JP2000025088A - Manufacture of polystyrene resin foamed laminated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a material conservation and a low cost by using a circular die as a die, laminating a high density foamed sheet side at an inside and a low density foamed sheet side at an outside, and extruding the laminated sheets, thereby obtaining a molding having stronger strength (particularly, a rib compression strength). SOLUTION: A circular die is used as a die. A high density foamed sheet side is disposed at an inside, a low density foamed sheet side is disposed at an outside, and the sheets are extruded. In one scope of a polystyrene resin foamed laminated sheets, the high and low density foamed sheets are laminated. The high density sheet preferably has a thickness of 0.2 to 2.8 mm, a mean foam size of 30 μm or more and three or more foams arranged in a thickness direction. The low density sheet preferably has a density of 0.22 to 0.042 g/cc, a thickness of 3.0 mm or less. A total thickness of the high and low density sheets is preferably a range of 0.7 to 3.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polystyrene resin foam laminated sheet comprising a high-density foam sheet and a low-density foam sheet.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a polystyrene resin foam molded article, a polystyrene resin foam sheet is heated in a molding machine to secondary foaming to a softened state, and molded and punched or molded by various molding methods. Punching is performed at the same time. In addition, various methods have been attempted to obtain strength, which is one of the necessary functions of a molded article. For example, the thickness of the molded article is increased, the weight is increased, and a plurality of ribs are formed on the molded article. And so on.

That is, in many cases, a tray container or the like has its contents put in the container, wraps the film, and is lined up at a store with the wrapped state. In the method of using such a tray container, since a large compressive force is applied to the container,
In order not to be deformed by the compressive force, the container is required to have a compressive strength enough to withstand these forces and at the same time a function not to buckle easily. In addition, it is necessary that the wrapped film can be kept in a stretched state in a stretched state for a long time, and for that purpose, it is necessary that the film can withstand its compressive strength for a certain time or more.

[0004] One method of imparting such a function to a polystyrene resin foam molded article while saving material is as follows.
It has been proposed that only the inside of a molded article be a high-density skin layer (see Japanese Utility Model Publication No. 63-6005). This is because in containers such as trays, when wrapping is performed, compressive stress is generated at the boundary between the side wall and the bottom on the inside, while tensile stress is spread over a wide range from the side wall to the bottom on the outside. Therefore, a high-density skin layer is formed only on the inner side of the molded product, so as to provide resistance to an extreme compressive stress generated on the inner surface.

[0005]

The above proposal is effective for imparting necessary strength to a polystyrene-based resin foam molded article. However, this method involves blowing air on the surface of a foam sheet. In order to form a high-density skin layer, the thickness of the high-density layer is limited to at most about 0.05 mm in consideration of formability and the like. Since it may not always be sufficient, it is necessary to additionally provide a rib.

When a reinforcing rib is provided, it may not be possible to form a deep container due to the relationship with moldability, and when a tray or the like is formed, depending on its shape, the overlapping height of the molded product (for transporting the container). , The bulkiness when superimposed) cannot be reduced, and there is a disadvantage that the bulkiness is increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the conventional foamed polystyrene resin sheet and its molded product. More specifically, the foamed sheet as a whole has the same thickness and the same thickness. It is possible to obtain a molded product that has the same strength as the molded product formed using a polystyrene resin foam sheet having a high density, but has higher strength (particularly, rib compression strength), thereby reducing material consumption and reducing costs. It is an object of the present invention to obtain a method for producing a polystyrene-based resin foam sheet capable of performing the following.

[0008]

In order to solve the above-mentioned problems, the present inventors have conducted a number of experiments and studies on polystyrene resin foam sheets and molded articles thereof. The sheet has at least a two-layer structure of a high-density foam sheet layer and a low-density foam sheet layer. The average cell diameter of the high-density foam sheet is 30 μm or more, and the number of cells in the thickness direction is three or more on average. It has been found that the above object can be achieved by molding a molded article such as a container with the high-density foam sheet side of the foam laminated sheet inside.

The present invention discloses a method for producing a polystyrene resin foam sheet having the above-mentioned characteristics, and produces a polystyrene resin foam laminated sheet in which sheets having different foam densities are laminated by a co-extrusion method. A method for producing, characterized in that a circular die is used as a die, and the high-density foam sheet side is extruded inside and the low-density foam sheet side is extruded outside.

In the present invention, the polystyrene resin includes a homopolymer or a copolymer of styrene, methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, paramethylstyrene, chlorostyrene, bromostyrene, vinyltoluene and vinylxylene. Is mentioned. Examples of the copolymer include polystyrene resins such as styrene-maleic anhydride copolymer, styrene-acrylic acid polymer, impact-resistant polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer and the like. .

