Polystyrene resin laminated foam sheet, and polystyrene resin laminated foam container

Abstract

To provide a polystyrene-based resin laminate foam sheet that is hard to cause a defective appearance in thermoforming, and a polystyrene-based resin laminate foam container in which the polystyrene-based resin laminate foam sheet is thermally foamed.SOLUTION: A polystyrene-based resin laminate foam sheet according to an embodiment has a non-foamed polystyrene-based resin layer laminated on at least one side of a polystyrene-based resin foam layer. The resin foam layer is formed by foaming polystyrene-based resin (I). The total content of styrene dimers and styrene trimers in the resin foam layer is 2,000 ppm or less. The non-foamed polystyrene-based resin layer contains polystyrene-based resin (II) and rubber-modified polystyrene-based resin in a weight ratio of 10:90 to 60:40. A weight-average molecular weight (Mw) and a Z-average molecular weight (Mz) of the polystyrene-based resin (II) fall within predetermined ranges.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polystyrene resin laminated foam sheet and a polystyrene resin laminated foam container. [Background technology]

[0002] Thermoplastic resin laminated foam sheets for container molding are manufactured by supplying thermoplastic resin together with a foaming agent and a foam regulator into an extruder, heating, melting, and kneading these materials in the extruder, cooling to a predetermined temperature, extruding the resin from a die into a sheet, foaming it, and then immediately cooling it to produce a foam sheet onto which a thermoplastic resin film is laminated. Another typical method for manufacturing containers using this thermoplastic resin laminated foam sheet involves heating the rolled thermoplastic resin laminated foam sheet to a certain temperature in the heating zone of a molding machine, and then thermoforming it into the desired container shape in the molding zone. Among such thermoplastic resin laminated foam sheets, polystyrene resin laminated foam sheets, which consist of a polystyrene resin foam layer and a polystyrene resin layer laminated together, are used in large quantities as a material for containers such as cup instant noodles.

[0003] The thermoforming described above is carried out by methods such as vacuum forming, pressure forming, vacuum pressure forming, match molding, and press molding, which instantly impart the product shape to the softened polystyrene resin laminated foam sheet.

[0004] In this type of thermoforming, the molding process involves a relatively fast deformation rate, making it difficult to produce molded products with uniform thickness and a beautiful appearance free from wrinkles. For example, in the case of containers for instant cup noodles, the raw material sheet undergoes a relatively deep drawing process in a short time, which can result in appearance defects due to uneven stretching of the polystyrene resin laminated foam sheet during thermoforming. A specific example of such appearance defects is the wavy-line gloss unevenness that appears on the outer surface of a container when a polystyrene resin laminated foam sheet is thermoformed so that the outer surface is a non-foamed layer. This wavy-line unevenness is sometimes called a "chill mark" and can detract from the aesthetic appearance of the resin molded product.

[0005] Incidentally, polystyrene resins contain a certain amount of oligomeric components such as styrene dimer and styrene trimer, which are polymerization residues. And for food containers such as cup noodles, it is required that the content of these oligomeric components be low.

[0006] However, low-oligomer grade polystyrene resins have a lower plasticizing effect due to styrene dimers and styrene trimers, resulting in inferior deformability near the softening point compared to general polystyrene resins. When used as a forming material for polystyrene resin laminated foam sheets to create deep-drawn containers, this can lead to the aforementioned problems of poor appearance due to uneven stretching.

[0007] In other words, when attempting to form a polystyrene-based resin laminated foam sheet using a low-oligomer grade polystyrene-based resin, the aforementioned problem of appearance defects due to uneven stretching occurs.

[0008] To solve these problems, conventional research has considered using polystyrene resins that possess a property called "strain-curing property," in which the stress resisting deformation increases in proportion to the strain speed during thermal melting, as a material for forming polystyrene resin laminated foam sheets (Patent Document 1). Since polystyrene resins with excellent strain-curing properties exhibit the function of suppressing uneven stretching during thermoforming, they can be used as a material for forming polystyrene resin laminated foam sheets for deep-drawn containers.

[0009] However, as shown in the examples of Patent Document 1 (Tables 2 to 4), even polystyrene resins with excellent strain-hardening properties can easily develop surface defects such as cracks and wrinkles during thermoforming if their maximum extension viscosity is excessively high (e.g., "Resin F" in Table 2).

[0010] Therefore, conventional polystyrene-based laminated foam sheets do not adequately suppress appearance defects during thermoforming. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2007-326261 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] The present invention was made to solve the above-mentioned conventional problems, and its main objective is to provide a polystyrene resin laminated foam sheet that is less prone to surface defects during thermoforming, and a polystyrene resin laminated foam container that is thermoformed from the polystyrene resin laminated foam sheet. [Means for solving the problem]

[0013] The polystyrene resin laminated foam sheet according to the embodiment of the present invention is A polystyrene resin laminated foam sheet in which a non-foamed polystyrene resin layer is laminated on at least one surface of a polystyrene resin foam layer, The polystyrene resin foam layer is formed by foaming a polystyrene resin (I), The total content ratio of styrene dimer and styrene trimer in the polystyrene resin foam layer is 2000 ppm or less, The non-foamed polystyrene resin layer contains a polystyrene resin (II) and a rubber-modified polystyrene resin in a weight ratio of polystyrene resin (II): rubber-modified polystyrene resin = 10:90 to 60:40, The weight average molecular weight (Mw) of the polystyrene resin (II) is 280,000 to 460,000, The Z average molecular weight (Mz) of the polystyrene resin (II) is 500,000 to 1,200,000.

[0014] As one embodiment, the polystyrene resin laminated foam sheet according to the embodiment of the present invention has a thickness of 0.5 mm to 4.0 mm.

[0015] As one embodiment, the polystyrene resin laminated foam sheet according to the embodiment of the present invention has a basis weight of 200 g / m , , [Figure 1] ,

[0018] , ~800 g / m 2 It is.

