JP6428138B2 - Coextrusion unstretched film and composite sheet for tray molding - Google Patents

Description

  The present invention relates to a non-stretched coextruded film suitable for tray molding and a composite sheet laminated with a resin sheet, which has gas barrier properties and heat sealability, can be printed, and has microwave oven resistance.

  In recent years, the food industry has become active in reducing food waste loss as a means of reducing environmental impact, reducing costs, and effectively using resources.

Therefore, in terms of packaging materials, we have contributed to these efforts by providing packaging materials and packaging methods that extend the shelf life of foods. For example, oxygen inflow and miscellaneous bacterial growth that cause food degradation are suppressed. The means to do is utilized.
Heat sterilization in sealed packaging and sealed packaging in an aseptic room are performed as methods for suppressing oxygen inflow and miscellaneous bacteria growth, and vacuum packaging and gas replacement packaging with gas barrier packaging materials can be used to further enhance the effect. Is used.

  In particular, foods with a short shelf life, such as meat, fresh fish, and side dishes, have traditionally been mainly wrapped around a resin tray that does not have a gas barrier property or just a lid that fits the resin tray. These packaged foods have a short shelf life and a large amount of sales, so reducing waste loss is an urgent issue.

  On the other hand, in food trays that handle these fresh foods, a design that expresses a sense of quality and cleanliness is emphasized, and printed polystyrene resin sheets and full-layer expanded polystyrene resin sheets are used. However, the polystyrene resin sheet cannot be deep-drawn because of its low heat-resistant rigidity, and cannot be used for a gas replacement package (gas pack) that is filled with an inert gas and sealed.

Therefore, a gas replacement package using a tray and a lid made of a gas barrier material has attracted attention.
As an example of the tray, Patent Document 1 discloses a technique in which a plastic film having a heat-fusible resin layer, a gas barrier layer, and an easy-peeling seal layer and a polypropylene resin sheet having a thickness of several hundreds of μm are heat-sealed and laminated. Is disclosed.

However, since the film has poor flatness, roll winding defects and avatars are likely to occur, resulting in defects such as missing prints and misalignments.
As a result, the decoration of food trays cannot be printed on film, so there is no other way than to do it by coloring sheets, and the tray design that greatly influences consumers' purchasing awareness has become limited. ing.
In addition, since the types of sheets to be heat-sealed are limited to polypropylene resin sheets and high-density polyethylene resin sheets, it can be applied only to solid color plain trays such as jelly cups and cooked rice containers, and has a large amount of production and sales. It cannot be used for trays for fresh food or side dishes.

  In Patent Document 2, a film having an ethylene-vinyl alcohol copolymer resin (EVOH) layer as an outer layer and a heat-sealable layer as an inner layer is formed for deep drawing and gas pack packaging, and has a thickness of several hundred μm. A technique for laminating an amorphous polyethylene terephthalate resin sheet with a dry laminate is disclosed.

  However, these films are suitable for laminating, but have a large amount of curl in terms of layer structure, so that printing tends to shift. Also. Although the composite sheet with the polyethylene terephthalate resin sheet is excellent in transparency, the heat resistance is low, and the thickness is increased in order to maintain rigidity against the weight of meat, sugar beet, etc., and the manufacturing cost is increased.

JP 2000-190435 A JP-A-8-281881

  The present invention is intended to solve the above-mentioned problems. An object of the present invention is to provide a non-stretched coextruded film and a resin sheet that have gas barrier properties and heat sealability, can be printed, and are suitable for tray molding. It is to provide a laminated composite sheet.

  As a result of intensive studies, the inventor has an outer layer, an intermediate layer, and an inner layer. The outer layer is composed of a polypropylene resin as a main component and a low-density polyethylene resin, and the intermediate layer is made of ethylene-vinyl acetate copolymer soap. An unstretched coextruded film having a heat-sealable layer comprising a polyolefin resin as a main component, and a polypropylene resin sheet on the outer layer side of the film, wherein at least one compound layer or metaxylene adipamide nylon resin layer is disposed , A composite obtained by laminating a resin sheet having a thickness of 300 μm or more selected from the group consisting of polyethylene terephthalate resin sheet, polystyrene resin sheet, heat-resistant foamed polystyrene resin sheet, polyvinyl chloride resin sheet, high density polyethylene resin sheet, and polyacrylonitrile resin sheet Able to solve this problem with a sheet Heading, which resulted in the completion of the present invention.

