JP3248650B2 - Multilayer film, multilayer sheet and container laminated with the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polypropylene resin,
It has a thermal adhesive property to a shape-forming resin sheet made of a polystyrene-based resin and the like, and has a low-odor property, a fragrance-retaining property and an excellent oxygen-barrier property. And a container formed from the same. The main application field is the food packaging material field, and by using this, it is possible to prevent the adsorption of plastic odor to foods, to retain food flavor components, and to prevent foods from deteriorating due to oxygen. More specifically, it can be used as a packaging material for aseptically processed cooked rice that can be distributed at room temperature or for retort foods.

[0002]

2. Description of the Related Art Conventionally, packaging materials for materials requiring oxygen barrier properties, such as retort foods, are polypropylene resin (hereinafter abbreviated as PP) and saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH). Is mainly composed of PP / adhesive layer (hereinafter abbreviated as AD) / EVOH
It is widely used as a sheet having a configuration such as / AD / PP. However, the disadvantage of this food packaging material is that since the surface that comes into contact with food is PP, odor components present in PP (decomposition products during production, hydrocarbons contained in PP, additives, etc.) However, there has been a problem that after packaging, the food is transferred to the food, or a flavor component of the food is adsorbed to the PP.

[0003]

As described above, there is no multi-layer sheet which is superior in low odor, fragrance retention and oxygen barrier properties and can be easily manufactured, and a packaging material having these characteristics is strongly used. Was desired. The present inventors have conducted intensive studies to improve properties such as low odor, fragrance retention, oxygen barrier properties, heat adhesion and moldability. As a result, polyester-based resins such as PET or polycarbonate-based resin layers, oxygen barrier A multi-layer film for heat bonding having a highly adhesive EVOH resin layer and an adhesive layer that can be thermally bonded to any shape-forming resin sheet, and heat-bonding this film to the shape-forming resin sheet by a simple method. As a result, it has been found that such a problem can be solved, and the present invention has been accomplished. Accordingly, an object of the present invention is to provide a packaging material having excellent properties such as low odor, fragrance retention, oxygen barrier properties, thermal adhesion, and moldability.

[0004]

That is, the present invention relates to a resin layer (A) comprising at least one resin selected from a polyester resin and a polycarbonate resin, an adhesive resin layer (B), and ethylene-acetic acid. (A) having a saponified vinyl copolymer resin layer (C) and an adhesive resin layer (D);
(B), (C) and (D) in order,
(D) is a multilayer film for heat bonding with a shape- forming resin sheet , characterized in that it is an adhesive layer capable of being thermally bonded to an arbitrary shape- forming resin sheet, and a surface layer on one side or both sides of the film. However, contains an inorganic filler, or, when preparing the multilayer film for thermal bonding by co-extrusion method, as a cast roll or touch roll contacting one or both sides of the multilayer film extruded from the die, the surface It is preferable that one or both surfaces of the multilayer film for thermal bonding is roughened by using a roughened one. Further, the present invention is a method for producing a multilayer sheet in which the surface of the adhesive resin layer (D) of the multilayer film is thermally bonded to one or both surfaces of the shape-forming resin sheet (E),
In the multilayer sheet, the shape-forming sheet (E) comprises 50 to 80% by weight of a polypropylene-based resin and 20 to 80% by weight of an inorganic filler.
It is preferable that the resin composition contains 50% by weight.
Further, the present invention is a container obtained by molding the multilayer sheet by thermal processing.

Hereinafter, the present invention will be described in detail. As the resin constituting the resin layer (A) of the present invention, a resin having low odor and excellent in fragrance retention, such as a polyester resin and a polycarbonate resin, is used. Examples of the polyester-based resin include polyethylene terephthalate (hereinafter abbreviated as PET) obtained by polycondensation of terephthalic acid and ethylene glycol having an ester bond in a polymer chain, and polystyrene obtained by polycondensation of terephthalic acid and butylene glycol. Butylene terephthalate (hereinafter abbreviated as PBT) is specifically exemplified. Further, isophthalic acid, sebacic acid, adipic acid, azelaic acid, and the like can be used as a comonomer of the dicarboxylic acid component in the polyester for the purpose of improving processing characteristics, and diethylene glycol, neopentyl glycol, and the like. PET and PBT in which 1,4-cyclohexanedimethanol or the like is introduced as a copolymer component can also be used. Further, a resin composition in which one or more of the above-mentioned polyester resins are mixed, and a resin composition in which a crystallization accelerator, a heat stabilizer, and various fillers are added are also suitably used.