[0016] The polystyrene resin laminated foam container according to the embodiment of the present invention is obtained by thermoforming the polystyrene resin laminated foam sheet according to the embodiment of the present invention.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a polystyrene resin laminated foam sheet in which appearance defects are unlikely to occur in thermoforming, and a polystyrene resin laminated foam container obtained by thermoforming the polystyrene resin laminated foam sheet.

Brief Description of the Drawings

[0019] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0020] In this specification, "(meth)acrylic" means acrylic and / or methacrylic, and "(meth)acrylate" means acrylate and / or methacrylate.

[0021] ≪Polystyrene resin laminated foam sheet≫ A polystyrene resin laminated foam sheet according to an embodiment of the present invention is a polystyrene resin laminated foam sheet in which a polystyrene resin layer is laminated on at least one side of a polystyrene resin foam layer. A polystyrene resin laminated foam sheet according to one embodiment of the present invention is a polystyrene resin laminated foam sheet in which one side of a polystyrene resin foam layer and one side of a polystyrene resin layer are laminated and integrated. A polystyrene resin laminated foam sheet according to another embodiment of the present invention is a polystyrene resin laminated foam sheet in which both sides of a polystyrene resin foam layer and one side of a polystyrene resin layer are laminated and integrated.

[0022] The thickness of the polystyrene resin laminated foamed sheet according to an embodiment of the present invention can be any appropriate thickness within a range not impairing the effects of the present invention. The thickness of the polystyrene resin laminated foamed sheet according to an embodiment of the present invention is preferably 0.5 mm to 4.0 mm, more preferably 1.0 mm to 3.5 mm, still more preferably 1.2 mm to 3.0 mm, and particularly preferably 1.5 mm to 2.5 mm.

[0023] The basis weight of the polystyrene resin laminated foamed sheet according to an embodiment of the present invention can be any appropriate basis weight within a range not impairing the effects of the present invention. The basis weight of the polystyrene resin laminated foamed sheet according to an embodiment of the present invention is preferably 200 g / m 2 ~800 g / m 2 and more preferably 220 g / m 2 ~700 g / m 2 and still more preferably 250 g / m 2 ~650 g / m 2 and particularly preferably 300 g / m 2 ~600 g / m 2 is.

[0024] FIG. 1 is a representative schematic cross-sectional view of a polystyrene resin laminated foamed sheet according to an embodiment of the present invention. In FIG. 1, a polystyrene resin laminated foamed sheet 100 according to an embodiment of the present invention has a polystyrene resin foamed layer 10 and a polystyrene resin layer 20 laminated thereon. A surface 10a on the side of the polystyrene resin foamed layer 10 is a surface on the side opposite to the polystyrene resin layer 20 of the polystyrene resin foamed layer 10. A surface 20a on the side of the polystyrene resin layer 20 is a surface on the side opposite to the polystyrene resin foamed layer 10 of the polystyrene resin layer 20.

[0025] <Polystyrene resin foamed layer> A polystyrene foam layer is typically formed by foaming polystyrene resin (I). More specifically, a polystyrene foam layer is preferably formed by heating, melting, and kneading polystyrene resin (I) together with various additives such as a foaming agent and, if necessary, a foam regulator in an extruder, cooling to a predetermined temperature, extruding it from a die into a sheet while foaming, and then immediately cooling it.

[0026] The polystyrene resin (I) may be of one type only, or of two or more types.

[0027] As the polystyrene resin (I) forming the polystyrene resin foam layer, any suitable polystyrene resin can be used as long as it does not impair the effects of the present invention. Examples of such polystyrene resins (I) include homopolymers of styrene monomers such as styrene, α-methylstyrene, vinyltoluene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethylstyrene, bromostyrene, and chlorostyrene; copolymers of the above styrene monomers; copolymers of the above styrene monomers with (meth)acrylic acid esters (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cetyl (meth)acrylate, (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, etc.); copolymers of the above styrene monomers with difunctional monomers (e.g., divinylbenzene, alkylene glycol dimethacrylate, etc.). The styrene monomer preferably contains at least styrene. The styrene content relative to the total amount of styrene monomer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0028] Examples of polystyrene-based resins (I) include block copolymers having rubber component blocks such as butadiene or isoprene and styrene blocks, and graft copolymers in which the rubber component blocks are grafted onto molecular chains made of styrene, as well as so-called high-impact polystyrene (HIPS).

[0029] In one embodiment, the polystyrene resin (I) may be a composite resin of a polystyrene resin (meaning polystyrene resin (I)) and a polyolefin resin. The ratio of polystyrene resin to polyolefin resin in the composite resin (polystyrene resin / polyolefin resin: mass ratio) is preferably 50 / 50 to 90 / 10, and more preferably 60 / 40 to 85 / 15. If the polystyrene resin content is too low, foaming and / or moldability may be insufficient. If the polystyrene resin content is too high, impact resistance and / or flexibility may be insufficient.

[0030] As the polyolefin resin, any suitable olefin resin can be used as long as it does not impair the effects of the present invention. There may be only one type of polyolefin resin, or there may be two or more types. Specific examples of polyolefin resins include polyethylene resins such as branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and crosslinked polymers of these polymers; polypropylene resins such as propylene homopolymer, propylene-vinyl acetate copolymer, ethylene-propylene random copolymer, propylene-1-butene copolymer, and ethylene-propylene-butene random copolymer; and others. Among these polyolefin resins, ethylene-vinyl acetate copolymer, high-density polyethylene, linear low-density polyethylene, and mixtures thereof are preferred. The low density is preferably 0.91 g / cm³. 3 ~0.94g / cm 3 More preferably, 0.91 g / cm³ 3~0.93g / cm 3 The density is preferably 0.95 g / cm³. 3 ~0.97g / cm 3 More preferably, 0.95 g / cm³ 3 ~0.96 g / cm³ 3 Medium density is a density between low density and high density.

[0031] Polystyrene resin (I) may be a polystyrene resin made from recycled raw materials.

