JP4515935B2 - Polystyrene-based resin foam laminate sheet and molded product thereof - Google Patents

Description

  The present invention relates to a polystyrene-based resin foam laminated sheet and a molded product thereof, and more particularly to a polystyrene-based resin foam laminated sheet by extrusion foaming excellent in oil resistance, particularly resistance to a medium chain fatty acid triglyceride, and a molded product thereof.

  Expanded polystyrene sheets and molded articles thereof have been widely used for food containers. In addition, a foamed polystyrene laminated sheet obtained by laminating a non-foamed resin layer on a foamed polystyrene sheet has been widely used in food containers. However, the expanded polystyrene sheet is poor in oil resistance, and polystyrene is plasticized at high temperature to oil containing 8 to 20 carbon fatty acids and medium chain fatty acid triglyceride called MCT which are widely used in foods. There was a problem that holes were generated in polystyrene containers.

  Conventionally, a heat-resistant and oil-resistant resin sheet containing a mixture of a polystyrene-based resin and a highly oil-resistant resin has been proposed as an attempt to impart oil resistance to the expanded polystyrene sheet for such problems (Patent Document 1). ).

  However, since the resin sheet described in Patent Document 1 is incompatible with polystyrene resins and those resins with high oil resistance, a compatibilizing agent is required to bring out the necessary physical properties. There is a problem in recyclability after use.

Japanese Patent No. 311238

  Conventionally, a food container in which the surface of a polystyrene foam is coated with polyacrylonitrile has been disclosed (Patent Document 2).

  However, in the food container described in Patent Document 2, since polyacrylonitrile is brittle and inferior in impact resistance and is incompatible with polystyrene, there may be a problem in recyclability.

JP 2000-33976 A

  Furthermore, it has been conventionally made to provide oil resistance by laminating an olefin resin film on expanded polystyrene, but there is a problem that the adhesiveness of the film and the recyclability of the molded container are poor.

  The present invention is a polystyrene resin having oil resistance, in particular, oil resistance to fatty acid ester oils such as medium chain fatty acid triglycerides at high temperatures, having low cost and excellent recyclability, and excellent thermoformability. It is an object to provide a foam laminated sheet.

The present invention is a polystyrene-based resin foam laminated sheet formed by laminating a non-foamed resin layer on at least one surface of an extruded foamed polystyrene-based resin foam sheet.
The laminated non-foamed resin layer is a polystyrene resin containing 18% by weight or more of an acrylonitrile component,
It is a polystyrene-based resin foam laminated sheet characterized by having an open cell ratio of 50% or less as the foam laminated sheet. Thereby, the said subject can be solved.

  In particular, the polystyrene resin containing 18% by weight or more of an acrylonitrile component is preferably a mixed resin of a styrene-acrylonitrile copolymer and rubber-modified polystyrene.

  According to the present invention, a polystyrene resin non-foamed resin layer containing 18% by weight or more of an acrylonitrile component is laminated on at least one surface of an extruded foamed polystyrene resin foam sheet, and the open cell ratio as a foam laminated sheet is 50. % Of less than or equal to 25%, it has oil resistance, especially oil resistance to fatty acid ester oils such as medium-chain fatty acid triglycerides at high temperatures, and has excellent recyclability at low cost. And, it can be set as the polystyrene type resin foam lamination sheet excellent in thermoformability.

  Therefore, by using such a sheet, the oil-resistant, particularly fatty acid ester such as medium-chain fatty acid triglyceride at high temperature, by thermoforming into a food container or the like so that the surface of the non-foamed resin layer is in contact with food containing oil It is possible to obtain a molded article having excellent recyclability at low cost while having oil resistance to the system oil.

  In addition, when the polystyrene resin layer containing 18% by weight or more of acrylonitrile is used inside the container, the container suppresses elution of styrene dimer and styrene trimer from the polystyrene resin foam sheet. In particular, it is preferable as a food container.

  When a mixed resin of a styrene-acrylonitrile copolymer and rubber-modified polystyrene is employed as the polystyrene resin containing 18% by weight or more of an acrylonitrile component, oil resistance, cost, and brittleness of the resin can be improved in a balanced manner.

(Polystyrene resin foam sheet)
The polystyrene-based resin foam sheet in the present invention is a conventionally known polystyrene-based resin, for example, polystyrene, rubber-modified polystyrene, styrene acrylic acid copolymer, styrene methacrylic acid copolymer, styrene maleic anhydride copolymer, or the like. It can be obtained by heat melting and kneading a resin and the like, a foaming agent and a cell regulator with an extruder and extrusion foaming. That is, the styrene resin is supplied to an extruder together with a foaming agent and melt kneaded. The melt-kneaded resin is directly extruded from a die adjusted to a temperature suitable for foaming and foamed into a sheet shape, or once extruded into a cylindrical shape and foamed, and then cut in an arbitrary line. Thus, a long strip foam sheet is produced. Examples of the foaming agent include a decomposable foaming agent, a gas or a volatile foaming agent.

