JP2003267422A - Lid material, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lid material of excellent drawing and packaging properties which uses no aluminum foil, and can be collected as plastics, or easily incinerated after the use. <P>SOLUTION: This lid material is a laminate film comprising at least a base layer and a heat seal layer. The base layer is formed of a resin composition of copolymer resin (A) of a specified composition of styrene monomer (a) and conjugate diene monomer (b), and copolymer resin (B) of polystyrene or acrylic monomer (c) and styrene monomer (d). In the lid material for draw molding, and a food vessel packaging body formed of the lid material, the ratio A/(A+B) is 0.70 to 0.90, and the ratio of the thickness of the base layer to the laminate film is 0.50 to 0.90. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lid material for food containers such as various lactic acid beverages, yogurt, milk, jelly and other dairy products. In the present invention, the unit representing the composition of the resin composition is a mass-based value unless otherwise specified.

[0002]

2. Description of the Related Art The lid of a polystyrene or polyethylene container in which foods such as lactic acid bacteria drinks, yogurt, milk, jelly and other dairy products have been conventionally packed is generally a printed aluminum foil and a polyethylene film. Also, a multilayer laminate in which a heat seal layer and the like are laminated is used. For example, as shown in FIG.
An anchor coat (52) of polyurethane or the like is formed on the surface of the aluminum foil (51) having a thickness of μm to improve the adhesion if necessary, and printing is performed.
An overcoat (54) of epoxy resin, cellulose, melanin resin or the like is applied to protect 3) and to prevent corrosion of the aluminum foil. On the other hand, a low density polyethylene film (56) having a thickness of about 10 to 30 μm is joined to the back surface side of the aluminum foil (51) through an anchor coat (55) similar to the above, and hot-melt adhesive is applied to the polyethylene film 16. The agent is applied to form the heat seal layer (57).

In such a cover material, the aluminum foil has an excellent barrier property against air, and protects the contents and has a dead-hold property (a property in which a folded state is maintained when the cover is opened). ), It is used for the purpose of making it easier for consumers to open and eat. The heat seal layer is provided to heat seal the lid and the container body to the extent that they can be opened by hand. On the other hand, when a consumer eats or drinks, these lids may be peeled off and a mouth may be put on the container. It is generally drawn to cover the side surface of the part. At this time, one of the main reasons that the aluminum foil is used for the lid material is that the aluminum foil is easy to draw at room temperature and retains its shape, like the dead hold property. . It is difficult to obtain such characteristics with a general thermoplastic resin film laminate, and the practicality thereof is poor.

On the other hand, in a food manufacturer, a lid formed by punching and drawing the above-mentioned lid material (hereinafter referred to as "molding lid") is capped in a container filled with food at high speed and accurately, and heat sealing is performed. The lid material punched out in advance is suction-conveyed onto a container filled with food, heat-sealed, and then drawn so as to cover the mouth of the container. After these steps, it is important that the drawn shape is kept constant, and in particular, the molding lid of the former method keeps the shape constant during conveyance to the capping step after drawing. Is an important factor.

Further, after the consumer has opened the molded lid and eats and drinks, the molded lid has conventionally been disposed of as waste and incinerated. However, in order to collect and reuse the used packaging materials in recent years, the separate collection of waste has been progressing in each local government, and the molding lid made of the laminate of the aluminum foil and the resin film described above completely Since it can not be separated into two, it has the excellent characteristics as described above, but it cannot be separated and collected and must be incinerated, and even when incinerated, the aluminum foil does not completely ash, so a large amount of unburned material Is left to occur. Furthermore, since aluminum foil is easy to tear, if it is accidentally mixed in food due to a trouble in the packaging process, aluminum foil cannot be removed because it cannot be detected by a metal detector, and a more resistant alternative material is developed. Is desired.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is a lid material which does not use aluminum foil and comprises a laminate of resin composition films that can be drawn at room temperature and is used as a plastic. It is intended to provide a lid material that can be recovered or can be easily incinerated.

