Heat-shrinkable multilayer film and heat-shrinkable label

Abstract

The present invention provides a heat shrinkable multilayer film that makes it possible to produce a heat shrinkable label having high seal strength regardless of interlaminar strength, and that also has excellent transparency. The present invention also provides a heat shrinkable label including the heat shrinkable multilayer film. Provided is a heat shrinkable multilayer film including: front and back layers each containing a polyester resin; an interlayer containing a polystyrene resin; and adhesive layers, wherein the front and back layers and the interlayer are stacked with the adhesive layers interposed therebetween, and the adhesive layers each contain a polyester resin having a glass transition temperature of 77? C. or lower.

Claims

1. A heat shrinkable multilayer film comprising: front and back layers each containing a polyethyleneterephthalate resin; an interlayer containing a polystyrene resin; and adhesive layers, wherein the front and back layers and the interlayer are stacked with the adhesive layers interposed therebetween, and the adhesive layers each contain a polyester resin having a glass transition temperature of 65? C. or higher and 73? C. or lower, the adhesive layers each contain 4 to 45% by weight of a polystyrene resin, 49 to 93% by weight of the polyester resin, and 0.8 to 26% by weight of a polyester elastomer, the polyester resin constituting the adhesive layers contains a dicarboxylic acid component and a diol component, wherein the polyester resin constituting the adhesive layers contains 67 to 100 mol % of a component derived from terephthalic acid and 0 to 33 mol % of a component derived from isophthalic acid in 100 mol % of the dicarboxylic acid component, and contains 63 to 100 mol % of a component derived from ethylene glycol, 0 to 22 mol % of a component derived from diethylene glycol, and 0 to 20 mol % of a component derived from 1,4-cyclohexanedimethanol in 100 mol % of the diol component, the polystyrene resin constituting the adhesive layers is a styrene butadiene copolymer, wherein a styrene content in 100% by weight of the polystyrene resin constituting the adhesive layers is 50 to 98% by weight and a butadiene content in 100% by weight of the polystyrene resin constituting the adhesive layers is 2 to 50% by weight, and the polyester elastomer constituting the adhesive layers contains a polyester as a hard segment and a polyether as a soft segment.

2. A heat shrinkable label comprising the heat shrinkable multilayer film according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view of a solvent seal portion of a heat shrinkable label.

(2) FIG. 2 is a schematic view of a separation state of a solvent seal portion.

(3) FIG. 3 is a schematic view illustrating a film peel method in interlaminar strength evaluation.

(4) FIG. 4 is a schematic view illustrating a film peel method in interlaminar strength evaluation.

DESCRIPTION OF EMBODIMENTS

(5) The following will describe the present invention in detail referring to examples, but the present invention should not be limited to these examples.

(6) The materials used in examples and comparative examples are listed below.

(7) (Polyester Resin)

(8) PET-1: aromatic polyester copolymer (glass transition temperature 69? C.), containing 100 mol % of a component derived from terephthalic acid as a dicarboxylic acid component and containing 65 mol % of a component derived from ethylene glycol, 20 mol % of a component derived from diethylene glycol, and 15 mol % of a component derived from 1,4-cyclohexanedimethanol as diol components.

(9) PET-2: aromatic polyester copolymer (glass transition temperature 70? C.), containing 70 mol % of a component derived from terephthalic acid and 30 mol % of a component derived from isophthalic acid as dicarboxylic acid components, and containing 100 mol % of a component derived from ethylene glycol as a diol component.

(10) PET-3: aromatic polyester copolymer (glass transition temperature 72? C.), containing 100 mol % of a component derived from terephthalic acid as a dicarboxylic acid component and containing 70 mol % of a component derived from ethylene glycol, 10 mol % of a component derived from diethylene glycol, and 20 mol % of a component derived from 1,4-cyclohexanedimethanol as diol components.

(11) PET-4: aromatic polyester copolymer (glass transition temperature 82? C.), containing 100 mol % of a component derived from terephthalic acid as a dicarboxylic acid component and containing 70 mol % of a component derived from ethylene glycol and 30 mol % of a component derived from 1,4-cyclohexanedimethanol as diol components.