  Among these, as the decomposition foaming agent, for example, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide, sodium borohydride and other inorganic degradable foaming agents, azodicarbonamide, azobissulfuramide, Azo compounds such as azobisisobutyronitrile and diazoaminobenzene, nitroso compounds such as N, N′-dinitrosopentanemethyleneterramine and N, N′-dimethyl-N, N′-dinitrosotephthalamide, benzenesulfonyl And hydrazide. These foaming agents may be used alone or in combination. In order to adjust the decomposition temperature, the amount of generated gas, and the decomposition rate, a known foaming aid may be added.

  Examples of gaseous blowing agents include nitrogen, carbon dioxide, propane, n-butane, i-butane, methyl ether and the like. Here, the gas means a gas at normal temperature (25 ° C.) and normal pressure (1 atm). On the other hand, examples of the volatile blowing agent include ether, petroleum ether, acetone, pentane, isopentane, hexane, isohexane, heptane, isoheptane and the like. Water can also be used. These can also be used in combination.

  Among the blowing agents, butanes such as normal butane, isobutane, or a mixture of both (mixed butane) are preferable. A mixed foaming agent obtained by adding propane to mixed butane is also preferable. This mixed foaming agent has an advantage that the foamed sheet can be made finer and the aging period of the foamed sheet can be shortened. When it is desired to make the bubble size about 40 μm or less, it is preferable to use nitrogen, carbon dioxide gas and water alone or in combination of two or more. Nitrogen and the like have the advantage of being inexpensive because they can be separated directly from the air.

  In extrusion foaming, other additives may be added together with the foaming agent. Examples of other additives include a bubble regulator. Specific examples include inorganic powders such as talc and silica, acidic salts such as polyvalent carboxylic acids, and reaction mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate. Increasing the amount of these bubble regulators may weaken the bubble film to heat, and the bubble film may be broken when the film is extruded and laminated to increase the open cell ratio. In order to prevent such a bubble film from being broken, it is preferable to use nitrogen or carbon dioxide as a foaming agent.

  Furthermore, you may add a ultraviolet absorber, antioxidant, a coloring agent, a lubricant, a flame retardant, an antistatic agent etc. as needed.

The polystyrene foam sheet in the present invention preferably has a density in the range of 0.05 to 0.5 g / cm ³ and a thickness of 0.8 to 5.0 mm. When the density is less than 0.05 g / cm ³ , the strength of the foam is lowered, and thus the strength of the container cannot be maintained when thermoformed into a container or the like. When the density is larger than 0.5 g / cm ³ , the heat insulating property as a foam is poor, which is not preferable. When the thickness is less than 0.8 mm, the container strength when thermoformed into a container or the like is lowered, which is not preferable. When the thickness is more than 5.0 mm, the thermoformability is inferior.

(Non-foamed resin layer)
For the non-foamed resin layer laminated on the polystyrene resin foam sheet, a polystyrene resin containing 18% by weight or more of an acrylonitrile component is used. This resin is preferably a mixed resin of a styrene-acrylonitrile copolymer (AS resin) and rubber-modified polystyrene. If the mixed resin of styrene-acrylonitrile copolymer and rubber-modified polystyrene is used as the non-foamed resin layer, the cost can be reduced more than when the styrene-acrylonitrile copolymer is used alone. In particular, the brittleness of the styrene-acrylonitrile copolymer can be improved.

  If the content of the acrylonitrile component is less than 18% by weight, the oil resistance against the medium-chain fatty acid triglyceride of the non-foamed resin layer is insufficient, and when molded into a container, the inner surface of the container is affected at high temperatures depending on the contents. Problems such as hole opening may occur. In addition, when the content of the acrylonitrile component is too large, there is no problem with respect to oil resistance to the medium-chain fatty acid triglyceride, but the compatibility with the polystyrene resin is lowered, and the styrene-acrylonitrile copolymer and the rubber-modified polystyrene are mixed. This is not preferable because the physical properties of the resin when used as a resin are lowered, and there is a problem in recyclability. The acrylonitrile component content is more preferably 18 to 28% by weight, and particularly preferably 18 to 25% by weight.

  The content of the acrylonitrile component contained in the styrene-acrylonitrile copolymer used in the present invention is preferably 20 to 30% by weight. If it is less than 20% by weight, not only the cost reduction effect when mixed with rubber-modified polystyrene, but also the brittleness improvement effect is small. If it exceeds 30% by weight, the compatibility with rubber-modified polystyrene is lowered, and the physical properties of the mixed resin are reduced. Since it falls, it is not preferable.