According to the non-stretched coextruded film of the present invention, it has gas barrier properties and heat seal properties, and can be printed, so that it can impart a decorative appearance to the tray. In addition, the composite sheet of the present invention can form a tray having a good sealing property with a lid, a packaging good for vacuum packs and inert gas packs. Extension and reduction of food and packaging waste loss were made possible.
Furthermore, since the sheet | seat to laminate | stack can be selected from various resin sheets, preparation of the tray which also has microwave oven heat resistance was attained.

Hereinafter, the outer layer, intermediate layer, inner layer, adhesive layer, and plastic sheet constituting the film of the present invention will be described.
In the present specification, “configured as a main component” is intended to allow other components to be included within a range that does not impede the action and effect of the resin constituting each layer. Furthermore, this term does not limit the specific content, but means that it occupies 50% by mass or more and 100% by mass or less, preferably 80% by mass or more and 100% by mass or less, of the total components of each layer. .

<Outer layer>
The outer layer of the film of the present invention is constituted by mixing a low-density polyethylene resin with a main component polypropylene resin.

  Although there is no restriction | limiting in particular in the kind of polypropylene resin used for an outer layer, From a viewpoint of transparency and dimensional stability, a propylene-ethylene copolymer and a propylene homopolymer are preferable.

  The type of low-density polyethylene resin is not particularly limited, but a high melt tension resin is effective for film thickness uniformity and defect suppression. It is preferable to use a large amount of high-pressure low-density polyethylene resin.

The mixing ratio of the low density polyethylene resin in the outer layer is preferably 5% by weight or more and 20% by weight or less. More preferably, the lower limit is 10% by weight or more and the upper limit is 15% by weight or less.
When the content is 5% by weight or more, an effect of suppressing the film thickness uniformity and avatar is exerted by increasing the melt tension of the film surface by resin mixing. On the other hand, if it exceeds 20% by weight, the cohesive strength in the layer is remarkably lowered, and the interlayer adhesion strength becomes insufficient.

Since the outer layer of the present invention is formed by mixing a polypropylene resin and a low density polyethylene resin, fine indentations can be formed on the outer layer surface due to the incompatibility of both, and printing inks and various coatings can be formed by the irregularities. The agent effectively adheres to the film surface, and the suitability for printing, coating and laminating is improved.
When the resin immediately after film formation having a fine uneven surface is highly reactive, the denaturation treatment by corona discharge further improves the suitability for printing, coating and laminating.
Fine irregularities on the outer layer surface can be observed and measured with an optical microscope or a surface roughness meter.

  Compared with the case of film formation only with polypropylene resin, mixing low density polyethylene resin with polypropylene resin has the effect of increasing the tension during film formation, making it possible to produce a thin film with a uniform thickness. It becomes. Further, it is possible to prevent the “avatar” phenomenon caused by the slow cooling crystallization partially progressing due to the undulation of the film and whitening.

For this reason, the film of the present invention is less likely to cause bumps and wrinkles when rolled, so that it is highly suitable for post-processing printing and lamination.
Therefore, the film of the present invention can be laminated with various resin sheets after performing extrusion lamination directly on the surface of the outer layer, or after printing on the surface of the outer layer without missing or misalignment.
In addition, a well-known technique can be used for the method of printing and coating to the outer layer surface of a film.

  The outer layer of the film of the present invention may be composed of two or more layers. In that case, without damaging the effect of the present invention by arranging a layer in which the above-mentioned polypropylene resin is mixed with the low-density polyethylene resin in the outermost layer. , To achieve the challenge.

  When the outer layer is arranged in addition to the outermost layer, it is preferable to use a polypropylene resin or a polyethylene resin and make it adjacent to the outermost layer. In particular, when a resin similar to the polypropylene resin used for the outermost layer is used, the interlayer affinity is good and rigidity can be imparted to the film, which is effective in improving the workability of the film.

  The thickness of the outer layer is preferably 8 μm or more and 30 μm or less as the total thickness of the outer layer, whether it is a single layer or two or more layers. The lower limit of the thickness is more preferably 10 μm or more, and further preferably 12 μm or more. The upper limit is more preferably 25 μm or less, and further preferably 20 μm or less.

If the thickness of the outer layer is 8 μm or more, stiffness (rigidity) of the entire film and processing suitability for printing and laminating are imparted, and if it is 30 μm or less, wrinkle generation in the printing and laminating steps can be suppressed.
Moreover, since the thickness of the outer layer affects the curl of the film depending on the ratio with the thickness of the inner layer, it is preferably 60% or more and 130% or less with respect to the thickness of the inner layer.