The co-extrusion method is a method in which the extruded resin is fused by passing it through a joining die to form a sheet. The polystyrene resin foam laminated sheet obtained by the co-extrusion method has advantages such as excellent economic efficiency, a wide product specification range of the foam laminated sheet, and excellent moldability. A laminated sheet can also be obtained by laminating a molded high-density foam sheet and a low-density foam sheet, but such a method requires a separate laminating step, is inefficient, and has a high density foaming property. It is difficult to make the thickness obtained by extrusion of a sheet or a low-density foamed sheet 250 μm or less, and it is difficult to control stretching,
There is a problem that a problem remains in elongation during molding. Also,
If the thickness of the polystyrene resin foam laminated sheet to be obtained is small, that is, if the thickness of the high-density foam sheet and / or the low-density foam sheet is small, the foam sheet may be shrunk by heat during bonding. In addition, since stretching cannot be controlled even when bonded with an adhesive or the like, the resulting foamed laminated sheet has disadvantages of poor elongation during molding and poor moldability. In the case of the co-extrusion method as in the present invention, the above-mentioned disadvantages can be easily avoided.

In the present invention, a circular die is used as a die, and a high-density foam sheet is placed inside (plug side).
Extrude the low density foam sheet to the outside. This is because if the low-density foam sheet is set inside, bubbles may be crushed by the plug, and it becomes difficult to adjust the thickness and density of the foam sheet.

The polystyrene resin foam laminated sheet produced by the present invention has a basic structure of a laminated structure of at least a low density foam sheet and a high density foam sheet. In one form of the polystyrene resin foam laminated sheet, a high-density foam sheet and a low-density foam sheet are laminated, and the high-density foam sheet has a thickness of 0.2 mm to 2.8 mm, an average cell diameter of 30 μm or more, and It is preferable that an average of three or more cells are arranged in the thickness direction, and the low-density foamed sheet preferably has a density of 0.22 g / cc to 0.042.
g / cc, the thickness is 3.0 mm or less, and the total thickness of the high-density foam sheet and the low-density foam sheet is 0.7 to 3.0.
Preferably it is in the range of 5 mm.

When the thickness of the high-density foamed sheet is less than 0.2 mm, when the polystyrene resin foamed laminated sheet of the present invention is formed into a molded product, the thickness at the boundary between the side wall and the bottom of the molded product is obtained. May be stretched to less than 0.2 mm during molding, and the buckling prevention effect is reduced. Further, even if the thickness exceeds 2.8 mm, the advantage is lost without increasing the buckling prevention effect. The effect of the cell diameter on the strength is large, and the average cell diameter is 30 μm or more, preferably 30 μm.
In the range of m to 250 μm, it was found that if the number of bubbles in the thickness direction was 3 or more, the buckling prevention effect was large, and the thickness of the high-density foam sheet only needed to be 0.2 mm. However, if the bubble diameter is less than 30 μm, the strength is not obtained.

The density of the low-density foam sheet is 0.22 g / c.
If the value exceeds c, the tension becomes higher than necessary to overcome the tensile stress of the molded article after molding, and the economic efficiency is reduced. Further, the density of the low-density foamed sheet is 0.042 g / c.
If the value is less than c, communication of air bubbles increases during co-extrusion of a laminated foamed sheet of a high-density foamed sheet and a low-density foamed sheet, resulting in poor elongation at the time of molding when obtaining a molded product, causing cracks. I do. Further, due to the communication of the bubbles, the strength of the molded product is reduced, and partial heating unevenness is apt to occur during heating in the molding machine at the time of molding, and the range of molding conditions is narrowed. In the case of co-extrusion, a density of 0.042 g / cc is the limit for extrusion stability.

In the present invention, a thermoplastic resin film may be laminated on at least one side of the polystyrene resin laminated foam sheet. Further, other foams may be laminated. For example, a three-layer structure of thermoplastic resin film / high-density foam sheet / low-density foam sheet, a four-layer structure of thermoplastic resin film / high-density foam sheet / low-density foam sheet / thermoplastic resin film, thermoplastic resin film / A combination of a five-layer structure of a high-density foam sheet / a low-density foam sheet / a high-density foam / thermoplastic resin film is exemplified.
When a thermoplastic resin film is attached to the low-density foam sheet side, a function of suppressing the elongation of the entire skin layer against tensile stress can be provided, and the strength of the foam sheet is improved. In this case, the structure is a high-density foam sheet / low-density foam sheet / thermoplastic resin film.