Further, the present invention is to provide a molding lid made of a laminate of resin composition films whose shape formed by drawing does not substantially change with time even if it does not contain an aluminum foil.

[0008]

Means for Solving the Problems As a result of extensive studies aimed at solving the above problems, the present inventor has found that a styrene resin composition having a specific composition is used instead of an aluminum foil as a base material layer. The inventors have found that a lid material that can be drawn at room temperature can be obtained, and have completed the present invention. That is, the present invention is a laminated film comprising at least a base material layer and a heat seal layer, wherein the base material layer comprises a resin composition containing the following resin (A) and resin (B) as main components, and the composition ratio is A /
(A + B) is 0.70 to 0.90 and the thickness ratio of the base material layer / laminated film is 0.50 to 0.90. Resin (A): a copolymer resin having a chain of a styrene-based monomer (a) and a conjugated diene-based monomer (b) and having a composition ratio b / (a + b) of 0.20 to 0.26. (B): Polystyrene, or a copolymer of an acrylic monomer (c) and a styrene monomer (d), or in the resin (B), an acrylic monomer (c)
Is methyl acrylate, and the composition ratio c / (c + d) is 0.
A draw forming lid material having a size of 25 or less is preferable. On the other hand, the present invention is a method for producing these lid members, and a food container package having a molded lid made of the lid members.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

Generally, the draw forming lid material is supplied to a maker that manufactures food in the form of, for example, a laminated film or sheet having the above-described structure wound into a roll, and punched into a circular shape there, and then a molding machine is used. As shown in FIG. 3, a molding lid (33) having a flat portion (31) in the shape of a container head and a skirt portion (32) having a fold is drawn at room temperature. Then, the container is covered with a container made of a thermoplastic resin composition such as polyethylene or polystyrene filled with the content and heat-sealed. The lid material using the above-mentioned aluminum foil that has been conventionally used is easily processed into the shape shown in FIG. 3 at the time of drawing. In order to replace this with a thermoplastic resin laminate, at least the resin laminate must maintain the shape of the skirt portion in the state of FIG. 3 even after drawing at room temperature.

If the shape-holding property of the draw-formed product is insufficient, the skirt portion will open with time (spring back phenomenon), and the mouth of the container cannot be covered. In addition, since there is a tendency to restore even during the production process, it may be difficult to accurately carry and cap the molding lid. If the molding lid is fragile, it may break during drawing or opening.
In that case, it cannot function as a lid. In order that the springback phenomenon after draw forming does not hinder the subsequent long-term continuous operation of conveying and capping, the skirt portion shown in FIG. 4, that is, the skirt diameter (42)
And the diameter of the molding lid top surface (41), the diameter of the molding lid top surface (4
As a guideline, the ratio to 1) should be kept within 4%.

As shown in FIG. 1, the cover material of the present invention basically comprises a base material layer (11) and a heat seal layer (13), and an adhesive layer (12) between them, if necessary. ) Is provided.

In the present invention, the styrene-based monomer (a) constituting the copolymer used for the base material layer (11) is styrene or α-methylstyrene, and the conjugated diene-based monomer (b). ) Is butadiene or isoprene. To produce a copolymer from these monomers, a method of stepwise polymerizing the monomers with an anionic polymerization initiator, a method of copolymerizing a mixture of both monomers in an inert solvent Or, it is manufactured by a method of appropriately combining these. The composition ratio b / (a + b) of the conjugated diene monomer in the copolymer is 0.20 to 0.26. 0.2
If it is less than 0, the film becomes brittle and cracks occur during drawing. If it exceeds 0.26, the obtained film has rubber-like mechanical properties, and the shape-holding property of the draw forming becomes insufficient, and the skirt portion (32) opens with time. It causes a phenomenon.

