JP2005288793A - Easily peelable composite film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high barrier lid material having good easy peelability to a bottom material having a seal layer of a resin layer, especially a polypropylene resin layer. <P>SOLUTION: In an easily peelable coextrusion composite film, a saponified ethylene-vinyl acetate copolymer layer, a polyamide resin layer, an adhesive resin layer, and the polypropylene resin layer (intermediate layer) are laminated in turn, and a resin layer (layer A) of a blend comprising a linear low density polyethylene resin and an amorphous or low-crystalline ethylene-α-olefin copolymer and the layer (layer B) of polypropylene resin polymerized by using a single site catalyst of 120-140°C melting point are formed in turn on the side of the polypropylene resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to an easily openable composite film that can be suitably used mainly for gas packaging lids or cup jelly lids in the food packaging field, and in particular, a bottom material having a sealing layer made of a polypropylene resin layer. In contrast, the present invention provides a high barrier lid material having good easy peel properties.

  Conventionally, as an easy peel material for polypropylene resin, (1) a so-called cohesive failure type which peels by cohesive failure using a blend layer of polypropylene resin and polyethylene resin or polystyrene resin as a seal layer, (2) adjacent to the polypropylene layer And (3) polypropylene resin / blend layer / polypropylene resin (seal side) are laminated in this order, and polypropylene resin and polyethylene resin or Furthermore, a blend of olefin copolymer rubber is used, and a type in which the blend layer is cohesive to break or peeled between the blend layer and the polypropylene resin layer is used.

  In patent document 1, this inventor has previously proposed as an easily openable composite film. According to this, on the polypropylene resin side of the laminated film (layer A), a resin layer composed of a linear low-density polyethylene resin and an amorphous or low-crystalline ethylene-α-olefin copolymer (layer B): ethylene-propylene A laminate layer of a resin layer made of a copolymer or an ethylene-propylene random copolymer and an amorphous or low crystalline ethylene-α olefin copolymer has been proposed.

Although the easy peel property of the easy peel layer is considerably improved in this laminated layer, the peeled portion occurs at two places between the polypropylene resin layer- (A) layer and the (A) layer- (B) layer, so that the peel surface is uniform. In addition, the peeled surface cannot be obtained with a clean surface. In the present invention, the strength is stable, uniform peeling occurs, and it is required to be usable without causing discomfort to the user when it is used as it is on a clean peeling surface as it is. It aims at improving.
Japanese Patent Laid-Open No. 11-34245

  With regard to the above configuration, (1) has poor transparency, and in particular for gas packs, the inside becomes invisible due to the unevenness of the sealing surface. Since (2) is an interfacial peeling type, the strength is not stable. (3) has a problem that the blend layer is a polypropylene resin and a polyethylene resin, resulting in a sea-island shape and poor transparency. Since (1) to (3) are usually supplied as a laminate raw material having almost no oxygen barrier property, lamination with a barrier material is indispensable. Propylene resin is mainly used for this laminate surface, and corona treatment is performed to improve adhesion, and there is a problem that the laminate strength is not stable because it is easily affected by moisture during the storage period.

  Accordingly, an object of the present invention is to provide an easy-open composite film that has transparency, easy peel strength stability, oxygen barrier properties, and laminate suitability, and is particularly excellent in easy peel properties with a polypropylene resin layer.

  The present invention has found an easy-open composite film capable of solving the above-mentioned problems, and the above object is achieved by the following means.

  That is, in the present invention, a saponified ethylene vinyl acetate copolymer layer, a polyamide resin layer, an adhesive resin layer and a polypropylene resin layer are sequentially laminated, and further on the polypropylene resin side (A layer): linear low density polyethylene resin And a resin layer composed of a blend of an amorphous or low crystalline ethylene-α-olefin copolymer and (B layer): a polypropylene resin layer polymerized using a single-site catalyst having a melting point of 120 to 140 ° C. It proposes an easy-open coextruded composite film characterized by being provided. Here, the total thickness of the (A) layer and the (B) layer is 2 to 20 μm, and the intermediate layer polypropylene resin layer is a propylene homopolymer or a propylene-ethylene random copolymer having a melting point of 150 to 165 ° C. Anti-fogging agent was kneaded into the layer on the seal layer side (any one of the three layers from the seal layer including the intermediate polypropylene) to impart anti-fogging properties, and easy peel strength was 2.9 to 14.7 N / 15 mm width That the polyamide resin layer is 6 nylon or 6-66 copolymer nylon, and the interlayer adhesive strength of the ethylene vinyl acetate copolymer saponified material layer, the polyamide resin layer, the adhesive resin layer and the polypropylene resin layer is 5. 9N / 15mm width or more or non-peelable, printed on the easy-open coextruded composite film or plain biaxially stretched It was dry laminated ethylene terephthalate film includes that were dry laminated printed or plain biaxially oriented polyamide film to the easy-open coextruded composite film.