Any thermoplastic resin film can be used provided that it has the property of being stretched by heat molding when forming a laminated foamed sheet. Examples of such a resin include styrene, methylstyrene, and styrene.
Ethyl styrene, isopropyl styrene, dimethyl styrene, p-methyl styrene, chloro styrene, bromo styrene, vinyl toluene, vinyl xylene homopolymer or copolymer, such as styrene-maleic anhydride copolymer, styrene - acrylic acid as the resin Copolymer, impact-resistant polystyrene, styrene-acrylonitrile resin,
Acrylonitrile-butadiene-styrene resin can be used. Particularly, a polystyrene resin and an impact-resistant polystyrene resin are preferable. In addition, a mixture of a polystyrene resin and high impact polystyrene or a high impact polystyrene alone, and a styrene-butadiene copolymer is dispersed in the high impact polystyrene in a salami structure, and the particle size is 0. .3 .mu.m to 10 .mu.m.

Further, 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 Copolymer, ethylene-unsaturated carboxylic acid ester copolymer (for example, ethylene-methyl methacrylate copolymer), ethylene-unsaturated carboxylic acid metal salt copolymer (for example, 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 Unsaturated carboxylic acid (for example, maleic anhydride) modified product, ethylene-
Propylene rubber, atactic polypropylene and the like, polyethylene, ethylene-propylene copolymer,
Examples thereof include a propylene-butene-1 copolymer, a mixture of two or more of these, and films such as polyethylene terephthalate and polybutylene terephthalate.

It is also a preferred embodiment to laminate a thermoplastic resin film having gas barrier properties. Examples of such a film having gas barrier properties include ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinylidene chloride, polyamide, and the like. Polyester, polyacrylonitrile, vinylidene chloride-based acrylonitrile copolymer, acrylonitrile-based methyl methacrylate-butadiene copolymer, nylon, biaxially oriented nylon, biaxially oriented polyethylene terephthalate, biaxially oriented polypropylene, high-density polyethylene, ionomer resin ( For example,
(Registered trademark Surlyn) or a metal-deposited film, and these may be used alone or in a laminate of these films.

In laminating the high-density foam sheet or the low-density foam sheet and the thermoplastic resin film, a lamination method using heat may be used in addition to the coextrusion method. At that time, the thermoplastic resin film is thermocompression-bonded from the opposite side of the joining surface with a heat roll. In this case, the surface of the roll to be heated and pressed is chrome plated or Teflon coated,
Prevents stickiness with the heated thermoplastic resin film. In addition, the joining surface may be heated by a heating device together with the thermocompression bonding by the heat roll.

The thickness of the thermoplastic resin film is 10 μm
To 500 μm, preferably 15 μm to 300 μm. The lower limit is less than 10 μm, and if less than 10 μm, the thermoplastic resin film may be perforated when molded into a container. In addition, about 5 micrometers is the limit which can be manufactured stably by the present extrusion technique. On the other hand, if the thickness is greater than 500 μm, burning and peeling will occur on the polystyrene resin foam sheet during lamination. In addition, since co-extrusion cannot be used, it is disadvantageous in terms of manufacturing cost. In addition,
A pigment such as titanium oxide may be mixed in the thermoplastic resin film in an amount of 5 parts by weight or less based on 100 parts by weight of the raw material at the time of film production. Further, the thermoplastic resin film, the high-density foam sheet and the low-density foam sheet may be colored in advance with a coloring agent or the like. Furthermore, by printing in advance on a thermoplastic resin film and laminating the printed surface on the inner side, a molded article with a glossy appearance and a clean surface can be obtained.

In the present invention, in order to obtain a foamed sheet having a desired density, the types and amounts of the foaming agent and the additive and the foaming temperature are appropriately adjusted. It is performed by putting a base resin, a foaming agent and additives necessary for foaming into an extruder so as to have a desired density, melt-kneading, and extruding from a die of the extruder. The base resin, the foaming agent, and the additive may be uniformly mixed before being supplied to the extruder. Further, the additive may be a so-called master batch which is previously added to a resin of the same type as the base resin at a high concentration.

As the foaming agent that can be used in the present invention, any known one can be used.
There are gaseous or volatile blowing agents. Examples of the decomposable blowing agent include, for example, inorganic decomposable blowing agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide, sodium borohydride, azodicarbonamide, azobissulfformamide, Azo compounds such as azobisisobutyronitrile and diazoaminobenzene, N, N'-dinitrosopentanemethylene terolamine and N, N'-dimethyl-
Nitroso compounds such as N, N'-dinitrosoterephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide and p, p'-oxypisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazino toeazine, barium Azocarboxylate and the like. These blowing agents may be used alone or in combination. Further, a known foaming aid can be added to adjust the decomposition temperature, the amount of generated gas, and the decomposition rate.

