Heat-shrinkable multi-layer film

Abstract

The present invention provides a heat shrinkable multilayer film that has low density, excellent shrinkage properties, and high rigidity, is less likely to suffer delamination, and also has excellent transparency. The present invention relates to a heat shrinkable multilayer film, containing: front and back layers; and an interlayer, the front and back layers each containing 60 to 80% by weight of a cyclic olefin resin and 20 to 40% by weight of an ethylene resin, the interlayer containing 50 to 80% by weight of an olefin resin and 20 to 50% by weight of a plastic resin, the interlayer containing 35 to 70 mol % of a propylene component, 1 to 10 mol % of an ethylene component, and 1 to 10 mol % of a butene component, based on 100 mol % of resin components constituting the interlayer.

Claims

1. A heat shrinkable multilayer film, comprising: front and back layers; and an interlayer, the front and back layers each containing 60 to 80% by weight of a cyclic olefin resin and 20 to 40% by weight of an ethylene resin, the interlayer containing 50 to 80% by weight of an olefin resin and 20 to 50% by weight of a plastic resin, the interlayer containing 35 to 70 mol % of a propylene component, 1 to 10 mol % of an ethylene component, and 1 to 10 mol % of a butene component, based on 100 mol % of resin components constituting the interlayer, and the plastic resin being a petroleum resin, a terpene resin, a rosin resin, or a hydrogenated derivative thereof, the plastic resin not being an olefin resin.

2. The heat shrinkable multilayer film according to claim 1, wherein the ethylene resin constituting the front and back layers is a linear low-density polyethylene.

3. The heat shrinkable multilayer film according to claim 1, having a density of lower than 1,000 kg/m.sup.3.

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

Description

DESCRIPTION OF EMBODIMENTS

(1) Embodiments of the present inventions are described below in detail with reference to examples. The present invention is not limited to the examples.

Examples 1 to 15 and Comparative Examples 1 to 10

(2) As raw material resins for front and back layers and an interlayer, resins listed in Table 1 were mixed according to the proportions shown in Tables 2 and 3. Thus, mixed resins for front and back layers and an interlayer were obtained.

(3) The mixed resins for a front layer, an interlayer, and a back layer were melted in different extruders. The mixed resins for a front layer and a back layer were melted at a barrel temperature of 210 C. and the mixed resin for an interlayer was melted at a barrel temperature of 180 C. The melted resins were extruded from a T-die and cooled and solidified on cooled rolls at 30 C. to prepare an unstretched sheet. This sheet was stretched with a tenter stretching machine at 90 C. to five times in the TD to produce a film which had a total thickness of 50 m and in which the front layer, the interlayer, and the back layer had thicknesses of 8.35 m, 33.3 m, and 8.35 m, respectively.

(4) The amounts of a propylene component, an ethylene component, and a butene component in the resin for the interlayer were measured by a nuclear magnetic resonance method (NMR).

(5) (Evaluation)

(6) The heat shrinkable multilayer films obtained in the examples and comparative examples were evaluated for the following parameters. Tables 2 and 3 show the results.

(7) (1) Density

(8) The films obtained in the examples and comparative examples were cut into samples (size: MD 100 mmTD 100 mm) to give specimens. The density of each obtained specimen was measured with a densimeter (Alfa Mirage Co., Ltd., Electronic Densimeter MD-300S) using an ethanol solvent. The densities of ten specimens were measured for each of the films obtained in the examples and comparative examples. The average of the measurements was calculated and evaluated in accordance with the criteria below.

(9) (Good): a density of lower than 1,000 kg/m.sup.3

(10) x (Poor): a density of 1,000 kg/m.sup.3 or higher

(11) (2) Heat shrinkage

(12) The films obtained in the examples and comparative examples were cut into samples (size: MD 100 mmTD 100 mm) to give specimens. Each obtained specimen was immersed into 90 C. hot water for 10 seconds. Then, the heat shrinkable multilayer film was taken out and immersed in 15 C. water for five seconds. The heat shrinkage in the TD was determined by the formula below. For heat shrinkage, three specimens were measured for each of the examples and comparative examples and the average of the measurements was calculated.
Heat shrinkage (%)={(100L)/100}100 (L represents the length in the TD after shrinking)

(13) The obtained heat shrinkage was evaluated in accordance with the criteria below.

(14) (Good): 60% or higher

(15) x (Poor): lower than 60%

(16) (3) Young's Modulus

(17) The films obtained in the examples and comparative examples were cut into samples (size: MD 250 mmTD 5 mm) to give specimens. Each obtained specimen was measured using Strograph VE-1D (Toyo Seiki Seisakusho, Ltd.) by a method in conformity with ASTMD882. For Young's modulus, seven specimens were measured for each of the examples and comparative examples and the average of the measurements was calculated. The obtained Young's modulus was evaluated in accordance with the criteria below.

