TWI712501B - Multilayer resin film and molded container - Google Patents

Abstract

The present invention provides a multilayer resin film comprising a polyolefin resin layer as a skin layer, a bonding layer, an oxygen barrier layer, and a polystyrene resin layer as a lower skin layer. The overall thickness of the film is 200-1300 μm, and the polyolefin resin layer The thickness of the film is 1~30% compared to the overall thickness of the film; the polyolefin resin layer is preferably formed of block polypropylene; the thickness of the oxygen barrier resin layer is preferably 10~50μm, and its oxygen transmission rate is preferably It is 10cc/m2. Day or less; its water vapor transmission rate is preferably 10g/m2. less than day. The multilayer resin film thus constituted has excellent thermoformability, oxygen barrier properties, water vapor barrier properties, and oil resistance, and can suppress warpage of the film.

Description

Multilayer resin film and molded container

The present invention relates to a multilayer resin film with high barrier properties and a molded container obtained by molding the film.

The containers of traditional soft drinks, fruit juice drinks, and hobby foods all use polystyrene resins with excellent thermoformability and rigidity. In recent years, multi-layer resin films and multi-layer containers made from them have been popularized. These products have a polystyrene resin layer as the outermost layer with a bonding layer of modified olefin resin in between, and then ethylene- The vinyl alcohol copolymer resin layer functions as a barrier to oxygen, thereby avoiding the deterioration of the quality due to oxidation of the contents (see Patent Document 1).

In addition, Patent Document 2 discloses a gas barrier film, which is characterized by using a gas barrier material containing a silicon-containing polymer and a thermoplastic resin, so that the glass transition temperature of the thermoplastic resin reaches 100°C or higher, and plasma is applied to the gas barrier material. In the injection treatment, the silicon-containing polymer is a polysilazane compound, and the thermoplastic resin is at least one selected from the group consisting of polycarbonate resin, cycloolefin resin, and polycarbonate resin.

In addition, an optical resin film having barrier properties and solvent resistance against gases or moisture such as oxygen and water vapor has also been disclosed (see Patent Document 3).

Specifically, it is characterized in that a coating film mainly composed of a polysilazane inorganic polymer is formed on at least one surface of an optically transparent resin film and then heated Curing treatment to provide a gas barrier layer with a thickness of about 0.02~5μm.

Patent Document 4 discloses a composite film in which a fragrance-retaining resin layer, an impact-resistant layer, a water vapor barrier resin layer, a gas barrier resin layer, and a thermoplastic support resin layer are laminated in this order. The fragrance-preserving resin layer is composed of a mixture of terephthalic acid, ethylene glycol, 1,4-cyclohexanedimethanol and other three-component copolymer resins and polybutylene terephthalate resin. The impact-resistant layer is composed of It is made of polyamide resin.

Patent Document 5 discloses a film having excellent barrier properties (especially oxygen barrier properties), moldability, and rigidity and other mechanical properties. It has a polypropylene resin layer laminated on one side of a barrier resin. The total thickness of the polypropylene resin layer accounts for 10-40% of the entire film thickness.

In general, when foods and other items stored in containers contain polyphenols, tannins, catechins, etc., they will undergo oxidative deterioration due to their own dissolved oxygen or oxygen intruding from the outside of the container. In addition, in addition to the above, for example, the bifidobacteria in yogurt can also be lost due to its own dissolved oxygen or oxygen intruding from the outside of the container, resulting in a decrease in the number of bacteria.

For containers that store liquids such as milk beverages with a lot of water in the ingredients, when there is no layer with water vapor barrier in the structure, the moisture in the ingredients will also escape to the outside of the container in the form of water vapor, making The thick liquid is not easy to pour out, or the phenomenon of discoloration occurs.

In addition, when transporting containers with food, in order to avoid damage to the container itself due to vibration and external temperature during transportation, and to prevent the quality of the food in the container from degrading, multiple containers are stacked in the packaging for protection, or It is carried out through a temperature-controlled transportation method. However, many foods stored in containers contain fats and oils. When there are polar groups in the molecular skeleton of the fats and oils, they will interact with the polar groups of the resin constituting the container. The reaction progresses to reduce the strength of the container. If care is not taken during handling and storage, the contents in the container will flow out due to the damage of the container.

The film disclosed in Patent Document 5 is an oil-resistant polypropylene resin formed on the outermost surface of the film, and a resin composed of a styrene resin, a styrene-diene copolymer, and an olefin resin is combined The layer serves as its supporting layer. However, laminating crystalline polypropylene resin and non-crystalline styrene resin will cause the molded container to easily warp, which will make the sealing between the lid and the container change. Poor or the appearance of the container becomes bad.