As the gas foaming agent, nitrogen, carbon dioxide,
Propane, n-butane, i-butane, methyl ether and the like. Here, the gas is normal temperature (25 ° C.),
It means that it is a gas at normal pressure (1 atm). On the other hand, examples of the volatile foaming agent include ether, petroleum ether, acetone, pentane, isopentane, hexane, isohexane, heptane, isoheptane, benzene, and toluene. Water can also be used. These can be mixed and used.

Of the above foaming agents, butane is preferred. When it is desired to reduce the bubble size to about 40 μm or less, it is preferable to use or use a combination of nitrogen, carbon dioxide and water.
Further, nitrogen and the like have an advantage of being inexpensive because they can be directly separated from air.

The additives necessary for foaming include, for example, a foam 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 foam regulators,
The foam film becomes weak to heat, and the foam film is broken at the time of extrusion lamination, and as a result, bubbles may increase. In order to prevent such an increase in air bubbles, it is preferable to use nitrogen or carbon dioxide as a foaming agent. Further, if necessary, an ultraviolet absorber,
Antioxidants, coloring agents, lubricants, flame retardants, antistatic agents, and the like may be added.

The melt-kneaded resin is once extruded into a cylindrical shape from a circular die adjusted to a temperature most suitable for foaming, and then cut into an arbitrary line to form a sheet. Here, when manufacturing a high-density foam sheet, it depends on the type of extruder and resin used, etc.
The extruder barrel temperature is maintained at about 140-260 ° C.
In addition, the foaming agent is added in an amount of 0.1 to 100 parts by weight of the base resin.
It is preferable to add from 07 to 3.3 parts by weight, and from 0.01 to 7.0 parts by weight of the foam regulator. On the other hand, when producing a low-density foamed sheet, the extruder barrel temperature is kept at about 140 to 260 ° C., although it depends on the type of extruder and resin used. Also, based on 100 parts by weight of the base resin, the foaming agent is 0.5 to 7.0 parts by weight, and the foam regulator is 0.01 to 7.0 parts by weight.
It is preferable to add 5.0 parts by weight.

Next, the thermoplastic resin film is melted in a known extrusion method, specifically, in an extruder, into a film material (comprising a resin, an additive, etc.), and a die (T die, coat hanger die, (A screw die or the like) to form a film. When laminating a thermoplastic resin film, it may be co-extruded with the foamed sheet. In the case where a thermoplastic resin film is bonded using an adhesive, the thickness of the adhesive is added to the film thickness.

Furthermore, air may be blown onto the surface of the high-density foam sheet and / or the low-density foam sheet to form a skin on the surface of the foam sheet. At this time, air of 5 ° C. to 80 ° C., preferably 5 ° C. to 45 ° C. (air ring inlet air temperature) is preferably applied to the high-density foam sheet side at 0.04 m ^{3 to} 0 m ² per 1 m ² of the foam sheet. .4m
³ spraying, 5 ° C. to 80 ° C. The low-density foam sheet side, preferably so that the air 5 ° C. to 45 ° C. giving 1 m ² per 0.02 m ³ ～0.3M ³ blown foam sheet. By forming the skin in this manner, effects such as improving the appearance, improving the printability, and further improving the strength of the ribs can be obtained.

[0030]

The present invention will be described below with reference to examples. 5 to 15 as a cell regulator in 100 parts by weight of polystyrene resin
0.6 to 3.0 parts by weight of talc powder of μm or by adding them by a masterbatch,
The mixture was charged into a batch-type continuous mixing device on a hopper of an extruder having a size of from 150 mm to 150 mm, uniformly mixed, and then supplied from the hopper to the extruder. The cylinder temperature of the extruder was set to a maximum setting temperature of 230 ° C., and butane gas (i-butane 6) was used as a blowing agent.
(5%, n-butane 35%) was added in an amount of about 1.0 to 3.5% by weight, and carbon dioxide gas was added in an amount of 0 to 2% by weight.