As the polycarbonate resin, those having a carbonate bond in a polymer chain can be used, and examples thereof include those obtained by reacting bisphenol A with phosgene. Further, for the purpose of improving the processing characteristics, other dihydric phenols other than bisphenol A include hydroquinone, 4,4-dihydroxydiphenyl, bis (4-hydroxyphenyl) alkane, bis (4-hydroxyphenyl) cycloalkane, bis ( Those obtained by copolymerizing a compound such as 4-hydroxyphenyl) sulfide or bis (4-hydroxyphenyl) ether as a copolymer are also preferably used. Further, a resin composition in which one or more of the above-mentioned polycarbonate resins are mixed, a heat stabilizer, and a resin composition in which various fillers are added are also preferably used. Further, for improving the processing performance, a mixture of one or more selected from the polyester-based resins and the polycarbonate resins is also preferably used.

In the resin layer (A) of the present invention, PET among polyester-based resins and divalent phenol other than bisphenol A as a comonomer among polycarbonate-based resins react as a comonomer from the viewpoint of performance and cost, and are suitable for processing. Particularly, those having improved properties are preferably used.

[0008] Next, the adhesive resin layer (B) and the adhesive resin layer (D) are not particularly limited as long as they have adhesiveness to the resin layer (A), the resin layer (C) and the shape-forming resin sheet. Without limitation, maleic anhydride, acid-containing vinyl monomer having polymerization reactivity such as acrylic acid, vinyl acrylate,
An ester-containing vinyl monomer having polymerization reactivity such as metamethyl acrylate, a copolymer of an olefin with a vinyl monomer having an epoxy group in the molecule, and the like are used.

Specifically, linear low density polyethylene copolymerized with maleic anhydride, ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate Copolymer (EMMA), ethylene-vinyl acetate copolymer (E
VA) and the like. Also, a mixture of these copolymers and a graft copolymer can be suitably used. In particular, due to thermal adhesion, that is, adhesiveness with a shape-forming resin sheet in heat lamination, extrusion lamination, etc., as the adhesive resin, an EVA-based resin having a Vicat softening point of less than 80 ° C. and a maleic anhydride-modified PE resin are used. Those containing as a main component are preferably used. Resin layer (B) and resin layer (D)
Although different resin types may be used, it is preferable to use the same resin in order to simplify the manufacturing process of a multilayer film described later.

Next, as the resin layer (C), a saponified ethylene-vinyl acetate copolymer having a high oxygen barrier property is used. Specifically, those having an ethylene ratio of 20 to 60 mol% and a saponification rate of vinyl acetate of 90% or more are suitably used. Among them, the ethylene ratio is 30 to 50 mol%
In particular, those having a saponification ratio of vinyl acetate of 95% or more are particularly preferred because of their excellent thermal stability during film formation.

[0011] The thickness ratio of the multilayer film is not particularly limited, and may be any thickness ratio. The thickness ratio of the multilayer film is as follows: resin layer (A) / resin layer (B) / resin layer (C) / resin layer (D) = (2 to 10) / (1) / (2
-10) / (1-3) are preferable, and good results are obtained in terms of low odor, fragrance retention, oxygen barrier properties, adhesiveness and moldability. Further, in consideration of the oxygen barrier property, the thickness of the resin layer (C) is preferably 5 μm or more. The total thickness of the multilayer film is not particularly limited, but is preferably in the range of 20 to 500 μ, particularly preferably in the range of 20 to 250 μ in consideration of the minimum thickness of the resin layer and the adhesiveness with the shapeable resin sheet. Range. If the total thickness exceeds 500 μm, heat conduction during thermocompression bonding becomes poor and adhesiveness is reduced, which is not preferable.

