JPH02188B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sheet-molded laminated plastic container, and more specifically, it is equipped with a styrene resin layer and a saponified ethylene-vinyl acetate copolymer layer, and has an excellent combination of transparency, gas barrier properties, and interlayer adhesion. The present invention relates to a sheet-molded laminated container. Containers made by molding styrene resin sheets into cup shapes, tray shapes, etc. through vacuum forming, pressure forming, plug assist molding, etc., are used for simple packaging of foods. has been done. This type of container has the advantages of being easy to mold, relatively inexpensive, and has excellent transparency. Among various thermoplastic resins, styrene resin has the highest gas permeability. It is one of the largest, and is clearly unsuitable for long-term storage of food contents under sealed conditions. In recent years, with the advancement of lamination technology, by laminating a resin layer with excellent gas barrier properties such as saponified ethylene-vinyl acetate copolymer to a resin with high gas permeability, it is possible to create a resin with low gas permeability. Therefore, it is widely practiced to manufacture containers with excellent content preservation properties. Given this technical background, it is natural that a multilayer container with high gas barrier properties should emerge, which is made by laminating a saponified ethylene-vinyl acetate copolymer layer on a styrene resin layer. The reason why this type of multilayer container has not yet appeared is probably because it was difficult to bond the styrene resin and the saponified ethylene-vinyl acetate copolymer. The present inventor has discovered that the styrene resin layer and the saponified ethylene-vinyl acetate copolymer layer can be bonded with a blend of acid-modified styrene resin and/or acid-modified petroleum resin and polyamide, and that this adhesive laminate discovered that it is possible to form sheets into cups, etc. That is, an object of the present invention is to provide a multilayer sheet molded container that has an excellent combination of gas barrier properties, transparency, and delamination resistance. Another object of the present invention is that the sheet can be easily formed into a cup or the like at a relatively low temperature, and even after the sheet is formed, the styrene resin layer and the barrier layer containing saponified ethylene-vinyl acetate copolymer can be easily formed. To provide a sheet-formed laminated container in which good interlayer adhesion is maintained between the layers. According to the present invention, the styrene resin layer and the barrier layer containing saponified ethylene-vinyl acetate copolymer are combined with an adhesive resin layer containing an acid-modified styrene resin and/or a blend of acid-modified petroleum resin and polyamide. There is provided a sheet-formed laminated container characterized in that it is formed by sheet-forming sheets laminated through a laminate. The invention will be explained in detail below. The first example showing an example of the sheet-molded laminated container of the present invention
In Figures 1 and 2, this container consists of a bottom part 1, a side wall 2 continuous to the bottom part, and a flange part 3 provided at the opening of the side wall. The side wall 2 is slightly flared upward. In FIG. 2, which shows an enlarged view of this container wall, a barrier layer containing a saponified ethylene-vinyl acetate copolymer is provided as an intermediate layer between an inner surface layer 4 and an outer surface layer 5, each of which is made of a styrene resin. 6 is provided, and an adhesive resin layer 7 containing acid-modified styrene resin and/or acid-modified petroleum resin and polyamide interposes between these inner and outer surface layers 4 and 5 and barrier layer 6 to firmly bond them. are doing. In the present invention, the acid-modified styrenic resin or acid-modified petroleum resin includes styrene resin and/or acid-modified petroleum resin.