<Intermediate layer>
The film of the present invention is provided with at least one ethylene-vinyl acetate copolymer saponified material layer or polymetaxylene adipamide resin layer as a gas barrier property layer in the intermediate layer, which is necessary for a gas barrier package. Has oxygen barrier properties.

The ethylene content of the saponified ethylene-vinyl acetate copolymer is not particularly limited, but from the viewpoint of film formation stability, the lower limit is preferably 27 mol% or more, more preferably 32 mol% or more, and the upper limit. Is preferably 47 mol% or less, and more preferably 44 mol% or less.
In view of the gas barrier effect, it is more preferable to dispose an ethylene-vinyl acetate copolymer saponified layer. In applications where heat resistance or deterioration due to moisture is a concern, it is preferable to dispose a polymetaxylene adipamide resin layer having excellent heat resistance and water resistance.

Oxygen gas barrier properties of the film of the present invention, from the viewpoint of food deterioration suppression, preferably ^{10cc / (m 2 · day ·} atm) or ^{less, 8cc / (m 2 · day} · atm) or less is more preferable.

The lower limit of the thickness of the gas barrier layer is preferably 2 μm or more, and more preferably 3 μm or more. The upper limit is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less.
When the thickness is 2 μm or more, an oxygen barrier property sufficient for the purpose of the present invention can be imparted, and stable film formation can be achieved. Moreover, by being 10 micrometers or less, besides being excellent in economical efficiency, the fall of pinhole resistance can be avoided. &#34;

<Inner layer>
The inner layer of the film of the present invention is provided with a heat seal layer.
The resin used for the heat seal layer is not particularly limited as long as it has heat seal properties. For example, propylene homopolymer, ethylene-propylene random or block copolymer, high density polyethylene, low density polyethylene, linear chain And various resins such as low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, polymethyl methacrylate, and ionomer.

Among these, propylene homopolymer, ethylene-propylene copolymer, and linear low density polyethylene are preferable in terms of heat resistance and heat sealability.
In particular, when a polypropylene resin having a melting point of 150 ° C. or higher is used, high heat resistance can be imparted, so that it can be more suitably used as a microwave heated food tray.

In addition, when an easy peel layer is arranged on the inner layer, it is easy to use when the consumer opens the food packaging, and the commercial value of the food tray is increased.
The easy peel strength is preferably 0.1 N / 15 mm width or more and 20.0 N / 15 mm width or less at 25 ° C.
The easy peel layer may be any of cohesive failure type, delamination type, and interfacial exfoliation type, but the selection of cohesive failure type or delamination type having a wide seal temperature setting range and excellent peel stability is more preferred.

  In the case of the cohesive failure type, at least one kind is selected from the resins listed as the material constituting the heat seal layer (resin A), and as a resin having low compatibility with the resin A, high-density polyethylene, It is obtained by selecting any one from low density polyethylene, polypropylene, polybutene, and ethylene-vinyl acetate copolymer (resin B) and mixing the resins A and B.

By adjusting the mixing ratio of the resin A and the resin B, it is possible to maintain a good heat seal property and obtain an appropriate easy peel strength.
The lower limit of the resin A is 55% or more, preferably 60% or more, more preferably 65% or more, and the upper limit is 90% or less, preferably 85% or less, more preferably 80% or less.
The lower limit of the resin B is 10% or more, preferably 15% or more, more preferably 20% or more, and the upper limit is 45% or less, preferably 40% or less, more preferably 35% or less.

  The heat seal layer may be composed of two or more layers. In that case, each layer may be made of the same resin or different resins. In the case of providing an easy peel layer, by arranging it in the innermost layer, appearance defects such as fluff due to peeling can be suppressed, and the influence of lowering the strength of the entire film is reduced.

  The thickness of the inner layer is not particularly limited, but the lower limit is 25% or more of the total thickness in order to obtain good heat-sealability and film-forming properties as the total thickness of the inner layer, whether it is a single layer or two or more layers. Preferably, it is 30% or more, and more preferably 35% or more. The upper limit is preferably 65% or less, more preferably 60% or less, and even more preferably 55% or less.

<Adhesive layer>
The film of the present invention can be provided with an adhesive layer as needed for the purpose of increasing the adhesive strength between the layers. There may be one or more adhesive layers.

