Heat-shrinkable multilayer film and heat-shrinkable label

Abstract

The present invention provides a heat shrinkable multilayer film that can prevent wrinkles or loosening after attachment when the film is attached to a container as a heat shrinkable label for dry heat shrinking, and a heat shrinkable label including the heat shrinkable multilayer film as a base film. Provided is a heat shrinkable multilayer film including: front and back layers each containing a polyester resin; and an interlayer containing a polystyrene resin, wherein the heat shrinkable multilayer film has a dimensional change in a TD represented by an equation (1) of −55 to −1000 μm as measured by thermomechanical analysis (TMA) in which the temperature of the heat shrinkable multilayer film under a load of 0.10 N is increased from 30° C. to 60° C. at a temperature increase rate of 5° C./min and then cooled from 60° C. to 10° C. at a temperature decrease rate of 5° C./min, the equation (1) being: Dimensional change=dimension in TD at 20° C. −dimension in TD at 60° C. (1).

Claims

1. A heat shrinkable multilayer film comprising: front and back layers each containing a polyester resin; an interlayer containing a polystyrene resin; a first adhesive layer between the front layer and the interlayer; and a second adhesive layer between the back layer and the interlayer, wherein the interlayer contains a polystyrene resin (A) having a Vicat softening temperature of 80° C. or higher in an amount of 10 to 50% by weight and a polystyrene resin (B) having a Vicat softening temperature of lower than 80° C. in an amount of 50 to 90% by weight, all of the polystyrene resin constituting the interlayer is an aromatic vinyl hydrocarbon-conjugated diene copolymer, each of the first and the second adhesive layers consists of at least one polyester elastomer, the heat shrinkable multilayer film has a dimensional change in a main shrinkage direction (TD) represented by an equation (1) of −55 to −1000 μm as measured, using a sample of the heat shrinkable multilayer film cut to a measurement reference length of 16 mm, by thermomechanical analysis (TMA) in which the temperature of the heat shrinkable multilayer film under a load of 0.10 N is increased from 30° C. to 60° C. at a temperature increase rate of 5° C./min and then cooled from 60° C. to 10° C. at a temperature decrease rate of 5° C./min, and a proportion of the dimensional change to the measurement reference length (the dimensional change/the measurement reference length×100) of 0.34 to 6.9%, wherein the equation (1) is: Dimensional change=dimension in TD at 20° C. −dimension in TD at 60° C. (1).

2. The heat shrinkable multilayer film according to claim 1, wherein the polystyrene resin (A) and the polystyrene resin (B) have a difference in Vicat softening temperature of 10° C. to 25° C.

3. The heat shrinkable multilayer film according to claim 1, wherein a ratio of a total thickness of the front and back layers to a thickness of the interlayer (total thickness of front and back layers/thickness of interlayer) is 0.17 to 0.50.

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

Description

DESCRIPTION OF EMBODIMENTS

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

(2) The following materials were used in examples and comparative examples.

(3) (Polyester Resin)

(4) Polyester resin A: polyester resin (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

(5) Polyester resin B: polyester resin (melting point 223° C.) containing 100 mol % of terephthalic acid as a dicarboxylic acid component and containing 100 mol % of a component derived from 1,4-butanediol as a diol component

(6) Polyester resin C: polyester resin (melting point 170° C.) containing 70 mol % of terephthalic acid and 30 mol % of isophthalic acid as dicarboxylic acid components and containing 100 mol % of a component derived from 1,4-butanediol as a diol component

(7) (Polystyrene Resin)

(8) Polystyrene resin A: styrene-butadiene copolymer (styrene 81.3% by weight, butadiene 18.7% by weight, Vicat softening temperature 81° C.)

(9) Polystyrene resin B: styrene-butadiene copolymer (styrene 79% by weight, butadiene 21% by weight, Vicat softening temperature 59° C.)

(10) Polystyrene resin C: styrene-butadiene copolymer (styrene 77.7% by weight, butadiene 22.3% by weight, Vicat softening temperature 71° C.)

(11) Polystyrene resin D: styrene-butadiene copolymer (styrene 72% by weight, butadiene 28% by weight, Vicat softening temperature 76° C.)