The copolymer (A) has a chain of a styrenic monomer (a) and a conjugated diene monomer (b) and has a weight average molecular weight of generally 60,000 to 250,000. It is in the range of. The form of the chain of (a) and (b) is not particularly limited, and not only the copolymer consisting of (a) chain / (b) chain / (a) chain but also, for example, the above-mentioned chain is repeated a plurality of times. It may be a so-called “multi-block copolymer” which is repeated, while the chain composed of (a) and (b) is 3
It may be a so-called “star block copolymer” in which 5 to 5 polyfunctional compounds are bonded. As for the molecular structure, each of the chains is a perfect chain, or (a) and (b) a random copolymer at the transition part of the (a) chain and the (b) chain as seen in JP-A-48-48456. Any of those having a so-called tapered block structure containing A resin such as polystyrene may be added to the composition of the present invention as long as the characteristics are not impaired.

The polystyrene of the resin (B) used in the base material layer (11) in the present invention is a polymer containing styrene as a main component and is generally called GP. On the other hand, the acrylic monomer (c) constituting the styrene-acrylic copolymer is methyl methacrylate,
Methacrylic acid esters such as ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and methyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, etc. are particularly preferable. Is methyl acrylate. The styrene-based monomer (d) is styrene or α-methylstyrene. In order to produce a copolymer from these monomers, suspension polymerization, bulk polymerization, solution polymerization and the like can be mentioned, but suspension polymerization is preferred. In suspension polymerization, it is easy to remove the heat of polymerization, and it is possible to polymerize up to a high conversion rate range, so unreacted monomers and styrene dimers,
The styrene trimer can be efficiently suppressed. The composition ratio c / (c + d) of the acrylic monomer in the copolymer is preferably 0.25 or less. When it exceeds 0.25, the compatibility with the copolymer (A) becomes poor, the base material layer is likely to tear, and the appearance also becomes poor.

The resin (B) used in the present invention is at least one selected from the above-mentioned compositions containing the polystyrene or the copolymer of the acrylic monomer (c) and the styrene monomer (d) as a main component. It consists of the above resin composition. By containing this resin (B), the springback after drawing and molding at room temperature, which is the subject of the present invention, is small, and the problems at the time of carrying and capping the molding lid are significantly suppressed, and at the same time the base material layer itself. The elastic modulus of is improved, and a lid having a sufficient waist can be obtained. As the elastic modulus of the base material layer, one value is that the tensile elastic modulus is 700 MPa or more in both the film take-up direction (MD) and the width direction (TD).

The method for producing the compound pellets used for the base material layer using the resin (A) and the resin (B) is not particularly limited, but it is preferable to use a twin-screw extruder for good dispersion. Also, the compounding ratio A / (A + B) is 0.70.
It is preferably 0.90 for the same reason.

The ratio of the thickness of the base material layer (11) to all the layers of the laminated film which is the cover material (1) is 0.50 to 0.90.
Is important, and preferably 0.60 to 0.8
It is 5. If this ratio is less than 0.50, the bending of the skirt portion (32) is eased with time immediately after the lid material (1) is drawn and the spread of the skirt portion exceeds 4%. It causes trouble when the lid is transported.
On the other hand, if it exceeds 0.90, the adhesive layer (12) and the heat seal layer (13) become too thin, and the required adhesive strength between the layers or the heat sealability with the container cannot be obtained. The total thickness of the cover material (1) is generally 100 to 300 μm from the viewpoint of drawability and economy.

The composition constituting the base material layer (11) of the present invention is stable as necessary within the range where there is no problem in draw formability and no problem occurs when transferring to the surface of the base material layer. Agent,
Additives such as lubricants and pigments can be added.