The multilayer film can be prepared by a known method, but a co-extrusion method is preferred. Specifically, there is a casting method using a multi-manifold die in which a resin constituting each layer is supplied to three or more extruders and laminating in a die, or a coat hanger die provided with a feed block. As another method, it is also possible to form each resin layer independently by casting or inflation film forming and then thermocompression-bond each resin layer in a prescribed order.

It is preferable that the surface of the multilayer film is rough due to the adhesion of the adhesive resin layer generated after winding the film to prevent blocking with the polyester resin or polycarbonate resin layer. As a method of roughening the surface, a method of adding an inorganic filler to the resin layer, and a cast roll for cooling and solidifying the film,
A method in which the surface of the touch roll is roughened is used.

Various resins can be used as the resin constituting the shape-forming resin sheet (E) of the present invention, as long as they can be vacuum-formed or pressure-formed after being bonded to the multilayer film by thermal bonding. A polypropylene-based resin, a polystyrene-based resin, and a polyethylene terephthalate-based resin are preferably used from the viewpoint of moldability and that no harmful gas is generated even when burned.

As the polypropylene resin constituting the sheet (E), the monomer is a propylene homopolymer of propylene alone, a block or random copolymer with other olefins such as ethylene, or a mixture with another polyolefin resin such as polyethylene. And the like. A composition comprising 50 to 80% by weight of the polypropylene resin and 20 to 50% by weight of an inorganic filler such as talc or calcium carbonate is particularly preferably used because of its good heat resistance.

Examples of the polystyrene resin constituting the sheet (E) include a styrene homopolymer, a rubber-reinforced high impact polystyrene (hereinafter abbreviated as HI-PS), a styrene-butadiene-styrene block copolymer and the like. . Further, copolymers such as methyl methacrylate, acrylonitrile, and n-butyl acrylate, which are copolymerizable with styrene, are also preferably used. These polystyrene resins can be used alone or in a mixture of two or more. In addition, polystyrene resin 50
A composition comprising about 80% by weight and 20 to 50% by weight of an inorganic filler can also be used.

Examples of the polyethylene terephthalate resin constituting the sheet (E) include a general polyethylene terephthalate obtained by polycondensation of ethylene glycol and terephthalic acid, crystallization suppression during molding, and improvement in processability. For example, a copolymer type product obtained by copolymerizing another comonomer component may be used. Specific examples of the comonomer component include dicarboxylic acid components such as isophthalic acid, sebacic acid, adipic acid, and azelaic acid, and glycol components include diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and butanediol. Is mentioned.

In the present invention, the shape-forming resin sheet (E)
Is preferably 50 to 1500 μm. The adhesion between the multilayer film and the shapeable resin sheet (E) is not particularly limited as long as the surface of the adhesive resin layer (D) of the multilayer film is thermally bonded to one or both surfaces of the shapeable resin sheet. Specifically, a multi-layer film and a sheet-like forming resin are simultaneously fed and heated / pressed, or a heat lamination method, or a multilayer film is supplied at the stage of forming the forming resin into a sheet-heat bonding. The extrusion lamination method is preferably used. Immediately before forming the multilayer sheet into a container, a method of supplying a multilayer film slit to the width of the container and a shapeable resin sheet to a heat laminating machine and thermally bonding the container to form a container is difficult to reuse. It is particularly preferable because the generation amount is small and the production cost is also low.

In the present invention, it is sufficient that the multilayer film is adhered to at least one surface of the shape-forming resin sheet, and an improvement in oxygen barrier properties, a low odor property on the outer surface of the package, and a fragrance retention property are expected. There is no limitation on bonding two or more layers of the same multilayer film to the same surface and bonding the multilayer film to both surfaces of the shape-forming resin layer. The thickness ratio and the total thickness of the multilayer film and the shapeable resin sheet in the multilayer sheet are not particularly limited, but when considering the moldability when shaping the multilayer sheet by vacuum forming or pressure forming,
The ratio of the multilayer film / the shapeable resin sheet = (1) / (1 or more), particularly preferably (1) / (1.5 or more).
Further, the total thickness is preferably from 100 to 2000 μ. When the total thickness is less than 100 μm or more than 2000 μm, the width of molding conditions for molding the container becomes very narrow, and it becomes difficult to obtain a good container.