Therefore, the above-mentioned Patent Document 1 to Patent Document 5 mainly focus on how to block the components that adversely affect the contents of the container such as oxygen and water vapor, but the above-mentioned oil resistance or the appearance and functionality of the container are affected. There are no relevant countermeasures for the additional performance of music.

Patent Document 1 Japanese Patent Laid-Open No. 11-58619

Patent Document 2 PCT International Patent WO2013175911A1 Publication

Patent Document 3 Japanese Patent Laid-Open No. 8-169078

Patent Document 4 Japanese Patent Laid-Open No. 2000-108288

Patent Document 5 Japanese Patent No. 3967899

The present invention is a product developed after considering the above problems. It provides a multilayer resin film with high barrier properties and a molded container manufactured by molding the film. The multilayer resin film has excellent thermoformability, oxygen barrier properties, and water vapor barrier properties. And oil resistance, and can suppress the warpage of the film and its after molding.

That is, a multilayer resin film of the present invention is formed by laminating multiple resin layers, including a polyolefin resin layer as a skin layer, a bonding layer, an oxygen barrier layer, and a polystyrene resin layer as a lower skin layer. The overall thickness of the film is The thickness of the polyolefin resin layer is 200 to 1300 μm, and the layer composition ratio is 1 to 30% compared with the thickness of the entire film.

In addition, as a preferred embodiment of the present invention, the polyolefin resin layer is formed of block polypropylene, where the block polypropylene refers to a homogeneous propylene block as a continuous phase and a dispersion of ethylene propylene rubber (EPR). Layer of stuff.

In addition, as a preferred aspect of the present invention, the thickness of the polyolefin-based resin layer has a layer composition ratio of 5% or more and less than 10% compared to the overall thickness of the film.

In addition, as a preferred aspect of the present invention, the oxygen barrier resin layer has a thickness of 10-50 μm, and its oxygen permeability is 10 cc/m ² ‧day or less.

In addition, the water vapor transmission rate of the multilayer resin film of the above-mentioned configuration is 10 g/m ² ‧day or less.

Furthermore, the present invention also provides a molded container formed by thermoforming the above-mentioned multilayer resin film, wherein the polyolefin resin layer in the multilayer resin film is located on the inner surface of the container.

The above-mentioned multilayer resin film and the molded container manufactured by molding the film have excellent thermoformability, oxygen barrier properties, water vapor barrier properties, and oil resistance, and can suppress the film and its warpage after molding.

10a: Polyolefin resin layer

11a, 11b: bonding layer

12: Oxygen barrier resin layer

13: Polystyrene resin layer

FIG. 1 is a schematic longitudinal sectional view of a laminated structure of a multilayer resin film according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a method for evaluating warpage of the multilayer resin film of the present invention.

Fig. 3 is a schematic diagram of a method for evaluating warpage of a molded container of the present invention.

Fig. 4 is a schematic diagram of the method for evaluating oil resistance of the present invention.

As shown in FIG. 1, a multilayer resin film according to an embodiment of the present invention has a structure in which a polyolefin resin layer 10a as a skin layer is laminated on the outermost surface of an oxygen barrier resin layer 12 via a bonding layer 11a, and On the opposite side, a polystyrene resin layer is laminated via the same bonding layer 11b. The overall thickness of the film is 200 to 1300 μm, and the thickness of the polyolefin resin layer is 1 to 30% compared to the overall thickness of the film. As a preferred embodiment, the thickness of the polyolefin resin layer is 2% or more and less than 10% of the total thickness of the film. As a further preferred aspect, the thickness of the polyolefin-based resin layer is 5% or more and less than 10% of the total thickness of the film.

Hereinafter, the above-mentioned multilayer resin film and a molded container manufactured by molding the film will be described in detail.

The layer structure of the multilayer resin film according to an embodiment of the present invention is: polyolefin resin layer/adhesive layer/oxygen barrier resin layer/adhesive layer/styrene resin layer, in short, skin layer/adhesive layer/oxygen barrier Layer/adhesion layer/lower skin layer The lower skin layer may be newly formed by mixing the multilayer resin film of the present invention, or a layer composed of waste resin generated in the manufacturing process of a molded container, or a layer composed of waste products recovered after thermal melting and processing.

In addition, on the side of the lower skin layer, for example, it can be printed directly or laminated The method of brushing the film to form the printing surface is not limited to this.