Examples of the resin that can be used as the adhesive layer include polyethylene such as low density polyethylene, linear low density polyethylene, medium density polyethylene, and high density polyethylene, and olefin resins such as polypropylene and ethylene-vinyl acetate copolymer.
In addition, for example, ethylene-vinyl acetate copolymer or ethylene elastomer, monobasic unsaturated fatty acid such as acrylic acid or methacrylic acid, or anhydride of dibasic fatty acid such as maleic acid, fumaric acid or itaconic acid A modified polyolefin resin in which is chemically bound can be exemplified.
Among them, it is preferable to use an adhesive resin based on polyethylene or polypropylene.

The thickness of the adhesive layer is not particularly limited, but the lower limit is preferably 3 μm or more and the upper limit is preferably 8 μm or less from the viewpoints of adhesiveness, workability, economy, and handleability.
When the thickness of the adhesive layer is 3 μm or more, the delamination strength can be improved. Further, if the adhesive layer is too thick, the transparency is deteriorated, the total thickness of the film is increased, and the manufacturing cost is increased. Therefore, the upper limit is desirably 8 μm or less.
<Whole film>

  The total thickness of the film of the present invention is 20 μm or more and 50 μm or less. The lower limit of thickness is preferably 20 μm or more, more preferably 25 μm or more, and further preferably 30 μm or more. The upper limit is preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less.

  When the total thickness is 20 μm or more, the suitability of printing and laminating that requires stiffness, flexibility, stretchability, thermal conductivity, and dimensional stability is improved. In addition, if the thickness is 50 μm or less, the thermal conductivity is good, so that it is excellent in processing suitability for thermal lamination and extrusion lamination, and it becomes easy to adjust conditions such as tension in the printing process, making tray production more efficient. Can be done.

The layer structure of the film of the present invention includes an outermost layer (A) in which a polypropylene resin and a low-density polyethylene resin are mixed, another outer layer (B), an adhesive layer (C), a gas barrier layer (D), and a heat seal layer 1 ( When represented by E), heat seal layer 2 (F), and easy peelable layer (G), the following layer order can be exemplified, and among these, (5) to (7) are preferred.
More preferable contents of the layer structure are when an ethylene-polypropylene copolymer is used for the other outer layer (B) and a polypropylene homopolymer or linear low density polyethylene is used for the heat seal layers (E) and (F). .

(1) A / D / E
(2) A / D / G

(3) A / C / D / C / E
(4) A / C / D / C / G

(5) A / B / C / D / C / E / E
(6) A / B / C / D / C / E / F
(7) A / B / C / D / C / E / G

  The film of the present invention can be produced using a known method. For example, a coextrusion inflation method, a coextrusion T-die method, and the like can be used. In particular, it is preferable to use a coextrusion T-die method from the viewpoint of uniformity of film thickness.

<Resin sheet>
Examples of the resin sheet used in the composite sheet of the present invention include, for example, a polypropylene resin sheet, a polyethylene terephthalate resin sheet, a polystyrene resin sheet, a heat-resistant foamed polystyrene sheet, a polyvinyl chloride resin sheet, a high-density polyethylene resin sheet, and a polyacrylonitrile resin. A sheet etc. can be mentioned.
Preferably, it is a high melting point polypropylene resin sheet from the viewpoint of resistance to microwave ovens, and a polystyrene resin sheet from the viewpoint that it is possible to give a design that gives rigidity and luxury as a food tray.

The form of the resin sheet may be a foamed sheet, an unstretched sheet, a stretched sheet, a colored sheet, a kneaded filler such as talc or titanium oxide, or a multilayer sheet using a recycled resin.
The thickness of the resin sheet is 100 μm or more and 1500 μm or less from the viewpoint of the rigidity, moldability, and lightness of the tray. Preferably they are 300 micrometers or more and 1000 micrometers or less. When the sheet form is a foamed sheet, it is lightweight and has formability and rigidity, so that it can be 2 mm or more and 5 mm or less, and preferably 3 mm or more and 4 mm or less.

  Examples of a method for laminating the film of the present invention with various resin sheets include known techniques such as extrusion lamination, dry lamination, and thermal lamination.

  Among them, extrusion lamination with polypropylene resin sheet, dry lamination with polypropylene resin sheet after printing, thermal lamination with foamed polystyrene resin sheet after printing and coating, rigidity, cost, impact resistance performance, design characteristics It is preferable from the viewpoint.