  Hereinafter, the present invention will be described in more detail.

  The ethylene vinyl acetate copolymer saponified resin (hereinafter referred to as “EVOH”) used in the present invention has an ethylene content of 29 to 47 mol% and a saponification degree of 95% or more, and is required to have a thickness. It can be set arbitrarily according to the sex. If the ethylene content of EVOH is less than 29 mol%, there is a problem that co-extrusion with the polyamide resin layer becomes difficult from the viewpoint of heat resistance, and if it exceeds 47 mol%, there is a problem that oxygen barrier properties are insufficient. If the EVOH saponification degree is less than 95%, the oxygen barrier property tends to be insufficient.

  As the polyamide resin (hereinafter referred to as “Ny”), 6-nylon, 6-66 nylon, 11 nylon, 12 nylon, 6-12 nylon, 610 nylon, 66 nylon, 6I-6T nylon and blends thereof are used. However, 6 nylon and 6-66 nylon are preferable from the viewpoint of interlayer adhesion strength with EVOH.

  The adhesive resin (hereinafter referred to as “AD”) is not particularly limited as long as it adheres Ny and polypropylene resin (hereinafter referred to as “PP”) with a required strength, but is modified with an unsaturated carboxylic acid or a derivative thereof. Such an unsaturated carboxylic acid is preferably used, and examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and citraconic acid. In addition, these unsaturated carboxylic acid esters and anhydrides such as maleic anhydride can also be used, and as derivatives, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, acetic acid Vinyl, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, sodium acrylate, or the like can be used. In addition, as the polyolefin resin, polyethylene, polypropylene, polybutene, and copolymers thereof, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, and the like can be used. For example, the product name Admer manufactured by Mitsui Chemicals, Inc. is commercially available and is preferably used.

  The intermediate PP resin may be a propylene homopolymer or a propylene-ethylene random copolymer having a melting point of 150 to 165 ° C. From the viewpoint of peelability from the layer (A) described below, homo PP having a firmer waist is preferred. If PP that is too soft is used, PP peels and the easy peel strength is not stable during peeling.

  Next, a resin layer (hereinafter referred to as (A) layer) comprising a blend of a linear low density polyethylene (hereinafter referred to as “LL-DPE”) and an amorphous or low crystalline ethylene-α-olefin copolymer. )) Is usually in the range of 30:70 to 90:10. If the ratio of LL-DPE is less than 30%, the peel strength with PP tends to be too strong. Conversely, if it exceeds 90%, the peel strength tends to be too weak, which is not preferable. As the α-olefin component of the amorphous or low-crystalline ethylene-α-olefin copolymer, a type mainly using propylene and butene is common, but there is no particular limitation.

  In addition, the third component may be added to the layer (A) to adjust the easy peel strength. For example, when LL-DPE is added, the easy peel strength can be reduced.

  The use of a polypropylene resin layer (hereinafter referred to as (B) layer) polymerized with a single-site catalyst having a melting point of 120 to 140 ° C. on the surface of the seal layer is more than the interlayer adhesive strength of PP / (A). This is because it is necessary to increase the interlayer adhesive strength between (A) / (B).

  Propylene polymerization catalysts have been conventionally polymerized using heterogeneous natta catalysts represented by titanium chloride and organoaluminum compounds, and are still used in large quantities industrially. Recently, a homogeneous catalyst composed of an organic transition metal compound typified by a metallocene compound and an aluminoxane has been developed, and this type of catalyst is called a single site catalyst.