The overall thickness of the film of the present invention is 200 to 1300 μm. If the overall thickness of the film is less than 200 μm, a thinner part will be formed on the thermoformed container, which will cause a reduction in the strength of the container, which is called the buckling strength, that is, the resistance to compression or pressure. In this way, for example, when the contents are stored on the inner surface of the container, the container may be deformed or damaged due to vibration or compression during transportation and storage. If the overall thickness of the film exceeds 1300 μm, the heat conduction in the thickness direction of the film may be poor during thermoforming, which may cause forming defects.

)的測定拉伸或壓縮所承受的荷重的裝置來測定容器變形時的荷重。但不限於此。只要能較好對其進行評價的方法均可。 As an evaluation method of the above-mentioned buckling strength, for example, after placing the flange part of the molded container down on a flat surface, put a certain load on the bottom surface of the container as the upper part and confirm the deformation, or It uses what is called a push-pull gauge (

) Is a device for measuring the load borne by tension or compression to measure the load when the container is deformed. But it is not limited to this. As long as the method can be better evaluated.

The molding method of the multilayer resin film of the present invention is not particularly limited, and conventional methods can be used. For example, use 4 or more single-screw extruders to melt and extrude each raw material resin, and obtain a multilayer resin film through a feed-block and a T-die, or through a multi-runner die The method of obtaining a multilayer resin film.

The thickness of the polyolefin resin layer 10a has a layer composition ratio of 1 to 30% compared to the thickness of the entire film. As a preferred embodiment, the thickness of the polyolefin resin layer is 2% or more and less than 10% of the total thickness of the film. As a further preferred aspect, the thickness of the polyolefin-based resin layer is 5% or more and less than 10% of the total thickness of the film. The layer composition ratio expressed here refers to a numerical ratio expressed as a percentage of the value obtained by dividing the thickness of the polyolefin resin layer by the overall thickness of the film. The layer composition ratio of the polyolefin resin layer 10a is for example If it is less than 1%, especially when the overall thickness of the film is thin, the polyolefin-based resin layer may not have a sufficient thickness and may not be able to exert its water vapor barrier function. On the other hand, if the layer composition ratio of the polyolefin-based resin layer 10a exceeds 30%, the crystalline polyolefin-based resin layer constituting the skin layer tends to shrink when heated during thermoforming. In contrast, the composition is lower The non-crystalline styrenic resin layer of the skin layer tends to become smaller during heat shrinkage during thermoforming. Due to the difference in heat shrinkage between the skin layer and the lower skin layer, the film or thermoformed container Will produce warpage.

The skin layer 10a composed of the polyolefin resin layer of the present invention is basically located on the inner surface (the surface in contact with the contents) of a container thermoformed with a film. This is formed by giving it water vapor barrier properties and oil resistance. In addition, for containers that need to store hot boiled water, resins that can withstand high temperatures above 90°C can also be used to make them have heat resistance.

The above-mentioned multilayer resin film has a water vapor transmission rate of 10g/m2. less than day. As a preferred option, its water vapor transmission rate is 5g/m2. less than day. If its water vapor transmission rate exceeds 10g/m2. Day, the content of the thermoformed container will be deteriorated or discolored due to the penetration of water, making its water vapor barrier function impossible.

As the polyolefin resin in the structure of the present invention, it includes, but is not limited to, ethylene, propylene, n-butene and other polyolefin single polymers with a carbon number of about 2-8.

As polyolefin resin, generally, high density polyolefin (HDPE), linear low density polyolefin (LLDPE), low density polyolefin (LDPE), etc. are mentioned. In addition, as the polypropylene resin, any of homopolymers, random copolymers, and block copolymers can be applied, but the present invention is preferably a block copolymer. As a block copolymer, the viscosity (Pa‧s) is 50000-1000000 when the measuring temperature is 190℃ and the shear rate is 100-300 (1/sec), The resin whose viscosity change at 190℃-230℃ is 0.5-15Pa‧s/℃ is better. The polyolefin resin used can be appropriately mixed and used as long as the appearance of the film or thermoformed container is not damaged.

As the oxygen barrier resin constituting the oxygen barrier resin layer 12, representative materials thereof include, but are not limited to, ethylene-vinyl alcohol copolymer resin, polyamide resin, polyvinyl alcohol, polyvinyl chloride, and the like. Among them, ethylene-vinyl alcohol copolymer resin is preferable from the viewpoint of processability and moldability.