Alternatively, an acid-modified resin obtained by reacting a petroleum resin with an unsaturated carboxylic acid or its anhydride, or a partially esterified acid-modified resin obtained by partially reacting this acid-modified resin with an alcohol can be suitably used. . As the styrene resin as a raw material, a resin obtained by cationic polymerization or radical polymerization of a styrene monomer such as styrene, vinyltoluene, α-methylstyrene, etc. is used. This styrenic resin is mainly composed of the above-mentioned styrene monomers, and further contains other ethylenically unsaturated monomers such as diolefins such as butadiene, acrylic esters, methacrylic esters, and acrylonitrile in the polymer chain. It may also be a copolymer. These styrenic resins may be partially hydrogenated to the extent that the essential nature of the styrene resin is not lost. The raw petroleum resin is a resin obtained by cationic polymerization of any fraction with a boiling point of -10 to 280°C obtained during cracking or reforming of petroleum in the presence of a Friedel-Crafts type catalyst, More specifically, C ₄ to C ₅ fractions such as cyclopentadiene,
Resins made by polymerizing or copolymerizing one or more of _C9 fractions such as α-methylstyrene, higher olefinic hydrocarbons up to _C11 , hydrogenated products thereof, etc. are used. . The ethylenically unsaturated carboxylic acids or their anhydrides to be reacted with the monomers of these raw resins include acrylic acid, methacrylic acid, maleic acid, maleic acid monomethyl ester, fumaric acid, fumaric acid monoethyl ester, and crotonic acid. , itaconic acid, citraconic acid, 5-norbornene-2,3-
Acid monomers such as dicarboxylic acids, maleic anhydride,
Acid anhydride monomers such as citraconic anhydride, itaconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, and tetrahydrophthalic anhydride may be used alone or in combination of two or more. Among these, maleic anhydride is most suitable for the purpose of the present invention. The acid-modified styrene resin and acid-modified petroleum resin used in the present invention have a compatibility and reactivity with the amide resin, and an adhesion with the saponified ethylene-vinyl acetate copolymer, ranging from 0.1 to 20. Mol%, especially 0.3
It is important to contain 15 to 15 mol% of an ethylenically unsaturated carboxylic acid or its anhydride as a copolymerization component, and if this copolymerization component is lower than the above range, the compatibility with the amide resin may deteriorate. As the ethylene-vinyl acetate copolymer saponified product disappears, the adhesive strength with the saponified ethylene-vinyl acetate copolymer tends to decrease to a range that is inappropriate for use as a container.On the other hand, if it exceeds the above range, the adhesive strength with the styrene resin layer decreases or The cohesive failure strength of the adhesive layer itself begins to decrease. In the graft modification reaction, the amount of the acid or acid anhydride monomer used may be any amount that will ultimately impart an acid concentration within the above-mentioned range to the hydrocarbon resin. These monomers and the raw material resin can be reacted in a melt system, a solution system, a solid-gas system, or a solid-liquid heterogeneous system. The addition reaction or grafting reaction between the two can also be initiated by heating, and it is recognized that, for example, in a melt system reaction, the reaction proceeds satisfactorily even without a catalyst. Of course, a radical initiator or other radical initiation means can also be used. Examples of initiators include organic peroxides such as dicumyl peroxide, t-butyl hydroperoxide, dibenzoyl peroxide, and dilauroyl peroxide, and azonitriles such as azobisisobutyronitrile and azobisisopropionitrile. etc. are used in catalytic amounts known per se. Radical initiation means include ionizing radiation such as X-rays, γ-rays, and electron beams; ultraviolet rays or a combination of ultraviolet rays and a sensitizer; mechanical radical initiation means such as kneading (mastication) and ultrasonic irradiation, etc. is used. For example, in a homogeneous solution reaction, a styrene resin and/or petroleum resin, monomer, and initiator are dissolved in an aromatic solvent such as toluene, xylene, or tetralin to perform grafting, and the resulting modified resin is precipitated. Collected as In a heterogeneous reaction, grafting is carried out by bringing the raw resin powder into contact with a monomer or a diluted monomer under irradiation with ionizing radiation. Furthermore, in a homogeneous melt system reaction, a blend of the raw resin, monomers, and optionally an initiator is melt-kneaded in a stirring vessel, extruder, kneader, etc. to obtain a modified resin. In any of these cases, the resulting modified resin may be subjected to washing, extraction, etc. in order to remove unpolymerized monomers, homopolymers, initiator residues, etc. The acid-modified resin thus obtained may be partially reacted with an alcohol to form a partially ester-modified hydrocarbon resin having an acid concentration within the above-mentioned range, and may be used in this form for the purpose of the present invention. can. In this case, as the alcohol, monohydric alcohols such as methanol, ethanol, and propanol, and polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin can be used. The conditions for esterification are known per se, and esterification may be carried out by such known means. In the present invention, polyamides include homopolyamides, copolyamides, and blends thereof. Examples of suitable homopolyamides are: polycapramide (nylon 6) poly-ω-aminoheptanoic acid (nylon 7) poly-ω-aminononanoic acid (nylon 9) polyundenamide (nylon 11) polylaurinlactam (nylon 12) poly Ethylenediamine adipamide (nylon 2,6) Polytetramethylene adipamide (nylon 4,