(12) (Polystyrene Resin)

(13) PS-1: styrene-butadiene block copolymer (styrene component 76% by weight, butadiene component 24% by weight, Vicat softening temperature 70? C., MFR 8 g/10 min)

(14) PS-2: styrene-butadiene block copolymer (styrene component 78% by weight, butadiene component 22% by weight, Vicat softening temperature 72? C., MFR 7 g/10 min)

(15) (Polyester Elastomer)

(16) TPE-1: non-modified polyester-polyether block copolymer containing a polyester as a hard segment and a polyether as a soft segment (produced by Du Pont-Toray Co., Ltd., Hytrel 2521, durometer hardness 55, glass transition temperature 45? C.)

Example 1

(17) An amount of 100% by weight of the polyester resin (PET-1) was used as a resin to constitute the front and back layers.

(18) An amount of 100% by weight of the polystyrene resin (PS-2) was used as a resin to constitute the interlayer.

(19) An amount of 75% by weight of the polyester resin (PET-1), 20% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as resins to constitute the adhesive layers.

(20) They were fed into extruders having a barrel temperature of 160? C. to 250? C., extruded into a five-layer sheet through a multilayer die at 250? C., and cooled and solidified on a take-up roll at 30? C. Subsequently, the sheet was stretched at stretching ratio of 6 times in a tenter stretching machine with a preheating zone set at 105? C., a stretching zone set at 90? C., and a heat setting zone set at 85? C., and then wound with a winder. Thus, a heat shrinkable multilayer film was obtained in which the direction perpendicular to the main shrinkage direction was the MD and the main shrinkage direction was the TD.

(21) The obtained heat shrinkable multilayer film had a total thickness of 40 ?m and had a five-layer structure (front or back layer (5.5 ?m)/adhesive layer (0.9 ?m)/interlayer (27.2 ?m)/adhesive layer (0.9 ?m)/front or back layer (5.5 ?m)).

Example 2

(22) An amount of 75% by weight of the polyester resin (PET-2), 20% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(23) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 3

(24) An amount of 75% by weight of the polyester resin (PET-3), 20% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(25) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 4

(26) An amount of 50% by weight of the polyester resin (PET-1), 45% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(27) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 5

(28) An amount of 90% by weight of the polyester resin (PET-1), 5% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(29) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 6

(30) An amount of 85% by weight of the polyester resin (PET-1), 10% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(31) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 7

(32) An amount of 79% by weight of the polyester resin (PET-1), 20% by weight of the polystyrene resin (PS-1), and 1% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(33) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 8

(34) An amount of 77% by weight of the polyester resin (PET-1), 20% by weight of the polystyrene resin (PS-1), and 3% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(35) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Example 9

(36) An amount of 55% by weight of the polyester resin (PET-1), 20% by weight of the polystyrene resin (PS-1), and 25% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(37) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

Comparative Example 1

(38) An amount of 75% by weight of the polyester resin (PET-4), 20% by weight of the polystyrene resin (PS-1), and 5% by weight of the polyester elastomer (TPE-1) were used as the resins to constitute the adhesive layers.

(39) Otherwise, the procedure was performed in the same manner as in Example 1, whereby a five layer-structure heat shrinkable multilayer film was obtained.

(40) (Evaluation)

(41) The heat shrinkable multilayer films obtained in the examples and the comparative examples were evaluated as follows. Table 1 shows the structures of the heat shrinkable multilayer films and the evaluation results.

(42) (1) Delamination Strength

(43) The heat shrinkable multilayer film was cut to a size of 100 mm in length?10 mm in width. The film was delaminated at part of a film end as shown in FIG. 3, followed by peeling in the 180? direction at a tensile speed of 200 mm/min as shown in FIG. 4 to measure the strength using Adhesion and Peeling Resistance Tester (HEIDON TYPE 17, produced by Shinto Scientific Co., Ltd.). Here, in each of the examples and comparative examples, the delamination strength was determined by measuring the delamination strength in TD and MD of four specimens and calculating the averages in TD and MD.

(44) (2) Seal Strength

(45) Two ends of the heat shrinkable multilayer film were bonded to each other using a solvent mixture of 100 parts by weight of 1,3-dioxolane and 30 parts by weight of cyclohexane. The 10-mm-wide area where the film ends were bonded, that is, a seal portion, was cut to a size of 100 mm in length?10 mm in width. The two adherends of the seal portion were partially peeled from each other, followed by peeling in the 180? direction at a tensile speed of 200 mm/min to measure the strength using Adhesion and Peeling Resistance Tester (HEIDON TYPE 17, produced by Shinto Scientific Co., Ltd.). Here, in each of the examples and comparative examples, the seal strength was determined by measuring the seal strength in TD of four specimens and calculating the average. The seal strength was evaluated in accordance with the following criteria.

