JPH0429541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated structure, and more specifically, a laminated structure comprising a resin layer made of a saponified ethylene-vinyl acetate copolymer and a polyolefin resin having a modified ethylene copolymer resin or a modified ethylene copolymer resin. In a laminated structure comprising at least a layer, the modified ethylene copolymer resin has a density obtained by copolymerizing ethylene and α-olefin.
0.890~0.950g/cc, melt index 0.01~
50g/10 minutes, 100 ethylene copolymers with more than 0 to less than 0.15 vinyl groups per 1000 carbons
Part by weight: unsaturated carboxylic acid or its derivative
This relates to a laminated structure characterized by using a modified ethylene copolymer resin grafted with 0.01 to 20 parts by weight, and has various excellent properties such as resistance to gas permeation such as oxygen, carbon dioxide, and aroma, and mechanical properties. It has such characteristics that it can be used as a packaging material for food packaging films and food containers. 2. Description of the Related Art Conventionally, thermoplastic resins, particularly polyolefin resins, have been widely used as packaging materials for foods due to their excellent transparency, flexibility, and hygienic properties. However, polyolefin resins have a drawback in that they have high permeability to gases such as oxygen and carbon dioxide, and food products cannot be stored for long periods of time. On the other hand, a saponified ethylene-vinyl acetate copolymer is generally known as a resin having the lowest gas permeability. One example of a film that takes advantage of the mutual properties of these resins is a laminated film made of a combination of different types of polymers. For example, among the laminated films, examples of food packaging films that require excellent gas barrier properties and heat sealing properties include laminated films made of the aforementioned polyolefin resin and saponified ethylene-vinyl acetate copolymer. . However, these resins have poor thermal fusion bonding properties, have weak adhesion between the two, and cause delamination, making them very impractical. In order to improve the above drawbacks, methods have been proposed in which the two resins are laminated by interposing an adhesive or by surface treatment, but these methods require complicated processes and pose hygiene problems. There are various problems, such as the fact that the molding method is difficult to use, and the adoption of efficient molding methods such as coextrusion methods is restricted. In addition, attempts have been made to improve the adhesion to saponified ethylene-vinyl acetate copolymer using a modified polyolefin resin in which an unsaturated carboxylic acid is grafted onto a polyolefin resin, but the adhesive strength is still insufficient. Not yet. The present invention was made to solve the above-mentioned problems, and aims to provide a laminated structure with excellent adhesiveness, and ultimately achieves resistance to permeation of gases such as oxygen, carbon dioxide, and aroma, and mechanical It has a variety of excellent properties such as physical properties, and is preferably used as a packaging material for food packaging films or food containers. As a result of intensive studies in line with this objective, the present inventors have found that by using a modified ethylene copolymer selected from a specific ethylene copolymer resin, ethylene-
The present invention was achieved by discovering that a laminated structure having extremely strong adhesive strength can be formed with a saponified vinyl acetate copolymer. That is, the present invention provides a laminated structure comprising at least a resin layer made of a saponified ethylene-vinyl acetate copolymer and a layer of a modified ethylene copolymer resin or a polyolefin resin having a modified ethylene copolymer. Density obtained by copolymerizing ethylene and α-olefin as ethylene copolymer resin
0.890~0.950g/cc, melt index 0.01~
50g/10 minutes, 100 ethylene copolymers with more than 0 to less than 0.15 vinyl groups per 1000 carbons
Part by weight: unsaturated carboxylic acid or its derivative
A laminated structure characterized by using a modified ethylene copolymer resin grafted with 0.01 to 20 parts by weight. The ethylene-α-olefin copolymer (hereinafter simply referred to as ethylene copolymer) used in the present invention includes ethylene-propylene copolymer, ethylene-butene-1 copolymer, and ethylene-hexene-1 copolymer. , ethylene-octene-1 copolymer, ethylene-4/methyl/pentene-1 copolymer, or mixtures thereof, and copolymers of ethylene and α-olefin having 3 to 12 carbon atoms are particularly preferred. . The method for producing the ethylene-α-olefin copolymer is not particularly limited, and includes gas phase polymerization using high, medium, and low pressure methods, slurry polymerization, and solution polymerization. The above ethylene copolymer has a density of 0.890 to 0.950.
g/cc, preferably 0.91-0.94 g/cc, melt index 0.01-50 g/10 min, preferably 0.1
~20g/10min, and those having a specific range of more than 0 to 0.15 or less terminal vinyl groups per 1000 carbons are selected. If the density is less than 0.890 g/cc, moldability will be poor, while if it exceeds 0.950 g/cc, adhesiveness will deteriorate, which is not preferred. Furthermore, if the melt index (hereinafter simply referred to as M) is less than 0.01 g/10 minutes or more than 50 g/10 minutes, molding becomes difficult and both are unfavorable. Furthermore, if the number of terminal vinyl groups in the molecule of the ethylene copolymer exceeds 0.15 per 1000 carbons, intramolecular crosslinking occurs during modification, resulting in a significant decrease in M, which is undesirable. The unsaturated carboxylic acids or derivatives thereof of the present invention are monobasic acids such as acrylic acid, methacrylic acid, and methyl methacrylic acid, dibasic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and hymic acid, or these acids. anhydride, ester, amide,
Examples include imides and metal salts, and at least one of these is used, with maleic acid or maleic anhydride being particularly preferred. The amount of the unsaturated carboxylic acid or its derivative used is 0.01 parts by weight per 100 parts by weight of the ethylene copolymer.
