JP2008114421A - Method for producing polystyrene based resin laminated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polystyrene based resin laminated sheet which is light in weight and high in heat insulation and strength and prevents the occurrence of defective adhesion called a blister formed by the remaining of a foaming agent in the interface part between a foamed polystyrene based resin sheet and a non-foamed film and the expansion and peeling form the interface part of the foaming agent by heating during thermoforming without spoiling the characteristics excellent in appearance and designability inherent for a polystyrene based resin laminated sheet. <P>SOLUTION: After heating is carried out in advance to adjust the temperature of the lamination surface of the foamed polystyrene based resin sheet to be 50°C or higher and below 70°C, the non-foamed film is laminated on the sheet to produce the polystyrene based resin laminated sheet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polystyrene resin laminated sheet, and more particularly to a method for producing a polystyrene resin laminated sheet obtained by laminating a non-foamed film on a polystyrene resin foam sheet.

  Polystyrene resin foam sheets are widely used as materials for food packaging containers because they are excellent in moldability, have high heat insulation properties, and can easily obtain lightweight and beautiful containers. Furthermore, a polystyrene-based resin laminated sheet obtained by laminating a non-expanded polystyrene resin on a polystyrene-based resin foamed sheet is excellent in strength and appearance, and is used in many cases as a food container such as instant noodles. However, recently, with the enforcement of the recycling law, the weight reduction of the foamed sheet layer has further progressed, and the difficulty of molding has increased remarkably, resulting in a problem of reduced strength of the molded container. For this reason, as a measure for increasing the strength, the surface is cooled during extrusion foaming to increase the density of the surface layer portion of the polystyrene resin foam sheet, and the amount of the remaining foaming agent is 2.3 to 3.0 weight. % Is proposed (for example, Patent Document 1).

However, increasing the amount of residual foaming agent means that the curing period for reducing the amount of foaming agent in the foamed sheet to an amount suitable for thermoforming becomes longer. Prior to sufficient curing, a polystyrene resin foam sheet and a non-foamed film are made uniform by thermally fusing a non-foamed polystyrene resin in a molten state through a heating roll from an extruder equipped with a T-die. Cannot be pressure-bonded to each other, and a poorly bonded portion is generated at the interface portion between the polystyrene resin foam sheet and the non-foamed film. Eventually, the foaming agent stays in the part, and peeling and expansion occurs from the interface due to heating at the time of thermoforming, and an appearance defect called blistering occurs, which makes it unusable as a product. For this reason, it must be stocked for a long time until the amount of the foaming agent in the foamed sheet is reduced to an appropriate amount for thermoforming, and a new problem that the cost of the molded product is high due to the cost of storage. There has occurred. These phenomena are particularly serious problems in winter.
Therefore, various efforts have been made to shorten the curing period of the polystyrene resin foam sheet from the viewpoint of cost reduction in the production of the polystyrene resin laminate sheet.

  For example, when a foamed sheet is manufactured and wound, a method of increasing the interval between the rolled sheets by increasing the winding tension, improving the air inflow efficiency, and shortening the curing period (for example, Patent Document 2) ) Has been proposed. However, when the winding tension is lowered, problems such as the meandering of the sheet in the process and the handling of the roll-wound sheet become extremely bad may occur, leading to deterioration of productivity.

In addition, propane having a permeability coefficient of butane or higher is used as a physical foaming agent in combination with butane (for example, Patent Document 3), carbon dioxide gas having a permeability coefficient five times that of air, water, ether having a boiling point of 140 ° C. or lower, There has also been proposed a method in which one or more dialkyl carbonates having a boiling point of 140 or less are used in combination with butane or the like using one or more types as physical foaming agents (for example, Patent Document 4). However, these methods focus only on reducing the amount of remaining foaming agent in the entire foamed sheet, and since this method has a small amount of residual foaming agent, high strength is achieved in the sheet for weight reduction. Can not do it.
JP-A-2005-319764 JP 9-48030 A JP 2001-105471 A JP2003-231169A

  This invention is for solving the above problems, and it aims at providing the polystyrene-type resin laminated sheet excellent in mechanical physical property and adhesiveness.