Examples of the rubber-modified polystyrene to be mixed with the styrene-acrylonitrile copolymer used in the present invention include styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, vinylxylene, vinylnaphthalene and the like, or a mixture and a butadiene rubber. A polymer obtained by polymerizing a polymer can be used. Polybutadiene, styrene-butadiene copolymer, and styrene-butadiene block copolymer are used as the butadiene rubber-like polymer. In the present invention, the molecular weight and the degree of branching of the budadiene polymer are not limited.
The amount of the butadiene rubber-like polymer of rubber-modified polystyrene used in the present invention is not particularly limited, but is preferably in the range of 1 to 15% by weight. The rubber-modified polystyrene used in the present invention is produced by a variety of methods for producing conventionally known rubber-modified polystyrene (HIPS resin), that is, bulk polymerization, bulk-suspension polymerization, emulsion polymerization and the like. The particle size of the dispersed particles comprising a butadiene rubber-like polymer is a known method, for example, stirring strength, the molecular weight of the produced styrene polymer, the amount of molecular weight modifier, the amount of solvent, the molecular weight of the butadiene rubber polymer used. It is adjusted by changing the kind of the polymerization initiator. It is also available as a commercially available HIPS resin.

  The rubber-modified polystyrene used in the present invention is preferably one in which a rubber-like polymer is dispersed in a polystyrene matrix, and the average dispersed particle diameter is preferably 2.0 μm or more. The average dispersed particle size is a particle size obtained by a measurement method defined later. An average dispersed particle size of less than 2.0 μm is not preferable because the oil resistance decreases when a mixed resin with a styrene-acrylonitrile copolymer is used. This is because when the amount of rubber contained is the same, the smaller the average dispersed particle size, the smaller the distance between the rubber particles, and in the case of polystyrene and rubber, the oil penetrates more easily into the rubber part. If the distance is small, the oil penetration speed as a whole increases, and it is considered that the oil resistance is affected. On the other hand, if the average dispersed particle size of the rubber component is too large, the impact resistance of the rubber-modified polystyrene resin itself is lowered, and the brittleness improvement effect of the mixed resin is reduced, which is not preferable. Therefore, a more preferable average dispersed particle size of the rubber component is 2.0 to 5.0 μm.

  In addition, if the rubber component contained in the laminated non-foamed resin layer is too much, the oil resistance is affected. Therefore, the rubber component contained in the mixed resin of the styrene-acrylonitrile copolymer and the rubber-modified polystyrene resin is 5% by weight. % Or less, and more preferably 3% by weight or less. On the other hand, in order to improve brittleness, 0.5% by weight or more is preferable. When the non-foamed resin layer of the foamed laminated sheet is highly brittle, the non-foamed resin layer may be broken and missing due to piercing by a crank pin of a molding machine and mixed into a molded product.

  The thickness of the non-foamed resin layer containing 18% by weight or more of the acrylonitrile component in the present invention is not particularly limited and may be appropriately determined within a range not impairing the effects and moldability of the present invention. For example, when forming into a food container, it is preferably 10 to 500 μm. If it is thinner than 10 μm, the non-foamed resin layer cannot follow the elongation at the time of molding, and the non-foamed resin layer is torn or extremely thin, so that the effects of the present invention cannot be obtained. If it exceeds 500 μm, the molding temperature range with the foamed layer will be greatly different at the time of molding, and the moldability of the foamed laminated sheet will be unfavorable. 20-150 micrometers is more preferable.

  Moreover, well-known additives, such as a pigment and a lubricant, can be added to the non-foamed resin layer to be laminated to such an extent that the effects of the present invention are not hindered.

(Production method)
The polystyrene-based resin foam laminated sheet in the present invention can be produced by a conventionally known method (such as an extrusion lamination method, a coextrusion method, a bonding method using an adhesive, or a fusion method using heat). First, as an extrusion laminating method, a polystyrene resin foam sheet is obtained by kneading a polystyrene resin and a foaming agent in an extruder and then extruding and foaming from a mold. Next, for example, by extruding a non-foamed resin layer (film) with an extruder equipped with a T-die, the foamed polystyrene-based resin foamed laminated sheet can be easily obtained by laminating the polystyrene-based resin foamed sheet.

  As a co-extrusion method, use two or more extruders, before extruding and foaming a polystyrene resin foam sheet, laminate a non-foamed resin layer in the mold and simultaneously extrude from the mold to make a polystyrene resin foam sheet. Is the way to get. Examples of the adhesive that can be used in a bonding method using an adhesive between a polystyrene resin foam sheet and a non-foamed resin layer (film) include ethylene-vinyl acetate copolymer and methyl methacrylate polymer elastomer. . The adhesive is usually used at a thickness of about 5 to 15 μm.

  The fusion method using heat is, for example, a method in which heat is applied to a polystyrene resin foam sheet with a hot roll and / or hot air, and then a non-foamed resin layer (film) extruded in advance is laminated. The surface of the heat roll is preferably subjected to chrome plating or Teflon (registered trademark) coating to prevent sticking with the heated foam.