(12) Polystyrene resin E: styrene-butadiene copolymer (styrene 80% by weight, butadiene 20% by weight, Vicat softening temperature 74° C.) Polystyrene resin F: styrene-butadiene copolymer (styrene 82% by weight, butadiene 18% by weight, Vicat softening temperature 75° C.)

(13) Polystyrene resin G: styrene-butadiene copolymer (styrene 82% by weight, butadiene 18% by weight, Vicat softening temperature 76° C.)

(14) (Polyester Elastomer)

(15) Polyester elastomer A: 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)

(16) Polyester elastomer B: modified polyester-polyether block copolymer elastomer containing a polyester as a hard segment and a polyether as a soft segment (produced by Mitsubishi Chemical Corporation, PRIMALLOY AP, durometer hardness 40)

(17) (Polystyrene Elastomer)

(18) Polystyrene elastomer: styrene-butadiene block copolymer (styrene 40% by weight, butadiene 60% by weight, Vicat softening temperature 76° C.)

Example 1

(19) Polyester resin A was used as a resin to constitute the front and back layers.

(20) A mixed resin containing 50% by weight of polystyrene resin A and 50% by weight of polystyrene resin B was used as a resin to constitute the interlayer.

(21) A mixed resin containing 59% by weight of polyester resin A, 10% by weight of polyester resin C, and 31% by weight of polystyrene resin D was used as a resin to constitute the adhesive layers.

(22) These resins 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.

(23) The obtained heat shrinkable multilayer film had a total thickness of 50 μm and had a five-layer structure (front or back layer (7 μm)/adhesive layer (1 μm)/interlayer (34 μm)/adhesive layer (1 μm)/front or back layer (7 μm)).

Example 2

(24) Polyester resin A was used as a resin to constitute the front and back layers.

(25) A mixed resin containing 30% by weight of polystyrene resin A and 70% by weight of polystyrene resin C was used as a resin to constitute the interlayer.

(26) A mixed resin containing 65% by weight of polyester elastomer A and 35% by weight of polystyrene resin D was used as a resin to constitute the adhesive layers.

(27) These resins 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.

(28) The obtained heat shrinkable multilayer film had a total thickness of 50 μm and had a five-layer structure (front or back layer (7 μm)/adhesive layer (1 μm)/interlayer (34 μm)/adhesive layer (1 μm)/front or back layer (7 μm)).

Example 3

(29) A mixed resin containing 80% by weight of polyester resin A and 20% by weight of polyester resin B was used as a resin to constitute the front and back layers.

(30) A mixed resin containing 32% by weight of polystyrene resin D and 68% by weight of polystyrene resin E was used as a resin to constitute the interlayer.

(31) Polyester elastomer B was used as a resin to constitute the adhesive layers.

(32) These resins 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.

(33) The obtained heat shrinkable multilayer film had a total thickness of 40 μm and had a five-layer structure (front or back layer (5.7 μm)/adhesive layer (0.7 μm)/interlayer (27.2 μm)/adhesive layer (0.7 μm)/front or back layer (5.7 μm)).

Example 4

(34) Polyester resin A was used as a resin to constitute the front and back layers.

(35) A mixed resin containing 40% by weight of polystyrene resin D, 54.3% by weight of polystyrene resin G, and 5.7% by weight of the polystyrene elastomer was used as a resin to constitute the interlayer.

(36) Polyester elastomer B was used as a resin to constitute the adhesive layers.

(37) These resins 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.

(38) The obtained heat shrinkable multilayer film had a total thickness of 35 μm and had a five-layer structure (front or back layer (3.8 μm)/adhesive layer (0.5 μm)/interlayer (26.4 μm)/adhesive layer (0.5 μm)/front or back layer (3.8 μm)).

Example 5

(39) Polyester resin A was used as a resin to constitute the front and back layers.

(40) A mixed resin containing 30% by weight of polystyrene resin A and 70% by weight of polystyrene resin C was used as a resin to constitute the interlayer.

(41) A mixed resin containing 30% by weight of polyester elastomer A and 70% by weight of polystyrene resin D was used as a resin to constitute the adhesive layers.

(42) These resins 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.