  The orientation of the film and composite sheet of the present invention is such that printing is performed on the outer layer surface of the film, a resin sheet is laminated on the surface, and in the tray molding, the inner layer of the film is on the inner side of the tray, and the resin sheet is on the outer side of the tray. Become.

Examples are shown below, but the present invention is not limited thereto.
<Evaluation method>
Films and composite sheets were prepared by the methods and configurations shown in each Example, and the following evaluation was performed.
In addition, the number in Table 1 shows the thickness (micrometer) of a sheet | seat, a layer, and a film.

(Evaluation of film)
The oxygen permeability of the produced film was measured using OX-TRAN manufactured by MOCON under the condition of 25 ° C. and 0% relative humidity.
As for the outermost layer of the produced film, the surface was observed for fine surface irregularities by optical microscope observation and surface roughness measurement (VertScan, manufactured by Ryoka System).

(Production of tray)
The produced composite sheet was molded into a tray having a size of about 20 cm × about 15 cm and a depth of about 30 mm under the conditions of 220 ° C. preheater heating and plug molding using a heating vacuum molding machine, and used for the test.

(Processability evaluation of film and composite sheet)
In a series of processing steps in which the produced film is printed and / or laminated with a resin sheet and tray molding is performed, a product with a good product yield of 70% or more with respect to the input film is “◯”, 30% or more Those less than 70% were evaluated as “Δ”, and those less than 30% or unprocessable were evaluated as “x”.
Examples of non-defective products include missing prints and misalignments, wrinkling in each process, laminate floating, mold shape reproducibility (corner and flat parts) and uneven thickness in tray molding.

(Production of food packaging)
The prepared tray is fried, filled with sausage, hamburger, and french fries, and the periphery of the lid and tray is heated using a gas replacement tray sealer at a seal temperature of 120 ° C and a seal time of 0.3 seconds. Sealed and an inert gas replacement sealed food package was produced.
In Examples 1 to 7, Example 12, Comparative Example 1 and Comparative Examples 3 to 6, in which the inner layer of the film is polypropylene, the biaxially stretched nylon 6 film (15 μm) and the unstretched polypropylene film ( In Examples 8 to 11 and Comparative Example 2 in which the inner layer of the film is a polyethylene film, a biaxially stretched nylon 6 film (15 μm) and a linear low density polyethylene film ( 50 μm) was used.

(Packaging evaluation)
The prepared food package was opened, heated for 1500 W for 30 seconds in a microwave oven, the contents food was taken out, and the state of the tray was visually observed.

  The openability of the package was evaluated as “◯” when it was easily opened by hand without using a tool, and “X” when a tool such as a blade was necessary.

  The suitability for microwave oven is “○” when no discoloration or melting deformation of the inner surface of the film, which is the food contact surface after microwave heating, is observed, “△” when discoloration occurs, and discoloration and melting deformation. What was generated was evaluated as “x”.

The resin component which comprises each layer of an Example is as follows.
r-PP + LD1: Mixing of 85% by mass of a prime polymer ethylene-propylene random copolymer “Prime Polypro” and 15% by mass of low density polyethylene “Novatech” manufactured by Nippon Polyethylene r-PP + LD2; Ethylene-propylene manufactured by Prime Polymer Mixing of 75% by mass of random copolymer “Prime Polypro” and 25% by mass of low density polyethylene “Novatech” manufactured by Nippon Polyethylene Co., Ltd. EVOH; Ethylene-vinyl alcohol copolymer “Eval” manufactured by Kuraray
MXD: Aromatic polyamide "MX Nylon" manufactured by Mitsubishi Gas Chemical Company
r-PP; Prime-polymer, an ethylene-propylene random copolymer “Prime Polypro”
h-PP; Polypropylene “Novatec PP” manufactured by Nippon Polypro Co., Ltd.
LLDPE1: Linear low density polyethylene “Umerit” manufactured by Ube Maruzen Polyethylene
LLDPE2; Prime Polymer's linear low density polyethylene “Ultzex”
EP1; Mixing of 70% by mass of polypropylene “Novatech PP” manufactured by Nippon Polypro Co., Ltd. and 30% by mass of low density polyethylene “Novatech” manufactured by Nippon Polyethylene EP2; 80% by mass of linear low density polyethylene “Nipolon L” manufactured by Tosoh Corporation Mixing 20% by mass of olefin elastomer “Tuffmer” manufactured by Mitsui Chemicals AD; Adhesive resin “Admer” manufactured by Mitsui Chemicals

PP film; CPP film (polypropylene homopolymer) manufactured by Mitsui Chemicals Tosero Co., Ltd. EVOH film; "Eval film" manufactured by Kuraray Co., Ltd.
Adhesive; Urethane adhesive

Examples 1-11, Comparative Examples 1-2
A film was prepared by the coextrusion T-die non-stretching method, and the outer layer side was subjected to corona treatment.
Hereinafter, the layer configuration order will be described from the outer layer side.

