JPH1158506A - Laminated polystyrene based resin expanded container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a side wall part of a deep-drawn container of which the drawing ratio is large, wherein the basic weight and the strength are well balanced, and there are no defects by a method wherein a minimum value of the basic weight in the side wall part of this container is made a specified % of a maximum value, and an air bubble diameter in the depth direction at the central part of the side wall is made a specified magnification of the air bubble diameter in the thickness direction. SOLUTION: An expanded container of which the deep drawing ratio is 0.9-1.8 is formed of a laminated sheet of a laminated polystyrene based expanded sheet between a thermoplastic resin film such as a polystyrene based resin or the like, and a polystyrene based resin expanded sheet for which a volatile foaming agent or a decomposable foaming agent is used. For the laminated polystyrene based expanded container, the basic weight of a minimum value at the side wall, part is made 55% or higher of the basic weight of a maximum value, and an air bubble diameter in the depth direction at the central part of the side wall of the container is made 2.0-4.5 times of the air bubble diameter in the thickness direction. When this value becomes less than 2.0 times, the strength becomes weak because the drawing in the depth direction is small, and when the value becomes 4.5 times or higher, making the side wall part a uniform thickness becomes difficult.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polystyrene resin foam container obtained by thermoforming a polystyrene resin foam sheet on which a film is laminated, and more particularly, to a deep drawn cup for storing food. The present invention relates to a deeply drawn laminated polystyrene resin foam container for storing instant noodles and the like.

[0002]

2. Description of the Related Art Conventionally, a container having a deep drawing ratio of 1.0 or more, which is a value obtained by dividing the depth of a container by the diameter of the container, is formed from a polystyrene resin foam sheet. However, it was difficult to form a foamed container having a uniform side wall strength and thickness. For example, Japanese Patent Application Laid-Open No. 6-335988 discloses that in order to form a deep drawn product, a foamed sheet laminated with a thermoplastic resin film is used, and a unit area per unit area before heating is increased by 1 unit.
It is proposed that the area needs to be increased by about 11%. However, there is a problem that the side wall of the container becomes thinner and the strength becomes weaker depending on the material and the basis weight of the film and the foam to obtain a molded product having a deep drawing ratio of 1.0 or more by this method.

[0003] Japanese Patent Publication No. 63-20702 discloses that a molded article is obtained by specifying an average number of cells in the thickness direction of 25 to 100 cells / m ² and a residual foaming gas of 0.5% by weight or more. Proposals have been made. However, the specification such as specifying the average number of bubbles and the amount of the remaining foaming agent is not enough to obtain a deep-bottomed container, and there is a problem in moldability, distribution of the thickness of the container, cup strength, etc. Challenges in the physical properties of

[0004] That is, a part of the side surface of the container is soft, the strength when held by hand is low, and it is deformed when hot water is poured,
In addition, there is a disadvantage that hot water is deformed when it is held by hand. When the deep drawing ratio is further reduced to 0.8 to 1.8, the bubble diameter in the depth direction at the center of the side wall of the container is distorted from 2.0 to 8.0 times the bubble diameter in the thickness direction. If the cell diameter is distorted, it is extremely difficult to make the side wall thickness uniform.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problem of the strength defect of the container side wall and provides a deep drawn laminated container having a uniform and strong container side wall. As a result of diligent research, he discovered that in order to form such a deep drawn container, the tensile strength associated with proper stretching of the laminated foamed sheet during thermoforming is important. The extrusion direction of the foamed sheet during molding (hereinafter referred to as MD) is controlled by controlling the stretching between the slit and the plug when extruding and foaming the polystyrene resin foamed sheet.
TD) and the direction perpendicular to the extrusion direction of the foamed sheet (hereinafter referred to as TD) are properly and well-balanced, and do not adhere to the heater of the molding machine or the mold of the opened molding machine. It has been found that by stretching the foamed sheet to such an extent that the foam sheet can be sagged, the basis weight, the thickness, and the stretching in the depth direction of the side surface of the container become uniform.