6) Polyhexamethylene adipamide (nylon 6,
6) Polyhexamethylene sebamide (nylon 6,
10) Polyhexamethylene dodecamide (nylon 6,
12) Polyoctamethylene adipamide (nylon 8,
6) Polydecamethylene adipamide (nylon 10,
6) Polydodecamethylene sebamide (nylon 10,
8) etc. Examples of suitable copolyamides include caprolactam/laurinlactam copolymer, caprolactam/hexamethylene diammonium adipate copolymer, lauryl lactam/hexamethylene diammonium adipate copolymer, hexamethylene diammonium adipate/hexamethylene diammonium Sebacate copolymer, ethylene diammonium adipate/hexamethylene diammonium adipate copolymer, caprolactam/hexamethylene diammonium adipate/hexamethylene diammonium sebacate copolymer, and the like. These homopolyamides and copolyamides are
It can also be used in the form of a so-called blend; for example, a blend of polycaprolactam and polyhexamethylene adipamide, a blend of polycaprolactam and a caprolactam/hexamethylene diammonium adipate copolymer, etc. can all be used for the purpose of the present invention. It is possible. Particularly desirable polyamides for the purposes of this invention include polycaprolactam (6-nylon), polyhexamethylene adipamide (6,6-nylon),
Polyhexamethylene sebaamide (6,10-nylon), 6,6/6,10 nylon copolymer, 6,
A 6/6 nylon copolymer or the like may be used. In the present invention, the final adhesive resin layer contains acid-modified styrenic resin and/or acid-modified petroleum resin and polyamide in a ratio of 100:1 to 1:3, preferably,
It is preferable to mix in the range of 50:1 to 1:2. If the acid-modified styrene resin and/or acetic petroleum resin component is larger than the above range, the adhesiveness with the saponified ethylene-vinyl acetate copolymer will be poor, and the cohesive failure strength of the adhesive layer itself will be reduced. starts to decrease. Furthermore, if the acid-modified styrene resin and/or acid-modified petroleum resin component is smaller than the above range, the adhesiveness with the styrene resin will decrease. In the present invention, the acid-modified styrene resin and/or the acid-modified petroleum resin may be used in various forms as long as the proportion of ethylenically unsaturated carboxylic acid or its anhydride falls within the above-mentioned range. That is, the ratio of acid-modified styrenic resin and/or acid-modified petroleum resin to unmodified styrene-based resin and/or petroleum resin, and ethylenically unsaturated carboxylic acid or its anhydride in the entire blend is within the above range. It can also be used by blending resins with various degrees of modification so that the proportion of ethylenically unsaturated carboxylic acid or its anhydride in the entire blend is within the above range. can. In the present invention, acid-modified styrenic resin and/or
Or acid-modified petroleum resin component and polyamide component,
The components may be present in the adhesive in the form of a so-called compatible mixture, or both components may be present in a chemically bonded state, or a combination of both components may be present. For example, it has been observed that the acid-modified styrenic resin and/or acid-modified petroleum resin component and the polyamide component react during melt blending to form a block copolymer. Formation of this block copolymer is generally confirmed by an increase in melt viscosity. This is recognized to be due to an amide forming reaction between the carboxylic acid or acid anhydride group and the terminal amino group of the polyamide. In the present invention, the styrene resin layer includes:
Any styrenic resin known per se may be used. This styrenic resin may be a styrene homopolymer or a copolymer of styrene and other monomers such as a conjugated diene or an acrylic monomer, but
From the viewpoint of impact resistance of the container, a styrene-conjugated diene copolymer mainly composed of styrene or a blend of polystyrene and a styrene-conjugated diene polymer is used.A copolymer or blend of these copolymers is used. In terms of impact resistance and moldability, it is desirable for the conjugated diene component to be present in an amount of 0.5 to 30% by weight, particularly 1 to 15% by weight, based on the total weight of the product. Butadiene, isobrene, etc. are advantageously used as the conjugated diene. These styrenic resins generally need only have a molecular weight sufficient to form a film. The saponified ethylene-vinyl acetate copolymer used for this laminate has an ethylene content of 20 to 80%.