Further, the cover material of the present invention comprises a base material layer (1) for reinforcing the base material layer (11) or for printing.
Various film layers can be provided on the side opposite to the heat seal layer (13) of 1). For example, a non-stretched polypropylene film, a biaxially stretched polypropylene film, a biaxially stretched polyester film and the like can be mentioned. The biaxially stretched film has a high elastic modulus and is resistant to bending, pulling and the like, and therefore increases resistance to tearing of the lid when opened. However, it is preferable to use a thin film as much as possible because it has an adverse effect on shape retention during drawing and tends to cause a springback phenomenon after drawing.

The heat-sealing layer (13) of the present invention is not particularly limited as long as it has an easy peeling property from the container material, but a hot-melt adhesive containing an ethylene-vinyl acetate copolymer and a wax as a main component, an acrylic resin. Adhesives and incompatible resin blend adhesives are preferably used. Examples of incompatible resin blends include high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, ethylene-propylene copolymer, ethylene- Vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, styrene-butadiene copolymer and hydrogenated product thereof,
Examples include blends of thermoplastic polyurethane and the like. The heat-sealing strength is preferably such that it can be easily opened by hand, and the thickness of the sealing layer is set so that the maximum value of the peel strength with respect to the container mouth is 10 N when the peel strength is 300 m / min. Now, adjust the composition.

In the present invention, it is preferable to provide the adhesive layer (12) as described above, if necessary. The adhesive layer (12) is intended to bond the base material layer (11) and the heat seal layer (13), and is not particularly limited, but a case where only an anchor coat such as polyurethane resin is used,
A case in which a polyolefin film is further laminated on the anchor coat layer, the base material layer without the anchor coat (11)
In some cases, a modified polyolefin film layer that can be directly adhered to is provided. The polyolefin film enhances the adhesion of the heat seal layer (13) to the container, and the lid material (1)
It has a function of providing airtightness as well as providing cushioning property.

The lid material (1) of the present invention can be manufactured by a usual method for manufacturing a multilayer film. For example, the base material layer (1
After monolayer extrusion film-forming 1) by T-die method, one side of the film is subjected to anchor coating and polyethylene is extruded and laminated with the heat-sealing layer (13) separately film-formed, or the substrate layer (11). ) Adhesive layer (12)
And a heat seal layer (13) are co-extruded and laminated by a feed block method or a multi-manifold method T-die, and further, a base material layer (11), an adhesive layer (12) and a multi-manifold method T-die are used. There is a method of coextruding the heat seal layer (13) at the same time.

The lid material of the present invention may be subjected to antistatic treatment, if necessary. As the antistatic agent, a surfactant type antistatic agent, a polymer type antistatic agent or the like can be applied by a gravure roll, a roll coater, a spray or the like. Also,
In order to apply these antistatic agents uniformly, it is desirable to perform corona treatment or ozone treatment on the surface before the antistatic agent treatment.

The lid material of the present invention is a container of the shape shown in FIG. 2 obtained by blow-molding a polystyrene-based container or a high-density polyethylene resin, or a polystyrene-based resin or polypropylene-based resin sheet is subjected to heat treatment such as vacuum forming. It can be used as a lid for a container produced by molding.

For example, in the case of food container packaging, the draw-forming lid material of the present invention is supplied to a maker that manufactures food in the form of a laminated film or sheet rolled into a roll,
Then, after punching out in a circular shape, as shown in FIG. 3, using a molding machine, the molding lid (3) provided with a flat portion (31) of the shape of the container head and a skirt portion (32) having a fold is kept at room temperature. Is drawn and drawn. Then, it is covered with a container made of the thermoplastic resin composition such as polyethylene or polystyrene filled with the contents, heat-sealed and combined with the container to form a food package.

[0027]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. (Example 1) Styrene-butadiene copolymer resin
(Made by Denki Kagaku Kogyo, trade name: Denka Clearen 730
L, styrene content 75%, butadiene content 25%)
80 parts and 20 parts of polystyrene resin (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: G14L) are melt-kneaded using a twin-screw extruder to form compound pellets, and a φ40 mm extruder (L
/ D = 26) to form a film having a thickness of 150 μm. Further, a film for substrate layer was obtained by subjecting the laminate surface to corona treatment after film formation.