  As a result of earnest research to solve the above problems, the present inventors have adjusted the surface temperature of the laminated surface of the polystyrene-based resin foam sheet having a high amount of residual foaming agent to be lightweight and high strength within a certain temperature range. Later, when a non-foamed film was laminated, the occurrence of poor adhesion at the interface portion could be suppressed, and it was found that a good polystyrene-based resin laminated sheet could be obtained stably even in a sheet having a high residual foaming agent.

  That is, the present invention is a method for producing a polystyrene resin laminated sheet obtained by laminating a non-foamed film on a polystyrene resin foam sheet, and the surface temperature of the laminated surface of the polystyrene resin foam sheet is 50 ° C. or higher and less than 70 ° C. After the heat treatment is performed in advance, a non-foamed film is laminated on the surface subjected to the heat treatment.

  The non-foamed film is preferably a non-foamed film of polystyrene resin, the thickness of the polystyrene-based resin foam sheet is 1 mm or more and 3 mm or less, and the thickness of the non-foamed film is 100 μm or more and 200 μm or less. preferable.

  The polystyrene resin laminated sheet obtained by the present invention is excellent in appearance and moldability.

Hereinafter, embodiments of the present invention will be described in detail.
In the method for producing a polystyrene-based resin laminate sheet of the present invention, the surface temperature of the laminate surface of the polystyrene-based resin foam sheet is heat-treated so as to be any temperature within a temperature range of 50 ° C. to less than 70 ° C., Laminate non-foamed film. Any known polystyrene resin foam sheet may be used as the polystyrene resin foam sheet used in the production of the polystyrene resin laminate sheet of the present invention. The process for producing a foam sheet by extrusion foaming can be performed by a widely used method. For example, a resin composition in which a nucleating agent is mixed with a polystyrene resin is melt-mixed using an extruder, and after the foaming agent is pressed in, the molten resin is further cooled to a temperature suitable for foaming. , Extrude into the low pressure range from the circular die (ie foaming by pressure release) to obtain a cylindrical foam, located inside the cylindrical foam to cool from the inner surface side of the cylindrical foam A method is known in which a foamed sheet can be obtained after being molded by a cylindrical cooling cylinder.

  The blowing agent used in the present invention is not particularly limited. For example, physical blowing agents such as propane, butane, pentane, or sodium bicarbonate-citric acid, azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutylnitrile, etc. Chemical foaming agents. In addition, industrially easily available butane-based blowing agents are frequently used. Especially, it is preferable to use the mixed butane which consists of 70-100 weight% of isobutane and 0-30 weight% of normal butane from a viewpoint of the thermoformability of a sheet | seat, and the retainability of a foaming agent gas.

As the nucleating agent used in the present invention, porous inorganic powders such as calcium carbonate, barium sulfate, silica, titanium oxide, clay, aluminum oxide, bentonite, diatomaceous earth, talc and the like can be used. Further, if necessary, in order to improve dispersion of the nucleating agent in the resin, a fatty acid metal salt such as ethylene bisstearylamide and magnesium stearate, a lubricant such as a fatty acid ester, and the like may be added.
The basis weight of the polystyrene-based resin foam sheet in the present invention is preferably 200 g / m ² or more. When the basis weight of the polystyrene resin foam sheet is less than 200 g / m ^2, there is a tendency that a container satisfying the container strength cannot be obtained. In addition, an increase in the basis weight of the polystyrene resin foam sheet leads to an improvement in container strength, but increases the cost. Therefore, it is preferable to set the amount to 400 g / m ² or less.

  The amount of the remaining foaming agent of the polystyrene-based resin foam sheet in the present invention is mainly determined by the amount of the foaming agent injected during the production by extrusion foaming of the polystyrene-based resin and the resin temperature of the polystyrene-based resin at the time of foaming. Further, increasing the density of the surface layer portion of the polystyrene-based resin foam sheet, which will be described later, has an effect of suppressing the dissipation of the foaming agent from the surface of the polystyrene-based resin foam sheet, and is effective in securing the amount of residual foaming agent.