  In the conventional heterogeneous catalyst, the active site of polymerization is not uniform. For this reason, for example, in the case of a copolymer of propylene and ethylene, the composition of the copolymer becomes heterogeneous. A rubber-like or grease-like polymer copolymerized with a large amount of ethylene is formed, and a uniform copolymer cannot be obtained.

  On the other hand, the homogeneous single-site catalyst has a uniform active site of the catalyst, and when propylene-ethylene is copolymerized, a uniform copolymer can be obtained depending on the mixing ratio. Therefore, the melting point of the copolymer depends on the mixing ratio of ethylene. It can be adjusted freely. Accordingly, focusing on the melting point of the copolymer, it is considered that the two heeled catalyst systems exhibit completely different behavior with respect to melting, and therefore the seat heel of the present invention exhibits different behavior.

  When co-extruded, (A) based on LL-DPE resin has better adhesion to (B) than intermediate PP, so peels between (A) / (B) when opened with easy peel Peeling is constantly performed between layers of PP / (A) without being performed, and the easy peel property is stabilized. JP-A-11-34245 uses a resin layer made of an ethylene-propylene random copolymer or a blend of an ethylene-propylene random copolymer and an amorphous or low-crystalline ethylene-α-olefin copolymer as a seal layer. However, in the case of using the layer (B) of the present invention practically in view of the stability of the adhesive strength with the layer (A), the hot tack property at the time of sealing, the contaminant sealing property, and the low temperature sealing property. Is much better.

  The total thickness of (A) + (B) is preferably 2 to 20 μm (more preferably 4 to 10 μm), and if it is less than 2 μm, the seal becomes unstable, and if it exceeds 20 μm, when opening after sealing (A) There is a possibility that the + (B) layer is not cut and a film remaining phenomenon occurs. Further, an antifogging agent can be kneaded into one or more layers of PP, (A), and (B) for gas packs to impart antifogging properties.

  As a cover material for a gas pack of a composite film having the above-described structure, it is generally difficult to seal a coextruded film alone in terms of heat resistance, and it is necessary to bond it to a biaxially stretched film in order to stabilize peeling. Examples of the biaxially stretched film include a stretched nylon film (hereinafter referred to as “ONy”), a stretched polypropylene film (hereinafter referred to as “OPP”), and a polyethylene terephthalate film (hereinafter referred to as “PET”). From the viewpoint of stability and printing pitch stability, those obtained by bonding a PET film and an ONy film are preferable. In particular, it is preferable to select PET when emphasizing printing pitch accuracy, and to select ONy when emphasizing the tension of the lid material after boiling the packed product. In addition, as the bottom material for gas pack deep drawing, PP, amorphous PET, polycarbonate (hereinafter referred to as “PC”), polystyrene (hereinafter referred to as “PS”), high impact polystyrene (hereinafter referred to as “HIPS”). Etc.) can also be used together.

  Further, the coextruded film of the present invention is characterized in that EVOH / Ny / AD / PP is further laminated in the order of (A) layer and (B) layer to thereby provide EVOH / Ny interlayer strength and Ny / AD interlayer. The strength can be made stronger than, for example, stacking in the order of EVOH / AD. It is preferable that the interlayer adhesion strength of EVOH, Ny, AD and PP is 5.9 N / 15 mm width or more, respectively, or cannot be peeled off. If the width is 5.9 N / 15 mm or less, peeling may occur in layers other than PP / (A) at the time of opening with easy peel, which is not preferable. In addition, EVOH has good suitability for dry lamination even without corona treatment, and thus enables strong adhesion to other substrates. Therefore, a smooth easy peel is possible without any peeling except for PP / (A).

  When a high-barrier base material is bonded to a conventional non-barrier composite film, there is generally a problem of insufficient delamination on the K-coating (polyvinylidene chloride coating) surface or transparent deposition surface, which is relatively easy for gas packs in particular. In a package having high peel strength, peeling occurs between other layers during easy peeling, and smooth opening cannot be performed.

  In the case of a deep-drawn gas pack, an easy peel strength is suitably 2.9 to 14.7 N / 15 mm width, preferably 4.9 to 11.8 N / 15 mm width. The interlayer strength between PP / (A) can be adjusted.