On the other hand, (a) styrene-butadiene block copolymer resin (commercial name: Denka Clearene, styrene content 80%, butadiene content 20%) manufactured by Denki Kagaku Kogyo Co., Ltd. (B) ethylene-butene-1 random copolymer (manufactured by Mitsui Chemicals, trade name: Toughmer A), (c) styrene-butadiene block copolymer (manufactured by JSR, trade name: STR resin, 40% styrene, butadiene) 60%), and (d) 40, 25, 25, 1 of impact-resistant polystyrene resin (manufactured by Toyo Styrene Co., trade name: Toyo Styrol HI-E6), respectively.
After blending so as to be 0%, the mixture was melt-kneaded at a temperature of 200 ° C. with a single-screw extruder (cylinder diameter 40 mm) to obtain compound pellets, and the single-screw extruder (cylinder diameter 40
mm), extrusion temperature 200 ° C, blow-up ratio 2.0
A film having a thickness of 30 μm was formed at a double speed and a take-up speed of 20 m / min. After forming the film, the laminate surface was subjected to corona treatment to obtain a seal layer film.

Next, using an extrusion laminator, the above-mentioned film for the base material layer is fed out from one side, and an isocyanate type two-pack type anchor coating agent (Takelac A97, trade name, manufactured by Takeda Yakuhin Kogyo Co., Ltd.) is applied to the corona treated surface by an anchor coater.
1, Takenate A3) was coated and dried, and the sealing layer film was fed from the other side, and a single screw extrusion laminator equipped with a T-die (cylinder diameter 65 mm).
The low density polyethylene resin (manufactured by Nippon Polychem Co., Ltd., trade name: Novatec LD) extruded at a temperature of 320 ° C. was extruded to a thickness of 20 μm and laminated to give a total thickness of 2
A lid material stock having a thickness of 00 μm was obtained.

Example 2 A polymerization vessel having an internal volume of 200 liters was charged with 70.4 kg of pure water and 30 parts of calcium phosphate tribasic.
After adding 0 g and stirring, styrene 64.6 kg, methyl methacrylate 15.4 kg, and benzoyl peroxide 267.2 g were added, and the mixture was sealed and reacted at 100 ° C. for 6 hours. After cooling this, it was neutralized, dehydrated and dried to obtain a copolymer resin (styrene content 78%, methyl methacrylate content 22%). 20 parts of the obtained resin and styrene-butadiene copolymer resin (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Denka Clearene 730L, styrene content 75
%, Butadiene content 25%) 80 parts by melt-kneading using a twin-screw extruder to form compound pellets, φ40 m
A film having a thickness of 150 μm was formed by an m extruder (L / D = 26). A film for the substrate layer was obtained by subjecting the laminate surface to corona treatment after film formation. Using this film, a lid material stock having a total thickness of 200 μm was obtained in the same manner as in Example 1.

Comparative Example 1 A styrene-butadiene copolymer resin (made by Denki Kagaku Kogyo Co., Ltd., trade name: Denka Clearene 730L, styrene content 75 as a base layer resin)
%, Butadiene content 25%) was used to obtain a raw lidstock material having a total thickness of 200 μm in the same manner as in Example 1.

(Comparative Example 2) The same procedure as in Example 1 was carried out except that the thickness of the base material layer was 40 μm and the thickness of the adhesive layer was 30 μm, to obtain a raw lidstock material having a total thickness of 100 μm. .

The tensile elastic moduli in the MD and TD directions of the films for the base material layers of Examples and Comparative Examples are JIS K7127.
In accordance with the above, the No. 4 test piece was used to measure with an Instron type tensile tester, and the measured values are shown in Table 1.