  As the amount of the remaining foaming agent (gas) increases in the polystyrene resin foam sheet, the gas pressure in the cell of the polystyrene resin foam sheet increases, and the container strength is improved. In order to obtain a sufficiently strong container, the amount of the remaining foaming agent in the polystyrene resin foam sheet in the present invention is preferably 2.3 to 3.0% by weight, and 2.5 to 2.8% by weight. It is more preferable that If the amount of the remaining foaming agent in the polystyrene-based resin foam sheet is less than 2.3% by weight, the container strength of the resulting container tends to decrease. In addition, when the amount of the remaining foaming agent exceeds 3.0% by weight, the foaming agent gas is dissipated from the polystyrene resin foam sheet during lamination with the polystyrene resin non-foamed film, and voids are generated at the lamination interface between the two. There is a tendency that the interface between the polystyrene-based resin non-foamed film and the polystyrene-based resin foamed sheet is peeled off during heating of molding (so-called blistering phenomenon), and the container appearance is greatly impaired.

  The closed cell ratio of the polystyrene resin foam sheet in the present invention is preferably 85% or more, and 90% in order to suppress the dissipation of the foaming agent gas in the polystyrene resin laminated foam sheet and maintain the strength properties over a long period of time. The above is more preferable. When the closed cell ratio of the polystyrene resin foam sheet is less than 85%, the remaining foaming agent in the foam sheet is quickly dissipated, the pressure inside the foam cannot be maintained, and the strength is greatly reduced. Since the secondary foaming power by heating is also reduced, good molding tends to be impossible. The closed cell ratio of the polystyrene resin foam sheet can be measured using an Air Comparison Pycnometer (for example, model 1930 manufactured by BECKMAN).

  In the present invention, when producing a polystyrene resin foam sheet by an extrusion foaming method, the surface layer portion of the polystyrene resin foam sheet is increased in density by blowing air onto the surface of the polystyrene resin foam sheet and rapidly cooling it. Can do. In order to obtain the target density of the surface layer portion, the temperature of the cooling air, the air volume, the wind speed, and the spraying position may be appropriately adjusted according to the sheet surface temperature immediately after extrusion, the extrusion resin discharge amount, the sheet take-up speed, etc. .

  The non-foamed film used for the production of the polystyrene-based resin laminate sheet of the present invention is not particularly limited as long as it is a resin film. Although it may be a film prepared from the same base resin as the polystyrene resin foam sheet or a different film, a polystyrene resin film is preferably used. The polystyrene resin film is, for example, impact-resistant polystyrene, styrene homopolymer, p-methylstyrene homopolymer, styrene-maleic anhydride copolymer, styrene-acrylonitrile copolymer, styrene-acrylic acid copolymer, It can be prepared from one or a combination of two or more selected from styrene-methacrylic acid copolymers, styrene-butadiene copolymers, styrene-butadiene-acrylonitrile copolymers, mixtures of polystyrene and polyphenylene oxide, and the like.

  Although the manufacturing method of a non-foamed film is not specifically limited, Generally, it manufactures using the manufacturing method of an extruded film. That is, it is obtained by melting the resin with an extruder and molding it into a film with a die. As this manufacturing method, an inflation method using a circular die and a T die method using a T die are generally used. In order to obtain a film having a thickness of several tens of μm, the inflation method is preferably used. In order to obtain a film, the T-die method can be preferably used.

  The means for heat treatment of the polystyrene resin foam sheet surface in the method for producing a polystyrene resin laminated sheet of the present invention is not particularly limited, and any means of contact heat treatment and non-contact heat treatment can be used.

  In the contact heat treatment, the polystyrene-based resin foam sheet is brought into direct contact with a high-temperature body such as a heating roll or a heating plate. Of these methods, the method of bringing the polystyrene resin foam sheet into contact with the heating roll is not limited, but as shown in FIG. 1, there is a method in which the polystyrene resin foam sheet 1 is wound around the surface of the heating roll 2 and brought into contact therewith. Illustrated. The contact time between the polystyrene-based resin foam sheet 1 and the heating roll 2 can be appropriately adjusted by changing the rotation speed and the contact length of the heating roll 2.