Ethylene-vinyl alcohol copolymer resin is usually obtained by saponifying ethylene-vinyl acetate copolymer. In order to make it have oxygen barrier properties, processability, and moldability, the ethylene content should be 10~65mol% (preferably 20~50mol) %), and the saponification degree should be above 90% (preferably above 95%).

In addition, examples of polyamide resins include the following: i.e., caprolactam, azacyclotridecane-2-one and other lactam polymers; 6-aminocaproic acid, 11-aminoundecanoic acid, Amino acid ester polymers such as 12-aminododecanoic acid; 1,6-hexanediamine, 1,10-diaminodecane, dodecanediamine, 2,2,4- or 2,4,4 -Aliphatic diamines such as trimethylhexamethylenediamine, alicyclic amines such as 1,3- or 1,4-bis(aminomethyl)cyclohexane, 4,4'-diaminodicyclohexylmethane, etc. Diamine units such as aromatic diamines such as xylylenediamine or p-xylylenediamine, and aliphatic carboxylic acids such as adipic acid, suberic acid and sebacic acid, and alicyclic carboxylic acids such as cyclohexanedicarboxylic acid Polycondensates formed by carboxylic acid units of aromatic carboxylic acids such as acid, terephthalic acid, isophthalic acid, etc.; and copolymers of the above substances.

Polyamide resins include nylon 6, nylon 9, nylon 11, nylon 12, nylon 66, nylon 610, nylon 611, nylon 612, nylon 6T, nylon 6I, nylon MXD6, nylon 6/66, and nylon 6/610. , Nylon 6/6T, nylon 6I/6T, etc., including nylon 6, nylon MXD6 Is the best.

In addition, the thickness of the oxygen barrier resin layer 12 is set to 10 to 50 μm (preferably 20 to 40 μm). If the thickness is less than 10μm, the oxygen barrier performance to prevent the content of the molded container from being degraded due to oxidation may not be achieved. In addition, if the thickness exceeds 50μm, resin dents may occur during the stamping of the thermoformed container and affect the container's performance. Exterior.

The oxygen permeability of the oxygen barrier resin layer 12 is 10cc/m2. Day or less (preferably 5cc/m2.day or less). If the oxygen transmission rate exceeds 10cc/m2. Day, the content of the thermoformed container will be oxidized and deteriorated, so it cannot fully exert its oxygen barrier function.

As the resin constituting the bonding layers 11a and 11b in this embodiment, a modified polyolefin polymer is suitable. Examples of the representative modified olefin polymers constituting the bonding layer include the following: namely, ethylene, propylene, n-butene, and other polyolefin single polymers containing about 2 to 8 carbon atoms; and these polyolefins and ethylene , Propylene, n-butene, isoamylene, n-pentene, 4-methylpentene-1, 1-hexene, 1-octene, n-decene, and other polyolefins with carbon number of about 2-20 Or polyolefin resins such as copolymers of vinyl compounds such as vinyl acetate, vinyl chloride, acrylic acid, 2-methacrylic acid, acrylate, methyl methacrylate, and polystyrene; or ethylene-propylene copolymers, ethylene- Polyolefin rubbers such as propylene-diene terpolymer, ethylene-1-butene copolymer, and propylene-1-butene copolymer are combined with acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, and Malic acid, itaconic acid, citraconic acid, tetrahydrophthalic acid and other unsaturated carboxylic acids, or carboxylic acid halides, amides, imines, anhydrates, esters and other derivatives (specifically, propylene dichloride , Maleimide, anhydrous maleic acid, anhydrous citraconic acid, monomethyl maleate, dimethyl maleate, glycidyl maleate, etc.) are modified under grafting reaction conditions. The resulting substance.

As a modified polyolefin polymer, unsaturated carboxylic acid or its anhydrate is used, especially Especially ethylene resin, propylene resin, ethylene-propylene or n-butene copolymer rubber modified by maleic acid or its anhydrate is preferable.

The thickness of the bonding layer is set to 5 to 50 μm (preferably 10 to 30 μm) regardless of the layer. If the thickness is less than 5 μm, sufficient interlayer bonding strength may not be obtained, and if the thickness exceeds 50 μm, resin dents may occur during pressing of the thermoformed container, which may affect the appearance of the container.