Example 1
PP + LD (6 μm) / r-PP (5 μm) / AD (4 μm) / EVOH (5 μm) / AD (4 μm) / r-PP (12 μm) / h-PP (4 μm)
A polypropylene resin sheet having a thickness of 500 μm was extrusion laminated on the outer layer side of the produced film to produce a composite sheet.

Example 2
Using the same film as in Example 1, printing was performed on the surface of the outer layer, and then dry lamination was performed on the outer layer side using a polypropylene resin sheet having a thickness of 500 μm and a urethane-based adhesive to prepare a composite sheet.

Example 3
A film was prepared in the same manner as in Example 1 except that the innermost layer was replaced with the easy peel EP1 layer, and a polypropylene resin sheet having a thickness of 500 μm was extruded and laminated on the outer layer surface to prepare a composite sheet.

Example 4
Using the same film as in Example 3, printing was performed on the surface of the outer layer, and then dry lamination was performed on the outer layer side using a polypropylene resin sheet having a thickness of 500 μm and a urethane-based adhesive to prepare a composite sheet.

Example 5
A film and a composite sheet were produced in the same manner as in Example 4 except that the EVOH layer was replaced with the MXD layer.

Example 6
Using the same film as in Example 3, an adhesive coating agent was applied to the outer layer surface with a printing machine, and thermally laminated with a 3000 μm thick foamed polystyrene resin sheet to prepare a composite sheet.

Example 7
Using the same film as in Example 3, printing was applied to the surface of the outer layer, an adhesive coating agent was applied to the printing surface with a printing machine, and thermal lamination was performed with a 3000 μm thick foamed polystyrene resin sheet to produce a composite sheet. did.

Example 8
In Example 1, except that the heat seal layer was replaced with the structure of LLDPE1 (12 μm) / LLDPE1 (4 μm), a film was prepared in the same manner, and an adhesive coating agent was applied to the outer layer surface with a printing machine. A laminated sheet was produced by thermal lamination with a 3000 μm thick polystyrene foam resin sheet.

Example 9
Using the same film as in Example 8, the surface of the outer layer was subjected to printing, and then the adhesive coating agent was applied to the printing surface with a printing machine, thermally laminated with a 3000 μm thick foamed polystyrene resin sheet, and a composite sheet was obtained. Produced.

Example 10
In Example 8, except that the heat seal layer was replaced with the LLDPE1 (12 μm) / EP2 (4 μm) structure, a film was prepared in the same manner, and an adhesive coating agent was applied to the outer layer surface of the film with a printing machine. Then, it was thermally laminated with a 3000 μm thick polystyrene foam resin sheet to produce a composite sheet.

Example 11
Using the same film as in Example 10, the outer layer surface was subjected to printing, and then an adhesive coating agent was applied to the printing surface with a printing machine, thermally laminated with a 3000 μm thick polystyrene foam sheet, and a composite sheet was obtained. Produced.

Example 12
A composite sheet was produced in the same manner as in Example 1 except that the outer layer was changed to r-PP + LD2 (6 μm).

Comparative Example 1
In Example 1, except that the outer layer and the heat seal layer were replaced with r-PP (20 μm), a film was prepared in the same manner, and a polypropylene resin sheet having a thickness of 500 μm was extruded and laminated on the outer layer surface to prepare a composite sheet. did.

Comparative Example 2
In Comparative Example 1, a film was prepared in the same manner except that the heat seal layer was changed to the structure of LLDPE2 (40 μm) / EP2 (10 μm), and a polypropylene resin sheet having a thickness of 500 μm was extruded and laminated on the outer layer surface. A sheet was produced.

Comparative Example 3
Various single layer films were laminated by a dry laminating method to produce a film having the following configuration.
PP film (20 μm) / Adhesive (3 μm) / EVOH film (5 μm) / Adhesive (3 μm) / PP film (20 μm)
On the outer layer side of the produced film, a polypropylene resin sheet having a thickness of 500 μm was dry-laminated using a urethane adhesive to produce a composite sheet.