Mol%, especially 25 to 0 mol% of ethylene-vinyl acetate copolymer, saponification rate of 90% or more, especially 96%
A polymer obtained by saponification as described above is desirable from the viewpoint of gas barrier properties.
This saponified ethylene-vinyl acetate copolymer is
Generally, a mixed solvent of 85% by weight of phenol and 15% by weight of water is used, and measured at 30℃, 0.07 to 0.17/
It is desirable to have an intrinsic viscosity of g. In the present invention, the gas barrier layer may be made of a saponified ethylene-vinyl acetate copolymer alone, or a blend of a saponified ethylene-vinyl acetate copolymer and another thermoplastic resin. It can also be used in ethylene-
A multilayer structure of a saponified vinyl acetate copolymer and another thermoplastic resin can also be used. For example, a saponified ethylene-vinyl acetate copolymer and various types of nylon form a homogeneous blend, and this blend exhibits excellent barrier properties against various gases such as oxygen, as well as excellent stretch formability. It is known that
Publication No.). Thus, in the present invention, a blend containing saponified ethylene-vinyl acetate copolymer and polyamide (nylon) resin in a weight ratio of 95:5 to 5:95 can be used as the gas barrier layer. In addition, blends of olefin resins such as polyethylene and polypropylene and saponified ethylene-vinyl acetate copolymers have a multilayer distribution structure in which the components in these blends are distributed in layers under certain melt extrusion conditions. This is known (Special Publication No. 51-30104). In the present invention, a saponified ethylene-vinyl acetate copolymer can also be used in the form of such a multilayer distribution structure. According to the present invention, an acid-modified styrene-based resin and/or an acid-modified petroleum resin, and a polyamide are interposed in adjacent positions between the styrene-based resin layer and the saponified ethylene-vinyl acetate copolymer-containing barrier layer. As a result, even when this laminated sheet is subjected to sheet molding, an extremely strong interlayer adhesive bond is formed, and the styrene resin sheet molded container is made of ethylene, which has excellent barrier properties against various gases such as oxygen and aromatic components. - By interposing the saponified vinyl acetate copolymer, it becomes possible to preserve the contents, that is, to prevent the contents from oxidative deterioration, to prevent the proliferation of microorganisms, and to prevent the disappearance of aroma components. Generally, when thermally adhering different resin layers, it is considered necessary to consider factors such as the occurrence of chemical bonds between the resin layers, differences in the chemical structures of the resins, and mutual mixing of the resins at the bonding interface. The acid-modified styrenic resin and acid-modified petroleum resin used in the present invention share a polymer chain skeleton with the styrene resin, and a strong bond is formed between the two resin layers due to the Juan der Baals force, and the adjacent resin It is recognized that a strong adhesive bond can be formed between the layers. In addition, polyamide forms a homogeneous blend with saponified ethylene-vinyl acetate copolymer,
Because of their extremely good compatibility, acid-modified styrene resins and acid-modified petroleum resins also form hydrogen bonds between hydroxyl groups and carboxylic acid groups or carboxylic acid anhydride groups with saponified ethylene-vinyl acetate copolymers. It is recognized that strong adhesive bonding is possible between the adjoining resin layers due to the formation of ester and ester bonds. Furthermore, acid-modified styrene resin and/or acid-modified petroleum resin and polyamide are melted at 210 to 330°C, preferably 220 to 310°C, using a known resin kneading device such as an extruder, kneader, or Banbury mixer. The copolymer obtained by reacting by kneading, or the acid-modified styrenic resin and acid-modified petroleum resin, is heated at a relatively low temperature, for example, 80 to 80°C.