As the polystyrene-based resin constituting the polystyrene-based resin layer 13 in this embodiment, the following can be cited: namely, polystyrene, 2-phenyl-1-propylene, 4-methylstyrene, and dimethylstyrene. Homopolymers or copolymers of polystyrene monomers such as styrene, p-tert-butyl styrene, and chlorostyrene; such as polystyrene-acrylonitrile copolymer (AS resin) and other polystyrene monomers Copolymers of other monomers, or the aforementioned polystyrene monomers and other polymers, such as polybutadiene, polystyrene butadiene copolymer, polyisoprene, polychloroprene, etc. In the case of vinyl rubber polymers, graft polymers that undergo graft polymerization, such as high impact polystyrene (HIPS resin), polystyrene-acrylonitrile graft polymer (ABS resin), and the like.

From the perspective of rigidity and moldability, polystyrene (GPPS resin) and high-impact polystyrene (HIPS resin) are suitable among polystyrene resins. They can be used alone or mixed in appropriate proportions.

As a polystyrene resin, the quality percentage of the butadiene rubber component should be 4-8%. The content of butadiene rubber components can be adjusted by a simple method of mixing GPPS and HIPS, but it can also be adjusted at the stage of manufacturing HIPS. If the above-mentioned mass percentage is less than 4%, sufficient container strength may not be achieved. If the above-mentioned mass percentage exceeds 8%, defects such as hot plate adhesion may especially occur during thermoforming using a hot plate.

The polystyrene resin layer 13 may be added with colorants such as pigments and dyes, silicone oil or alkyl ester release agents, fibrous reinforcing agents such as glass fibers, talc, Granular lubricants such as kaolin and cristobalite, salt compounds such as sulfonic acid and alkali metals, or anti-charge agents such as polyglycols, additives such as ultraviolet absorbers and antibacterial agents. At the same time, the waste resin generated in the manufacturing process of the multilayer resin film and the molded container of the present invention can also be mixed and used.

The thickness of the polystyrene-based resin layer 13 in this embodiment is set to 200 to 900 μm (preferably 300 to 700 μm). If the thickness is less than 200μm, each part of the container may not reach the same thickness after molding, and excellent thermoformability may not be achieved. At the same time, if the thickness exceeds 900μm, it will be difficult to conduct heat in the film thickness direction during thermoforming. Molding defects may occur.

The molded container of an embodiment of the present invention, as shown in FIG. 3, is formed by thermoforming the multilayer resin film of the present invention. As a thermoforming method, there can be mentioned the usual vacuum forming, pressure forming, or the plunger assisting method in which one side of the plunger is in contact with the film, or a pair of male and female molds are contacted with both sides of the film to form, which is called Molding methods for mold molding, etc. But the method is not limited to this. At the same time, as a method of heating and softening the film before forming, a well-known film such as non-contact heating by radiant heating by infrared heaters, or hot plate heating by directly contacting the film with a heated hot plate to soften it, etc. heating method.

In addition, the molding temperature during thermoforming will be set reasonably in consideration of the melting point of the resin. However, if the film heating temperature is too low, the shape of the container after thermoforming will be insufficient, and if the film heating temperature is too high, adhesion will occur. In the hot plate and other bad conditions, it needs to be set to a suitable temperature.

Examples and comparative examples will be listed below to further specifically describe the present invention, but the present invention is not limited to the scope of the examples and the like.

The resin raw materials used in the examples are as follows.

(1) Polyolefin resin layer

PP resin: "3080" (produced by Formosa Plastics Corporation, MI: 8.5g/10min. (190℃, 2.16kgf), Block-PP)

(2) Oxygen barrier resin layer

Ethylene-vinyl alcohol copolymer (EVOH) "EVAL J171B"

(Manufactured by Kuraray, MI: 1.7g/10min (190℃, 2.16kgf), ethylene content 32mol%)

(3) Bonding layer

Modified polyolefin polymer (modified PO) "MODIC F502C"

(Produced by Mitsubishi Chemical Corporation, MI: 1.3g/10min (190℃, 2.16kgf))

(4) Polystyrene resin layer

HIPS resin: "4241" (produced by Total Petrochemicals, MI: 4.0g/10min.

(200℃，5.0kgf))

In addition, the multilayer resin film was thermoformed under the following conditions to obtain the container shown in FIG. 3.

Equipment used: Vacuum pressure forming machine produced by Asano Research Institute

Heater: non-contact far infrared heater

Film surface temperature: Adjust to the appropriate film surface temperature according to the composition of the film

In addition, the following methods are used for various evaluations of multilayer resin films and containers OK, and the results are shown in Table 1.