[0032] The polystyrene resin (I) may also contain resins other than polystyrene resins and polyolefin resins, such as (meth)acrylic resins, polyphenylene ether resins such as poly(2,6-dimethylphenylene-1,4-ether), poly(2,6-diethylphenylene-1,4-ether), and poly(2,6-dichlorophenylene-1,4-ether), styrene-butadiene-styrene copolymer rubber (SBS), styrene-isoprene-styrene block copolymer rubber (SIPS), styrene-butadiene-butylene-styrene copolymer rubber (SBBS), styrene-ethylene-butylene-styrene block copolymer rubber (SEBS), styrene-ethylene-propylene-styrene block copolymer rubber (SEPS), and acrylonitrile-butadiene-styrene copolymer, in order to improve impact resistance, etc.

[0033] As a blowing agent, any suitable blowing agent can be used as long as it does not impair the effects of the present invention. Examples of such blowing agents include at least one selected from propane, i-butane, n-butane, i-pentane, n-pentane, N2, CO2, N2 / CO2, water, mixtures of water with compounds having groups such as -OH, -COOH, -CN, -NH3, -OSO3H, -NH, CO, NH2, -CONH2, -COOR, -CHSO3H, -SO3H, -COONH4, and mixtures thereof. Preferably, the blowing agent is at least one selected from i-butane and n-butane, in order to better express the effects of the present invention. Organic blowing agents may also be used as blowing agents. Examples of organic blowing agents include azodicarboxylic acid amide, dinitropentamethylenetetramine, and 4,4'-oxybis(benzenesulfonyl hydrazide).

[0034] The foaming ratio of the polystyrene resin foam layer is preferably 1.5 to 20 times, in order to better exhibit the effects of the present invention.

[0035] The polystyrene foam layer may contain additives such as foam regulators, stabilizers, UV absorbers, antioxidants, colorants (including pigments), deodorizers, foaming nucleators, nucleating agents, lubricants, flame retardants, and antistatic agents. The additives may be one type or two or more types.

[0036] Examples of foam regulators include inorganic powders such as talc and silica; acidic salts of polycarboxylic acids; and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate.

[0037] Examples of stabilizers include calcium-zinc-based heat stabilizers, tin-based heat stabilizers, and lead-based heat stabilizers.

[0038] Examples of UV absorbers include cesium oxide-based UV absorbers and titanium dioxide-based UV absorbers.

[0039] Examples of antioxidants include cerium oxide, cerium oxide / zirconia solid solution, cerium hydroxide, carbon, carbon nanotubes, titanium dioxide, and fullerenes.

[0040] Examples of colorants include titanium dioxide, carbon black, titanium yellow, iron oxide, ultramarine, cobalt blue, calcined pigments, metallic pigments, mica, pearl pigments, zinc oxide, precipitated silica, and cadmium red.

[0041] Examples of deodorizers include silica, zeolite, zirconium phosphate, and hydrotalcite calcined products.

[0042] The thickness of the polystyrene resin foam layer can be any appropriate thickness as long as it does not impair the effects of the present invention. In the polystyrene resin laminated foam sheet according to the embodiment of the present invention, the thickness of the polystyrene resin foam layer is preferably 0.5 mm to 4.0 mm, more preferably 1.0 mm to 3.5 mm, even more preferably 1.2 mm to 3.0 mm, and particularly preferably 1.5 mm to 2.5 mm. The polystyrene resin foam layer may also be referred to as a polystyrene resin foam sheet.

[0043] The basis weight of the polystyrene foam layer can be any appropriate basis weight as long as it does not impair the effects of the present invention. Preferably, the basis weight of the polystyrene foam layer is 120 g / m², as this allows for better expression of the effects of the present invention. 2 ~400g / m 2 More preferably 130 g / m² 2 ~350g / m 2 And more preferably 150 g / m² 2 ~300g / m 2 The most preferred amount is 180 g / m². 2 ~270g / m 2 That is the case.

[0044] The average bubble diameter of the polystyrene foam layer can be any appropriate average bubble diameter within a range that does not impair the effects of the present invention. The average bubble diameter of the polystyrene foam layer is preferably 80 μm to 300 μm, more preferably 90 μm to 250 μm, even more preferably 100 μm to 220 μm, and particularly preferably 110 μm to 200 μm, in order to better express the effects of the present invention.

[0045] The polystyrene foam layer preferably has an apparent density of 0.045 g / cm³, as measured by the method described in JIS K7222:1999 "Foamed Plastics and Rubber - Measurement of Apparent Density," which allows the effects of the present invention to be more fully realized. 3 ~0.300g / cm 3 More preferably, 0.070 g / cm³ 3 ~0.250g / cm 3 That is the case.

[0046] The polystyrene foam layer has a continuous cell ratio, preferably 20% or less, and more preferably 10% or less, which is measured from the volume (V2) measured by the 1-1 / 2-1 atm method in accordance with ASTM D2856-87 and the apparent volume (V1) of the foam layer based on the following formula. Open cell percentage (%) = 100 × [(V1 - V2) / V1]

[0047] The polystyrene resin foam layer is of low oligomer grade, and the total content of styrene dimer and styrene trimer in the polystyrene resin foam layer is preferably 2000 ppm or less, more preferably 1800 ppm or less, even more preferably 1500 ppm or less, and particularly preferably 1200 ppm or less. The polystyrene resin laminated foam sheet according to the embodiment of the present invention can exhibit the effect of being less prone to appearance defects during thermoforming, even when using a low oligomer grade polystyrene resin foam layer.

[0048] <Polystyrene resin layer> Polystyrene resin layers are typically non-foamed polystyrene resin layers.