On the other hand, 0.4 to 1.5 parts by weight of talc powder of 5 to 15 μm as a cell regulator based on a polystyrene resin having a melt index (referred to as MI value) different from that of the above-mentioned polystyrene resin, and Hydrocellol CF-40S (Dainippon Seika Kogyo Co., Ltd.) 0.2
1.0 part by weight and 2 parts of a color masterbatch (20% kneading) were added, and the mixture was put into a batch type continuous mixing device on a hopper of an extruder having an inner diameter of 90 mm to 150 mm.
The mixture was uniformly mixed and supplied from a hopper to an extruder. The cylinder temperature of the extruder was set to a maximum set temperature of 245 ° C., and butane gas (i-butane 60%, n-butane 40
%) Was added to the confluence die in a balance with an extruder for extruding a high-density foam sheet.

The resins of the two types mixed together by the joining die are both flowed into a mold having a diameter of 126 mm, and immediately after being extruded into a cylindrical shape through a slit, air is applied to the inside and outside of the balloon to cool the foam sheet. Thus, the polystyrene resin foam laminated sheet of the present invention was obtained, and this foam laminated sheet was subjected to evaluation and used as an example.

[Example 1] MI value 4.1 (catalog value)
Polystyrene resin (trade name: Denkastyrol HRM)
-5: manufactured by Denki Kagaku Kogyo Co., Ltd.) To 100 parts by weight, 0.8 part by weight of talc powder having a size of 5 to 15 μm was added as a bubble regulator, and the mixture was continuously mixed in a hopper of an extruder having an inner diameter of 90 mm in a batch system. After being charged into the apparatus and uniformly mixed, the mixture was supplied from a hopper to an extruder. The cylinder temperature of the extruder was set to a maximum setting temperature of 230 ° C., butane gas (i-butane 65%, n-butane 35%) was added as a blowing agent at about 2.5% by weight, and the mixture flowed into the joining die at a rate of 76 kg / hour. .

On the other hand, a polystyrene resin having an MI value of 1.9 (catalog value) (trade name: Denkastyrol HRM-2:
100 parts by weight of Denki Kagaku Kogyo Co., Ltd., 0.8 parts by weight of talc powder having a size of 5 to 15 μm as a cell regulator and Hydrocelol CF-40S (manufactured by Dainippon Seika Kogyo Co., Ltd.) 6 parts by weight were added, and this was
It is put into the batch type continuous mixing device on the hopper of the extruder,
The mixture was uniformly mixed and supplied from a hopper to an extruder. The cylinder temperature of the extruder is set to a maximum temperature of 245 ° C., and butane gas (i-butane 60%, n-butane 40%) is used as a foaming agent.
Was added to the merging die at a rate of 77 kg / hour.

The resins of the two types combined by the joining die are both flowed into a mold having a diameter of 126 mm, and immediately after being extruded into a cylindrical shape through a slit, air is applied to the inside and outside of the balloon to cool the foam sheet. did. Air temperature is 27 ℃
, And the amount sprayed, the inside of the high density foam sheet side 0.10 m ³ / m ^2, the outside of the low-density foam sheet side was 0.07m ³ / m ^2.

The high-density foamed sheet has a thickness of about 0.5 mm and a weighing of 106 g / m ² (density of 0.21
2 g / cc) and the low-density foam sheet thickness is about 1.9.
mm, weighing 104 g / m ² (density 0.055 g / cc)
Met. That is, the overall thickness of the obtained foamed laminated sheet was 2.4 mm, and the weight thereof was 210 g / m ² . The average cell diameter of the high-density foam sheet is 71 μm,
It was calculated that an average of 7.0 bubbles existed in the thickness direction.

The thickness of the foamed sheet was measured with a micrograph, and the basis weight was measured by taking ten 1 cm squares from the foamed sheet and dividing them into a high density and a low density with a razor.
The density was calculated from the basis weight and the thickness. In addition, if either the high-density foam sheet or the low-density foam sheet is colored, separation becomes easy and work becomes easy.

The average cell diameter D is obtained by cutting a high-density foam sheet into cloth in the machine direction (MD), setting the length in the thickness direction to L, and setting the number of cells (excluding skin) between L to N. D = L / N, and indicates the average diameter of bubbles existing between L. In addition, the number of bubbles between the L was similarly measured with a micrograph. The raw material of the foamed laminated sheet is dimensioned as 19
Using a molding die of 5 (length) x 120 (width) x 25 (height) mm, using a single-shot molding machine (Sekisui Chemical Co., Ltd. specifications), the oven temperature is about 280 to 350C, and the mold closing time is about 3.5. Molded in seconds.

The thickness (mm) of the side part, the bottom part and the boundary part of the molded product was measured by a micrograph. In addition, AIKOH ENGINEERING's load measuring machine Model 1310DS
Was used to measure the repulsive force when the molded container was compressed by 10 mm (400 mm / min). Further, the high-density foam sheet side of the molded product was sliced at about 300 μm, and the density was measured. Table 1 shows the measured values.