(1) Evaluation of film warpage

As shown in Fig. 2, at an angle of 45° with respect to the flow direction (MD) and width direction (TD) of the film, cut a 120mm length cut, and then measure the maximum warpage height of the film with a ruler.

(2) Evaluation of container warpage

As shown in Figure 3, 20 containers are formed in multiple rows, and the size of each container is 44 mm in the horizontal direction, 55 mm in the vertical direction, and a draw ratio of 0.5. After placing the flange part of the multi-row molded part down on a flat surface, measure the maximum height from the flat surface to the raised part of the container/flange part with a ruler.

(3) Evaluation of oil resistance

The oil resistance evaluation of the film was performed using the method shown in FIG. 4.

A film test piece with a width of 15 mm and a length of 200 mm is fixed in an arc shape between the fixing devices under stress, and gauze soaked in soybean oil is placed on the uppermost part. At this time, the width of the fixture is 130 mm. In addition, be careful not to let soybean oil enter the sides of the film. In order to prevent the soybean oil in the gauze from drying out, soybean oil was dripped on the gauze every certain day, and the evaluation was performed for 30 consecutive days, and the following criteria were used to determine whether there were film cracks or breaks.

A: No cracks or breaks occurred at all

B: There is a little crack on the surface of the film

C: The film is completely broken

(4) Determination of oxygen transmission rate

The oxygen transmission rate of the film was measured by the following method.

[Measurement method] According to GB/T 1038 standard

Equipment used: VAC-V1 detection device produced by Labthink

Measurement conditions: 23℃×65%R.H.

Sample setting: In view of the practicality of the container after molding, when setting the sample, ensure that the orientation can allow oxygen to pass through the lower skin side of the film sample.

(5) Measurement of water vapor transmission rate

The water vapor transmission rate of the film was measured by the following method.

[Measurement method] According to GB/T 1037 standard

Equipment used: W3/031 detection device produced by Labthink

Measurement conditions: 40℃×90%R.H.

(6) Formability

Using the mold for molding the container shown in Fig. 3, the moldability during thermoforming was evaluated according to the following criteria.

A: Good formability

B: The thickness of some parts of the container after molding is thin

C: The shaping properties like the molding die are not obtained. Or find defects in molding appearance.

<Example 1>

Using three 45mm single-screw extruders, one 65mm single-screw extruder, and one 105mm single-screw extruder, the PP resin is used in the polyolefin resin by the feed-block method to obtain It has a layer structure of 40 μm for the polyolefin resin layer 10a, 15 μm for the bonding layer 11a, 40 μm for the oxygen barrier resin layer 12, 15 μm for the bonding layer 11b, and 340 μm for the polystyrene resin layer 13. A multilayer resin film with a layer composition ratio of 9% and a total thickness of 450 μm.

For the multilayer resin film obtained above, the water vapor transmission rate was measured. As shown in Table 1, the water vapor transmission rate was 0.8g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 1, the oxygen transmission rate is 0.5cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 13 mm. Furthermore, the moldability of the container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

<Example 2>

In the same manner as in Example 1, the polyolefin resin layer 10a was 150 μm/the bonding layer 11a was 15 μm/the oxygen barrier resin layer 12 was 40 μm/the bonding layer 11b was 15 μm/the polystyrene resin layer 13 was 680 μm. Layer structure, the polyolefin resin layer has a layer composition ratio of 17%, and a multilayer resin film with a total thickness of 900 μm.

For the multilayer resin film obtained above, the water vapor transmission rate was measured. As shown in Table 1, the water vapor transmission rate was 0.7g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 1, the oxygen transmission rate is 0.4cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 15 mm. Furthermore, the moldability of the container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

<Example 3>

In the same manner as in Example 1, the polyolefin resin layer 10a was 80μm/ the bonding layer 11a was 15μm/ the oxygen barrier resin layer 12 was 40μm/ the bonding layer 11b was The 15 μm/polystyrene resin layer 13 has a layer structure of 950 μm, the polyolefin resin layer has a layer composition ratio of 7%, and a multilayer resin film with a total thickness of 1100 μm.

For the multilayer resin film obtained above, the water vapor transmission rate was measured. As shown in Table 1, the water vapor transmission rate was 0.7g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 1, the oxygen transmission rate is 0.6cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 9 mm. Furthermore, the moldability of the container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

<Example 4>

In the same manner as in Example 1, a polyolefin-based resin layer 10a of 50 μm/joining layer 11a of 10 μm/oxygen barrier resin layer 12 of 30 μm/joining layer 11b of 10 μm/polystyrene-based resin layer 13 of 900 μm was obtained. Layer structure, the polyolefin resin layer has a layer composition ratio of 5% and a multilayer resin film with a total thickness of 1000 μm.