Next, the blanks of the lid material of the above-mentioned Examples and Comparative Examples are punched out, drawn, carried, generally used for filling a small beverage container, the lid is attached to the container (capping), and heat is applied. Evaluation was performed using a device for sealing (CH15 manufactured by Shikoku Kakoki Co., Ltd., changed to ultrasonic heating method). 1) Drawability: Drawability at room temperature is 24 mm in diameter,
When a lid having a skirt length of 5.5 mm was formed, the spread of the skirt tip was measured immediately after and 1 minute after that, and the spread was displayed from the diameter of the top surface. Further, the ratio (%) of the measured value immediately after to the top surface diameter is displayed. 2) Conveyance / capping property: It was evaluated whether the lid formed by drawing was conveyed smoothly without being clogged in the shooter and was properly attached to the container. The evaluation criteria are shown in Table 2.

Table 1 shows the evaluation results of the drawability and the transport / capping property. The lid materials produced according to the examples had good drawability and were also suitable for conveyance and capping. On the other hand, the lid materials of Comparative Example 1 and Comparative Example 2 were unusable because the strength of the waist, the drawability and the carrying / capping property were insufficient.

[0036]

[Table 1]

[0037]

[Table 2]

EFFECT OF THE INVENTION The lid material obtained by the present invention is a laminate of thermoplastic resin composition films which can be drawn by using a lid material which does not use aluminum foil, and the shape of the drawn shape hardly changes with time. The lid is obtained. This molding lid has excellent packaging suitability, and the molding lid peeled off from the container after using the container is an environmentally friendly packaging material that can be recovered as plastic or can be easily incinerated without leaving an incineration residue that does not incinerate. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a layer structure of a lid member of the present invention.

FIG. 2 is a schematic diagram showing a state in which the molding lid covers the head of the container.

FIG. 3 is a perspective view showing the shape of a draw-formed lid.

FIG. 4 is a schematic diagram showing the definition of the spread amount of the skirt portion of the draw-formed lid.

FIG. 5 is a cross-sectional view showing a layer structure of a commonly used draw forming lid member using an aluminum foil.

[Explanation of symbols]

1 lid material 11 Base material layer 12 Adhesive layer 13 Heat seal layer 2 containers 3 Molding lid 31 Molded lid top surface 32 Molded lid skirt 41 Molded lid top surface diameter 42 skirt diameter 51 aluminum foil 52 Anchor coat 53 print layer 54 overcoat 55 anchor coat 56 polyethylene film 57 Hot melt adhesive

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B32B 27/30 B32B 27/30 BF term (reference) 3E084 AA04 AA12 AA24 AA25 AB01 BA01 BA09 DA01 DC08 FA09 FD13 GB08 4F100 AK12A AK12B AK12J AK25A AK25J AK28A AK28J AK51G AK65B AK73B AL01A AL02B AL05A AL05B AR00B AT00A BA02 CB00 DA03 GB16 GB23 JL01 JL12B YY00A YY00B

Claims (4)

[Claims] 1. A laminated film comprising at least a base material layer and a heat-sealing layer, wherein the base material layer comprises a resin composition containing the following resin (A) and resin (B) as main components, and a composition ratio: A / (A + B) is 0.70 to 0.90 and the thickness ratio of the base material layer / laminated film is 0.50 to 0.
90 is a lid material for drawing. Resin (A): a copolymer resin having a chain of a styrene-based monomer (a) and a conjugated diene-based monomer (b) and having a composition ratio b / (a + b) of 0.20 to 0.26. (B): Polystyrene or a copolymer of acrylic monomer (c) and styrene monomer (d) 2. In the resin (B), the acrylic monomer (c) is methyl acrylate, and the composition ratio is c / (c +
The draw forming lid member according to claim 1, wherein d) is 0.25 or less. 3. A method for producing a lid, which comprises drawing the laminated film according to claim 1 or 2. 4. A food container package having a lid made of the lid material according to claim 1.