(46) Good: The seal strength was 2.4 N/10 mm or greater.

(47) Poor: The seal strength was smaller than 2.4 N/10 mm.

(48) The relation of the seal strength with the delamination strength was evaluated in accordance with the following criteria.

(49) Good: The delamination strength in either TD or MD was 0.5 N/10 mm or smaller, and the seal strength was 2.4 N/10 mm or greater.

(50) Fair: The delamination strength in both TD and MD was greater than 0.5 N/10 mm, and the seal strength was 2.4 N/10 mm or greater.

(51) Poor: The seal strength was smaller than 2.4 N/10 mm.

(52) (3) Haze

(53) The haze of the obtained heat shrinkable multilayer film was measured using NDH 5000 (produced by Nippon Denshoku Industries Co., Ltd.) by a method in conformity with JIS K 7136, and evaluated in accordance with the following criteria.

(54) Good: The haze was smaller than 6%.

(55) Poor: The haze was 6% or greater.

(56) TABLE-US-00001 TABLE 1 Example Example Example Example Example 1 2 3 4 5 Constituent Front and Polyester resin PET-1 100 100 100 100 100 resin back layers (% by Interlayer Polystyrene resin PS-2 100 100 100 100 100 weight) Adhesive Polystyrene resin PS-1 20 20 20 45 5 layer Polyester elastomer TPE-1 5 5 5 5 5 Polyester resin PET-1 75 50 90 PET-2 75 PET-3 75 PET-4 Dicarboxylic Terephthalic acid 100 70 100 100 100 acid (mol %) Isophthalic acid 30 Diol (mol %) Ethylene glycol 65 100 70 65 65 Diethylene glycol 20 10 20 20 1.4- 15 20 15 15 Cyclohexanedimethanol Glass transition temperature (? C.) 69 70 72 69 69 Evaluation Delamination strength (N/10 mm) MD 0.9 0.9 0.4 0.8 0.3 TD 0.9 0.9 0.4 0.8 0.4 Seal strength (N/10 mm) N/10 mm 3.5 4.0 3.6 4.1 2.5 Evaluation Good Good Good Good Good Relation with delamination strength Fair Fair Good Fair Fair Haze (%) 4.2 4.8 4.9 5.5 4.2 Good Good Good Good Good Compar- Example Example Example Example ative 6 7 8 9 Example 1 Constituent Front and Polyester resin PET-1 100 100 100 100 100 resin back layers (% by Interlayer Polystyrene resin PS-2 100 100 100 100 100 weight) Adhesive Polystyrene resin PS-1 10 20 20 20 20 layer Polyester elastomer TPE-1 5 1 3 25 5 Polyester resin PET-1 85 79 77 55 PET-2 PET-3 PET-4 75 Dicarboxylic Terephthalic acid 100 100 100 100 100 acid (mol %) Isophthalic acid Diol (mol %) Ethylene glycol 65 65 65 65 70 Diethylene glycol 20 20 20 20 1.4- 15 15 15 15 30 Cyclohexanedimethanol Glass transition temperature (? C.) 69 69 69 69 82 Evaluation Delamination strength (N/10 mm) MD 0.8 0.4 0.8 1.0 0.4 TD 0.8 0.8 0.8 1.0 0.3 Seal strength (N/10 mm) N/10 mm 4.1 2.4 3.2 4.5 2.3 Evaluation Good Good Good Good Poor Relation with delamination strength Fair Good Fair Fair Poor Haze (%) 4.6 4.5 4.1 5.6 5.5 Good Good Good Good Good

INDUSTRIAL APPLICABILITY

(57) The present invention can provide a heat shrinkable multilayer film that makes it possible to produce a heat shrinkable label having high seal strength regardless of interlaminar strength, and that also has excellent transparency. The present invention can also provide a heat shrinkable label including the heat shrinkable multilayer film.

REFERENCE SIGNS LIST

(58) 1 front or back layer 2 interlayer 3 adhesive layer