  In the present invention, as a method of laminating a polystyrene resin foam sheet and a non-foamed resin layer containing 18% by weight of an acrylonitrile component, laminating by coextrusion is preferable from the viewpoint of suppressing manufacturing cost. In the coextrusion method in which the polystyrene resin foam sheet in the present invention and the non-foamed resin layer containing 18% by weight or more of the acrylonitrile component are laminated, the viscosity of the foamed layer resin and the viscosity of the non-foamed layer resin are greatly different. As in the case of a method for producing an extruded foam sheet using a general circular mold, if the mold temperature is set to approximately the same as the extrusion temperature of the foamed resin, the temperature is low for non-foamed resin. For this reason, the non-foamed resin has a viscosity that is too high to prevent flow in the mold, resulting in a problem of uneven lamination with the foamed layer. In order to avoid this problem, in the present invention, the mold temperature is set to a temperature suitable for the extrusion of the non-foamed resin (substantially the extrusion temperature of the non-foamed resin), and the portion where the foamed layer resin is in contact with the mold, for example, When the foam layer comes to the inside of the circular mold, the two cores with greatly different viscosities should be laminated uniformly by setting the core part inside the mold below the extrusion temperature of the foam layer resin. I can do it. If the mold temperature is set to a temperature suitable for extrusion of non-foamed resin, it is too high compared to the extrusion temperature of the foamed resin layer. May cause problems such as deterioration of thermoformability.

  The open cell ratio of the polystyrene-based resin foam-based laminate sheet in the present invention is preferably 50% or less, and more preferably 30% or less. When the open cell ratio exceeds 50%, the thermoformability is deteriorated, and the strength and heat insulation of the obtained molded product are lowered.

  The polystyrene-based resin foam laminate sheet in the present invention is a polystyrene-based resin foam laminate sheet characterized by laminating a non-foamed resin layer containing 18% by weight or more of an acrylonitrile component on a polystyrene resin foam sheet. The non-foamed resin layer is laminated on at least one side of the polystyrene-based resin foam sheet. When laminated on one side of the polystyrene-based resin foam sheet, at least one non-foamed resin layer such as a printing film or another foamed sheet may be laminated on the other side.

(Thermoforming)
The polystyrene-based resin foam sheet obtained as described above can be secondarily molded by a known method and molded into a food packaging container or the like. At that time, by forming the surface on which the non-foamed resin layer containing 18% by weight or more of the acrylonitrile component is laminated so as to come to the inside of the container, the container can be prevented from being eroded by the oil contained in the food. Moreover, it is also preferable because elution of the styrene dimer and styrene trimer from the foamed sheet to the food can be suppressed.

  In extrusion foaming a polystyrene resin foam sheet, as shown in FIG. 1, using a tandem type extruder consisting of a No. 1 extruder 1 having a diameter of 40 mm and a No. 2 extruder 5 having a diameter of 65 mm, As a mixed raw material obtained by mixing 0.6 part by weight of talc as a bubble regulator with respect to 100 parts by weight of a trade name “HRM-26” (GPPS general-purpose polystyrene manufactured by Toyo Styrene Co., Ltd.) 2 and heated and melted in the barrel of No. 1 extruder 1, 3.7 parts by weight of mixed butane (normal butane / isobutane = 70/30) as a foaming agent is injected from the press-in part 3 and mixed. The raw material was melt kneaded and then transferred to the No. 2 extruder 5 through the transfer unit 4, cooled uniformly in the barrel of the No. 2 extruder 5, and then flowed into the joining die 9. The resin temperature at this time was 151 ° C., and the discharge amount from the No. 2 extruder 5 was 15 kg / hr.

On the other hand, AS resin (trade name “Stylac AS769” manufactured by Asahi Kasei Co., Ltd.) is used as a non-foamed resin layer.
77 parts by weight of acrylonitrile component content (26% by weight) and rubber modified polystyrene resin (trade name “HIPS E641N” manufactured by Toyo Styrene Co., Ltd., average rubber dispersion particle size 2.5 μm) of 23 parts by weight of mixed resin of extruder 6 having a diameter of 32 mm After being supplied to the hopper 7 and melt-kneaded, it was introduced into the merging die 9. The resin temperature at this time was 193 degreeC, and the discharge amount of the extruder 6 was 7 kg / hr.

  The two kinds of resins joined to the joining die 9 were both fed into the annular slit die 10 having a slit diameter of 80 mm and extruded into a cylindrical shape from the slit portion 102 (interval 0.61 mm) at the tip of the die 10. At this time, the core portion 101 of the annular slit die 10 was cooled with air, and the core temperature was set to 150 ° C.