[0049] The thickness of the polystyrene resin layer can be any appropriate thickness as long as it does not impair the effects of the present invention. In the polystyrene resin laminated foam sheet according to the embodiment of the present invention, the thickness of the polystyrene resin layer is preferably 5.0 μm to 250 μm, and more preferably 10 μm to 200 μm. The polystyrene resin layer may typically be referred to as a polystyrene resin film. The thickness of the polystyrene resin layer is preferably less than the thickness of the polystyrene resin foam layer, more preferably 1 / 5 or less the thickness of the polystyrene resin foam layer, and even more preferably 1 / 10 or less the thickness of the polystyrene resin foam layer.

[0050] The polystyrene resin layer preferably has a melt tension at 200°C of 10 cN to 40 cN, more preferably 12 cN to 35 cN, even more preferably 15 cN to 30 cN, and particularly preferably 18 cN to 28 cN. By adjusting the melt tension of the polystyrene resin layer at 200°C to within the above range, the effects of the present invention can be more fully realized. If the melt tension of the polystyrene resin layer at 200°C is too low and outside the above range, it becomes difficult to apply appropriate stretching to the polystyrene resin layer side of the polystyrene resin laminated foam sheet when manufacturing polystyrene resin laminated foam containers by thermoforming. As a result, when thermoforming under conditions such as high cycles, surface defects such as unevenness may occur on the polystyrene resin layer side, and abnormalities such as ink bleeding may occur in the printing process to enhance the design. If the melt tension of the polystyrene resin layer at 200°C is too high and falls outside the above range, when manufacturing polystyrene resin laminated foam containers by thermoforming, the tension of the polystyrene resin layer may be too high, potentially resulting in insufficient elongation and causing internal cracks, sometimes referred to as "cracks," to occur in the polystyrene resin laminated foam containers.

[0051] The polystyrene resin layer contains polystyrene resin (II) and rubber-modified polystyrene resin. The weight ratio of polystyrene resin (II) to rubber-modified polystyrene resin contained in the polystyrene resin layer is preferably 10:90 to 60:40, more preferably 15:85 to 55:45, even more preferably 20:80 to 50:50, and particularly preferably 25:75 to 45:55. By adjusting the weight ratio of polystyrene resin (II) to rubber-modified polystyrene resin contained in the polystyrene resin layer to within the above range, the effects of the present invention can be further expressed. This is because, by adjusting the weight ratio of polystyrene resin (II) to rubber-modified polystyrene resin contained in the polystyrene resin layer to within the above range, it is possible to achieve both the rigidity characteristic of polystyrene resin and the impact resistance characteristic of rubber-modified polystyrene in a polystyrene resin laminated foam container manufactured by thermoforming.

[0052] The total content ratio of polystyrene resin (II) and rubber-modified polystyrene resin in the polystyrene resin layer is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, even more preferably 90% to 100% by weight, and particularly preferably 98% to 100% by weight. By adjusting the total content ratio of polystyrene resin (II) and rubber-modified polystyrene resin in the polystyrene resin layer to within the above range, the effects of the present invention can be more fully realized.

[0053] Specifically, the polystyrene resin layer is preferably formed by heating, melting, and kneading a resin composition containing polystyrene resin (II) and rubber-modified polystyrene resin in an extruder together with various additives as needed, cooling to a predetermined temperature, and then extruding it from a die into a film. More specifically, in manufacturing a polystyrene resin laminated foam sheet according to an embodiment of the present invention, preferably, as described later, a resin composition containing polystyrene resin (II) and rubber-modified polystyrene resin is heated, melted, and kneaded in an extruder together with various additives as needed, cooling to a predetermined temperature, and then extruding it from a die into a film, which is then laminated onto the surface of the polystyrene resin foam layer.

[0054] The polystyrene resin (II) contained in the polystyrene resin layer may be the same as the polystyrene resin (I) described above for forming the polystyrene resin foam layer, as long as it does not impair the effects of the present invention. The polystyrene resin (II) contained in the polystyrene resin layer may be the same as or different from the polystyrene resin (I) that forms the polystyrene resin foam layer.

[0055] The polystyrene resin (II) may be of one type only, or of two or more types.

[0056] For polystyrene resin (II), the MFR is preferably 0.4 g / 10 min to 5.0 g / 10 min, more preferably 0.6 g / 10 min to 4.0 g / 10 min, even more preferably 0.8 g / 10 min to 3.5 g / 10 min, and particularly preferably 1.0 g / 10 min to 3.0 g / 10 min, in order to better exhibit the effects of the present invention.

[0057] The polystyrene resin (II) is preferably weight-average molecular weight (Mw) of 240,000 to 460,000, more preferably 260,000 to 440,000, even more preferably 280,000 to 420,000, and particularly preferably 300,000 to 400,000, in order to better exhibit the effects of the present invention.

[0058] The polystyrene resin (II) is preferably such that its average molecular weight (Mz) is 500,000 to 1,200,000, more preferably 600,000 to 1,100,000, even more preferably 700,000 to 1,000,000, and particularly preferably 800,000 to 950,000, in order to better exhibit the effects of the present invention.

[0059] In order to better exhibit the effects of the present invention, the polystyrene resin (II) preferably has a ratio of Z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz / Mw) of 1.9 to 3.5, more preferably 2.0 to 3.2, and even more preferably 2.1 to 3.0.

[0060] The rubber-modified polystyrene resin contained in the polystyrene resin layer may be one in which the molecules themselves have been modified, or one in which the bulk state has been modified. Examples of such rubber-modified polystyrene resins include copolymers of one or more styrene monomers and one or more rubber component monomers, and blends of one or more polystyrene resins and one or more rubbers.

[0061] Examples of rubber-modified polystyrene resins include, for example, so-called high-impact polystyrene resin (HIPS), and mixed resins of styrene homopolymers such as high-impact polystyrene resin (HIPS) and general-purpose polystyrene resin (GPPS).

[0062] When using a mixed resin of high-impact polystyrene resin (HIPS) and general-purpose polystyrene resin (GPPS) as a rubber-modified polystyrene resin, it is preferable to include 40% by weight or more of high-impact polystyrene resin (HIPS) in the mixed resin from the viewpoint of imparting impact resistance, etc.