  Easy peel strength is measured by cutting a seal part when heat-sealed with a 500 μm PP single-layer sheet at the optimum sealing temperature into a strip of 15 mm width, and peeling off with a tensile tester at a tensile strength of 200 mm / min. It measures the strength of the.

  Moreover, since Ny is arranged in the coextruded film in the product of the present invention, the pinhole resistance is better as compared with a normal biaxially stretched product using a PP-based easy peel material.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

  The films of Examples 1 to 3 and Comparative Examples 1 to 5 were formed by the coextrusion method or a combination of the coextrusion method and the dry laminating method, and evaluated. (/ Is co-extrusion, // is dry lamination) The numerical values in the following examples indicate the layer thickness in μm.

(Example 1)
PET // EVOH / Ny / AD / PP / (A) / (B)
16 10 15 5 32 5 3
PET: Diafoil H500 (Brand name: Biaxially stretched product manufactured by Mitsubishi Chemical Polyester Film)
EVOH: ethylene content 38 mol% type Ny: 66-66 copolymer Ny with 66 nylon ratio 15%
AD: ADMER QF551 (trade name: manufactured by Mitsui Chemicals)
PP: Homo PP (melting point 164 ° C.)
(A): C4 type LL-DPE (82%)
Toughmer A4085 (trade name: manufactured by Mitsui Chemicals) (18%)
(B): Wintech WFX4T (trade name: manufactured by Nippon Polypro Co., Ltd.)

(Example 2)
PET // EVOH / Ny / AD / PP / (A) / (B)
12 20 10 10 22 3 5
PET: Diafoil H500 (Biaxially stretched product manufactured by Mitsubishi Chemical Polyester Film)
EVOH: ethylene content 44 mol% type Ny: 6 nylon AD: Admer QF551 (Mitsui Chemicals)
PP: PP of random copolymer type with ethylene (melting point 155 ° C.)
(A): C6 type LL-DPE (85)
Toughmer P0680 (trade name: manufactured by Mitsui Chemicals) (15)
(B): Wintech WFX4T

(Example 3)
ONy // EVOH / Ny / AD / PP / (A) / (B)
25 10 15 5 32 5 3
ONy: Santo Neil SNR (manufactured by Mitsubishi Plastics, Inc., biaxially stretched polyamide film)
EVOH: ethylene content 38 mol% type Ny: 66-66 copolymer Ny with 66% nylon ratio 15%
AD: ADMER QF551 (Mitsui Chemicals)
PP: Homo PP (melting point 164 ° C.)
(A): C4 type LL (82)
Toughmer A4085 (Mitsui Chemicals) (18)
(B): Wintech WFX4T

(Comparative Example 1)
PET // Transparent deposition PET // PP1 / (PP2 + PE)
16 12 45 5
PP1: Homo PP (melting point 164 ° C.)
(PP2 + PE) ---- Cohesive failure layer
PP2: ethylene-propylene random copolymer (melting point 145 ° C.) (70)
PE: Low density polyethylene (30)

(Comparative Example 2)
PET // transparent deposited PET // PP / low crystalline polyolefin 16 12 45 5
PP: Homo PP (melting point 164 ° C.)
Low crystalline polyolefin: ethylene-butene 1 copolymer

(Comparative Example 3)
PET // Transparent deposition PET // PP1 / Blend resin / PP2
16 12 40 5 5
PP1: Homo PP (melting point 164 ° C.)
Blend resin: ethylene-propylene random copolymer (melting point 145 ° C.) (48)
LDPE (50)
Toughmer P0680 (2)
PP2: ethylene-propylene random copolymer (melting point 145 ° C.)

(Comparative Example 4)
PET // EVOH / Ny / AD / PP / (A) / (B)
16 10 15 5 32 5 3
PET: Diafoil H500 (Biaxially stretched product manufactured by Mitsubishi Chemical Polyester Film)
EVOH: ethylene content 38 mol% type Ny: 66-66 copolymer Ny with 66 nylon ratio 15%
AD: ADMER QF551 (Mitsui Chemicals)
PP: Homo PP (melting point 164 ° C.)
(A): C4 type LL (82)
Toughmer A4085 (Mitsui Chemicals) (18)
(B): ethylene-propylene random copolymer (melting point 145 ° C.)