  Thereafter, a resin in which a foaming agent is mixed forms a foamed layer, and a cylindrical foam with a non-foamed resin layer laminated on the foamed layer is cooled by the cooling mandrel 12 and then attached to the rear part of the cooling mandrel 12 The foamed laminated sheet 17 shown in Table 1 was obtained by incising the cylindrical foams 15 and 16. In FIG. 1, 13 a, 13 b, 13 c, and 13 d are rolls for transferring the foam laminated sheet 17 cut by the cutters 15 and 16, and 14 a and 14 b are winding rolls for the foam laminated sheet 17. In FIG. 2, reference numeral 21 denotes a foam layer resin discharged from the No. 2 extruder 5 through the discharge portion 8a, and reference numeral 22 denotes a non-foam layer resin discharged from the extruder 6 through the discharge portion 8b.

  The non-foamed resin layer is composed of AS resin (trade name “Stylac AS 769” manufactured by Asahi Kasei Co., Ltd., acrylonitrile component content 26% by weight) and rubber modified polystyrene resin (HIPS H758K manufactured by Nippon Polystyrene Co., Ltd., average rubber dispersed particle size of 3.5 μm). ) A foamed laminated sheet was obtained in the same manner as in Example 1 except that the mixed resin was 23 parts by weight. At this time, the discharge amount of the foamed resin layer from the No. 2 extruder 5 was 14 kg / hr, and the resin temperature at this time was 152 ° C. The discharge amount of the non-foamed resin layer in the extruder 6 was 7 kg / hr, and the resin temperature at that time was 200 ° C. The core temperature of the annular slit die 10 was cooled to 150 ° C.

  The non-foamed resin layer is composed of 77 parts by weight of AS resin (trade name “Stylac AS 769” manufactured by Asahi Kasei Co., Ltd.) and 23% by weight of rubber-modified polystyrene resin (trade name “CR350” manufactured by Nippon Polystyrene Co., Ltd., average rubber dispersed particle size 2.9 μm). A foamed laminated sheet was obtained in the same manner as in Example 1 except that the mixed resin was used. At this time, the discharge amount of the foamed resin layer from the No. 2 extruder 5 was 13 kg / hr, and the resin temperature at this time was 150 ° C. The discharge amount of the non-foamed resin layer in the extruder 6 was 7 kg / hr, and the resin temperature at that time was 195 ° C. The core temperature of the annular slit die 10 was cooled to 150 ° C.

  The non-foamed resin layer is composed of 77 parts by weight of AS resin (trade name “Stylac AS 769” manufactured by Asahi Kasei Co., Ltd.) and 23 weight by weight of rubber-modified polystyrene resin (trade name “HIPS E785N” manufactured by Toyo Styrene Co., Ltd., average rubber dispersed particle size 1.3 μm). A foamed laminated sheet was obtained in the same manner as in Example 1 except that the mixed resin was partly mixed. At this time, the discharge amount of the foamed resin layer from the No. 2 extruder 5 was 14 kg / hr, and the resin temperature at this time was 152 ° C. The discharge amount of the non-foamed resin layer in the extruder 6 was 7 kg / hr, and the resin temperature at that time was 202 ° C. The core temperature of the annular slit die 10 was cooled to 150 ° C.

  After heating the polystyrene-based resin foam laminated sheet obtained in Example 1 in a heating furnace, thermoforming so that the non-foamed resin layer comes to the male mold of the bowl-shaped mold, and the inside of the bowl is the non-foamed resin layer A molded article covered with was obtained. Moreover, when the elution amount of the styrene dimer and the styrene trimer in this molded product container was measured, the total elution amount was 10.4 ppb.

  A polystyrene resin film (thickness 20 μm) having a pattern printed on the surface of the polystyrene resin foam laminated sheet obtained in Example 1 on which the non-foamed resin layer was not laminated was thermally laminated and laminated. Next, this laminated sheet was processed in the same manner as in Example 4 to obtain a ridge-shaped molded product with a handle on the outside.

[Comparative Example 1]
A foamed laminated sheet was obtained in the same manner as in Example 1 except that the non-foamed resin layer was GPPS general-purpose polystyrene (trade name “HRM-26” manufactured by Toyo Styrene Co., Ltd.). At this time, the discharge amount of the foamed resin layer from the No. 2 extruder 5 was 13 kg / hr, and the resin temperature at that time was 151 ° C. The discharge amount of the non-foamed resin layer in the extruder 6 was 7 kg / hr, and the resin temperature at that time was 190 ° C. The core temperature of the annular slit die 10 was cooled to 150 ° C.

[Comparative Example 2]
The non-foamed resin layer was a mixed resin of 60 parts by weight of AS resin (trade name “Stylac AS 769” manufactured by Asahi Kasei Co., Ltd.) and 40 parts by weight of rubber-modified polystyrene resin (trade name “HIPS E641N” manufactured by Toyo Styrene Co., Ltd.). A foamed laminated sheet was obtained in the same manner as Example 1. At this time, the discharge amount of the foamed resin layer from the No. 2 extruder 5 was 13 kg / hr, and the resin temperature at that time was 152 ° C. The discharge amount of the non-foamed resin layer in the extruder 6 was 7 kg / hr, and the resin temperature at that time was 192 ° C. The annular slit die core temperature was cooled to 150 ° C.