Examples 2 to 10 and Comparative Example 1
A foamed laminated sheet was obtained in the same manner as in Example 1 and molded using the same molding machine with the same mold dimensions as in Example 1 and evaluated. At that time, the total thickness of the foamed laminated sheet and the weighing as a whole were determined in Example 1.
The thickness and basis weight of the high-density foam sheet and the low-density foam sheet were made different by adjusting the discharge amount of the extruder. However, on the low-density side in Example 2, a resin obtained by repelletizing a market used tray was used (MI value: 6.7). Comparative Example 1 is a case where a low-density foamed sheet has a single-layer structure.

Each value was measured in the same manner as in Example 1. Table 1 shows the measured values together with the values of Example 1.
Shown in Looking at Comparative Example 1, the rib compressive strength shows a value lower than those of most Examples. Here, in Example 5, since the thickness of the high-density foam sheet was too thin, the thickness of the boundary between the side portion and the bottom portion of the molded product became thin,
Further, since the number of bubbles existing in the thickness direction of the high-density foamed sheet is small, buckling occurs, and the rib compressive strength is reduced, which is not always preferable. In Example 6, since the high-density foamed sheet was thin and had a high density, and the number of bubbles existing in the thickness direction of the high-density foamed sheet was small, the strength also decreased, and buckling occurred. In Example 8, since the density of the low-density foam sheet was too low, the communication of air bubbles was large, and the rib strength was greatly reduced. Furthermore, in Example 10, it is understood that the rib strength was lowered due to the small average cell diameter of the high-density foam sheet and the small cells. Example 1
When the foamed laminated sheet is molded so that the low-density foamed sheet is inside the container side, the rib compression strength of the container is 64.
It dropped to 0 g.

From these facts, when comparing with the same weight and the same weight, at least the high density side (coming inside the molded product)
It can be seen that when the thickness of the foamed sheet is 0.2 mm or more, the strength is greatly increased in the case of the multilayer sheet as compared with the single-layer foamed sheet.

[0043]

[Table 1]

[Examples 11 to 14, Comparative Example 2] Example 1
A foam laminated sheet was obtained in the same manner as described above. At that time, similarly, the thickness and basis weight of each of the high-density foam sheet and the low-density foam sheet were varied by adjusting the discharge amount of the extruder. However, the total thickness of the foam laminated sheet is in the same range of 3.1 mm to 3.5 mm, and the total basis weight is 301 g / m ^{2 to} 308 g / m.
^The range of ² was almost the same. Comparative Example 2 had a single-layer structure of a low-density foam sheet.

Using these raw materials, a dimension 162 (length)
A box-shaped container of × 132 (width) × 54 (depth) mm was molded in the same manner as in Example 1, and each value was measured and evaluated in the same manner as in Example 1 for each. Table 2 shows the results. Looking at Examples 11 to 14 and Comparative Example 2, in this case also, the thickness and basis weight (accordingly, density) of the foamed sheet are almost the same, but the rib compressive strength of Comparative Example 2 is the same as Example. It shows a lower value than that of. Further, in Example 14, since the thickness of the low-density foamed sheet was too thick, the bending strength was almost the same as the bending strength of Comparative Example 2, and the size of the mold was poor and the elongation was insufficient.

Examples 15 to 19 In the same manner as in Example 1, foamed laminated sheets were obtained. Also in this case, the thickness and basis weight of each of the high-density foam sheet and the low-density foam sheet were made different by adjusting the discharge amount of the extruder. The total thickness of the foam laminated sheet is 2.15 mm or more
And about the same range of 2.4 mm, a basis weight of the entire addition was approximately the same range of ^{210g / m 2 ~214g / m 2} . In Example 15, an OPS film (100 μm thick) was laminated on the high-density foam sheet side by a hot roll. In Example 16, HI was applied to the low-density foam sheet side.
A PS film (100 μm thickness) was laminated by an extrusion method. In Example 19, a commercially available barrier film Sumilite CEL (manufactured by Sumitomo Bakelite Co., Ltd.) (80 μm thickness) was laminated on the high-density foam sheet side by a hot roll.
In Examples 17 and 18, HI was applied to the low-density foam sheet side.
A PS film (about 100 μm) was laminated by an extrusion method.