Since it softens at a temperature of 150°C, it is presumed that good wetting and mixing of the resins occur at the bonding interface during thermal bonding, resulting in good thermal bonding properties. In the sheet molded container of the present invention, an acid-modified styrenic resin and/or an acid-modified petroleum resin, and a polyamide ( Any multilayer structure can be adopted within the range that satisfies the condition that ADH) are present in an adjacent positional relationship. For example, the ST/
In addition to the symmetrical five-layer structure of ADH/HEVA/ADH/ST, the three-layer structure of ST/ADH/HEVA, ST/
4-layer structure of ADH/HEVA/ADH, HEVA/
It can take any layered structure such as a five-layered structure of ADH/ST/ADH/ST. In this laminate, the styrene resin layer and saponified ethylene-vinyl acetate copolymer layer are:
The thickness ratio of the styrene resin layer to the adhesive resin layer is 1000:1 to 1:100, while the thickness ratio of the styrene resin layer to the adhesive resin layer is 10000:1 to 1:10. It is desirable from the viewpoint of properties such as properties and delamination resistance. In addition, the thickness of the laminate as a whole is determined from the viewpoints of shape retention, light weight, economic efficiency, etc.
It is desirable that the thickness be in the range of 0.001 to 10 mm. According to the present invention, first, a sheet having the above-mentioned laminated structure is manufactured. This multilayer sheet is produced by preparing a film or sheet of styrene resin and a film or sheet of ethylene-vinyl acetate copolymer in advance, and then combining these films or sheets with acid-modified styrenic resin and/or acid-modified resin. Manufactured by thermal bonding through layers of a blend of petroleum resin and polyamide. The above-mentioned adhesive resin can be applied in any form such as a melt, film, powder, solution, suspension, etc. Thermal bonding can be carried out by hot-pressing stacked films or sheets, or by placing them between heated rolls. This is easily done by passing it through. Alternatively, multilayer sheets can also be produced by coextrusion, in which case styrene resin, adhesive resin and ethylene-
Three extruders corresponding to each saponified vinyl acetate copolymer are used, and each molten resin flow from these extruders is extruded through a multilayer die in the laminated positional relationship described above to form a multilayer sheet. do. This multilayer sheet is subjected to a sheet forming method known per se, such as vacuum forming, pressure forming, plug assist forming, etc., at the softening temperature of the styrenic resin or the temperature at which the styrene resin can be stretched.
Form into containers in the shape of cups, trays, etc. Although it is generally preferable to use the sheet-molded container of the present invention as a so-called transparent container, it can also be used as an opaque container by, for example, adding pigments, fillers, etc. to the styrene resin layer. Furthermore, as shown in FIG. 3, by forming the outer surface layer with a foamed layer 5a of styrene resin, this container can also be provided with heat shielding properties or heat retention properties at the same time. Although the expansion ratio of the styrene resin can be varied, it is generally desirable to set it to 1.1 to 70 times. The invention is illustrated by the following example. Example 1 Polycaprolactam Amiran 1017 (manufactured by Toray Industries)
Acid-modified polystyrene with a maleic anhydride content of 10 mol% (number average molecular weight 60,000,
(measured by GPC) were mixed in pellet form using a Henschel mixer, and then kneaded at 250°C using a Banbury mixer. The blend obtained by varying the blend ratio of polycaprolactam and acid-modified polystyrene and kneading them in the above manner was used as an adhesive to bond a 500 μm thick sheet of polystyrene Styron #475 (manufactured by Asahi Dow) with ethylene-vinyl acetate. A 300μ thick sheet of saponified polymer EVAL F (manufactured by Kuraray) was adhered using a hot press. The sample was prepared by holding it in a hot press at 230°C for 2 minutes and then holding it at a pressure of 1 kg/cm ² for 10 seconds. However, in order to prevent foaming, the above-mentioned sheets and the like are thoroughly vacuum-dried. The sample was cut into a 10 mm wide strip, and after holding a polystyrene sheet and an EVAL sheet in each chuck using Tensilon (manufactured by Toyo Baldwin), peeling was performed at 180°C by pulling at a speed of 200 mm/min at room temperature. Ta. The adhesive layer of the sample had an average thickness of 7 μm. The results are shown below.