Comparative Example 4
In Comparative Example 3, a composite sheet was produced in the same manner except that the outer layer surface was printed.

Comparative Example 5
A commercial product having the following constitution produced by multilayer coextrusion was used.
PP (110 μm) / AD (10 μm) / EVOH (20 μm) / AD (10 μm) / PP (40 μm)

Comparative Example 6
A commercial product having the following constitution produced by multilayer coextrusion was used.
PP (200 μm) / AD (20 μm) / EVOH (40 μm) / AD (20 μm) / PP (200 μm)

In Examples 1 to 12, the outermost layer was formed by mixing a low-density polyethylene resin with a polypropylene resin, so that the melt tension at the time of film formation was high, the thickness of the film was uniform, and the wavy white avatar A film without generation was obtained. In addition, by mixing incompatible resins, the outermost layer surface has a minute uneven shape, and the surface roughness Sa is 0.2 to 0.3 nm, and the printing ink and adhesive coat are excellent in adhesion and adhesion. It was. From these, the appearance after lamination with various resin sheets became good.
In Example 12, when the tray was molded and opened, peeling occurred inside the resin sheet near the fusion interface between the film and the resin sheet.

The oxygen gas permeability of the films of Examples 1 to 11 was ^{2 to 5} cc / (m ² · day · atm).

  In Examples 1 to 6, polypropylene resin was used for the outer layer and the heat seal layer, and the thickness of the outer layer was 69% of the thickness of the inner layer, so that no deformation occurred in the microwave heating test.

On the other hand, in Comparative Examples 1 and 2, since the outer layer was formed of only the polypropylene resin, vertical streaks and avatars were generated on the film, resulting in frequent appearance defects.
In Comparative Examples 5 to 6, since the outer layer was a film composed of only a polypropylene resin and having a large thickness, the mechanical suitability for a printing machine or the like was poor, and printing and laminating could not be performed.
In Comparative Examples 3 to 4, since the film was produced by the dry lamination method instead of the coextrusion method, the flexibility was poor and the moldability was poor, and the foaming phenomenon of the adhesive layer occurred after the lamination.

  From these evaluation results, it can be seen that the film of the present invention is excellent in processing suitability for printing and laminating with a resin sheet, and easy to impart easy peel properties and microwave oven heat resistance.

The non-stretched coextruded film and composite sheet of the present invention have good gas barrier properties, heat sealability, easy-openability, and printability. The decorativeness imparted by printing (a sense of quality and cleanliness) increases the commercial value of food trays and packages, and can greatly affect the awareness of sellers and purchasers. Furthermore, because of the sealing and sealing properties with the lid, and the good packaging properties of vacuum packs and inert gas packs, it has been possible to extend the food package taste and shelf life, and to reduce food and packaging waste loss. . Also, by selecting various resin sheets as the sheets to be laminated, it is possible to produce a tray that also has microwave oven heat resistance.
As mentioned above, the film and composite sheet of this invention can contribute to the improvement of convenience over food manufacturing industry, a sales industry, a packaging material industry, and a consumer.

Claims (4)

A non-stretched co-extruded film for producing a composite sheet for tray molding by laminating a resin sheet having a thickness of 300 μm or more, comprising an outer layer, an intermediate layer, and an inner layer, and the outermost layer on the laminating side is made of 50 polypropylene resin And a mixture ratio of the low-density polyethylene resin is 5% by mass or more and 20% by mass or less, and the intermediate layer has at least a saponified ethylene-vinyl acetate copolymer layer or a metaxylene adipamide nylon resin layer. An unstretched coextruded film having one layer and having a heat seal resin layer containing a polyolefin resin as a main component in an inner layer.   From the group of polypropylene resin sheet, polyethylene terephthalate resin sheet, polystyrene resin sheet, heat-resistant foamed polystyrene resin sheet, polyvinyl chloride resin sheet, high-density polyethylene resin sheet, polyacrylonitrile resin sheet on the outer layer side of the film according to claim 1 A composite sheet for tray molding, wherein one kind of selected resin sheet having a thickness of 300 μm or more is laminated.   The film according to claim 1 or the composite sheet according to claim 2, wherein the outermost layer surface of the film is printed. Tray or package was molded using the composite sheet according to claim 2-3.