[0063] As the high-impact polystyrene resin (HIPS), any suitable high-impact polystyrene resin (HIPS) can be used, as long as it does not impair the effects of the present invention. Examples of such high-impact polystyrene resins (HIPS) include those in which styrene-butadiene copolymers are dispersed in a salami-like structure and have a particle size of 0.3 μm to 10 μm. Furthermore, examples of polystyrene resins (II) that form the polystyrene resin layer include linear low-density polyethylene, high-density polyethylene, low-density polyethylene, propylene homopolymer, ethylene-propylene random polymer, ethylene-propylene block polymer, ethylene-propylene-butene-terpolymer, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymer (e.g., ethylene-methyl methacrylate copolymer), ethylene-unsaturated carboxylic acid metal salt copolymer (e.g., ethylene-magnesium acrylate (or zinc) copolymer), propylene-vinyl chloride copolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer, propylene-olefin copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer), polyethylene or polypropylene modified with unsaturated carboxylic acids (e.g., maleic anhydride), ethylene-propylene rubber, atactic polypropylene, polyethylene terephthalate, polybutylene terephthalate, and mixtures thereof.

[0064] The polystyrene resin layer may contain additives such as stabilizers, UV absorbers, antioxidants, colorants (including pigments), deodorizers, lubricants, flame retardants, and antistatic agents. There may be only one additive or two or more. For further explanation, refer to the explanation of additives that can be added to the polystyrene resin foam layer.

[0065] ≪Method for manufacturing polystyrene resin laminated foam sheets≫ The method for producing a polystyrene resin laminated foam sheet according to the embodiments of the present invention may employ any suitable method as long as it does not impair the effects of the present invention. The method for producing a polystyrene resin laminated foam sheet according to the embodiments of the present invention is representative in that it can better demonstrate the effects of the present invention. (1) Polystyrene resin foaming layer manufacturing process, (2) Polystyrene resin layer manufacturing and lamination process, This includes (2) above, and may also include (3) a heat treatment step and (4) a winding step. A method for producing a polystyrene resin laminated foam sheet according to an embodiment of the present invention preferably includes (1) a polystyrene resin foam layer manufacturing step and (2) a polystyrene resin layer manufacturing and lamination step in this order.

[0066] In the manufacturing process of polystyrene foam layers, typically, polystyrene resin (I) is heated, melted, and kneaded in an extruder with various additives such as a foaming agent and, if necessary, a foam regulator. After cooling to a predetermined temperature, it is extruded from the die in a sheet form and foamed, and then immediately cooled. This produces a sheet-like polystyrene foam layer. If a foaming gas is used as the foaming agent, the manufactured polystyrene foam layer is left to stand for a while, and any remaining foaming gas in the polystyrene foam layer is replaced with air.

[0067] In the polystyrene foam layer manufacturing process, specifically, for example, a molten mixture containing polystyrene resin (I), a foaming agent, and various additives such as foam regulators added as needed is extruded from the discharge port of a circular die to form a cylindrical foam. The foam is then pulled up while the inner surface of the foam is brought into sliding contact with the outer surface of a cooling mandrel, which has a larger diameter than the discharge port and is positioned downstream of the circular die (forward in the extrusion direction). The foam is expanded in diameter by the cooling mandrel and cooled from the inside. The foam is then continuously cut in the extrusion direction by a cutter provided downstream of the cooling mandrel to unfold it into a flat sheet.

[0068] In the polystyrene resin layer manufacturing and lamination process, typically, a resin composition containing polystyrene resin (II) and rubber-modified polystyrene resin is heated, melted, and kneaded in an extruder along with various additives as needed. After cooling to a predetermined temperature, it is extruded from the die in a film form and laminated onto the surface of a polystyrene resin foam layer before it has completely cooled. During this lamination process, the polystyrene resin foam layer is subjected to heat treatment. This results in a laminate of a polystyrene resin foam layer and a polystyrene resin layer.

[0069] In the manufacturing and lamination process of polystyrene resin layers, specifically, for example, it can be carried out by an extrusion lamination method using a flat die on a polystyrene resin foam layer. Such an extrusion lamination method can be carried out using, for example, a conveying mechanism for horizontally conveying the polystyrene resin foam layer, an extrusion mechanism for extruding molten polystyrene resin (II) and the resin composition onto the upper surface of the horizontally conveyed polystyrene resin foam layer, and a thickness correction mechanism for regulating the total thickness of the polystyrene resin foam layer and the molten resin composition coated on the polystyrene resin foam layer. The conveying mechanism can be composed of, for example, a feeder that can unwind the polystyrene resin foam layer sequentially from the outside by rotating a roll of raw material wound into a roll in the opposite direction to the winding direction, and a winding machine that can rewind the polystyrene resin foam layer unwound from the feeder into a roll. The extrusion mechanism can be composed of a flat die having an opening width equal to the width of the polystyrene resin foam layer, and an extruder with the flat die attached to its tip. The thickness correction mechanism can be configured as a thickness correction device having a thickness correction roll consisting of two rolls whose length is longer than the width of the polystyrene resin foam layer, the two thickness correction rolls having their rotation axis direction horizontal and arranged parallel to each other vertically, and the spacing between their outer surfaces can be adjusted by moving them closer together or further apart.

[0070] In the polystyrene resin layer manufacturing and lamination process, more specifically, the raw material roll is set in a feeder, the polystyrene resin foam layer unfurled from the feeder is passed between thickness correction rolls and its leading end is set in the winding machine, the spacing between the outer surfaces of the thickness correction rolls is set to a spacing corresponding to the thickness of the polystyrene resin laminated foam sheet to be formed, and the extruder is set up so that the resin composition heated and melted from a flat die is extruded onto the upper surface of the polystyrene resin foam layer in front of the thickness correction rolls. In other words, by cooperating a dispensing machine and a winding machine to move the polystyrene foam layer in the longitudinal direction, and by dispensing the resin composition that has been heated and melted so that it spreads throughout the entire width of the polystyrene foam layer from a flat die, the polystyrene foam layer with its upper surface laminated with the heated and melted resin composition is passed between thickness correction rolls, and the upper thickness correction roll sufficiently cools the laminated resin composition and smooths its surface, thereby producing a polystyrene foam sheet in which a polystyrene foam layer having a uniform thickness in the plane is laminated on top of the polystyrene foam layer.