Using these raw materials, a dimension 162 (length)
A box-shaped container of × 132 (width) × 54 (depth) mm was molded in the same manner as in Example 1, and each value was measured and evaluated in the same manner as in Example 1 for each. Table 2 shows the results.
Shown in Regarding Examples 15 to 19, the thickness and basis weight (accordingly, the density) of the foamed sheet were almost the same in this case, but the rib compression strengths of Examples 17 and 18 were all the same. The values are lower than those of the high-density foam sheets of Examples 17, 16, and 19. In Example 17, similarly to Example 16, the high-density foam sheet was thin and had a high density. Since the number of bubbles existing in the thickness direction was small, the strength was also lowered, the bubbles on the low-density foam sheet side were broken, and buckling occurred. Further, in Examples 15, 16, and 19, since the films were laminated, the molded articles having the same dimensions as those of Examples 11 to 13 exhibited high rib compressive strength.

Example 20 95 parts by weight of a heat-resistant polystyrene resin having an MI value of 4.1 (trade name: Asahi Kasei Polystyrene G9001: Asahi Kasei Corporation): an elastomer resin having an MI value of 13 (trade name: Tufprene A: Asahi Kasei Corporation) To 5 parts by weight, a talc powder of 5 to 15 μm as a cell regulator was added in an amount of 0.6 part by weight based on 100 parts by weight of the resin, and supplied to an extruder having an inner diameter of 90 mm in the same manner as in Example 1. The extruder cylinder temperature was set to a maximum set temperature of 265 ° C., and butane gas (i-butane 35%, n-
About 3.1% by weight of butane (65%)
At the merged die.

On the other hand, 100 parts by weight of a heat-resistant styrene resin having an MI value of 1.4 (trade name: Asahi Kasei Polystyrene G9001: Asahi Kasei Kogyo Co., Ltd.) was used as a cell adjuster in an amount of 5-1.
0.8 parts by weight of 5 μm talc powder and 20 parts of takuru powder
Parts by weight and 2 parts by weight of a master batch of an impact resistant resin kneaded with 5 parts by weight of calcium stearate,
This was supplied to an extruder having an inner diameter of 90 mm to 150 mm in the same manner as in Example 1.

The cylinder temperature of the extruder is set at a maximum set temperature of 2.
75 ° C. and butane gas (i-butane 65
%, N-butane 35%) was added by a separate diaphragm type high pressure pump at about 6.1% by weight, and the mixture was flowed into the joining die at a rate of 78 kg / Hr.

The resins of the two types combined by the joining die are both flowed into a mold having a diameter of 120 mm, and immediately after being extruded into a cylindrical shape through a slit, air is applied to the inside and outside of the balloon to cool the foamed sheet. did. Air temperature is 31 ℃
, And the amount sprayed, the inside of the high density foam sheet side 0.12 m ³ / m ^2, the outside of the low-density foam sheet side was 0.08m ³ / m ^2.

This foamed sheet has a high-density foamed sheet having a thickness of about 0.8 mm and a basis weight of 112 g / m ² (density of 0.14
g / cc), and the low-density foam sheet has a thickness of about 1.6 m.
m, and the basis weight was 101 g / m ² (density: 0.063 g / cc). That is, the total thickness of the foamed sheet was 2.4 mm, and the basis weight was 213 g / m ² . The average bubble diameter of the high-density foamed sheet was 221 μm, and the calculation was such that an average of 3.6 bubbles existed in the thickness direction.

On the high-density foam sheet side of the two-layer foam laminated sheet, Asahi Kasei polystyrene G9001 having an MI value of 1.4 and tufprene A (MI value 13) were mixed at a ratio of 9: 1 to form a 90 mm-sized resin. The temperature of the cylinder was set to 280 ° C. by an extruder, and a film of about 100 μm was extrusion-laminated using a T-die.

Using this laminated raw material, the dimension 162 (length) × 132 (width) is set such that the high density side is on the inside.
A box-shaped container of × 54 (depth) mm was molded. The molding was performed at a molding temperature of about 300 ° C. to 380 ° C. and a mold clamping time of 4.9 seconds. In the same manner as in Example 1, the thickness of the side part, the bottom part, and the boundary part of the molded product were measured by a micrograph. Also,
The rib compression strength was measured. The values are shown in Table 2.

In this case, in Example 16, since the film was stuck on the low density side, the increase in the force against local compressive stress generated on the inner surface of the container was small, and the laminated barrier film used in Example 19 was For the reason that it is softer than the film of Example 20, it shows a higher rib compressive strength as compared with those of Examples 16 and 19 even though it is a molded article of the same dimensions.