The container in the present invention includes various containers which can be formed by subjecting the multilayer sheet to heat processing. The molding method is not particularly limited, and specific examples include vacuum molding using heat, pressure, and negative pressure, and pressure molding. In addition, as containers produced by these moldings,
Examples include cups and trays. In addition, as a final container form, a form in which the resin layer (A) is disposed on the inner surface of the container (the surface that comes into contact with the item to be packaged) is desirable. However, if a fragrance retaining resin such as PET is used for the shape-forming resin layer, the same effect can be obtained regardless of whether the resin layer (A) is used for the inner or outer surface of the container. The position is not particularly limited.

[0021]

The present invention will be described in detail with reference to the following examples. In addition, the resin property evaluation methods and the various measurement methods of the multilayer film, the laminate sheet, and the container described in each of Examples and Comparative Examples will be described later.

Example 1 Polyethylene terephthalate (abbreviated as PET) with IV = 0.75 as the resin layer (A), and EVA resin (manufactured by Mitsubishi Kasei Co., Ltd.) as the resin layer (B) and the resin layer (D). Trade name "AX143E"), saponified ethylene-vinyl acetate copolymer (EVOH, Kuraray Co., Ltd., trade name "E-151B", MI = 1.
6, ethylene content 44 mol%).

(Coating) Using a co-extrusion facility equipped with three 40 mmφ extruders, a feed block for laminating three types and four layers, and a coat hanger die, the resin is supplied, and the resin layer (A) is cast by a casting method. ) / Resin layer (B) / resin layer (C) / resin layer (D) in the order of 20 μm.
A multilayer film of three types and four layers of / 10 μ / 30 μ / 10 μ was prepared. In addition, in order to roughen the resin layer (A) which becomes a surface at the time of film formation, the cast touch roll used what was roughened.

(Various evaluations) Table 1 shows the results of various evaluations of the multilayer film obtained. It can be seen that the product of the present invention shows sufficient oxygen barrier properties, interlayer adhesive strength, shapeable resin adhesive strength, low odor, and fragrance retention.

Example 2 The same resin and composition ratio as in Example 1 except that an acid-modified PE (polyethylene) (trade name “SF600” manufactured by Mitsui Petrochemical Co., Ltd.) was used as the resin layer (B). To form a multilayer film. The same evaluation as in Example 1 was performed, and the results are shown in Table 1. Good results were obtained with various characteristics.

Example 3 Modified PC (polycarbonate) (manufactured by Nippon GE Plastics Co., Ltd., trade name "SP101") as the resin layer (A)
0)), except that resin was used and the composition ratio was the same as in Example 1 to prepare a multilayer film. The same evaluation as in Example 1 was performed, and the results are shown in Table 1. Good results were obtained with various characteristics.

Example 4 A resin layer (A) was prepared in the same manner as in Example 1 except that a blend of 80% by weight of PET with IV = 0.75 and 20% by weight of PBT with IV = 0.7 was used. A film was formed so as to have a resin and a composition ratio to prepare a multilayer film. The same evaluation as in Example 1 was performed, and the results are shown in Table 1. Good results were obtained with various characteristics.

Example 5 The same resin and composition as in Example 1 except that a blend of 80% by weight of PET with IV = 0.75 and 20% by weight of modified PC (SP1010) was used as the resin layer (A). The film was formed so as to have a ratio, and a multilayer film was prepared. The same evaluation as in Example 1 was performed, and the results are shown in Table 1. Good results were obtained with various characteristics.

Example 6 As the resin layer (B) and the resin layer (D), 80% by weight of an EVA resin (trade name “AX143E” manufactured by Mitsubishi Kasei Co., Ltd.) and 20% by weight of acid-modified PE (SF600) were used. %, Except that a blend was used to form a multilayer film. Example 1
The same evaluation was performed and the results are shown in Table 1. Good results were obtained with various characteristics.

Comparative Example 1 PP (MI = 1, homopolymer type) as the resin layer (A)
A film was formed so as to have the same resin and composition ratio as in Example 1 except for using, to prepare a multilayer film. The same evaluation as in Example 1 was performed, and the results are shown in Table 1. This film is
It was inferior to Examples in terms of fragrance retention and low odor.