[Table] From these results, it was found that when acid-modified polystyrene alone was used as an adhesive, satisfactory adhesive strength could not be obtained due to the brittleness of the adhesive itself. Furthermore, polycaprolactam alone cannot be used as an adhesive because it does not have the ability to bond with polystyrene. However, by blending polycaprolactam and acid-modified polystyrene, the fragility of acid-modified polystyrene is eliminated, and adhesion with polystyrene is achieved due to compatibility with acid-modified polystyrene. It is expected that adhesion with EVAL may occur upon interaction with maleic anhydride. Example 2 Using an adhesive with the blend ratio described in Example 1, EVAL (manufactured by Kuraray) was used as an intermediate layer, and Example 1
A sheet having a symmetrical five-layer structure as described in the specification with inner and outer polystyrene layers was prepared by coextrusion. Furthermore, as the inner and outer layer extruder, it has a built-in full-flight type screw with a diameter of 65 mm and an effective length of 1430 mm.
Also, one equipped with a melt channel that branches into two flow paths, one equipped with a full-flight type screw with a diameter of 50 mm and an effective length of 1100 mm as an intermediate layer extruder, and one with a diameter of 50 mm and an effective length as an adhesive layer extruder. A multi-layer 5-layer T die was used, which had a built-in full-flight screw with a length of 110 mm and a melt channel that branched into two flow paths. The produced sheet had a width of 200 mm and a wall thickness of 1.1 mm. Here, as the blended adhesive, pellets were dry-blended using a Henschel mixer and supplied to the hopper. These sheets were plug-assisted vacuum formed under normal polystyrene molding conditions, and the inner diameter was 100 mm.
An attempt was made to form a cylindrical cup with a diameter of 200 mm, a wall thickness of 0.5 mm, and an internal volume of 1.57 mm. Among the blended adhesives, A, B, and C were able to create a moldable sheet. D,E
There were cracks in some parts. A part of the molded cup was cut out, immersed in 10 g of Congo Red in aqueous solution, and the intermediate layer and adhesive layer in the cross section were dyed at 90°C.The layer structure was determined by microscopic observation. The thickness ratio of outer layer:adhesive layer:middle layer:adhesive layer:inner layer was 45:2.5:5:2.5:45. The side walls of the molded cups A, B, and C were cut out, and the peel strength was measured in the same manner as in Example 1. In this case, a knife was inserted into the middle layer to forcibly separate it into two layers, which were then held in the chuck of Tensilon. The results are shown below.

[Table] Cut out the original sheets A, B, and C and the side wall of the cup, and measure the oxygen permeability Qo ₂ (20℃,
0% RH). In addition, the layer composition ratio was determined as described above, and the thickness of each layer was determined. A gas permeation tester manufactured by Toyo Tester Kogyo Co., Ltd. was used. This is measured as follows. After the sample was fixed between two chambers, one chamber was evacuated to a low pressure of 10 ^-2 mmHg or less (low pressure side), and then the other chamber (high pressure side) was dehumidified with calcium chloride. Replace the oxygen gas so that the pressure is 1 atm. Then, the temporal change in pressure increase on the low pressure side is read with a recorder, and the oxygen gas permeability Qo ₂ is measured. From the oxygen permeability thus determined, the oxygen permeability coefficient of the intermediate layer was determined as follows. Po ₂ = (1.52 × 10 ^-15 ) × h / (1 / Qo ₂ -1 / (Qo ₂ )
_PS ) Po ₂ : Oxygen permeability coefficient of the intermediate layer (cc・cm/cm ²・
sec・cmHg) Qo ₂ : Oxygen permeability of multilayer sample (cc/m ²・
day・atm) (Qo ₂ ) _PS : Oxygen permeability of single polystyrene sample (cc・m ²・day・atm) (Qo ₂ ) _PS is the total thickness of polystyrene in a multilayer sample (adding the thickness of the adhesive layer The oxygen permeability of single polystyrene samples of the same thickness h: Thickness of the intermediate layer (μ) The haze (ASTM D1003-61) was measured for each sample cut out from the cup and sheet.The sampling part of the cup was The center was set at the side wall of the cup.Respective measurement results are shown below.