(18) (Good): 1.5 GPa or higher in the MD and 2.0 GPa or higher in the TD

(19) x (Poor): lower than 1.5 GPa in the MD or lower than 2.0 GPa in the TD

(20) (4) Natural Shrinkage

(21) The films obtained in the examples and comparative examples were cut into specimens (size: MD 100 mmTD 100 mm). Each obtained specimen was allowed to stand in a thermostat (Yamato Scientific Co., Ltd., IL-82) at an interior temperature of 40 C. for seven days. Then, the dimensional change in the TD was measured. For natural shrinkage, two specimens were measured for each of the examples and comparative examples and the average of the measurements was calculated. The obtained natural shrinkage was evaluated in accordance with the criteria below.

(22) (Good): lower than 3.0%

(23) x (Poor): 3.0% or higher

(24) (5) Tensile Elongation at Break

(25) The films obtained in the examples and comparative examples were cut into specimens (gauge length: 40 mm, width: 10 mm). Each obtained specimen was measured using Strograph VE-1D (Toyo Seiki Seisakusho, Ltd.) by a method in conformity with JISK-6732. The measurement atmosphere temperature was 5 C., and the test rate was 100 mm/min. For tensile elongation at break, five specimens were measured for each of the examples and comparative examples and the average of the measurements was calculated. The obtained tensile elongation at break was evaluated in accordance with the criteria below.

(26) (Good): 100% or higher

(27) x (Poor): The specimen was broken at lower than 100%.

(28) (6) Haze

(29) The films obtained in the examples and comparative examples were cut into specimens (size: 50 mm100 mm). Each obtained specimen was measured using a haze meter (Nippon Denshoku Industries Co., Ltd., NDH5000) by a method in conformity with JISK-7136. For haze, four specimens were measured for each of the examples and comparative examples and the average of the measurements was calculated. The obtained haze was evaluated in accordance with the criteria below.

(30) (Good): lower than 7.0%

(31) x (Poor): 7.0% or higher

(32) (7) Delamination Strength

(33) The films obtained in the examples and comparative examples were cut into strips (width: 10 mm). Each obtained specimen was measured with an adhesion and peeling resistance tester (Shinto Scientific Co., Ltd., HEIDON TYPE 17) for delamination strength between the front or back layer and the interlayer of the film. For delamination strength, four specimens were measured for each of the examples and comparative examples, and the average of the measurements was calculated. The obtained delamination strength was evaluated in accordance with the criteria below.

(34) (Good): 0.4 N/cm or higher

(35) x (Poor): lower than 0.4 N/cm

(36) TABLE-US-00001 TABLE 1 Glass Vicat Melting transition softening Density MFR (g/10 min) point temperature temperature Composition (kg/m.sup.3) 190 C. 230 C. ( C.) ( C.) ( C.) Front and back C0C1 Cyclic olefin resin (Ethylene-norbornene copolymer) 1010 5.5 65 layers LL1 Ethylene resin (C6 linear low-density polyethylene) 913 2.0 113 96 Interlayer PP1 Propylene resin (propylene-ethylene-butene random terpolymer, propylene: 91 mol %, ethylene: 921 5.5 130 115 3 mol %, butene: 6 mol %) PP2 Propylene resin (propylene-ethylene random 900 5.0 132 120 bipolymer, propylene: 93 mol %, ethylene: 7 mol %) HC1 Plastic resin (alicyclic hydrogenated petroleum resin, 999 125* number average molecular weight 750, refractive index 1.535 (20 C.)) TPE1 Olefin elastomer resin (propylene-butene random 900 3.0 7.0 75 67 bipolymer, propylene: 74 mol %, butene: 26 mol %) TPE2 Olefin elastomer resin (ethylene-butene random 885 3.6 6.7 72 55 bipolymer, ethylene: 82 mol %, butene: 18 mol %) *softening temperature ( C.)