In this way, the MD and TD are stretched appropriately,
When the secondary heating is performed by improving the balance, the bubble diameter increases in the thickness direction, and even when a container having a deep drawing ratio of 0.9 to 1.8 is formed, the bubble diameter in the depth direction at the center of the side wall is increased in the thickness direction. Could be adjusted to be 2.0 to 4.5 times the bubble diameter of. On the other hand, if the tensile strength due to the stretching of the laminated foamed sheet is too small, the stress of the sheet is lost when the container is formed, which causes the thickness of the side wall of the container to be reduced. Conversely, when the container is molded, if the tensile strength of the laminated foamed sheet is too high, the elongation will be poor, and the unevenness of the mold will be weak, and if the sheet is further stretched, molding will not be possible. Thus, it has been found that proper stretching and its balance are important in deep drawing. In this way, the top, center,
It was found that the basis weight and thickness of the lower portion were adjusted by adjusting the stretching in the MD and TD directions, and thus it was possible to solve the conventional strength defect of the container side wall.

That is, the present invention comprises a foamed container having a deep drawing ratio of 0.9 to 1.8 formed by laminating a laminated polystyrene resin foam sheet of a thermoplastic resin film and a polystyrene resin foam sheet. The minimum basis weight in the side wall portion is 55% or more of the maximum basis weight, and the depth direction bubble diameter in the side wall center portion of the container is 2.0 to 4.5 times the thickness direction bubble diameter. It is a laminated polystyrene resin foam container characterized by the following. In the present invention,
A laminated polystyrene resin foam container in which the difference in thickness, which is a value obtained by dividing the difference between the maximum thickness and the minimum thickness at the center of the side wall of the container by the maximum thickness, is 25% or less, or in the center of the side wall of the container. The minimum thickness is 80% to 120% of the minimum thickness at the upper and lower portions of the side wall.
The laminated polystyrene resin foam container 2 is one of the most preferable embodiments.

In the present invention, styrene, methyl styrene, ethyl styrene, isopropyl styrene, dimethyl styrene and the like are used as the polystyrene resin used for the polystyrene resin foam sheet. Homopolymer or copolymer of paramethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, vinylxylene, for example, styrene-maleic anhydride copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile resin ,
Acrylonitrile-butadiene-styrene resin is exemplified. When heat resistance is required, a heat-resistant polystyrene resin can be used. For example, a styrene copolymer containing 3 to 15% by weight of acrylic acid, methacrylic acid, acrylonitrile, and maleic anhydride is preferable.

The polystyrene resin used in the present invention may further contain a rubber such as butadiene rubber, elastomer, ethylene propylene rubber, ethylene butadiene rubber, or a copolymer of isoprene, chloroprene, or a copolymer of butadiene and styrene. The mixing amount is preferably about 0.05 to 15% by weight. The reason for this is that if it is less than 0.05% by weight, it may crack during handling depending on the combination with the thermoplastic resin film to be laminated. This is because printability may deteriorate depending on the shape. Further, the above rubber component is mixed with a polystyrene resin, and 0.1 to 40% by weight of a polyolefin resin such as polyethylene, polypropylene, an ethylene / propylene copolymer, or an ethylene-vinyl acetate copolymer is mixed to improve heat resistance. Can be better. However, when strength is required, it is necessary to control the rubber content to 5% by weight or less.

[0010] A foaming agent or the like is added to such a polystyrene resin, and extrusion foaming is performed to obtain a foamed sheet. At this time, 0.5 to 15% by weight of a filler of inorganic fine powder can be added to improve mold release, surface appearance, heat resistance, and the like. Examples of such a filler include fillers of general inorganic fine powders such as talc, calcium carbonate, shirasu, gypsum, carbon black, while carbon, magnesium carbonate, clay, and natural silicic acid, and metal powders. It may be used in the form of a master batch before being charged into the container.
Further, as a compounding agent, for example, a bubble regulator, a pigment, and the like may be added.