[Table] As described above, it was found that even when the cup was formed, the adhesive strength did not decrease and the strength of the sheet was maintained. It is also seen that cup molding does not cause cracks in the intermediate layer, which is a gas barrier layer, and that its gas barrier properties are maintained. When Adhesive C was used, the gas barrier properties appeared to be slightly improved, probably due to the contribution of the gas barrier properties of polycaprolactam. Furthermore, it can be seen that although the transparency is somewhat lower than that of a single polystyrene molded product, it is not significant. Example 3 The following acid-modified polystyrene was obtained by changing the maleic anhydride content of the acid-modified polystyrene in Example 1.

[Table] In the same manner as in Example 1, a laminate sheet of polystyrene and EVAL was prepared using the above acid-modified polystyrene as an adhesive, and the peel strength was measured. The mixing ratio of polycaprolactam and acid-modified polystyrene was 3:7. The results are shown below.

[Table] When the adhesive layer is F or G, the polystyrene portion and the polycaprolactam portion undergo phase separation within the adhesive layer, making the adhesive layer extremely brittle. When the adhesive layer was I, no phase separation occurred within the adhesive layer, so it is thought that the adhesive layer simply became hard and brittle due to the high degree of acid modification. Therefore, it is understood that the degree of modification of acid-modified polystyrene needs to be selected within an appropriate range. Example 4 Maleic anhydride content was 8 mol % by graft copolymerizing maleic anhydride by the method described in the specification.
Acid-modified petroleum resin was created. The petroleum resin used as raw material is aromatic hydrocarbon tree (Vetrogin #120).
(manufactured by Mitsui Petrochemical Industries, acid value 0.10) was used. This acid-modified petroleum resin and polyhexamethylene adipamide (Leona 1200S manufactured by Asahi Kasei) were blended in a pellet form in a Henschel mixer at a weight ratio of 7:3. Using this blend as an adhesive, high-impact polystyrene (Dialex HT88A manufactured by Mitsubishi Monsanto Kasei) was used as the inner and outer layers, and EVAL F (manufactured by Kuraray) was used as the middle layer.
A sheet having a symmetrical five-layer structure as described in the specification was produced by coextrusion. For comparison, similar sheets were also created using acid-modified petroleum resin alone and polyhexamethylene adipamide alone as adhesives. When the layer structure was determined by the method described in Example 2,
Both sheets had the following ratio: outer layer: adhesive layer: middle layer: adhesive layer: inner layer = 300:25:50:25:300 (unit: μm). These sheets are formed using normal vacuum and pressure forming to form square cups (diameter 8.5cm x 8.5cm, height 4.5cm).
cm) was obtained. However, when hexamethylene adipamide alone was used as the adhesive, complete delamination occurred between the inner and outer layers and the intermediate layer, so the cup was not molded. A cup with a blended adhesive layer as an adhesive layer is designated as J, a cup with a petroleum resin as an adhesive layer as an adhesive layer is designated as K, and for comparison, a cup molded from a single sheet of 650 μm high impact polystyrene is designated as L. For multilayer cups, peel strength was determined using the method described in Example 2. In addition, the oxygen permeability of the cup was measured as follows. Put a small amount of distilled water into the cup to be measured, and while keeping the inside of the cup at 100% RH, replace the inside of the cup with nitrogen gas in a vacuum, and then seal it with a heat-sealed aluminum foil lid that virtually prevents oxygen from passing through. A rubber for gas chromatography inlet was attached to the lid using a silicone adhesive. The cup at 24℃, 60%RH
The concentration of oxygen permeated into the cup was determined using a gas chromatograph, and oxygen gas at 24°C was stored at 100% RH inside the cup and 60% RH outside the cup according to the following formula. Transmittance (Qo ₂ ) was calculated. Qo ₂ = m × Ct / 100 / t × O _P × A [cc × m ²・day・atm
] m: Amount of nitrogen gas filled into the cup [ml] t: Storage period in the humid temperature chamber [day] Ct: Oxygen concentration inside the cup after t days [Vol] A: Effective surface area of the cup [m ² ] O _P :Oxygen gas partial pressure (=0.209) [ATM] The results are shown below.