(43) The obtained heat shrinkable multilayer film had a total thickness of 40 μm and had a five-layer structure (front or back layer (5.7 μm)/adhesive layer (0.7 μm)/interlayer (27.2 μm)/adhesive layer (0.7 μm)/front or back layer (5.7 μm)).

Example 6

(44) Polyester resin A was used as a resin to constitute the front and back layers.

(45) A mixed resin containing 30% by weight of polystyrene resin A and 70% by weight of polystyrene resin F was used as a resin to constitute the interlayer.

(46) A mixed resin containing 60% by weight of polyester elastomer B and 40% by weight of polystyrene resin D was used as a resin to constitute the adhesive layers.

(47) These resins 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.

(48) The obtained heat shrinkable multilayer film had a total thickness of 40 μm and had a five-layer structure (front or back layer (5.7 μm)/adhesive layer (0.7 μm)/interlayer (27.2 μm)/adhesive layer (0.7 μm)/front or back layer (5.7 μm)).

Example 7

(49) Polyester resin A was used as a resin to constitute the front and back layers.

(50) A mixed resin containing 30% by weight of polystyrene resin A and 70% by weight of polystyrene resin F was used as a resin to constitute the interlayer.

(51) Polyester elastomer A was used as a resin to constitute the adhesive layers.

(52) These resins 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.

(53) The obtained heat shrinkable multilayer film had a total thickness of 35 μm and had a five-layer structure (front or back layer (3.8 μm)/adhesive layer (0.5 μm)/interlayer (26.4 μm)/adhesive layer (0.5 μm)/front or back layer (3.8 μm)).

Example 8

(54) Polyester resin A was used as a resin to constitute the front and back layers.

(55) A mixed resin containing 40% by weight of polystyrene resin D, 54.3% by weight of polystyrene resin G, and 5.7% by weight of the polystyrene elastomer was used as a resin to constitute the interlayer.

(56) Polyester elastomer B was used as a resin to constitute the adhesive layers.

(57) These resins 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.

(58) The obtained heat shrinkable multilayer film had a total thickness of 40 μm and had a five-layer structure (front or back layer (5 μm)/adhesive layer (0.5 μm)/interlayer (29 μm)/adhesive layer (0.5 μm)/front or back layer (5 μm)).

Example 9

(59) Polyester resin A was used as a resin to constitute the front and back layers.

(60) Polystyrene resin E was used as a resin to constitute the interlayer.

(61) Polyester elastomer A was used as a resin to constitute the adhesive layers.

(62) These resins 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.

(63) The obtained heat shrinkable multilayer film had a total thickness of 40 μm and had a five-layer structure (front or back layer (5.7 μm)/adhesive layer (0.7 μm)/interlayer (27.2 μm)/adhesive layer (0.7 μm)/front or back layer (5.7 μm)).

Comparative Example 1

(64) Polyester resin A was used as a resin to constitute the front and back layers.

(65) A mixed resin containing 40% by weight of polystyrene resin D, 54.3% by weight of polystyrene resin G, and 5.7% by weight of the polystyrene elastomer was used as a resin to constitute the interlayer.

(66) Polyester elastomer B was used as a resin to constitute the adhesive layers.

(67) These resins 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.

(68) The obtained heat shrinkable multilayer film had a total thickness of 25 μm and had a five-layer structure (front or back layer (5 μm)/adhesive layer (0.5 μm)/interlayer (14 μm)/adhesive layer (0.5 μm)/front or back layer (5 μm)).

(69) (Evaluation)

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

(71) (1) Thermomechanical Analysis (TMA)

(72) Each of the heat shrinkable multilayer films obtained in Examples 1 to 9 and Comparative Example 1 was cut to 26 mm in length×4.7 mm in width such that the TD (main shrinkage direction) corresponded to the longitudinal direction, whereby a sample having a measurement site with a measurement reference length of 16 mm was prepared.

(73) The temperature of the obtained sample was increased from 30° C. to 60° C. at a temperature increase rate of 5° C./min with a load of 0.1 N using a thermomechanical analyzer (produced by TA Instruments, TMA Q400).

(74) The temperature was then cooled from 60° C. to 10° C. at a temperature decrease rate of 5° C./min to measure the difference between a dimensional change from the measurement reference length at the measurement site at 60° C. and a dimensional change from the measurement reference length at the measurement site at 20° C. The dimensional change was calculated by the following equation.