As the foaming agent which can be used in the present invention, various volatile foaming agents, decomposition type foaming agents and the like can be used. The volatile blowing agent, a hydrocarbon, propane, i- butane, n- butane, i- pentane, n- pentane or a mixture thereof, _{and, N 2, CO 2, N} 2 / CO 2, water, water And -O
_{H, -COOH, -CN, -NH 3} , -OSO 3 H, -N
_{H, CO, NH 2, -CONH} 2, -COOR, -CHS
Examples thereof include a mixture having a group of O ₃ H, —SO ₃ H, —COON ₄ , or —COONH ₄ .

Further, as decomposition type foaming agents, azodicarboxylic acid amide, dinitropentamethylenetetramine, 4,
A foaming agent such as 4 'oxybis (benzenesulfonyl hydrazide) can be mentioned. Further, a combination of an organic acid such as sodium bicarbonate or citric acid or a salt thereof with a bicarbonate, or the like can also be used. In addition, for example, a combination of an organic acid such as sodium bicarbonate citric acid or a salt thereof and a bicarbonate can also be used, but these can be used even if they are coated with a low molecular olefin, liquid paraffin, tallow oil, or the like. . In addition, a mixture of these may be used, and two or more of these may be mixed. All of these can also be obtained as a masterbatch with a powder, flake, or thermoplastic resin.

The expansion ratio of the polystyrene resin foam sheet of the present invention is about 1.2 to 15 times. Preferably it is 1.3 to 10 times. The thickness of the polystyrene-based resin foam sheet is appropriately selected depending on the thickness of the wall constituting the tray and the container of this type. Usually about 0.3-5.0mm,
Preferably, it is about 0.5 to 3.0 mm.

In the present invention, the above-mentioned polystyrene resin can be used as the thermoplastic resin film to be laminated on the polystyrene resin foam sheet. In addition, a mixed resin of a polystyrene-based resin and impact-resistant polystyrene, impact-resistant polystyrene, a styrene-butadiene block copolymer, and the copolymer may be dispersed in a salami structure. . The styrene-butadiene block copolymer preferably has a large particle diameter of 0.3 to 10 μm.

Other resins usable for the thermoplastic resin film include linear low density polyethylene, high density polyethylene, low density polyethylene, polypropylene, ethylene / propylene random polymer, ethylene / propylene block polymer, ethylene / propylene butene copolymer. , Ethylene-vinyl acetate 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-
Unsaturated carboxylic acids of vinyl chloride copolymer, propylene-butene copolymer, propylene-maleic anhydride copolymer, propylene-olefin copolymer (propylene-ethylene copolymer, propylene-butene-1 copolymer) polyethylene or polypropylene (for example, Maleic anhydride) modified products, ethylene-propylene rubber, atactic polypropylene, etc., such as polyethylene, ethylene-propylene copolymer, and propylene-butene-1.
Copolymers, mixtures of two or more of these, and films of polyethylene terephthalate, polybutylene terephthalate, and the like. As the polypropylene resin film, any of non-stretched, uniaxially stretched, and biaxially stretched films can be used. In particular, a non-stretched film is preferable because of good moldability.

In the thermoplastic resin film, 0.01 to 3% by weight of silicone oil can be mixed and used. If the silicone oil content is less than 0.01% by weight, effects such as improvement of releasability at the time of molding the container and prevention of blocking cannot be expected.
In addition, slippage between the container and the blanket of the printing press becomes worse, and printability also deteriorates. If the content is 3% by weight or more, the extrusion stability during film production deteriorates, and the appearance of the film also deteriorates.