[0071] It is preferable to allow an appropriate curing period for the polystyrene foam layer between the polystyrene foam layer manufacturing process and the polystyrene foam layer manufacturing and lamination process. After the polystyrene foam layer manufacturing process, it is preferable to cure the polystyrene foam layer at a temperature of 20°C to 40°C for about 10 to 30 days before carrying out the polystyrene foam layer manufacturing and lamination process.

[0072] The heat treatment process can be carried out using common heating devices such as hot air fans, radiant heaters, and heat rolls. Typically, this is done by blowing hot air at 50°C to 120°C from a distance of 10 cm to 25 cm from the surface of the polystyrene resin laminated foam sheet, thereby heating the polystyrene resin laminated foam sheet from the polystyrene resin layer side. The heat treatment process may also be performed on the polystyrene resin laminated foam sheet after it has passed through the straightening roll in the polystyrene resin layer manufacturing and lamination process, but before it is wound onto the winding machine. In other words, the heat treatment process may be carried out immediately after the polystyrene resin layer manufacturing and lamination process. Alternatively, the heat treatment process may be carried out after the polystyrene resin laminated foam sheet has been wound into a roll, for example, after a period of 12 hours to 10 days.

[0073] In the winding process, the laminate of polystyrene foam layer and polystyrene resin layer is wound up using winding equipment such as a roll.

[0074] ≪Polystyrene-based laminated foam container≫ A polystyrene resin laminated foam container according to an embodiment of the present invention is formed by thermoforming a polystyrene resin laminated foam sheet. One embodiment of the polystyrene resin laminated foam container according to an embodiment of the present invention is formed in a container shape such that the polystyrene resin layer is on the outside of the container.

[0075] To manufacture a polystyrene resin laminated foam container according to an embodiment of the present invention using a polystyrene resin laminated foam sheet according to an embodiment of the present invention, the polystyrene resin laminated foam sheet, wound into a roll, is heated to a constant temperature in the heating zone of a molding machine, and then molded into the desired container shape in the molding zone. The container shape can be various shapes, such as a bowl shape, a cup shape, a box shape, or a tray shape.

[0076] The polystyrene resin laminated foam container according to an embodiment of the present invention is typically formed into a container shape such that, as shown in FIG. 4, the polystyrene resin laminated foam sheet according to the embodiment of the present invention has a polystyrene resin foam layer on the inside and a polystyrene resin layer on the inside. In FIG. 4, the inside of the container of the polystyrene resin laminated foam container 1000 is 200, and the outside of the container is 300.

Example

[0077] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods for each property are as follows.

[0078] <Melt Tension> The melt tension was measured using a twin-bore capillary rheometer "Rheologic5000T" manufactured by Thiasos as the measuring device. The melt tension was measured with a capillary die having a diameter of 2.095 mm, a length of 8 mm, and an inlet angle of 90 degrees (conical) set in the above measuring device, and a pulley for tension detection located 27 cm below this capillary die. First, the measuring sample was filled into a barrel with a diameter of 15 mm heated to a test temperature of 200°C. The filled measuring sample was preheated for 5 minutes to melt it. The melt was extruded from the capillary die in a string shape while maintaining a constant piston descent speed (0.07730 mm / s). After passing this string through the pulley for tension detection, it was wound up using a winding roll. The initial winding speed was set at 4 mm / s. The winding speed was gradually increased with an acceleration of 12 mm / s 2 until. The average of the maximum and minimum values of the tension immediately before the point where the string was cut was taken as the melt tension (MT) of the measuring sample.

[0079] <Measurement of MFR> The measurement of the melt mass flow rate (MFR) for the polystyrene resin was carried out in accordance with the method described in Method B of JIS K 7210:1999 "Plastics - Test Method for Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) of Thermoplastic Plastics". Equipment: Semi-automatic melt indexer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Test temperature: 200℃ Test load: 5.0 kgf Operation method: B method Heating time: 5 minutes

[0080] <Weight average molecular weight> The weight-average molecular weight (Mw) refers to the weight-average molecular weight in terms of polystyrene (PS) measured using gel permeation chromatography (GPC). Specifically, the weight-average molecular weight was measured as follows: 6 mg of the sample was dissolved in 6 mL of THF (tetrahydrofuran) (immersion time: 6 ± 1 hr (complete dissolution)) to obtain the sample solution. The sample solution was filtered using a non-aqueous 0.45 μm syringe filter manufactured by Shimadzu GLC Corporation to obtain the filtrate. The obtained filtrate was measured using gel permeation chromatography (GPC) under the following measurement conditions, and the weight-average molecular weight (Mw) was determined from a pre-prepared standard polystyrene calibration curve. (Equipment used) Tosoh Corporation's "HLC-8320GPC EcoSEC" gel permeation chromatograph (with built-in RI detector and UV detector) (column) Sample side Guard column = TSK guardcolumn SuperMP(HZ)-H (4.6mm I.D. × 2cm) × 1 piece, manufactured by Tosoh Corporation. Measurement column = TSKgel SuperMultiporeHZ-H (4.6mm I.D. × 15cm) manufactured by Tosoh Corporation × 2 in series Reference side TSKgel Super HZ1000 (6.0mm I.D. x 15cm) x 1 piece, manufactured by Tosoh Corporation. (Various conditions) Column temperature = 40°C Mobile phase=THF Mobile phase flow rate Sample pump = 0.2 mL / min Reference pump = 0.2 mL / min Detector = RI detector Sample concentration = 0.1 wt% Injection volume = 20μL Measurement time = 26 min Sampling pitch = 200 msec (method) The standard polystyrene samples used for the calibration curve were "STANDARD SM-105" and "STANDARD SH-75" manufactured by Showa Denko K.K., with weight-average molecular weights of 5,620,000, 3,120,000, 1,250,000, 442,000, 151,000, 53,500, 17,000, 7,660, 2,900, and 1,320. The standard polystyrene samples for the calibration curve described above were divided into groups A (5,620,000, 1,250,000, 151,000, 17,000, 2,900) and B (3,120,000, 442,000, 53,500, 7,660, 1,320). After weighing (2 mg, 3 mg, 4 mg, 4 mg, 4 mg) of group A, they were dissolved in 30 mL of THF, and similarly, (3 mg, 4 mg, 4 mg, 4 mg, 4 mg) of group B were dissolved in 30 mL of THF. The standard polystyrene calibration curve was obtained by injecting 20 μL of the prepared solutions of A and B, measuring the results, and then creating a calibration curve (linear equation) from the retention times obtained. The weight-average molecular weight was calculated using this calibration curve.