[Comparative Example 3]
The non-foamed resin layer is a mixed resin of 77 parts by weight of AS resin (trade name “Stylac AS 769” manufactured by Asahi Kasei Co., Ltd.) and 23 parts by weight of rubber-modified polystyrene resin (trade name “HIPS E641N” manufactured by Toyo Styrene Co., Ltd.). A foamed laminated sheet was obtained in the same manner as in Example 1 except that the core portion of the die 10 was not cooled. At this time, the discharge amount of the foamed resin layer from the No. 2 extruder 5 was 13 kg / hr, and the resin temperature at that time was 152 ° C. The discharge amount of the non-foamed resin layer in the extruder 6 was 7 kg / hr, and the resin temperature at that time was 193 ° C. The core temperature of the annular slit die 10 was 180 ° C.

  Also, after heating the obtained polystyrene-based resin foam laminated sheet in a heating furnace, it is thermoformed so that the non-foamed resin layer comes to the male mold of the bowl-shaped mold, and the inside of the bowl is covered with the non-foamed resin layer. An attempt was made to obtain a molded product. However, since the air-blowing rate was high and the heated sheet was not subjected to secondary foaming, the thickness was not increased, and only a molded product having a low strength and poor mold release was obtained.

[Comparative Example 4]
After heating the polystyrene-based resin foam laminated sheet obtained in Comparative Example 1 in a heating furnace, thermoforming so that the non-foamed resin layer comes to the male mold of the bowl-shaped mold, and the inside of the bowl is the non-foamed resin layer A molded article covered with was obtained. Moreover, when the elution amount of the styrene dimer and the styrene trimer in the molded product container was measured, the total elution amount was 67.3 ppb.

<Method of measurement>
Table 1 shows the foam sheet density (g / cm ³ ), open cell ratio (%), sheet thickness (mm), and oil resistance in each of the foam laminate sheets of Examples 1 to 5 and Comparative Examples 1 to 3 manufactured as described above. It shows about property and moldability, respectively. These evaluations were measured and compared according to the following measurement methods. The measurement method for each test item is described below.

[Foamed sheet density]
The volume V (cm ³ ) of each foamed sheet sample was measured with a caliper, and obtained from the weight W (g) of the sample using the following formula.
Foam sheet density (unit: g / cm ³ ) = W / V

[Open cell ratio]
It measured according to the measuring method of ASTM D2856-87. Specifically, the volume V of the foam sheet sample measured by the 1-1 / 2-1 atmospheric pressure method using an air comparison type hydrometer 1000 type manufactured by Tokyo Science Co., Ltd., and the same sample measured with a caliper It was obtained by the following equation from the volume V _0.
Open cell ratio (unit: volume%) = (V ₀ −V) / V ₀ × 100

[Sheet thickness]
The thickness of the foam sheet was measured with a 5-point thickness gauge in the sheet width direction, and the average value was defined as the thickness (unit: mm) of the foam sheet.

[Content of acrylonitrile component]
A non-foamed resin layer-containing resin sample containing acrylonitrile component is precisely weighed about 100 to 1000 μg, wrapped in a ferromagnetic metal body having a Curie point of 590 ° C. (Pyrofoil: manufactured by Nihon Analytical Industrial Co., Ltd.), and Curie Point Pyro The acrylonitrile monomer decomposed and produced by the riser JHP-3 type (manufactured by Nippon Analytical Industries, Ltd.) was measured using a gas chromatograph Auto System (manufactured by Perkin Elmer) and a detector (FID). The measurement conditions are heating (590 ° C. × 5 sec), oven temperature (280 ° C.), needle temperature (300 ° C.), and the column is DB-5 (φ0.25 mm × 30 m (film thickness 0.25 μm)) manufactured by J & W. ) Was used. The column temperature condition was maintained at 50 ° C. for 1 minute, then raised to 100 ° C. at 10 ° C./minute, further raised to 320 ° C. at 40 ° C./minute, held at 320 ° C. for 3.5 minutes, carrier gas (He) Carrier flow rate (1 mL / min), column inlet pressure (12 psi), inlet temperature (300 ° C.), detector temperature (300 ° C.). SCIENTIFIC as standard sample
POLYMER PRODUCTS. Quantification was performed by an absolute calibration curve method using Inc. St / AN = 75/25 (CAS # 9003-54-7). When mixed with other polystyrene resins, the acrylonitrile component content was calculated from the mixing ratio.