When kneading the silicone oil into the thermoplastic film, the amount of the kneading that can be kneaded with the resin in the resin is up to about 0.2% by weight. Above this level, the resin slips and does not stably bite into the screw. Therefore, in order to mix more than 0.2% by weight up to 3% by weight, the resin is kneaded with a mixing roll such as a calender roll and pelletized, or added during polymerization or pelletization after polymerization. Or a press-fitting method in which the material is press-fitted in the middle of the extruder.

The silicon oil is used in an amount of 0.01% by weight to 0.1% by weight.
Knead in 2% by weight resin, and if more effect is required, knead in 0.01% to 0.2% by weight resin, then apply silicone oil on the film without unevenness Thus, the resin kneaded with 0.01% to 0.2% by weight of resin and further coated with silicone oil does not cause printing unevenness. Further, an antistatic material such as stearic acid monoglyceride can be kneaded together with the silicone oil. In addition, silicone oil may be mixed into the polystyrene resin foam sheet, so that foam moldability and the like can be improved. Alternatively, printing may be performed on a thermoplastic resin film into which silicon has been kneaded, and then the printed surface or the non-printed surface may be bonded to a polystyrene resin foam sheet. In addition, when a thermoplastic resin film is mixed with 0.1 to 3.0% by weight of a white filler such as titanium white or calcium carbonate, printability is improved,
The drag line disappears.

As a method of laminating a foamed polystyrene resin sheet and a thermoplastic resin film, a film provided with an adhesive layer is often bonded to a foamed sheet.
In this case, ethylene-vinyl acetate copolymer, ethylene-
Partially saponified vinyl acetate copolymer, a layer formed by extrusion laminating chlorinated polyethylene, chlorinated polypropylene, etc., polybutadiene, polyisoprene, styrene-butadiene copolymer,
A layer formed by extrusion laminating a mixture of a styrene-isoprene copolymer or the like with a polyolefin resin such as polypropylene or polyethylene is used as an adhesive layer. Further, the adhesive layer, polyvinyl acetate, polyvinyl chloride, vinyl resin such as polyvinylidene chloride, nitrocellulose, ethyl cellulose, cellulose resin such as cellulose acetate, epoxy resin, acrylonitrile-butadiene copolymer, etc. An adhesive dissolved in an organic solvent may be applied to a thermoplastic resin film and then dried to obtain a dry laminate.

As another method, when a thermoplastic resin film is laminated on a sheet-like foam in a die, the lamination may be performed using a merging die (for example, a crosshead die). The lamination may be performed by flowing in. When the foamed sheet is laminated after being extruded and foamed, a thermoplastic resin film extruder may be combined with a take-off machine to extrude the film and continuously laminate the film. It may be performed by appropriately laminating a resin film on a sheet-like foam.

When used as a food container, a foamed polystyrene resin sheet, a barrier film, and a thermoplastic resin film with a barrier film in advance are used to extend the shelf life of the contents. Are used. Specific examples of the barrier film include an ethylene / vinyl acetate copolymer, polyvinyl alcohol, polyvinylidene chloride, polyamide, polyester, polyacrylonitrile, vinylidene chloride / acrylonitrile copolymer, and acrylonitrile methyl methacrylate. Butadiene copolymer, nylon 6, biaxially oriented nylon, biaxially oriented polyethylene terephthalate, biaxially oriented polypropylene.
Examples thereof include high-density polyethylene, ionomer resin (for example, Surlyn®), a metal-deposited film alone, or a laminate of these.

In the present invention, when laminating the polystyrene resin foam sheet and the barrier film,
In addition to extrusion, there is a method of performing heat lamination, in which a film is heated and pressed from the side opposite to the joining surface with a hot roll. In this case, it is preferable to apply chrome plating or Teflon coating to the surface of the roll to be heated and pressed to prevent stickiness with the heated film. In the present invention, it is more preferable that the bonding surface is also heated by the heating device together with the thermocompression bonding by the heat roll.