For the multilayer resin film obtained above, the water vapor transmission rate was measured. As shown in Table 1, the water vapor transmission rate was 0.7g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 1, the oxygen transmission rate is 0.7cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 7 mm. Furthermore, the moldability of the container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

<Example 5>

In the same manner as in Example 1, the polyolefin resin layer 10a was 30 μm/ the bonding layer 11a was 20 μm/ the oxygen barrier resin layer 12 was 40 μm/ the bonding layer 11b was 20 μm/ the polystyrene resin layer 13 was 1090 μm. Layer structure, the layer composition ratio of the polyolefin resin layer is 3%, and the total thickness is a multilayer resin film of 1200μm.

The water vapor transmission rate of the multilayer resin film obtained above was measured. As shown in Table 1, the water vapor transmission rate was 0.7g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 1, the oxygen transmission rate is 0.6cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 5 mm. Furthermore, the moldability of a container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

In the above-mentioned Examples 1 to 5, the polyolefin resin is PP resin, and the polyolefin resin can also be a single polymer of polyolefin having a carbon number of about 2 to 8 such as ethylene, propylene, and n-butene. Any kind of. In this case, the same effects as the above-mentioned Embodiments 1 to 5 can be obtained.

On the other hand, compared with Example 1, the total thickness of the polyolefin resin layer or the thickness of the polystyrene resin layer as the skin layer is reduced, or the polystyrene resin layer is used to form the water vapor barrier layer As a comparative example, the performances of the modified examples such as those were evaluated as follows.

<Comparative Example 1>

A 65mm single-screw extruder was used to obtain a film with a single-layer structure of 450 μm polystyrene resin layer. Compared with Example 1, this comparative example is characterized in that the resin film is only Single layer structure composed of polystyrene resin layer.

For the single-layer resin film obtained in this comparative example, the water vapor transmission rate was measured. As shown in Table 2, the water vapor transmission rate was 7.0 g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 2, the oxygen transmission rate is 350cc/m2. day. In addition, as a result of the oil resistance evaluation of the single-layer resin film, the oil resistance was C, and as a result of the warpage evaluation of the single-layer resin film, the warpage of the single-layer resin film was 12 mm. Furthermore, the moldability of the container molded using the single-layer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

Compared with the evaluation standards, the oxygen transmission rate far exceeds 10cc/m2. At the same time, in the evaluation of its oil resistance, the film was completely broken and its oil resistance was unacceptable.

<Comparative Example 2>

A multilayer resin film was obtained in the same manner as in Example 1 except that the skin layer was made of polystyrene resin.

For the multilayer resin film obtained in this comparative example, the water vapor transmission rate was measured. As shown in Table 2, the water vapor transmission rate was 4.2 g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 2, the oxygen transmission rate is 1.2cc/m2. day. In addition, as a result of the oil resistance evaluation of the multilayer resin film, the oil resistance was C, and as a result of the warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 15 mm. Furthermore, the moldability of the container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as A. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

As a result of comparison with each evaluation standard, the film was completely broken in the oil resistance evaluation, and the oil resistance was unacceptable.

<Comparative Example 3>

In the same manner as in Example 1, the polyolefin resin layer 10a was 200 μm/the bonding layer 11a was 15 μm/the oxygen barrier resin layer 12 was 40 μm/the bonding layer 11b was 15 μm/the polystyrene resin layer 13 was 330 μm. Layer structure, the polyolefin resin layer has a layer composition ratio of 33%, and a multilayer resin film with a total thickness of 600 μm.

For the multilayer resin film obtained above, the water vapor transmission rate was measured. As shown in Table 2, the water vapor transmission rate was 0.7g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 2, the oxygen transmission rate is 0.8cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 43 mm. Furthermore, the moldability of a container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as C. As a result of evaluating the warpage of the molded container, the warpage of the molded container was 12 mm.

As a result of comparison with each evaluation standard, the warpage of the multilayer resin film was 43 mm, and the warpage of the container molded with the multilayer resin film was 12 mm, which did not solve the problems of the prior art. In addition, as a result of the moldability evaluation, the shapeability as the molding die was not obtained, and therefore the molded container was unacceptable.