~20 parts by weight, preferably 0.03 to 10 parts by weight.
The amount of the above unsaturated carboxylic acid or its derivative is
If the amount is less than 0.01 part by weight, the adhesiveness will decrease and the desired effect will not be obtained. Further, if the amount exceeds 20 parts by weight, the resin may become colored or gelatinized, causing generation of foreign matter, which is not preferable. The modified ethylene copolymer resin used in the present invention is obtained by grafting 0.01 to 20 parts by weight of an unsaturated carboxylic acid or a derivative thereof to 100 parts by weight of the above ethylene copolymer in the presence of an organic peroxide. , the modification is carried out by melt-mixing in an extruder or in a kneading machine such as a Banbury mixer, or by a method of modifying by melt-mixing in an extruder or a kneading machine such as a Banbury mixer, or by a method of modifying by melt-mixing in an extruder or a kneading machine such as a Banbury mixer, or by a method of modifying with benzene, xylene,
Methods such as heating and mixing in a solvent such as aromatic hydrocarbons such as toluene or aliphatic hydrocarbons such as hexane, heptane, octane, etc. are not particularly limited. It is preferable to do so. The above modified ethylene copolymer resin can be used by using the modified product as it is, or by adding a predetermined amount of the modified product to a polyolefin resin such as unmodified polyethylene or polypropylene or a compatible thermoplastic resin. Good too. The above blend may be either a dry blend or a melt blend. Examples of the organic peroxides include benzoyl peroxide, lauryl peroxide, azobisisobutyronitrile, dicumyl peroxide, t-butyl hydroperoxide, α,α'-bis(t-butylperoxydiisopropyl) Organic peroxides such as benzene, di-t-butyl peroxide, and 2,5-di(t-butylperoxy)hexyne are preferably used. The laminate structure of the present invention has a resin layer made of a saponified ethylene-vinyl acetate copolymer (hereinafter simply referred to as EVAL) and a resin layer made of the modified ethylene copolymer resin or a polyolefin resin containing the modified ethylene copolymer resin. It consists of at least one layer. The structure of the laminate of the present invention is as described above.
It includes a multilayer laminate consisting of a structure consisting of a modified polyolefin resin layer (hereinafter referred to as MPO) blended in a predetermined amount with other thermoplastic resins, such as EVAL.
Layer/MPE layer/PO layer, EVAL layer/MPO layer/PO
It includes various forms such as layers, MPE layer/EVAL layer/MPE layer/PO layer. The saponified ethylene-vinyl acetate copolymer in the present invention preferably has an ethylene content of 20 to 50 mol% and a degree of saponification of the vinyl acetate portion of 90 mol% or more. In addition, the above-mentioned thermoplastic resin is a copolymer of polyethylene and α-olefin produced by high-, medium-, and low-pressure methods,
Ethylene-vinyl acetate copolymer, polypropylene, copolymers of propylene and other α-olefins, polyolefin resins such as polybutene-1, poly4-methyl-pentene-1, polyvinyl chloride resins, polyvinylidene chloride resins Examples include resins, polyamide resins, polyester resins, polyvinyl alcohol resins, and mixtures thereof. The method for manufacturing the laminated structure of the present invention includes extrusion molding methods such as the multilayer inflation method and T-die method, in which resins melted in an extruder are joined at the tip of the die to form a laminated structure using a multilayer die. Other methods such as blow molding and injection molding are also applicable. The laminated structure of the present invention has mechanical strength, water resistance,
It has various properties such as moisture resistance, gas permeation resistance, and heat sealability, and is applied to films, sheets, tubes, containers (bottles), etc., and is used for foods, drugs, cosmetics, etc. that require particularly high barrier properties. It is useful as a packaging material in many fields. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 (Production of modified ethylene copolymer) Ethylene-butene-1 copolymer (density 0.921
g/cc, melt index 1.0 g/10 minutes, 0.09 terminal vinyl groups/10 ³ C) 0.3 parts by weight of maleic anhydride and 2,5 dimethyl, 2,5 di(tert-butyl peroxy) Hexin-3
0.05 part by weight was added, stirred and blended using a Henschel mixer, and the blend was heated at 230°C using an extruder.