The thermoplastic resin film has a thickness of 5 to 6
It is appropriate to use one of 00 μm. In some cases, a thermoplastic resin film may be laminated on both surfaces. If the thickness of the film is less than 5 μm, the elongation during molding will be poor, and the mechanical strength of the obtained molded product will be low and unreasonable. On the other hand, if the thickness exceeds 600 μm, after forming, when punching out, bubbles in the lip portion are liable to be communicated with each other, so that the problem that the film and the foamed sheet are separated easily occurs, which is disadvantageous in terms of economy. Not suitable. A more preferred thickness of the thermoplastic resin film is 30 to 500 μm.

In the laminated polystyrene resin foam container of the present invention, the minimum basis weight on the side wall of the container is 55% or more of the maximum basis weight. The closer to 100%, the more stable the strength. If this value is less than 55%, when the container is held by hand, the strength is partially weak and is not practical.
Further, in the present invention, the bubble diameter in the depth direction at the center portion of the side wall of the container needs to be 2.0 to 4.5 times in the thickness direction. The reason for this is that if it is less than 2.0 times,
This is because the strength in the depth direction is small and thus the strength is weakened, which is not preferable. On the other hand, if it exceeds 4.5 times, it is difficult to make the side wall uniform in thickness, which is not preferable. In the present invention, the difference in thickness, which is a value obtained by dividing the difference between the maximum thickness and the minimum thickness at the center of the side wall of the container by the maximum thickness, is 25.
% Is preferable. If this thickness difference exceeds 25%,
When holding the center part of the container by hand, the strength is weakened. Further, if the difference in the thickness of the container in the peripheral direction is 20% or more, the container is distorted when hot water is poured.

In the present invention, the minimum thickness at the center of the side wall of the container is 80% to 12%.
It is preferably 0%. If this value is less than 80% or too much 120%, when the container is held by hand, the strength is low and the container is not practical. It is better to be as close to 100% as possible. In the present invention, the basis weight of the bottom of the container is also preferably 70% to 130% of the flat basis weight of the side wall of the container, and more preferably 80% to 120%. When strength is required for the side wall of the container at the time of use, the basis weight of the side wall of the container is set to 100 to 130% of the basis weight of the bottom. When strength is required for the bottom, the basis weight of the bottom is reduced. Side wall weight of 10
Preferably it is 0 to 130%.

The laminated foam sheet used in the container of the present invention has a deformation (heating length of MD) / (length of TD after heating) of 0.90 due to deformation due to heating for molding. l.
It is preferable that the heating deformation ratio obtained by dividing the length after heating for molding by the length before heating for molding is 0.95 to 1.10. More preferably, the ratio of the length of the MD after heating / the length of the TD after heating is 0.97 to 1.1. The heating deformation ratio obtained by dividing the length after heating for molding by the length before heating for molding is 0.97 to 1.08 for both MD and TD. Here, the heating for molding is the temperature and time when the laminated foamed sheet is actually molded by a molding machine. It is preferable that at least one of the front and back surfaces of the thermoplastic resin laminated foam sheet of the present invention satisfies these values, but it is more preferable that the front and back sides satisfies these values.

The above-mentioned thermoplastic resin laminated foamed sheet has a blow-up ratio of 1.8, which is a ratio obtained by dividing the plug diameter by the die slit diameter when extrusion foaming is performed using a cylindrical mold. ~ 3.5, 0.25-1.2mm gap of die slit, extruder temperature 150 ~ 265 ° C
And the temperature of the molten resin in the vicinity of the mold outlet is 145 to 18
It is obtained at 5 ° C. The amount of extrusion varies depending on the extruder used, but in general, it depends on the extruder used.
What is necessary is just to set suitably at 5-400 kg / H.

