
A foam was obtained in the same manner as in Example 1 except that the blending amount of PE-LLD1 was changed to 5% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

Example 4
In Example 1, a foam was obtained in the same manner except that PE-LLD1 (linear low-density polyethylene resin) was replaced with PE-LLD2 and the compatibilizing agent was removed. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 5)
A foam was obtained in the same manner as in Example 1, except that PE-LLD1 (linear low density polyethylene resin) was replaced with PE-LLD3 (linear low density polyethylene resin). The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 6)
In Example 1, a foam was obtained in the same manner except that PE-LD1 (linear low density polyethylene resin) was replaced with PE-LD1 (branched low density polyethylene) and the compatibilizer was removed. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 7)
A foam was obtained in the same manner as in Example 1, except that PE-LLD1 (linear low density polyethylene) was replaced with PE-VLD1 (very low density polyethylene). The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 8)
A foam was obtained in the same manner as in Example 1, except that the amount of PE-LLD1 (linear low density polyethylene) added was changed to 4% by weight and the amount of the compatibilizer added was changed to 1.2% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

Example 9
A foam was obtained in the same manner as in Example 1, except that the blending amount of PE-LLD1 (linear low density polyethylene resin) was 25% by weight and the addition amount of the compatibilizer was 5 parts by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Example 10)
A foam was obtained in the same manner as in Example 1 except that the colorant 1 was replaced with the colorant 2 and the blending amount was 0.9% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 11)
In Example 10, a foam was obtained in the same manner except that Colorant 2 was replaced with Colorant 3. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 12)
In Example 10, a foam was obtained in the same manner except that Colorant 2 was replaced with Colorant 4. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 13)
In Example 10, a foam was obtained in the same manner except that the colorant 2 was replaced with the colorant 5 and the blending amount was 0.2% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 14)
In Example 10, a foam was obtained in the same manner except that the colorant 2 was replaced with the colorant 6 and the blending amount was 0.2% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 15)
In Example 10, a foam was obtained in the same manner except that the colorant 2 was replaced with the colorant 7 and the blending amount was 0.2% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 16)
In Example 10, a foam was obtained in the same manner except that Colorant 2 was replaced with Colorant 8 and the blending amount was 0.2 wt%. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Example 17)
In Example 1, foaming was carried out in the same manner except that PE-LLD1 (linear low density polyethylene resin) was replaced with PE-HD1 (high density polyethylene resin) and the amount of compatibilizer was changed to 5% by weight. Got the body. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 4.

(Comparative Example 1)
In Example 1, a foam was obtained in the same manner except that PE-LLD1 (linear low density polyethylene resin) and a compatibilizing agent were not added. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 5.

(Comparative Example 2)
In Example 2, a foam was obtained in the same manner except that the blending amount of PE-LLD1 (linear low density polyethylene resin) was 2% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 5.

(Comparative Example 3)
In Example 2, a foam was obtained in the same manner except that the blending amount of PE-LLD1 (linear low density polyethylene resin) was 50% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. Although the effect of preventing the separation of the colored resin was observed, the streaky colored resin layer was disturbed and the appearance was poor. The results are shown in Table 5.

(Comparative Example 4)
In Example 1, foaming was similarly performed except that PE-LLD1 (linear low-density polyethylene-based resin) was replaced with EVA1 (ethylene-vinyl acetate copolymer) and the amount of the compatibilizer was changed to 5% by weight. Got the body. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 5.

(Comparative Example 5)
In Example 1, foaming was similarly performed except that PE-LLD1 (linear low-density polyethylene resin) was replaced with EVA2 (ethylene-vinyl acetate copolymer) and the amount of the compatibilizer was changed to 5% by weight. Got the body. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 5.

(Comparative Example 6)
In Example 1, a foam was obtained in the same manner except that PE-LLD1 (linear low-density polyethylene resin) was replaced with PP1 (polypropylene resin 1) and the amount of compatibilizer was changed to 5% by weight. It was. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 3.

(Comparative Example 7)
In Example 1, a foam was obtained in the same manner except that PE-LLD1 (linear low-density polyethylene resin) was replaced with PP2 (polypropylene resin) and the amount of compatibilizer was changed to 5% by weight. . The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 5.

(Comparative Example 8)
In Example 1, a foam was obtained in the same manner except that PE-LLD1 (linear low-density polyethylene-based resin) was not added and the amount of the compatibilizer was changed to 10% by weight. The moldability of the obtained foam, the detachability of the colored resin, and the appearance were evaluated. The results are shown in Table 5.

  In Table 3-5, each characteristic was measured and evaluated as follows.