[0056]

[Table 2]

[Examples 21 to 25, Comparative Example 3] Example 1
A foam laminated sheet was obtained in the same manner as described above. At that time, the thickness and the density of the high-density foam sheet and the thickness and the density of the low-density foam sheet were all substantially equal to each other, and the high-density foam sheet was formed so that only the average cell diameter was different. Using these raw materials, a container having dimensions of 162 (length) × 132 (width) × 54 (height) mm was formed in the same manner as in Example 1, and each container was formed in the same manner as in Example 1 for each. The values were measured and evaluated. Table 3 shows the results.

Also in this case, the rib strength of Comparative Example 3 which is a single layer of a low-density foamed sheet is lower than those of Examples 21 to 25. In Example 24, the average cell diameter was 8 with respect to the high-density foamed sheet having a thickness of 0.23 mm.
5 μm, the number of bubbles existing in the thickness direction of the high-density foam sheet is as small as 2.7, and in Example 25, the average cell diameter was 23 μm with respect to the thickness of the high-density foam sheet of 0.28 mm, Due to the cell diameter being too small, the rib strength of the molded article shows a lower value than the others.

[Examples 26 and 27, Comparative Examples 4 and 5] Table 3
Using the foamed laminated sheets shown in Examples 26 to 27 and Comparative Examples 4 to 5 while adjusting the clearance of the mold, 95
When a cup of (diameter) mm × 65 (depth) mm was molded, the foamed laminated sheets of Examples 26 and 27 and Comparative Example 4 could be molded, but the foamed laminated sheet of Comparative Example 5 was difficult to mold. Next, 95 (diameter) mm x 85 (depth) m
When a cup of m was molded, the foamed laminated sheet of Example 26 could be molded, but the laminated foamed sheets of Example 27 and Comparative Example 4 were difficult to mold, and the laminated foamed sheet of Comparative Example 5 could not be molded. From this, it can be said that a foamed sheet having a higher density has better moldability, and a foamed sheet has a better moldability as a laminated sheet of a high-density foamed sheet and a low-density foamed sheet as compared with a single-layered sheet.

As described above, in the polystyrene resin foam laminated sheet in which the high-density foam sheet and the low-density foam sheet are laminated, the high-density foam sheet has a thickness of 0.2 mm.
-2.8 mm, a sheet having an average cell diameter of 30 µm or more and having three or more cells in the thickness direction is preferable, and a low-density foam sheet has a density of 0.22 g / cc to 0.042 g / c.
c, if the thickness is 3.0 mm or less, the strength is greater than the single-layer sheet compared to the single-layer sheet of the same thickness, and the two-layer sheet and the single-layer sheet have a total effect. It was found that if the magnification (density) was the same, the formability of the two-layer sheet was much better.

[0061]

[Table 3]

[0062]

According to the production method of the present invention, a circular die is used and the high-density foam sheet is on the inside (plug side). It is easy to adjust the thickness and density of the resin foam sheet. Further, in the present invention, using a circular die by a co-extrusion method, the thickness of each of the high-density foam sheet and the low-density foam sheet is set to 250.
Since it can be manufactured to a thickness of less than μm and can be fused and laminated, the polystyrene resin laminated foam sheet has a wide range of specifications and excellent moldability.

Further, by using the polystyrene resin foam laminated sheet produced by the production method of the present invention, the same thickness as the conventional polystyrene resin foam sheet can be obtained.
Even when molded with the same density of laminated sheets, a molded product having high rib compression strength and good moldability can be obtained. Thereby, it becomes possible to manufacture a molded article made of a polystyrene resin foam sheet having the required strength at a low cost and at low cost.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29K 105: 04 B29L 9:00

Claims (5)

[Claims] 1. A method for producing a polystyrene resin foam laminated sheet in which sheets having different foam densities are laminated by a co-extrusion method, wherein a circular die is used as a die, and a high-density foam sheet side is placed inside. And extruding with the low-density foam sheet side as the outside. 2. The method according to claim 1, wherein a plug is used after the circular die. 3. The high-density foam sheet has a thickness of 0.2 mm or more.
The method for producing a polystyrene resin foam laminated sheet according to claim 1 or 2, wherein three or more bubbles are arranged in the thickness direction at an average of 2.8 mm. 4. The high-density foam sheet has an average cell diameter of 30 μm.
The method for producing a polystyrene-based resin foamed laminated sheet according to claim 3, wherein the thickness is not less than m. 5. The low-density foam sheet has a density of 0.22 g.
The method for producing a foamed polystyrene-based resin sheet according to any one of claims 1 to 4, wherein the ratio is from 0.1 / cc to 0.042 g / cc.