Further, after being extruded from a cylindrical mold and foamed into an annular sheet, it is cooled by air. The cooling air amount at this time is about 0.04 to 0.3 m ³ / m ² ,
Further, the temperature is preferably within 5 seconds immediately after the extrusion at about 10 ° C to 80 ° C. In particular, the blow-up ratio is set between the 2 / 5th power and the 3 / 5th power of the expansion ratio, and the extrusion rate is such that the island pattern in the extrusion direction of the foamed sheet disappears within 1/3 of the distance from the mold slit to the plug. It is advisable to adjust the take-up speed and cooling conditions. The bubble shape at the center 2/3 of the thickness of the foam sheet is 0.9 ≦ TD / VD ≦ 1.5,
0.9 ≦ MD / VD ≦ 1.5. However, in this equation, the cell diameter is MD, TD, or VD (thickness direction).

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Regarding the laminated polystyrene resin foam container of the present invention, a production example of a thermoplastic resin laminated foam sheet used for molding the foamed container and representative physical properties of the sheet,
And examples of moldability evaluation, container properties, strength,
This will be described with reference to a comparative example. (Examples 1-4) The diameter is 115 mm and the diameter is 150 mm
Using a tandem-type extruder to which the above extruders were connected, a polystyrene resin foam sheet was extrusion-foamed as follows. First, in a hopper of an extruder having a diameter of 115 mm, a talc of 0.3 to 2 was prepared using a master batch of 20 parts by weight of talc with respect to 100 parts by weight of polystyrene (trade name: HRM-2, manufactured by Denki Kagaku Kogyo KK). The mixture was added and mixed so as to be parts by weight, and the mixture was extruded at 150 ° C.
After mixing and melting while heating to ２６265 ° C., 1.0 to 3.0% by weight of a foaming agent having a ratio of normal butane / isobutane of 7/3 based on polystyrene is injected, mixed, and then connected. Introduced into an extruder with a diameter of 150 mm, and 10 to 1 in comparison with the case of a conventional polystyrene resin foam sheet.
It is cooled to a temperature of about 140 to 110 ° C., which is 5 ° C. lower, and extruded in the range of a slit diameter of a cylindrical mold of 160 to 340 mm and a slit interval of 0.2 to 0.6 mm. , And cut at two places to obtain two polystyrene foam sheets having a width of about 1000 mm. Immediately after the extrusion, the foamed sheet was cooled, and the amount of air for this cooling was 0.05 to 0.25 m ³ /
m ² and the temperature of the air were adjusted to 20 to 70 ° C.

Further, using an extruder having a diameter of 90 mm, 90 parts by weight of high impact polystyrene (trade name: HIE-4, manufactured by Denki Kagaku KK) was added to the extruder.
10 parts by weight of a brand name: Tuftec H1014 (manufactured by Asahi Kasei Kogyo Co., Ltd.) as a rubber component was put into a hopper and melted. Laminated on the sheet, Examples 1 to
Each of the laminated foam sheets described in No. 4 was manufactured.
Next, the laminated foamed sheet having a side of 600 mm was placed on the side of the laminated foamed sheet so that the film side of the laminated foamed sheet was outside the container.
In the press part of the molding machine with the convex mold on the upper side and the concave mold on the lower side after heating, the concave mold and the convex mold are pressed and at the same time, the concave mold is evacuated and attached to the mold. It was released and released. Eighteen containers were molded. The shape of the container is such that the inner diameter of the opening is 110 mm, the width of the opening lip having a semicircular cross section is 4 mm, the outer dimension of the lowermost part of the side wall is 75 mm, and the height is 1
21 mm inverted truncated cone shape. Table 1 shows the physical properties of the laminated foam sheet, the physical properties of the container, and the evaluation of the moldability. Each of the examples was a container having good deep drawability and having no partial defect in strength on the side wall.

[0031]

[Table 1]

Here, the heating temperature for molding is set at an intermediate temperature between the heater in the molding machine heating zone and the foamed sheet. The heating time for molding was 25, 21, 21, and 28 seconds in Examples 1, 2, 3, and 4, respectively. Here, the heating time is empirically set to about 80 to 95% of the overheating time. Here, the overheating time indicates a state in which the foamed sheet is heated to the ambient temperature of the heating zone of the molding machine and heated to melt the surface, or the time when the thickness starts to decrease, which is the shorter one.