[Table] From the above, it was found that almost the same gas barrier properties were obtained when the blend was used as an adhesive and when acid-modified polystyrene alone was used as an adhesive, and the adhesive strength itself was also to a certain extent. are different. Therefore, after filling the above three types of cups with water and heat-sealing the lids, we conducted a drop test from a height of 50 cm 10 times at room temperature. After the test, oxygen permeability was measured in the same manner as above. The results are shown below.

[Table] There is no significant difference in the oxygen permeability of cup J with the blend adhesive and cup L with polystyrene alone. On the other hand, the differences in Cup K using acid-modified polystyrene as an adhesive were large, suggesting that some damage occurred to the intermediate layer, which is a gas barrier layer, or that delamination occurred. In other words, since the acid-modified polystyrene used as the adhesive was brittle, it was destroyed by the impact of the drop, and it is thought that the gas barrier layer was damaged or delamination occurred at that time.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example of the container of the present invention, FIG. 2 is an enlarged sectional view of the container wall of the container of FIG. 1, and FIG. 3 is the layer structure of the container wall of the container of the present invention. FIG. 3 is an enlarged sectional view showing another example. Reference numeral 1 indicates the bottom, 2 indicates the side wall, 3 indicates the flange, 4 indicates the inner surface layer, 5 indicates the outer surface layer, 6 indicates the barrier layer, and 7 indicates the adhesive resin layer.

Claims (1)

[Scope of Claims] 1. The styrene resin layer and the barrier layer containing saponified ethylene-vinyl acetate copolymer are combined into an adhesive resin layer containing a blend of acid-modified styrenic resin and/or acid-modified petroleum resin and polyamide. A sheet-formed laminated container characterized in that it is formed by subjecting sheets laminated via a sheet to sheet-forming. 2. In the blend, at least a portion of the acid-modified styrenic resin and/or acid-modified petroleum resin and at least a portion of the polyamide are combined to form a block copolymer, as set forth in claim 1. Laminated container. 3. The laminated container according to claim 1, wherein in the blend, the acid-modified styrenic resin and/or acid-modified petroleum resin component and the polyamide component are present in a weight ratio of 100:1 to 1:3. 4. The acid-modified styrene resin and/or the acid-modified petroleum resin contains 0.1 to 20 mol% of ethylenically unsaturated carboxylic acid or its anhydride as a copolymerization component. Laminated container. 5 The styrenic resin is composed of a styrene-conjugated diene copolymer mainly composed of styrene, or a blend of polystyrene and styrene-conjugated diene copolymer, and the styrenic resin as a whole is
The laminated container according to claim 1, characterized in that it contains 0.5 to 30% by weight of a conjugated diene component. 6. The laminated container according to claim 1, wherein the saponified ethylene-vinyl acetate copolymer has an ethylene content of 20 to 80 mol% and a degree of saponification of 90% or more. 7 The styrene resin layer and the saponified ethylene-vinyl acetate copolymer layer have a thickness ratio of 1000:1 to 1:100, and the styrene resin layer and the adhesive resin layer have a thickness ratio of 1000:1 to 1:100.
The laminated container according to claim 1, characterized in that the layered container is present at a thickness ratio of 10000:1 to 1:10. 8. The laminated container according to claim 1, wherein the styrenic resin layer is made of a styrene resin foam.