(Thermoformability)
Thermoformability was evaluated as follows.
○ ... Good formability (no molding defects)
× ・ ・ ・ Strength reduction is observed in the molded product

  In addition, the moldability is 120 mm in length and 200 mm in width under conditions of a heater temperature of 330 ° C. and a heating time of 7 seconds ± 1 second by match mold vacuum forming using a molding machine manufactured by Asano Laboratories, product number FKS-0631-10. X Thermoforming was performed using a tray mold having a depth of 25 mm, a side wall thickness of the stack portion of 1.5 mm, and a stack height average center distance of 2.85 mm. The minimum gap created by the upper and lower molds of the mold was 1.5 mm at the stack portion.

(Evaluation of detachability of colored resin 1)
The detachability of the colored resin was evaluated as follows.
A white cloth was placed on the colored resin of the laminated foam cut out to a size of 40 mm × 45 mm, and a load of 450 g / cm ² was applied thereon, and the laminate foam was reciprocated 100 times.
The dropping property of the colored resin was evaluated by measuring the color difference values ΔL ^* , Δa ^* , Δb ^* , which are changes in L ^* a ^* b ^* of the fabric before and after the friction test. Note that the smaller the color difference value, the less the color transfer to the cloth, that is, the less the falling off of the colored resin.
L ^* is an indicator of brightness: the higher the value, the brighter the light.
a ^* is a red / green index; the larger the value, the stronger red.
b ^* is an index of yellow and blue; the larger the value, the stronger yellow.
In addition, the measurement of L ^* a ^* b ^* was measured by the reflection method using the Nippon Denshoku Industries make and spectroscopic color meter product number SE2000.

(Appearance evaluation)
The appearance of the foam was evaluated according to the following criteria.
◎ ・ ・ ・ Streak pattern is formed as expected ○ ・ ・ ・ Slightly distorted pattern is formed, but the expected streak pattern is formed × ・ ・ ・ Simulated streak pattern is formed It has not been

(Thickness of foam)
The thickness of the foam was determined as an arithmetic average value of thickness (mm) measured at 10 points at equal intervals from one end to the other end along the width direction of the foam.

(Apparent density of foam)
The apparent density of the foam is the weight (g) of a test piece of 10 cm × 10 cm × (foam thickness) cut out from 5 randomly selected locations over the entire width of the foam from the outer dimensions of the test piece. The apparent density of each sample was determined by dividing by the required volume (cm ³ ), and the average value of the obtained values was taken as the apparent density.

  From the above results, the foams of Examples 1 to 17 had a streaky colored resin formed in the width direction on the surface, and were excellent in wood grain appearance. Moreover, it was a good foam with excellent thermoformability and almost no detachment of the colored resin.

  On the other hand, the foams of Comparative Examples 1 to 8, except for Comparative Example 3, the decorative properties and the moldability are good, but the detachment of the colored resin is observed although it is a severe condition of applying a load and rubbing 100 times. It was done. In Comparative Example 3, the polyethylene resin added in a large amount was poorly dispersed, and the colored resin streaks were disturbed and did not become good products.

1 Polystyrene resin foam (foam)
2 Polystyrene resin foam layer (foam layer)
DESCRIPTION OF SYMBOLS 3 Colored resin 4 Polystyrene resin for forming colored resin 5 Polyethylene resin for forming colored resin 6 Colorant for forming colored resin 7 Volatile plasticizer 8 Resin melt for forming colored resin 9 Foam layer Polystyrene resin for forming 10 Physical foaming agent 11 Resin melt for forming foam layer 12 First extruder 13 Second extruder 14 Coextrusion annular die

Claims (6)

A polystyrene-based resin foam in which a colored resin containing a polystyrene-based resin and a colorant is layered on at least one surface of a polystyrene-based resin foam layer,
The colored resin further includes at least one polyethylene-based resin selected from linear low-density polyethylene, branched low-density polyethylene, ultra-low-density polyethylene, and high-density polyethylene,
A polystyrene-based resin foam, wherein the content of the polyethylene-based resin in the colored resin is 4 to 40% by weight. The polystyrene resin foam according to claim 1, wherein the density of the polyethylene resin is 0.94 g / cm ³ or less.   The ratio (η2 / η1) of the melt viscosity (η2) of the polyethylene resin to the melt viscosity (η1) of the polystyrene resin in the colored resin is 0.5 to 1.5. Item 3. The polystyrene resin foam according to Item 1 or 2.   The polystyrene resin foam according to any one of claims 1 to 3, wherein the polyethylene resin is a linear low density polyethylene. The polystyrene resin foam according to any one of claims 1 to 4, wherein a lamination amount of the colored resin is in a range of 3 to 50 g / m ² per side of the polystyrene resin foam. 6. The polystyrene type according to claim 1, wherein the apparent density of the polystyrene resin foam is 0.04 to 0.35 g / cm ³ and the thickness is 0.5 to 10 mm. Resin foam.