(Comparative Examples 1 to 4) In Example 1, the foamed sheet immediately after being extruded was introduced into an extruder having a diameter of 115 mm, cooled to about 155 to 129 ° C., and formed a slit gap of 0.5 to 0.8 mm. The cooling air amount is 0.05-0.
Extrusion was carried out in the same manner, except that it was 15 m ³ / m ² . The container was obtained by thermoforming in the same manner as in Example 1. Table 2 shows the results.
It is as follows. The bubbles of the sheet of Comparative Example 1 were large in the thickness direction during heating during molding. As a result, when molded, (cell diameter in the depth direction) / (cell diameter in the thickness direction) = 1.
It was 7. When the container was cut open and examined, the lower part of the side wall was thin. In Comparative Example 2, since the bottom of the cup was thin, the strength was weak when holding the container by hand, and the container was unusable. The container of Comparative Example 3 had a thin side wall under the opening lip, and was not usable. The air bubbles of the sheet of Comparative Example 4 were long in the MD and TD, and particularly long in the TD direction. When the sheet is formed, (cell diameter in the depth direction) /
(Bubble diameter in the thickness direction) = 4.2. When the center of the container was held by hand, the strength was low and the container was unusable. Also, when the container is cut open, the central side wall is thin.

[0034]

[Table 2]

(Example 5)
Into a 5 mm extruder, 0.5 part of talc is added to 100 parts of polystyrene (G-13-55, manufactured by Nippon Steel Chemical Co., Ltd.), and after mixing and melting, a blowing agent butane (i) is added to polystyrene.
(2.8% by weight of butane / n-butane) was injected, mixed, and cooled. On the other hand, HIPS
(Stylon 475D, manufactured by Asahi Kasei) was charged from a hopper and melted, and then combined with the styrene containing butane. The slit gap was 0.6 mm and the slit diameter was 110 m.
Extrusion foam at about 110Kg / H from a mold with m
The balloon was cooled and molded with a cylindrical plug having an air volume of 0.1 m ³ / m ² and a temperature of 50 ° C., and then cut to obtain a two-layer foamed sheet having a width of 1000 mm. When the film was peeled off and measured, the film thickness was 200 μm, the foamed sheet was 2.2 mm thick,
The magnification was 5.2 times. The molding was performed in the same manner as in Example 1. Table 1 shows the results.

(Example 6) HIPS 25 µm (D type, manufactured by Towa Kako) was laminated on the foam side with a hot roll on the foamed two-layer sheet obtained in Example 5, to obtain a three-layer foamed sheet. The molding was performed in the same manner as in Example 1. Table 1 shows the results. (Example 7) In Example 1, polystyrene was replaced with a styrene-acrylic acid copolymer (G
-9001, manufactured by Asahi Kasei Co., Ltd.) and the same apparatus and the same blending as in Example 1 except that the blowing agent was also changed to normanbutane / isobutane = 35/65. The molding was performed in the same manner as in Example 1. Table 1 shows the results.

Example 8 A multilayer foamed sheet was obtained by laminating an eval multilayer film (90 μm, manufactured by Sumitomo Bakelite) on the foamed sheet obtained in Example 1 with a hot roll. The molding was performed in the same manner as in Example 1. Table 1 shows the results.