A modified ethylene copolymer (MPE) was obtained by grafting with a residence time of 100 seconds. (Manufacture of laminate structure) Using an inflation molding machine, the MPE and ethylene-vinyl acetate saponified resin (trade name: EVAL ED-F, manufactured by Kuraray Co., Ltd., EVAL) are supplied to a multilayer die. They were combined and laminated at a temperature of 230°C in front of the die lip to form a two-layer injection film. The thickness of the laminated film (laminated structure) at that time is MPE70μ/
EVAL is 30μ. A test piece with a width of 25 mm was created from the above laminated film, and tested at an angle of 180 using a Tensilon method tensile tester.
The adhesive strength was defined as the interlayer peel strength when the film was pulled at a take-up speed of 50 mm/min, and the results are shown in Table 1. The terminal vinyl group in the molecule was determined by preparing a 6 mm thick sheet, measuring the absorbance at a wavelength of 11.03 μm using an infrared absorption spectrum, and using the following formula. pieces/1000C=Klog I. I×1/d where: d; Density of polyethylene; Thickness of sheet I. ;Base absorbance I;Characteristic absorption light intensity K;Constant (0.116 for wavelength 11.03μ) Example 2 Ethylene-propylene copolymer (density 0.922
g/cc, MI1.0g/10 min, terminal vinyl group 0.08/
A laminate structure was manufactured in the same manner as in Example 1 except that 10 ³ C) was used in place of the ethylene-butene-1 copolymer in Example 1, and the adhesive strength was measured in accordance with Example 1. The results are shown in Table 1. Example 3 In place of the ethylene-butene-1 copolymer of Example 1, ethylene-hexene-1 copolymer (density
0.912g/cc, MI1.0g/10min, terminal vinyl group 0.08
A laminated structure was manufactured in the same manner as in Example 1, except that 1/10 ³ C) was used, and the adhesive strength was measured in accordance with Example 1. The results are shown in Table 1. Example 4 30% by weight of MPE prepared in Example 1 was mixed with unmodified ethylene-butene-1 copolymer (density 0.921
g/cc, MI 0.25 g/10 min, terminal vinyl group 0.09/
A modified product (MPE+L-LDPE) containing 70% by weight of 10 ³ C) (hereinafter referred to as L-LDPE) was obtained. A laminated structure was produced using this modified product in the same manner as in Example 1, and the adhesive strength was measured in accordance with Example 1, and the results are shown in Table 1. Example 5 Low density polyethylene (density 0.922 g/cc, MI 0.25
g/10 minutes, trade name: Nisseki Rexron F102, manufactured by Nippon Petrochemicals Co., Ltd., to obtain a modified product (MPE+LDPE) in which 30% by weight of LDPE was mixed. Using this modified material, the same EVAL and LDPE (Nisseki Rexron F102) as in Example 1 were used, and a three-layer die was installed in an inflation machine, and EVAL/MPE+
Obtained a three-layer structure of LDPE/LDPE and EVAL/MPE
The adhesive strength between +LDPE was measured and the results are shown in Table 1. Comparative Example 1 In place of the ethylene-butene-1 copolymer of Example 1, an ethylene-propylene copolymer outside the range used in the present invention (density 0.918 g/cc, MI 55 g/10
An attempt was made to obtain a laminate in the same manner as in Example 1 using 0.07 terminal vinyl groups/10 ³ C), but MPE
was too soft to be molded. Comparative Example 2 Ethylene-butene-outside the range used in the present invention
1 copolymer (density 0.921g/cc, MI1g/10min,
A laminated structure was produced in the same manner as in Example 1 using 0.2 terminal vinyl groups/10 ³ C), and the adhesive strength was measured. The results are shown in Table 1. As a result, the adhesive strength is 0.5
It was low at Kg/2cm width. Comparative Example 3 A laminated structure was manufactured in the same manner as in Example 1 except that an ionomer resin (manufactured by Mitsui Polychemical Co., Ltd.) was used as the modified material, and the adhesive strength was measured and the results were reported in the first example.
Shown in the table. As a result, the adhesive strength was 0.3Kg/2cm
It was wide and low. 【table】

Claims (1)

[Scope of Claims] 1. A laminated structure comprising at least a resin layer made of a saponified ethylene-vinyl acetate copolymer and a layer of a modified ethylene copolymer resin or a polyolefin resin containing a modified ethylene copolymer resin. , the density obtained by copolymerizing ethylene and α-olefin as the modified ethylene copolymer resin
0.890~0.950g/cc, melt index 0.01~
50g/10 minutes, 100 ethylene copolymers with more than 0 to less than 0.15 vinyl groups per 1000 carbons
Part by weight: unsaturated carboxylic acid or its derivative
A laminated structure characterized by using a modified ethylene copolymer resin grafted with 0.01 to 20 parts by weight. 2 The ethylene copolymer is ethylene-butene-
1. The laminated structure according to claim 1, wherein the laminated structure is a copolymer. 3. The laminate structure according to claim 1 or 2, wherein the unsaturated carboxylic acid or its derivative is maleic anhydride.