[0081] <Measurement of the total content ratio of styrene dimer and styrene trimer in polystyrene resin foam layer> Approximately 0.2 g of sample was taken from the polystyrene foam laminated sheet, ensuring that the weight ratio of the polystyrene foam layer to the polystyrene foam layer was maintained. This sample was dissolved in 10 ml of methyl ethyl ketone, added dropwise to 35 ml of methanol to reprecipitate, and stirred for approximately 1 hour. Next, the reprecipitated solution was filtered through No. 5A filter paper into a 50 ml volumetric flask and dissolved in 50 ml of methanol. Then, 10 μl of the internal standard pyrene (1000 ppm methanol solution) was placed in a 2 ml volumetric flask and dissolved in 2 ml of the methanol solution in the 50 ml volumetric flask to prepare the sample solution. Next, GC / MS measurements were performed using this sample solution under the following conditions. The peak areas of the three styrene dimer peaks and five styrene trimer peaks in the resulting chromatogram were quantified using a pre-prepared calibration curve for styrene oligomers, which was used as the relative sensitivity to the peak area of ​​pyrene, an internal standard. The calibration curves for styrene dimer and styrene trimer were prepared using standard substances manufactured by Kanto Chemical Co., Ltd. The total content (in ppm) in the polystyrene resin was calculated from the total amount of styrene dimer and styrene trimer obtained in this way. (GC / MS measurement conditions) Equipment: Shimadzu Corporation gas chromatograph mass spectrometer "QP5050A (GC=GC-17A)" Column: ZB-5MS (manufactured by Phenomenex, 0.25 μm × 0.25 mmφ × 30 m) GC oven heating conditions: Initial temperature 100°C (1 minute) First stage heating rate: 10°C / min (holds up to 190°C for 2.5 minutes) Second stage heating rate: 10°C / min (up to 300°C) Final temperature 300℃ (2.5 minutes) Inlet temperature: 240℃ Detector temperature: 260℃ Detector: 1.25kV Carrier gas: Helium Total flow: 15.3mL / min Column flow rate: 1.0 mL / min Carrier gas pressure: 75kPa Test solution injection volume: 2 μl (using autosampler) Split ratio: 1 / 12

[0082] <Laminated polystyrene foam container> Container A, having the cross-sectional shape shown in Figure 3, was manufactured by thermoforming a polystyrene resin laminated foam sheet. Container A was manufactured with the polystyrene resin foam layer facing inward (the polystyrene resin layer facing outward). Furthermore, container A had an inner diameter of 140 mm at its opening, an inner diameter of 100 mm at its bottom, a depth of 80 mm, and a diaphragm ratio of 0.57. To manufacture container A, a press molding apparatus was used that had a cavity (concave mold) with 6 x 6 = 36 recesses corresponding to the outer shape of container A, and a plug (convex mold) with the same number of protrusions corresponding to the inner shape of container A. Container A was manufactured by continuously supplying a long, strip-shaped polystyrene resin laminated foam sheet to this press molding apparatus in the length direction. The molding conditions were as follows: a molding cycle of 5.0 seconds per shot (36 units), a set temperature of 350°C for the cavity-side heater, and a set temperature of 260°C for the plug-side heater. Additionally, the set temperature of the mold on the cavity side was 60°C, and the set temperature of the mold on the plug side was 120°C. Furthermore, the molding timing was set so that the cavity and plug come into contact with the polystyrene resin laminated foam sheet almost simultaneously and the molding process begins.

[0083] <Evaluation of container appearance> The appearance of the 36 containers produced in the first shot, immediately after the press molding machine was started, and the 36 containers produced in the 30th shot, when the mold was presumably sufficiently heated after repeated molding, were observed. Then, the containers in each example and comparative example were examined for any abnormalities in appearance, such as wrinkles or internal cracks. We evaluated the results by marking "○" for cases where no abnormalities were found and "×" for cases where abnormalities were found.

[0084] <Evaluation of curved surface printing> The outer surface of the container was printed using a curved surface printing machine. The printed surface was visually inspected, and it was judged as "○" if no "fading" in the printing was observed, and "×" if "fading" in the printing was observed.