(37) TABLE-US-00002 TABLE 2 Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8 Constitutional Front and back C0C1 70 70 70 70 70 70 70 70 resin layers LL1 30 30 30 30 30 30 30 30 (% by weight) Interlayer PP1 65 58 50 30 55 59 58 46 PP2 HC1 20 32 44 50 35 35 40 45 TPE1 15 10 6 10 9 TPE2 10 10 6 2 Interlayer composition (mol %) Propylene component 70 60 50 35 50 54 53 49 Ethylene component 2 2 2 9 10 6 3 1 Butene component 8 6 4 6 5 5 4 5 Evaluation Density Measured value (kg/m.sup.3) 930 938 951 970 944 948 951 955 Evaluation Heat shrinkage Measured value (%) 60 61 63 65 60 60 61 64 Evaluation Young's Measured value (GPa, MD) 1.5 1.5 1.6 1.6 1.5 1.5 1.6 1.6 modulus Measured value (GPa, TD) 2.0 2.0 2.1 2.1 2.0 2.0 2.1 2.1 Evaluation Natural Measured value (%) 2.8 2.7 2.6 2.6 2.8 2.7 2.6 2.5 shrinkage Evaluation Tensile elongation Measured value (%) 330 320 312 300 290 282 275 320 at break Evaluation Haze Measured value (%) 6.5 6.3 6.1 6.2 6.0 5.8 5.6 6.2 Evaluation Delamination Measured value (N/cm) 0.8 0.8 0.8 0.7 0.8 0.8 0.8 0.7 strength Evaluation Example Example Example Example Example Example Example 9 10 11 12 13 14 15 Constitutional Front and back C0C1 70 70 70 70 80 60 70 resin layers LL1 30 30 30 30 20 40 30 (% by weight) Interlayer PP1 49 50 30 20 54 54 PP2 20 35 50 HC1 26 35 45 45 40 40 40 TPE1 25 15 5 6 6 10 TPE2 Interlayer composition (mol %) Propylene component 63 56 50 51 53 53 54 Ethylene component 1 2 2 3 2 2 4 Butene component 10 7 3 1 5 5 3 Evaluation Density Measured value (kg/m.sup.3) 942 947 953 961 950 940 948 Evaluation Heat shrinkage Measured value (%) 63 62 62 61 63 60 61 Evaluation Young's Measured value (GPa, MD) 1.5 1.6 1.6 1.7 1.6 1.5 1.5 modulus Measured value (GPa, TD) 2.0 2.1 2.1 2.2 2.1 2.0 2.0 Evaluation Natural Measured value (%) 2.8 2.7 2.5 2.4 2.6 2.8 2.7 shrinkage Evaluation Tensile elongation Measured value (%) 300 285 278 270 280 320 340 at break Evaluation Haze Measured value (%) 6.0 5.9 5.7 5.6 5.2 6.5 6.5 Evaluation Delamination Measured value (N/cm) 0.8 0.8 0.7 0.7 0.6 0.8 0.7 strength Evaluation

(38) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Constitutional Front and back C0C1 70 70 70 70 70 resin layers LL1 30 30 30 30 30 (% by weight) Interlayer PP1 78 25 60 10 40 PP2 HC1 22 60 29 61 28 TPE1 15 29 32 TPE2 11 Interlayer composition (mol %) Propylene component 71 34 54 31 60 Ethylene component 2 1 11 0 1 Butene component 5 5 6 8 11 Evaluation Density Measured value (kg/m.sup.3) 939 1005 954 1010 941 Evaluation x x Heat Measured value (%) 55 61 56 62 58 shrinkage Evaluation x x x Young's Measured value (GPa, MD) 1.5 1.7 1.3 1.4 1.3 modulus Measured value (GPa, TD) 2.0 2.2 1.7 1.8 1.7 Evaluation x x x Natural Measured value (%) 2.7 2.8 3.2 3.2 3.5 shrinkage Evaluation x x x Tensile Measured value (%) 290 30 320 10 300 elongation at Evaluation x x break Haze Measured value (%) 5.1 7.5 8.7 8.7 8.5 Evaluation x x x x Delamination Measured value (N/cm) 0.7 0.2 0.8 0.1 0.7 strength Evaluation x x Comparative Comparative Comparative Comparative Comparative Example 6 Example 7 Example 8 Example 9 Example 10 Constitutional Front and back C0C1 70 85 55 70 70 resin layers LL1 30 15 45 30 30 (% by weight) Interlayer PP1 55 55 75 35 PP2 60 HC1 40 39 39 15 55 TPE1 6 6 10 TPE2 10 Interlayer composition (mol %) Propylene component 56 54 54 68 39 Ethylene component 4 2 2 10 1 Butene component 0 5 5 6 5 Evaluation Density Measured value (kg/m.sup.3) 980 960 952 945 1020 Evaluation x Heat Measured value (%) 54 63 55 56 62 shrinkage Evaluation x x x Young's Measured value (GPa, MD) 1.6 1.6 1.2 1.3 1.6 modulus Measured value (GPa, TD) 2.1 2.1 1.7 1.7 2.1 Evaluation x x Natural Measured value (%) 2.5 2.9 3.4 3.3 2.5 shrinkage Evaluation x x Tensile Measured value (%) 20 290 330 340 10 elongation at Evaluation x x break Haze Measured value (%) 6.5 5.1 7.2 6.3 7.2 Evaluation x x Delamination Measured value (N/cm) 0.2 0.3 0.7 0.8 0.1 strength Evaluation x x x

INDUSTRIAL APPLICABILITY

(39) The present invention provides a heat shrinkable multilayer film that has low density, excellent shrinkage properties, and high rigidity, as well as excellent adhesiveness and transparency.