Next, the test methods and terms used in the table are as follows. (Evaluation of Formability) Each laminated foam sheet having a side of 600 mm was clamped in four directions to form 18 cups. The shape of the container is such that the inner diameter of the opening is 110 mm, the width of the opening lip having a semicircular cross section is 4 mm, the outer dimension of the lowermost part of the side wall is 75 mm, and the height is 1
It is a 21 mm inverted truncated cone. ：: Good molding all △: Crack inside cup or thin side wall ×: Cannot be molded

(Strength of molded article) Compressive strength: The molded cup was compressed from the bottom at a speed of 400 mm / min using a Tensilon measuring instrument.
Measure the strength when the cup buckles. Rip strength: Measure the strength when compressed by 10 mm from the outside of the cup opening at a pushing speed of 400 mm / min of a Tensilon measuring instrument. The central part of the container side wall refers to a central part 中央 excluding an upper part and a lower part ４ in a container side wall and a depth direction.
The upper and lower portions of the container side wall refer to the upper 1/4 and lower 1/4 in the container side wall and the depth direction.

(Bubble diameter ratio in the depth direction at the center of the side wall of the container) The center of the side wall of the container was cut open, and ten bubbles near the center were arbitrarily selected with an electron microscope, and the value was measured. (Basic weight) The side wall of the container was cut into 1 cm ² squares, and the weight was measured. The unit was converted to g / m ² .

The container in Example 1 was cut open and the area 1c
When cut into squares of m ² and the weight and thickness were measured, the basis weight was 305 g / m ² , which was the maximum basis weight of the side wall portion, under the lip portion of the container corresponding to the MD of the sheet.
The minimum grammage of the side wall was the lowest part of the side wall of the container corresponding to the TD of the sheet. Its grammage was 207 g / m ² . On the other hand, the maximum thickness at the center of the side wall was 1.82 mm, and the minimum thickness at the center of the side wall was 1.66 mm. The minimum thickness of the side wall portion, the upper portion, and the lower portion was 1.46 mm at the bottom of the side wall portion of the container corresponding to the TD of the sheet.

[0042]

The present invention comprises a foamed container in which a laminated polystyrene resin foam sheet of a thermoplastic resin film and a polystyrene resin foam sheet is molded, and the minimum basis weight on the side wall portion of the container is the maximum value. 55% or more of the basis weight of the container, the bubble diameter in the depth direction at the center of the side wall of the container is 2.0 to 4.5 times the bubble diameter in the thickness direction, and the deep drawing ratio is 0.9 to 1.8. Anyway, on the side wall of the foam container,
This is a laminated polystyrene resin foam container with a uniform basis weight and strength and no defects. That is, a part of the side wall of the container is not soft, and the strength when held by hand is sufficient.
No deformation due to hot water. Therefore, a container having a required strength can be prepared with a small amount of resin.

Further, according to the present invention, since the difference between the maximum thickness and the minimum thickness at the center portion of the side wall of the container, which is a value obtained by dividing the difference by the maximum thickness, is within 25%, the thickness can be balanced. It is a laminated polystyrene resin foam container with good appearance. Further, the present invention is a laminated polystyrene resin foam container excellent in the compressive strength of the side wall of the container, since the minimum thickness of the center portion of the container side wall is 80 to 120% of the minimum thickness of the upper and lower portions of the side wall.

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Claims (3)

[Claims] 1. A foamed container having a deep drawing ratio of 0.9 to 1.8 formed by molding a laminated polystyrene resin foam sheet of a thermoplastic resin film and a polystyrene resin foam sheet, wherein a side wall portion of the container is formed. The minimum basis weight is 55% or more of the maximum basis weight, and the depth direction bubble diameter at the center of the side wall of the container is 2.0 to 4.5 of the thickness direction bubble diameter.
A laminated polystyrene resin foam container characterized in that it is twice as large. 2. The laminate according to claim 1, wherein the difference in thickness, which is a numerical value obtained by dividing the difference between the maximum thickness and the minimum thickness at the center of the side wall of the container by the maximum thickness, is within 25%. Polystyrene resin foam container. 3. The laminated polystyrene resin foam container according to claim 1, wherein the minimum thickness at the center of the side wall of the container is 80 to 120% of the minimum thickness at the upper and lower portions of the side wall.