[Oil resistance]
First, the foamed laminated sheets obtained in each of the examples and comparative examples are thermoformed into a tray shape having a length of 100 mm, a width of 190 mm, and a height of 20 mm so that the non-foamed resin laminated surface comes inside. Next, medium-chain fatty acid triglyceride (trade name “Coconard Rk” manufactured by Kao Co., Ltd.) is placed in the molded tray so as to cover the entire bottom surface of the tray, and 100 ° C. for 10 minutes with a safe ben dryer manufactured by Satake Chemical Machinery Co., Ltd. After heating, the medium-chain fatty acid triglyceride at the bottom of the container after heating was removed and the bottom of the molded product was wiped clean, and the state of the bottom non-foamed resin layer was observed. If the bottom of the container does not change and cannot be scraped when scratched with a nail, the condition of the bottom of the container does not change, but if the bottom of the container is scratched with a nail, it can be scraped. The case where a hole was opened at the bottom and the bottom was softened by a medium-chain fatty acid triglyceride in the container was rated as x.

[Average rubber dispersion particle size]
First, from the foamed laminated sheet obtained in the comparative example, the foamed layer is scraped off with a cutter knife or the like to separate only the non-foamed resin layer. Next, after the separated non-foamed resin layer was heated at 120 ° C. for 1 hour to relieve internal stress, a TEM photograph was taken by the following method, and the particle diameter of about 1,000 projected rubber particles was measured and averaged. Was the average rubber dispersed particle size. At this time, the average particle diameter of the ellipse-shaped particles was defined as the particle size.

Cross-section observation (transmission electron microscope photography)
Apparatus: Transmission electron microscope H-7600 (manufactured by Hitachi, Ltd.)
Pretreatment: Epoxy resin embedding Osmium tetroxide stained (OsO4) ultrathin section preparation sample embedded in epoxy resin, ultrathin section LEICA ULTRACUT UCT (Leica Microsystems) made ultrathin section The microscope was magnified 1000 times with a microscope H-7600 (manufactured by Hitachi, Ltd.), and a TEM photograph was taken. Osmic acid crystal (manufactured by Nissin EM Co., Ltd.) was used as a staining agent.

[Elution amount of styrene dimer and styrene trimer]
i) Preparation of eluate After 570 ml of double-distilled heptane (distilled twice to recycle the heptane used for elution) was used as the elution solvent in the sample container, and after elution at 25 ° C. for 1 hour, From this elution, 300 ml was collected and concentrated to 1 ml at 50 ° C. using a fully automatic concentrator (Turbobap 500). 40 μl of internal standard solution (pyrene 100 μg / ml) was added immediately before the measurement, and then 2 ml with n-heptane. To make a test solution.

ii) GCMS analysis SIM measurement was performed under the following conditions, and quantified with a calibration curve of styrene oligomer prepared in advance in the peak area of 4 dimer peaks and 6 trimer peaks and the peak area of the internal standard substance in the chromatogram. . Calibration curves for dimers and trimers were made using standard materials manufactured by Kanto Chemical.
GCMS analysis condition equipment: GCMS QP5050 (GC = Shimadzu GC-17A) (Shimadzu Corporation)
Column: DB-5 (manufactured by J & W) φ0.25mm × 30m Film thickness 0.25μm
Split ratio: 1:10
Inlet temperature: 240 ° C
Interface temperature: 260 ° C
Column temperature: 70 ° C. (1 min) Temperature rise 15 ° C./min→260° C. (0 min) Temperature rise 10 ° C./min→300° C. (3 min)
Carrier gas: Helium (1.2ml / min)
Test solution injection volume: 1 μl (using an autosampler)

[Styrene dimer, styrene trimer content]
First, from each foamed laminated sheet obtained in Examples and Comparative Examples, the foamed layer is scraped off with a cutter knife or the like, and only the non-foamed resin layer is separated. Next, 0.2 g of a sample from the separated non-foamed resin layer is dissolved in 10 ml of MEK, reprecipitated with 40 ml of methanol, and stirred for about 1 hour. NO. Filter into a 50 ml volumetric flask with 5A filter paper and make up with methanol. 40 μl (100 ppm) of internal standard solution pyrene was placed in a 2 ml volumetric flask, and the volume was increased with the solution in the 50 ml volumetric flask, and GCMS analysis was performed.

GCMS Analysis Conditions SIM measurement was performed under the following conditions, and quantified by a calibration curve of styrene oligomer prepared in advance with the peak area of 4 dimer peaks and 6 trimer peaks in the chromatogram and the peak area of the internal standard substance. Calibration curves for dimers and trimers were made using standard materials manufactured by Kanto Chemical.
Measuring device: Shimadzu Corporation gas chromatograph mass spectrometer QP-5050A (GC = Shimadzu GC-17A)
Column: DB-5 (manufactured by J & W) φ0.25 mm × 30 m, film thickness 0.25 μm
Inlet temperature: 240 ° C
Interface temperature: 280 ° C
Column temperature: 70 ° C. (1 min) temperature rise 15 ° C./min→260° C. (0 min) temperature rise 10 ° C./min→300° C. (3 min)
Carrier gas: Helium (1.2 ml / min) Detector (1.25 kV) Measurement mode: SIM
Internal standard: Pyrene