Comparative Example 2 As the resin layer (B) and the resin layer (D), PP (MI = 1,
Except for using a homopolymer type), a film was formed to have the same resin and composition ratio as in Example 1 to prepare a multilayer film. The same evaluation as in Example 1 was performed, and the results are shown in Table 1. This film was inferior in interlayer adhesiveness and adhesiveness with the shape-forming resin layer (E) other than PP.

Example 7 The resin layer (D) of the multilayer film obtained in Example 1 was thermally laminated with a formable resin sheet (E) made of PP filled with talc 30% to obtain a multilayer sheet. The molded container using this had no problem in appearance. Further, the container obtained by subjecting the multilayer sheet to thermal processing had sufficient oxygen barrier properties, and was excellent in low odor and fragrance retention.

Example 8 The same procedures as in Example 7 were carried out except that the multilayer film described in Example 3 was used, and the evaluation results shown in Table 2 were obtained. The container obtained in this example was also excellent in moldability, low odor, and fragrance retention.

Example 9 The same procedure as in Example 7 was carried out except that the multilayer film described in Example 5 was used, and the evaluation results shown in Table 2 were obtained. The container obtained in this example was also excellent in moldability, low odor, and fragrance retention.

Comparative Example 3 PP containing 30% talc (hereinafter abbreviated as PP-F), E
Using VA resin and EVOH resin, layer structure PP-F /
EVA / EVOH / EVA / PP-F (composition ratio 250 /
20/30/20 / 250μ) 3 sheets 5
The layers were formed by a co-extrusion method using a cast method, and a container having the same shape was molded and evaluated by the method described in Example 7, and the evaluation results are shown in Table 2. This comparative example is described in Examples 7, 8,
Compared with No. 9, the fragrance retention and the low odor were extremely poor.

Comparative Example 4 A non-stretched PET film having a thickness of 20 μm was prepared by using PP-F / EVA / EVOH / E with a total thickness of 0.57 mm described in Comparative Example 3.
A multilayer sheet having a VA / PP-F configuration was dry-laminated with a polyurethane adhesive. A container having the same shape was formed by the method described in Example 7 so that the unstretched PET film was inside the container, and the container was evaluated. The evaluation results are shown in Table 2. This comparative example is inferior to Examples 7, 8, and 9 in low odor.

(Resin Characteristic Evaluation Method) (1) Intrinsic Viscosity (IV) Intrinsic viscosity (IV) means phenol / tetrachloroethane (weight ratio: 50/50) as a solvent and a solution concentration of 0.5 g / It shows the viscosity measured using a Ubbelohde viscometer in a thermostat at 30 ° C. at 10 ml. (2) MI MI indicates the weight of the resin flowing per 10 minutes under the conditions of 190 ° C. and a load of 2.16 kg according to JIS K7210. (Various measuring methods for multilayer films, multilayer sheets, and containers) (3) Oxygen barrier property Oxygen permeability measuring instrument (OXTRAN-10 / 5, Mocon Corporation)
At 0A), the oxygen permeability is measured at 23 ° C. and 50% RH. (4) Interlayer adhesion Resin layer (A) / resin layer (B) / resin layer (C) / resin layer (D) resin layer (B) and resin layer (C) of three-layer four-layer film
Was peeled off to obtain a two-layer, two-layer film. The adhesive interface of the two-layer film was peeled off, and the peel strength was measured. 180 ° peel angle, 15mm width, pulling speed 200mm /
The peel test was performed under the condition of min, and the value at that time was defined as the interlayer adhesive strength. The unit of the interlayer adhesive strength is g / 15 mm.