(Comparative Example 5)
PET // Ny / EVOH / AD / PP / (A) / (B)
16 15 10 5 32 5 3
PET: Diafoil H500 (Biaxially stretched product manufactured by Mitsubishi Chemical Polyester Film)
EVOH: ethylene content 38 mol% type Ny: 66-66 copolymer Ny with 66 nylon ratio 15%
AD: ADMER QF551 (Mitsui Chemicals)
PP: Homo PP (melting point 164 ° C.)
(A): C4 type LL (82)
Toughmer A4085 (Mitsui Chemicals) (18)
(B): Wintech WFX4T

<Evaluation method>
The packs obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were evaluated for transparency, sealing properties, film residue, and interlayer strength by the following methods, and the results are shown in the table.

  A pack product was produced with a deep-drawing packaging machine R530 (manufactured by Multi-Back) and evaluated.

Bottom material sheet: PP / AD / EVOH / AD / PP (PP melting point: 160 ° C.)
230 20 30 20 200
Molding temperature: 160 ° C
Sealing temperature: optional Size of packed product: Vertical 170mm x Horizontal 127mm rectangle Seal width: 5mm width frame seal / Transparency A haze of 8% or less obtained by measuring the original sheet of the lid material film with a spectrophotometer (○), and more than 8% was (×).
-Seal start temperature The seal temperature was increased from 120 ° C in increments of 10 ° C, and the minimum seal temperature at which sealing could be performed was confirmed.
・ Easy peel strength stability Sealing is performed at the optimum seal temperature (guideline: seal start temperature + 20 ° C), 10 points of easy peel strength are measured, and strength fluctuation is less than ± 50% of the average value. (◯) and those exceeding ± 50% were defined as (×).
・ Easy peel stability When the lid is peeled off, only the target part (interlayer or cohesive failure layer) is peeled off (○), and when the target part is peeled off (×) did.
Interlaminar strength When the lid was peeled off, it was peeled off between layers of normal easy peel (○), and peeled completely other than normal easy peel between layers (×), partially occurred The thing was made into ((triangle | delta)).

  The experimental results are shown in Table 1. In the examples of the present application, it was confirmed that the seal portion was peeled cleanly.

Claims (10)

  A saponified ethylene vinyl acetate copolymer layer, a polyamide resin layer, an adhesive resin layer and a polypropylene resin layer (referred to as an intermediate layer) are sequentially laminated, and further on the polypropylene resin side (A layer): linear low density polyethylene resin And a resin layer composed of a blend of an amorphous or low crystalline ethylene-α-olefin copolymer (layer B): a polypropylene resin layer polymerized using a single site catalyst having a melting point of 120 to 140 ° C. An easy-open coextruded composite film characterized by being sequentially provided.   The easy-open coextruded composite film according to claim 1, wherein the total thickness of the (A) layer and the (B) layer is 2 to 20 μm.   The easy-open coextruded composite film according to claim 1, wherein the intermediate layer polypropylene resin layer is a propylene homopolymer.   The easy-open coextruded composite film according to claim 1, wherein the intermediate layer polypropylene resin layer is a propylene-ethylene random copolymer having a melting point of 150 to 165 ° C.   2. The easy-open coextruded composite according to claim 1, wherein an antifogging agent is kneaded into a layer on the seal layer side (any one of three layers including the intermediate polypropylene from the seal layer) to impart antifogging properties. the film.   The easy-open coextruded composite film according to claim 1, having an easy peel strength of 2.9 to 14.7 N / 15 mm width.   The easy-open coextruded composite film according to claim 1, wherein the polyamide resin layer is 6 nylon or 6-66 copolymer nylon.   The easy adhesion according to claim 1, wherein the saponified ethylene vinyl acetate copolymer layer, the polyamide resin layer, the adhesive resin layer, and the polypropylene resin layer each have an interlaminar adhesive strength of 5.9 N / 15 mm width or more and cannot be peeled off. Openable coextruded composite film.   An easy-open composite film printed on the easy-open coextruded composite film or dry laminated with a plain biaxially stretched polyethylene terephthalate film.   An easy-open composite film, wherein the easy-open coextruded composite film is printed or plain laminated with a plain biaxially stretched polyamide film.