  In the non-contact heat treatment, the laminated surface of the polystyrene-based resin foam sheet is heated using a hot air device 3, a hot air heating furnace, an infrared heater, or the like. In this case, it is necessary to set conditions so that secondary foaming does not occur inside the foam sheet. In any case, in the heat treatment, the temperature of the surface of the polystyrene-based resin foam sheet is set to any one of temperatures in the temperature range of 50 ° C. or higher and lower than 70 ° C. At a temperature lower than 50 ° C., the effect of gas diffusion in the surface layer portion is not observed. At a temperature higher than 70 ° C., the heated surface of the polystyrene resin foam sheet undergoes secondary foaming, the surface properties and strength change, the deformation of the polystyrene resin foam sheet becomes excessively large, and the width and thickness are appropriate for molding. It will be out of range. Furthermore, when a heat roll is used for the heat treatment, the polystyrene-based resin foam sheet is fused to the heat roll, and the foam sheet cannot run.

  Thus, the method of laminating a non-foamed film on the polystyrene-based resin foam sheet subjected to the heat treatment is not particularly limited. For example, while extruding a non-foamed film from an extruder, a method of laminating a film on a heat-treated surface of a polystyrene-based resin foam sheet with a pressure roll, a non-foamed film manufactured in a separate process in advance and a polystyrene-based resin foam sheet Examples thereof include a method of heat-sealing and a method of laminating a polystyrene resin foam sheet and a non-foamed film with an adhesive.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

(Example 1) Polystyrene-based resin foam sheet is 100 parts by weight of polystyrene resin (manufactured by PS Japan, G0002), 0.3 parts of talc (manufactured by Hayashi Kasei Co., Ltd., Talkan PK) as a foam regulator, and as a lubricant. 0.02 part by weight of magnesium stearate was added to make a polystyrene resin composition. The polystyrene-based resin composition is charged into a 115-180 mmφ tandem extruder, and the mixture is melted in a first-stage extruder heated to a preset temperature of 200 ° C., and a butane-based gas (isobutane 85 wt% as a blowing agent). / 15% by weight mixture of normal butane) 14L / hr was injected and cooled with a second stage extruder so that the resin temperature would be 150 ° C, then extruded and foamed into the atmosphere from a circular die set at 150 ° C. I let you. The take-off rate was 9m / min, non-foamed film 30 ° C. of the cold air of 1.5 m ³ / min to a plane without stacking, the cold air of 25 ° C. to laminated surfaces in air volume of 4.5 m ³ / min of air spraying, width 1050 mm, basis weight 250 g / m ^2, non-laminated surface, each surface portion density 0.25 g / cm ³ of the laminate surface, 0.45 g / cm ^3, closed cell content of 90% polystyrene extruded foam sheet Got. The obtained foamed sheet was cured at a temperature of 25 ° C. for 20 days.

The surface of the obtained polystyrene-based resin foam sheet having a density of 0.45 g / cm ³ was subjected to contact heat treatment using a heating roll. That is, a non-foamed polystyrene resin film (PS Japan, Stylon 475D) having a thickness of 127 μm was extruded onto the heat-treated surface of the polystyrene resin foam sheet immediately after heating the heating roll to 60 ° C. and contact heating at a speed of 26 m / min. Laminated by lamination. In the obtained polystyrene resin laminated sheet, the foamed sheet and the non-foamed film were uniformly bonded.

  (Example 2) A polystyrene-based resin laminated sheet was obtained in the same manner as in Example 1 except that the heating roll was heated to 90 ° C. In the obtained laminated sheet, the foamed sheet and the non-foamed film were uniformly bonded.

(Example 3) Similar to Example 1, except that the surface of the polystyrene resin foam sheet obtained in Example 1 having a density of 0.45 g / cm ³ was subjected to a heat treatment with a 150 ° C wind of a hot air device. Thus, a polystyrene resin laminated sheet was obtained. In the obtained laminated sheet, the foamed sheet and the non-foamed film were uniformly bonded.