(5) Adhesiveness of Shapeable Resin Sheet A multi-layer film (adhesive resin layer is an adhesive surface) and a shapeable resin sheet (E) by a heat laminating machine at a roll surface temperature of 80 ° C. 0.5mm thick, 30% talc added P
P (30% talc added to homopolymer type PP), 0.5
A HI-PS having a thickness of mm and a PET sheet having a thickness of 0.5 mm were supplied at a line speed of 2 m / min to perform thermal lamination. 15mm heat-laminated sheet
The film was taken out in width, and a peeling test was performed at a peel angle of 180 ° and a pulling speed of 200 mm / min using the adhesive interface between the multilayer film and the shapeable resin sheet as the peeling interface. The adhesive strength with the sheet (E) was used. The adhesive strength with the shape-forming resin sheet is g
/ 15 mm. (6) Low odor property Using a multilayer film, make the resin layer (A) come on the inner surface, make a bag with an inner volume of 200 cc, seal the bag with the air filled therein, and place it in an 80 ° C. oven. Insert time. 1
After a lapse of time, the odor inside the bag is sensory evaluated. (7) Perfume retention Using a multilayer film, a resin layer (A) is provided on the inner surface, a bag with an inner volume of 200 cc is prepared, and orange juice is put into the bag so as not to generate a head space and sealed. Store this orange sauce at 10 ° C for one month. The taste of the orange juice is subjected to a sensory evaluation.

(Formability and Container Evaluation Method) (8) Formability A multilayer film obtained by heat laminating a multilayer film and a shapeable resin sheet (E) was used, and each opening was 95 m long.
A round cup having a diameter of mφ and a height of 45 mm was molded by a vacuum molding machine, and the appearance of the cup was observed to evaluate the moldability. (9) Oxygen barrier property PP-F is used as the shape-forming resin layer (E) in the molding container.
The opening of the molded product using the sheet is attached to stainless steel foil with epoxy resin. The environment outside the container is 23 ℃ 50% R
H air and oxygen permeability meter [MOCON OXTR
AN-10 / 50A], the oxygen permeability of this container was measured. (10) Low-odor property Of the above-mentioned molding container, PP is used as the shape-forming resin sheet (E).
The molded product obtained using the -F sheet was covered with a 0.03 mm aluminum foil, placed in an oven at 80 ° C, and heated for 30 minutes. After heating, the container was taken out, and the odor inside the container was organoleptically evaluated. (11) Perfume-retaining property Of the above-mentioned molded container, PP is used as the shape-forming resin sheet (E)
-Fill the molded product obtained using the F sheet with orange juice so that there is no head space, seal with an EVA hot melt adhesive using aluminum foil of 0.03 mm as a lid, and store at 10 ° C for one month. Save for a while. One month later, the package was opened and the flavor of the orange juice was sensory evaluated.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

As described above, the present invention has a thermal adhesive property to a shape-forming resin sheet made of a polypropylene-based resin, a polystyrene-based resin, or the like, and has excellent low odor, fragrance retention, and oxygen barrier properties. The present invention provides a multilayer film for thermal bonding, a multilayer sheet obtained by thermally bonding the multilayer film and a shape-forming resin sheet, and a container formed by molding the same. Can be used as

Claims (6)

(57) [Claims] 1. A resin layer (A), an adhesive resin layer (B), and a saponified ethylene-vinyl acetate copolymer resin layer (C) comprising at least one resin selected from a polyester resin and a polycarbonate resin. ) And an adhesive resin layer (D), and are constituted in the order of (A), (B), (C) and (D), wherein (D) can be thermally bonded to an arbitrary shapeable resin sheet. A shapeable resin sheet characterized by a
Multi-layer film for adhesion of heat. 2. The film according to claim 1, wherein one or both surface layers of the film contain an inorganic filler and have a roughened surface.
2. The multilayer film for thermal bonding according to item 1. 3. When the multilayer film for thermal bonding according to claim 1 is produced by a co-extrusion method, the surface of the multilayer film extruded from a die is roughened as a cast roll or a touch roll in contact with one or both surfaces thereof. A method for producing a multilayer film, characterized in that the surface is roughened by using a roughened one. 4. A multilayer sheet wherein the surface of the adhesive resin layer (D) of the multilayer film according to any one of claims 1 to 3 is thermally bonded to one or both surfaces of the shape-forming resin sheet (E). Manufacturing method. 5. The multilayer sheet produced by the method according to claim 4, wherein the shape-forming sheet (E) comprises a resin composition containing 50 to 80% by weight of a polypropylene resin and 20 to 50% by weight of an inorganic filler. 6. A container obtained by molding the multilayer sheet according to claim 4 by thermal processing.