[0085] <Resin materials> The following resin materials were used in the manufacture of the polystyrene-based laminated foam sheet. (1) Impact-resistant polystyrene resin (rubber-modified polystyrene resin) manufactured by Toyo Styrene Co., Ltd., product name "E641N", MFR: 3.6g / 10min (2) Impact-resistant polystyrene resin (rubber-modified polystyrene resin) manufactured by Toyo Styrene Co., Ltd., product name "E640N", MFR: 2.7g / 10min (3) Impact-resistant polystyrene resin (rubber-modified polystyrene resin) manufactured by PS Japan, product name "475D", MFR: 2.2g / 10min (4) Polystyrene resin (GPPS), GP1, MFR: 2.0g / 10min, Mw=325000, Mz=892000, Mz / Mw=2.74, Melt tension=21.9cN (0.219N) (5) Polystyrene resin (GPPS), GP2, MFR: 2.1g / 10min, Mw=311000, Mz=902000, Mz / Mw=2.90, Melt tension=19.5cN (0.195N) (6) Polystyrene resin (GPPS), GP3, MFR: 1.3g / 10min, Mw=359000, Mz=822000, Mz / Mw=2.29, Melt tension=18.5cN (0.185N) (7) Polystyrene resin (GPPS), GP4, MFR: 1.4g / 10min, Mw=340000, Mz=855000, Mz / Mw=2.51, Melt tension=27.9cN (0.279N) (8) Polystyrene resin manufactured by PS Japan, product name "G0002", MFR: 2.0g / 10min, Mw=271000, Mz=480000, Mz / Mw=1.77, melt tension=8.7cN (0.087N) (9) Polystyrene resin (polystyrene-based resin) manufactured by Toyo Styrene Co., Ltd., product name "HRM52N", MFR: 2.6g / 10min, Mw=261000, Mz=491000, Mz / Mw=1.88, melt tension=7.4cN (0.074N)

[0086] [Manufacturing Example 1] A mixed butane containing isobutane in a ratio of 62% by weight and normal butane in a mass ratio is melt-kneaded with polystyrene resin (PS Japan Co., Ltd., product name "G0002", MFR: 2.0g / 10min) in an extruder to prepare a molten mixture containing the mixed butane at a ratio of 3.34% by weight in the extruder, and this molten mixture is extruded and foamed to a thickness of 2.05mm and a basis weight of 240g / m².2 , density 0.117g / cm 3 A polystyrene foam sheet (1) was manufactured. The total content of styrene dimer and styrene trimer in the polystyrene foam layer (1) was 845 ppm.

[0087] [Example 1] (Manufacturing of polystyrene-based laminated foam sheets) After curing the polystyrene foam sheet (1) (which will become the polystyrene foam layer) obtained in Production Example 1 at room temperature (20°C to 40°C) for 28 days, the blended resin composition (1) shown in Table 1 was laminated to one side of the polystyrene foam sheet (1) by heating and melting it under conditions where the resin temperature reached 250°C, resulting in one side of the polystyrene foam sheet (1) with a thickness of 114 μm and a basis weight of 120 g / m². 2 A polystyrene resin laminated foam sheet (1) was formed by laminating a polystyrene resin layer. A heat treatment process was performed on the obtained polystyrene resin laminated foam sheet (1) by blowing 90°C hot air from a position 15 cm away from the surface on the polystyrene resin layer side, thereby heating the polystyrene resin laminated foam sheet (1) from the polystyrene resin layer side. The results are shown in Table 1.

[0088] [Example 2] A polystyrene-based resin laminated foam sheet (2) was obtained in the same manner as in Example 1, except that the blended resin composition (2) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0089] [Example 3] A polystyrene-based resin laminated foam sheet (3) was obtained in the same manner as in Example 1, except that the blended resin composition (3) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0090] [Example 4] A polystyrene-based resin laminated foam sheet (4) was obtained in the same manner as in Example 1, except that the blended resin composition (4) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0091] [Example 5] A polystyrene-based resin laminated foam sheet (5) was obtained in the same manner as in Example 1, except that the blended resin composition (5) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0092] [Comparative Example 1] A polystyrene-based resin laminated foam sheet (C1) was obtained in the same manner as in Example 1, except that the blended resin composition (C1) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0093] [Comparative Example 2] A polystyrene-based resin laminated foam sheet (C2) was obtained in the same manner as in Example 1, except that the blended resin composition (C2) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0094] [Comparative Example 3] A polystyrene-based resin laminated foam sheet (C3) was obtained in the same manner as in Example 1, except that the blended resin composition (C3) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0095] [Comparative Example 4] A polystyrene-based resin laminated foam sheet (C4) was obtained in the same manner as in Example 1, except that the blended resin composition (C4) shown in Table 1 was used instead of the blended resin composition (1). The results are shown in Table 1.

[0096] [Table 1] [Industrial applicability]

[0097] The thermoplastic resin laminated foam sheet according to an embodiment of the present invention can be suitably used as a material for containers such as cup-type instant noodles. The polystyrene resin laminated foam container according to an embodiment of the present invention can be suitably used as a container for cup-type instant noodles. [Explanation of Symbols]

[0098] 100 Polystyrene-based resin laminated foam sheet 10 Polystyrene foam layer 10a Side surface of the polystyrene foam layer 20 Polystyrene resin layer 20a Side surface of the polystyrene resin layer 1000 foam containers 200 Inside the container 300 Outside the container

Claims

1. A polystyrene resin laminated foam sheet in which a non-foamed polystyrene resin layer is laminated on at least one surface of a polystyrene resin foam layer, The polystyrene resin foam layer is formed by foaming polystyrene resin (I), The total content ratio of styrene dimer and styrene trimer in the polystyrene resin foam layer is 2000 ppm or less. The non-foamed polystyrene resin layer contains polystyrene resin (II) and rubber-modified polystyrene resin in a weight ratio of polystyrene resin (II):rubber-modified polystyrene resin = 10:90 to 60:

40. The weight-average molecular weight (Mw) of polystyrene resin (II) is between 280,000 and 460,000. The average molecular weight (Mz) of polystyrene resin (II) is between 500,000 and 1,200,000. Polystyrene resin laminated foam sheet.

2. A polystyrene resin laminated foam sheet according to claim 1, having a thickness of 0.5 mm to 4.0 mm.

3. Basis weight 200 g / m² 2 ~800g / m 2 The polystyrene resin laminated foam sheet according to claim 1 or 2.

4. A polystyrene resin laminated foam container, in which a polystyrene resin laminated foam sheet according to any one of claims 1 to 3 is thermoformed.

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