  (Example 4) A polystyrene-based resin laminated sheet was obtained in the same manner as in Example 3 except that the air temperature of the hot air device was 250 ° C. In the obtained laminated sheet, the foamed sheet and the non-foamed film were uniformly bonded.

(Example 5) ^On the surface of the polystyrene resin foam sheet obtained in Example 1 having a density of 0.45 g / cm ³ , a heating roll was heated to 90 ° C, and then heat treatment was performed with 150 ° C wind from a hot air device. A polystyrene-based resin laminate sheet was obtained in the same manner as in Example 1 except that it was applied. In the obtained laminated sheet, the foamed sheet and the non-foamed film were uniformly bonded.

(Comparative Example 1) A polystyrene-based resin laminated sheet was obtained in the same manner as in Example 1 except that no heat treatment was performed. In the obtained laminated sheet, blistering occurred at the interface between the foamed sheet and the non-foamed film.

  (Comparative Example 2) A polystyrene-based resin laminated sheet was obtained in the same manner as in Example 1 except that the heating roll was heated to 40 ° C. In the obtained laminated sheet, blistering occurred at the interface between the foamed sheet and the non-foamed film.

  (Comparative Example 3) The surface properties of the surface layer portion of the laminated surface of the polystyrene resin foam sheet heated to 120 ° C. with the heating roll changed due to excessive heat. A blister occurred at the interface between the obtained foamed sheet and the non-foamed film.

(Comparative Example 4) The surface of the polystyrene resin foam sheet obtained in Example 1 having a density of 0.45 g / cm ³ was subjected to heat treatment with 100 ° C. wind from a hot air apparatus. Other than that was carried out similarly to Example 3, and obtained the polystyrene-type resin laminated sheet. In the obtained laminated sheet, blistering occurred at the interface between the foamed sheet and the non-foamed film.

(Comparative Example 5) A heating roll was heated to 60 ° C on the surface of the polystyrene-based resin foam sheet obtained in Example 1 having a density of 0.45 g / cm ³ , and then heat-treated with 250 ° C wind from a hot air device. A polystyrene-based resin laminate sheet was obtained in the same manner as in Example 1 except that it was applied. In the obtained laminated sheet, blistering occurred at the interface between the foamed sheet and the non-foamed film.

After cutting out a 54 cm square veneer from the obtained polystyrene-based resin laminated foam sheet, after curing the veneer for 10 days in a room at 25 ° C., using a single molding machine, the ambient temperature (up / down) 152/141 ° C. The presence or absence of occurrence of a blister (a phenomenon of peeling between the polystyrene resin foam sheet and the film during molding heating) at 30 seconds after heating was confirmed. The evaluation criteria at that time are as follows.
○: No occurrence of blistering is observed.
X: The occurrence of a blister is recognized.
The evaluation results are shown in Table 1.

In the manufacturing method of the polystyrene-type resin lamination sheet of this invention, it is the schematic showing the process of processing the lamination surface of a polystyrene-type resin foam sheet with a hot roll and a hot air apparatus.

Explanation of symbols

1: Foam sheet 2: Heating roll 3: Hot air device 4: Nip roll 5: Cooling roll 6: T die 7: Non-foamed resin layer 8: Laminated film 9: Expander roll 10: Laminated foam sheet

Claims (3)

  A method for producing a polystyrene-based resin laminated sheet obtained by laminating a non-foamed film on a polystyrene-based resin foamed sheet, which is preheated so that the surface temperature of the laminated surface of the polystyrene-based resin foamed sheet is 50 ° C. or higher and lower than 70 ° C. A process for producing a polystyrene-based resin laminate sheet, comprising: laminating a non-foamed film on the treated surface after the treatment.   The method according to claim 1, wherein the non-foamed film is a non-foamed film of polystyrene resin.   3. The method for producing a polystyrene-based resin laminated sheet according to claim 1, wherein the polystyrene-based resin foam sheet has a thickness of 1 mm to 3 mm, and the non-foamed film has a thickness of 100 μm to 200 μm. .

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