[Formability]
As for moldability, each foamed laminated sheet obtained in Examples and Comparative Examples is oven-heated, and a container having an inner diameter of 140 mm, an inner diameter of the bottom of 100 mm, and a depth of 80 mm is pressed with a molding die. In this case, the case where no cracks, cracks, tears or the like occurred was marked with ◯, and the case where cracks, cracks, tears, etc. occurred was marked with ×. In addition, in order to affect the strength of the molded product, a product satisfying T2 / T1 ≧ 1.2 when the thickness of the foamed laminated sheet before oven heating is T1, and the thickness of the sheet after heating is T2, is indicated by ○, T2 / The thing which becomes T1 <1.2 was set to x, and it was set as the evaluation of the following table comprehensively.

〔Comprehensive evaluation〕
In the evaluation of oil resistance and moldability, if the oil resistance and moldability are both ○, the overall evaluation ◎, if the oil resistance is △ and the moldability is ○, the overall evaluation ○, if the oil resistance is ×, the overall evaluation × In the case where the moldability was x, the overall evaluation was x.

  As shown in Table 1, the foamed laminated sheets of Comparative Example 1 and Comparative Example 2 in which the non-foamed resin layer is composed of a polystyrene resin that does not contain 18% by weight or more of the acrylonitrile component have poor oil resistance, but the acrylonitrile component A foamed laminated sheet composed of a polystyrene-based resin containing 18% by weight or more has good oil resistance. Further, in the rubber-modified polystyrene resin, Examples 1 to 4 in which the average dispersed particle size of the rubber component contained in the resin is 2.0 μm or more have good oil resistance, but the average dispersed particle size is less than 2.0 μm. In Example 5, the oil resistance is reduced. In Comparative Example 3, the core part inside the mold was not cooled and exceeded the extrusion temperature of the foamed layer resin, so that the open cell ratio increased and the moldability decreased. In Examples 1 to 5, since the core part inside the mold is cooled and set to a temperature equal to or lower than the extrusion temperature of the foam layer resin, two types of resin layers can be uniformly laminated, and moldability is improved. It is good. Further, the example in which the rubber component contained in the non-foamed resin layer to be laminated is 5% by weight or less has good oil resistance, and the example in which the rubber component is contained by 0.5% by weight or more is thermoforming. Occasionally, the non-foamed resin sheet is not lost by the crankpin, and brittleness is improved.

In the present invention, the laminated non-foamed resin layer is a polystyrene-based resin containing 18% by weight or more of an acrylonitrile component, and the foamed laminated sheet has an open cell ratio of 50% or less as the foamed laminated sheet. It becomes possible to provide resistance to oil such as medium chain fatty acid triglyceride, which can be a problem in food containers. In addition, according to the present invention, it is possible to provide a polystyrene-based resin foam laminated sheet that is inexpensive and has excellent recyclability and excellent thermoformability.
Therefore, the foamed laminated sheet of the present invention can be suitably used for food containers such as foamed polystyrene food containers.

FIG. 1 is a conceptual diagram showing an example of an apparatus for producing the foamed laminated sheet of the present invention by coextrusion. FIG. 2 is a schematic enlarged view showing the confluence die and the annular slit die in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 No. 1 extruder 2 Hopper 3 Press-in part 4 Transfer part 5 No. 2 Extruder 6 Extruder 7 Hopper 8a Discharge part 8b Discharge part 9 Merge die 10 Annular slit die 11 Cooling air ring 12 Cooling mandrel 101 Core part 102 Slit part

Claims (4)

In the polystyrene-based resin foam laminated sheet formed by laminating a non-foamed resin layer on at least one side of the extruded polystyrene-based resin foam sheet,
The laminated non-foamed resin layer is a polystyrene resin containing 18% by weight or more of an acrylonitrile component,
Open cell ratio of the foamed laminate sheet is Ri der than 50%
The polystyrene resin containing 18% by weight or more of an acrylonitrile component is a mixed resin of a styrene-acrylonitrile copolymer and a rubber-modified polystyrene,
The polystyrene-based resin foam laminated sheet, wherein the rubber-modified polystyrene has an average rubber dispersed particle diameter of 2.0 m or more . 2. The polystyrene-based resin foam laminated sheet according to claim 1, wherein a content of an acrylonitrile component in the styrene-acrylonitrile copolymer is 20 to 30% by weight. The polystyrene-based resin foam laminated sheet according to claim 1 or 2, wherein the mixed resin of the styrene-acrylonitrile copolymer and the rubber-modified polystyrene contains 0.5 to 5% by weight of a rubber component. A molded product obtained by thermoforming the non-foamed resin layer of the polystyrene-based resin foam laminated sheet according to any one of claims 1 to 3 inside.

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