(75) Dimensional change (μm)=dimensional change (μm) from measurement reference length at 20° C.−dimensional change (μm) from measurement reference length at 60° C.

(76) (2) Displacement Width

(77) Labels having a lay flat width of 132 mm and a length of 90 mm were produced using the heat shrinkable multilayer films obtained in Examples 1 to 9 and Comparative Example 1.

(78) A covering type shrink tunnel K-1000 (produced by Kyowa Denki Co., Ltd.) was set at a tunnel temperature of 90° C., an air flow of 20 Hz, and a belt speed of 25 Hz (transit time: 25 seconds) and used as tunnel 1.

(79) Separately, a covering type shrink tunnel K-100 (produced by Kyowa Denki Co., Ltd.) was set at a tunnel temperature of 100° C., an air flow of 40 Hz, a belt speed of 25 Hz (transit time: 25 seconds) and used as tunnel 2.

(80) Subsequently, each obtained label was attached to a spray bottle (Kabi Killer® spray bottle, capacity: 400 mL, width: 102 mm, depth: 57 mm, height: 164 mm), and passed through tunnel 1, then a room temperature atmosphere for 7 seconds, and then tunnel 2. The label was thus shrunk, and then left to stand for 24 hours.

(81) A load of up to 10 N was applied to the label of the obtained labelled container in the circumferential direction, and the displacement width in the circumferential direction was measured. A displacement width of 0 to 10 mm indicates that the loosening of the film can be sufficiently reduced.

(82) TABLE-US-00001 TABLE 1 Compar- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ative ple ple ple ple ple ple ple ple ple Exam- 1 2 3 4 5 6 7 8 9 ple 1 Heat Front Constit- Polyester resin A 100 100 80 100 100 100 100 100 100 100 shrink- and uent Polyester resin B — — 20 — — — — — — — able back resin multi- layers (% by layer weight) film Thickness (μm) 7 7 5.7 3.8 5.7 5.7 3.8 5 5.7 5 Inter- Constit- Polystyrene resin 50 30 — — 30 30 30 — — — layer uent A (Vicat softening resin temperature: 81° C. (% by Polystyrene resin 50 — — — — — — — — — weight) B (Vicat softening temperature: 59° C. Polystyrene resin — 70 — — 70 — — — — — C (Vicat softening temperature: 71° C. Polystyrene resin — — 32 40 — — — 40 — 40 D (Vicat softening temperature: 76° C. Polystyrene resin — — 68 — — — — — 100 — E (Vicat softening temperature: 74° C. Polystyrene resin — — — — — 70 70 — — — F (Vicat softening temperature: 75° C. Polystyrene resin — — — 54.3 — — — 54.3 — 54.3 G (Vicat softening temperature: 76° C. Polystyrene elastomer — — — 5.7 — — — 5.7 — 5.7 (Vicat softening temperature: 76° C. Thickness (μm) 34 34 27.2 26.4 27.2 27.2 26.4 29 27.2 14 Ad- Constit- Polyester resin A 59 — — — — — — — — — hesive uent Polyester resin C 10 — — — — — — — — — layer resin Polyester elastomer A — 65 — — 30 — 100 — 100 — (% by Polyester elastomer B — — 100 100 — 60 — 100 — 100 weight) Polystyrene resin D 31 35 — — 70 40 — — — — Thickness (μm) 1 1 0.7 0.5 0.7 0.7 0.5 0.5 0.7 0.5 Total Thickness (μm) 50 50 40 35 40 40 35 40 40 25 (Front layer thickness + back 0.412 0.412 0.419 0.288 0.419 0.419 0.288 0.345 0.419 0.714 layer thickness)/interlayer thickness Evalu- Dimentional change (μm) −588 −80 −237 −61 −118 −148 −80 −106 −189 −52 ation Displacement width (mm) 4 5 6 6 6 7 8 8 8 12

INDUSTRIAL APPLICABILITY

(83) The present invention can provide a heat shrinkable multilayer film that can prevent wrinkles or loosening after attachment when the film is attached to a container as a heat shrinkable label for dry heat shrinking, and a heat shrinkable label including the heat shrinkable multilayer film as a base film.