<Comparative Example 4>

In the same manner as in Example 1, a polyolefin resin layer 10a of 25 μm/joining layer 11a of 10 μm/oxygen barrier resin layer 12 of 30 μm/joining layer 11b of 10 μm/polystyrene resin layer 13 of 120 μm was obtained Layer structure, the layer composition ratio of the polyolefin resin layer is 13%, and the total thickness is a multilayer resin film of 195 μm.

For the multilayer resin film obtained above, the results of the water vapor transmission rate measurement As shown in Table 2, its water vapor transmission rate is 0.9g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 2, the oxygen transmission rate is 1.0cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 11 mm. Furthermore, the moldability of a container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as B. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

As a result of comparison with each evaluation standard, its moldability was evaluated as B. During use, when the thinner part of the container ruptured after molding, water vapor or oxygen would invade, reducing its barrier properties.

<Comparative Example 5>

In the same manner as in Example 1, the polyolefin resin layer 10a was 40μm/ the bonding layer 11a was 15μm/ the oxygen barrier resin layer 12 was 40μm/ the bonding layer 11b was 15μm/ the polyolefin resin layer (the lower skin layer and the skin The layer adopts the same resin) a layer structure of 340 μm, the layer composition ratio of the polyolefin resin layer is 84%, and the total thickness is a multilayer resin film of 450 μm.

For the multilayer resin film obtained above, the water vapor transmission rate was measured. As shown in Table 2, the water vapor transmission rate was 0.7g/m2. day. In addition, the results of oxygen transmission rate measurement, as shown in Table 2, the oxygen transmission rate is 0.8cc/m2. day. In addition, as a result of oil resistance evaluation of the multilayer resin film, the oil resistance was A, and as a result of warpage evaluation of the multilayer resin film, the warpage of the multilayer resin film was 9 mm. Furthermore, the moldability of a container molded using the multilayer resin film was also evaluated, and the moldability was evaluated as B. As a result of evaluating the warpage of the molded container, the warpage of the molded container was zero.

As a result of comparison with each evaluation standard, its moldability was evaluated as B. During use, when the thinner part of the container ruptured after molding, water vapor or oxygen would invade, reducing its barrier properties.

According to the results of the foregoing Examples 1-3 and Comparative Examples 1-5, the multilayer resin film of the present invention is formed by laminating multiple resin layers, and includes a polyolefin resin layer as a skin layer, a bonding layer, an oxygen barrier layer, and The polystyrene resin layer of the lower skin layer has an overall thickness of 200 to 1300 μm, and the thickness of the polyolefin resin layer is 1 to 30% compared to the overall thickness of the film. It has excellent thermoformability and oil resistance, and can suppress warpage of the film.

In addition, the oxygen barrier resin layer has a thickness of 10-50 μm, and its oxygen permeability is 10 cc/m ² ‧day or less. Moreover, the water vapor transmission rate of the multilayer resin film of the above-mentioned structure is 10 g/m ² ‧day or less.

Therefore, the multilayer resin film constituted as described above has excellent thermoformability, oxygen barrier properties, water vapor barrier properties, and oil resistance, and can suppress warpage of the film.

In addition, the molded container manufactured by molding the multilayer resin film constituted as described above has excellent thermoformability, oxygen barrier properties, water vapor barrier properties, and oil resistance, and can suppress warpage after molding.

10a: Polyolefin resin layer

11a, 11b: bonding layer

12: Oxygen barrier resin layer

13: Polystyrene resin layer

Claims (6)

A multilayer resin film is formed by laminating multiple resin layers, and is characterized in that the multilayer resin film has a polyolefin resin layer as a skin layer, a bonding layer, an oxygen barrier layer, and a polystyrene resin layer as a lower skin layer, The overall thickness of the film is 200 to 1300 μm, and the thickness of the polyolefin resin layer is 1 to 30% compared to the overall thickness of the film. The multilayer resin film according to the first item of the patent application, wherein the polyolefin resin layer is formed of block polypropylene. The multilayer resin film as described in item 1 or 2 of the scope of patent application, wherein the thickness of the polyolefin resin layer is 5% or more and less than 10% of the total thickness of the film. The multilayer resin film described in item 3 of the scope of patent application, wherein the oxygen barrier layer has a thickness of 10-50 μm, and its oxygen transmission rate is 10cc/m ² ‧day or less. The multilayer resin film described in item 4 of the scope of patent application, wherein the water vapor transmission rate of the multilayer resin film is 10g/m ² ‧day or less. A molded container formed by thermoforming a multilayer resin film as described in any one of items 1 to 5 of the scope of patent application, and the polyolefin resin layer in the multilayer resin film is located on the inner surface of the container.

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